System for optimizing evoked response signal generation during electrode lead insertion procedures

Abstract

A diagnostic system is disclosed configured to direct an acoustic stimulus generator to apply an acoustic stimulus having a stimulus frequency to a recipient of a cochlear implant during an insertion procedure in which an electrode lead of the cochlear implant is inserted into a cochlea of the recipient, direct the cochlear implant to record, using an electrode disposed on the electrode lead, an evoked response signal during the insertion procedure, the evoked response signal representative of amplitudes of a plurality of evoked responses occurring within the recipient in response to the acoustic stimulus applied to the recipient, and incrementally step the stimulus frequency through a sequence of decreasingly lower values as the electrode lead is inserted into the cochlea, the sequence of decreasingly lower values beginning with an initial value and ending with a final value lower than the initial value.

Description

[0001] BACKGROUND

[0002] During an insertion procedure in which an electrode lead is installed within a cochlea, it can be desirable to monitor evoked responses (e.g., cochlear electrogram ("ECoG" or "ECochG") potentials) that occur within a recipient in response to acoustic stimulation applied to the recipient. These evoked responses can be indicative of the positioning of the electrode within the cochlea, indicative of trauma that can have occurred to the cochlea during the insertion procedure, indicative of residual hearing of different regions of the cochlea as the electrode lead is inserted, and / or indicative of various other factors related to the insertion procedure. BRIEF DESCRIPTION OF DRAWINGS

[0003] The accompanying drawings illustrate various embodiments and are a part of the specification. The illustrated embodiments are merely examples and do not limit the scope of the disclosure. Throughout the drawings, the same or like reference numerals designate the same or like elements.

[0004] Figure 1 An exemplary cochlear implant system is illustrated in accordance with the principles described herein.

[0005] Figure 2 A schematic structure of a human cochlea is illustrated in accordance with the principles described herein.

[0006] Figure 3 An exemplary diagnostic system is illustrated in accordance with the principles described herein.

[0007] Figures 4-5 An exemplary implementation of a diagnostic system is illustrated in accordance with the principles described herein. Figure 3

[0008] Figures 6A-6F An exemplary insertion procedure to insert an electrode lead into a cochlea of a recipient is illustrated in accordance with the principles described herein.

[0009] Figure 7 How an excitation spread measurement can be performed for an electrode lead being inserted into a cochlea of a recipient is illustrated in accordance with the principles described herein.

[0010] Figures 8-12 An exemplary graph of an evoked response signal that can be generated is shown in accordance with the principles described herein.

[0011] Figure 13 An exemplary method is illustrated in accordance with the principles described herein.

[0012] Figure 14 An exemplary computing device is illustrated in accordance with the principles described herein. DETAILED DESCRIPTION​

[0013] Systems and methods for optimizing evoked response signal generation during electrode lead insertion procedures are described herein. For example, a diagnostic system can direct an acoustic stimulus generator to apply acoustic stimuli having a stimulus frequency to a recipient of a cochlear implant during an insertion procedure in which an electrode lead communicatively coupled to the cochlear implant is being inserted into the recipient's cochlea. The diagnostic system can direct the cochlear implant to record evoked response signals using electrodes disposed on the electrode lead during the insertion procedure. The evoked response signals are representative of amplitudes of a plurality of evoked responses that occur within the recipient's body in response to the acoustic stimuli applied to the recipient. The evoked responses can each be ECoG potentials (e.g., cochlear microphonic potentials, action potentials, summating potentials, etc.), auditory nerve responses, brainstem responses, complex action potentials, stapedius reflexes, and / or any other type of neural or physiological response that can occur within the recipient's body in response to the acoustic stimuli applied to the recipient. The evoked responses can originate from neural tissue, hair cell to nerve synapses, inner hair cells, or outer hair cells, or other sources.

[0014] As the electrode lead is inserted into the cochlea, the diagnostic system can step the stimulus frequency through a sequence of decreasingly lower values that begins with an initial value and ends with a final value that is lower than the initial value. This stepping of the stimulus frequency through each of the decreasingly lower values is based on an intracochlear positioning of the electrodes used to record the evoked responses, as described herein.

[0015] For example, the diagnostic system can maintain data representative of a sequence of decreasingly lower values to which the stimulus frequency can be set. An example sequence of decreasingly lower values includes 4 kHz, 2 kHz, 1 kHz, 500 Hz, and 250 Hz. These values are merely exemplary, and additional or alternative values can also be included in the sequence, as can serve a particular implementation.

[0016] Prior to the start of the electrode lead insertion procedure, the diagnostic system can set the stimulus frequency to an initial value (e.g., 4 kHz) included in the sequence of decreasingly lower values. As the electrode lead is being inserted (e.g., by a surgeon or other user) into the recipient's cochlea of the cochlear implant, the diagnostic system can direct the acoustic stimulus generator to apply acoustic stimuli having this initial stimulus frequency value to the recipient while the most distal electrode disposed on the electrode lead (or any other designated electrode on the electrode lead) records evoked responses that occur in response to the acoustic stimuli. As the electrode lead is advanced further into the cochlea, the diagnostic system can determine that the electrode has passed through an intracochlear characteristic frequency location corresponding to the initial stimulus frequency value. This characteristic frequency location can be based on, for example, a cochlear tonotopic map.

[0017] In response to determining that the electrode passes through the characteristic frequency location corresponding to the initial stimulation frequency value, the diagnostic system can cause the stimulation frequency to decrease from the initial value to a next decreased value (e.g., 2 kHz) in the sequence of decreasingly decreased values. After the diagnostic system determines that the electrode lead passes through the characteristic frequency location within the cochlea corresponding to the next decreased value, the diagnostic system can again cause the stimulation frequency to decrease to a next decreased value (e.g., 1 kHz) in the sequence of decreasingly decreased values. This process can be repeated for the remaining values included in the sequence of decreasingly decreased values as the electrode lead is further inserted into the cochlea.

[0018] As another example, the diagnostic system can direct the acoustic stimulation generator to apply acoustic stimulation having a plurality of stimulation frequencies to a recipient of a cochlear implant during an insertion procedure in which an electrode lead of the cochlear implant is inserted into a cochlea of the recipient (e.g., concurrently). The diagnostic system can direct the cochlear implant to record a plurality of evoked response signals using the electrodes disposed on the electrode lead during the insertion procedure, the evoked response signals each corresponding to a different stimulation frequency included in the plurality of stimulation frequencies. The diagnostic system can plot a graph of the evoked response signals via the display device in substantially real-time as the insertion procedure is being performed by switching between displaying each evoked response signal included in the plurality of evoked response signals such that, at any given time, only a single evoked response having the highest amplitude compared to the other evoked responses in the plurality of evoked response signals is displayed by the display device.

[0019] By incrementally stepping the stimulation frequency through a sequence of decreasingly decreased values as the electrode lead is further inserted into the cochlea, and / or by applying acoustic stimulation having a plurality of stimulation frequencies and plotting a graph, as described above, the systems and methods described herein can optimize evoked response signal generation during an electrode insertion procedure in a manner that delivers more accurate, useful, and efficient feedback to a user compared to techniques that use only a single stimulation frequency value (e.g., 500 Hz) for the entire electrode insertion procedure. For example, the graph of the evoked response signals can be presented to the user in substantially real-time during the insertion procedure, which can allow the user to visually ascertain the positioning of the electrode within the cochlea, trauma that can be occurring to the cochlea during the insertion procedure, and / or various other factors associated with the insertion procedure. To illustrate, the evoked response signal should peak and begin to decrease each time the electrode passes through the characteristic frequency location associated with the current value of the stimulation frequency. However, if the decrease occurs before the electrode passes through the characteristic frequency location, this can indicate that the electrode lead is causing damage to the cochlea. Such information would not be ascertainable in techniques that use only a single stimulation frequency value (e.g., 500 Hz) for the entire electrode insertion procedure. These and other benefits and advantages of the systems and methods described herein will become apparent from this document.

[0020] Figure 1 The figure illustrates an exemplary cochlear implant system 100. As shown, the cochlear implant system 100 may include a microphone 102, a sound processor 104, a headpiece 106, a cochlear implant 108, and electrode leads 110, wherein a coil is disposed in the headpiece. The electrode leads 110 may include an array of electrodes 112 disposed on a distal portion of the electrode leads 110, and the electrodes are configured to be inserted into the recipient's cochlea to stimulate the cochlea when the distal portion of the electrode leads 110 is inserted into the cochlea. One or more other electrodes (e.g., including ground electrodes, not explicitly shown) may also be disposed on other portions of the electrode leads 110 (e.g., on the proximal portion of the electrode leads 110) to, for example, provide a current return path for the stimulation current generated by the electrodes 112 and remain outside the cochlea after the electrode leads 110 are inserted into the cochlea. As shown, the electrode leads 110 may be pre-bent to suitably fit within the helical shape of the cochlea. Additional or alternative components may also be included within the cochlear implant system 100, as may be for a particular implementation.

[0021] As shown in the figure, the cochlear implant system 100 may include various components configured to be located outside the recipient's body, including but not limited to a microphone 102, a sound processor 104, and a headpiece 106. The cochlear implant system 100 may further include various components configured to be implanted inside the recipient's body, including but not limited to a cochlear implant 108 and electrode leads 110.

[0022] Microphone 102 can be configured to detect audio signals presented to the user. Microphone 102 can be implemented in any suitable manner. For example, microphone 102 may include a microphone configured to be positioned near the entrance to the ear canal within the outer ear, such as the T-MIC from Advanced Bionics. TM Microphone. Such a microphone can be held in the outer ear near the entrance of the ear canal during normal operation by means of a stalk or stem attached to an ear hook, which is configured to selectively attach to the sound processor 104. Alternatively or additionally, the microphone 102 may also be implemented by one or more microphones disposed in the headpiece 106, one or more microphones disposed in the sound processor 104, one or more beamforming microphones, and / or any other suitable microphone that may serve a particular implementation.

[0023] The sound processor 104 can be configured to direct the cochlear implant 108 to generate and apply electrical stimulation (also referred to herein as "stimulation current") representative of one or more audio signals (e.g., detected by the microphone 102, input via an auxiliary audio input port, input via a clinician programmer interface (CPI) device, etc.) to one or more stimulation sites associated with a recipient's auditory pathway (e.g., the auditory nerve). Exemplary stimulation sites include, but are not limited to, one or more locations within the cochlea, the cochlear nucleus, the inferior colliculus, and / or any other nuclei in the auditory pathway. To this end, the sound processor 104 can process the one or more audio signals in accordance with a selected sound processing strategy or program to generate appropriate stimulation parameters for controlling the cochlear implant 108. The sound processor 104 can be housed within any suitable housing (e.g., a behind-the-ear ("BTE") unit, a body-worn device, the headpiece 106, and / or any other sound processing unit that can serve a particular implementation).

[0024] In some examples, the sound processor 104 can transmit stimulation parameters (e.g., in the form of data words included in a forward telemetry sequence) and / or power signals to the cochlear implant 108 wirelessly via a wireless communication link 114 (e.g., a wireless link between a coil disposed within the headpiece 106 and a coil physically coupled to the cochlear implant 108) between the headpiece 106 and the cochlear implant 108. It will be appreciated that the communication link 114 can include a bidirectional communication link and / or one or more dedicated unidirectional communication links.

[0025] The headpiece 106 can be communicatively coupled to the sound processor 104 and can include an external antenna (e.g., a coil and / or one or more wireless communication components) configured to facilitate selective wireless coupling of the sound processor 104 to the cochlear implant 108. Additionally or alternatively, the headpiece 106 can be used to selectively and wirelessly couple any other external device to the cochlear implant 108. To this end, the headpiece 106 can be configured to be attached to a recipient's head and positioned such that the external antenna housed within the headpiece 106 is communicatively coupled to a corresponding implantable antenna (which can also be implemented by a coil and / or one or more wireless communication components) included within or otherwise associated with the cochlear implant 108. In this manner, stimulation parameters and / or power signals can be wirelessly transmitted between the sound processor 104 and the cochlear implant 108 via the communication link 114.

[0026] The cochlear implant 108 may include any suitable type of implantable stimulator. For example, the cochlear implant 108 may be implemented by an implantable cochlear stimulator. Alternatively or alternatively, the cochlear implant 108 may include a brainstem implant and / or any other type of cochlear implant that is implantable in the recipient and configured to apply stimulation to one or more stimulation sites located along the recipient's auditory pathway.

[0027] In some examples, the cochlear implant 108 may be configured to generate electrical stimulation representing an audio signal processed by the sound processor 104 (e.g., an audio signal detected by the microphone 102) based on one or more stimulation parameters sent to it by the sound processor 104. The cochlear implant 108 may also be configured to apply electrical stimulation to one or more stimulation sites (e.g., one or more intracochlear regions) within the recipient body via electrodes 112 disposed along electrode leads 110. In some examples, the cochlear implant 108 may include a plurality of independent current sources, each associated with a channel defined by one or more of the electrodes 112. In this way, different levels of stimulation current can be simultaneously applied to multiple stimulation sites via multiple electrodes 112.

[0028] Figure 2 The diagram illustrates a schematic structure into which the electrode lead 110 can be inserted into a human cochlea 200. For example... Figure 2 As shown, the cochlea 200 is spiral-shaped, beginning at a base 202 and ending at a apex 204. The cochlea 200 contains auditory nerve tissue 206. Figure 2 The auditory nerve tissue is indicated by an X. The auditory nerve tissue 206 is structured within the cochlea 200 in a tonal topological manner. Relatively low frequencies are encoded at or near the apex 204 of the cochlea 200 (also referred to as the "apical region"), while relatively high frequencies are encoded at or near the base 202 (also referred to as the "basal region"). Therefore, electrical stimulation applied via an electrode located in the apical region (i.e., the "apical electrode") allows the receptor to perceive relatively low frequencies, while electrical stimulation applied via an electrode located in the basal region (i.e., the "basal electrode") allows the receptor to perceive relatively high frequencies. On a particular electrode lead, the demarcation between the apical and basal electrodes may vary depending on the insertion depth of the electrode lead, the anatomy of the recipient cochlea, and / or any other factors that may serve a particular implementation.

[0029] Figure 3FIGURE illustrates an example diagnostic system 300 that can be configured to implement any of the operations described herein. As shown, diagnostic system 300 can include, without limitation, a storage facility 302 and a processing facility 304 that are selectively and communicatively coupled to one another. Facilities 302 and 304 can each include or be implemented by hardware and / or software components (e.g., processors, memories, communication interfaces, instructions stored in memory for execution by a processor, etc.). In some examples, facilities 302 and 304 can be distributed among multiple devices and / or multiple locations, as can serve a particular implementation.

[0030] Storage facility 302 can maintain (e.g., store) executable data used by processing facility 304 to implement any of the operations described herein. For example, storage facility 302 can store instructions 306 that can be executed by processing facility 304 to implement any of the operations described herein. Instructions 306 can be implemented by any suitable application programs, software, code, and / or other executable data instances. Storage facility 302 can also maintain any data received, generated, managed, used, and / or sent by processing facility 304.

[0031] Processing facility 304 can be configured to implement (e.g., execute instructions 306 stored in storage facility 302 to implement) various operations. For example, processing facility 304 can direct an acoustic stimulus generator to apply an acoustic stimulus having a stimulus frequency to a recipient of a cochlear implant during an insertion procedure in which an electrode lead communicatively coupled to the cochlear implant is inserted into a cochlea of the recipient, direct the cochlear implant to record (e.g., detect) an evoked response signal using electrodes disposed on the electrode lead during the insertion procedure (e.g., during all or only a portion of the insertion procedure), and incrementally step the stimulus frequency through a sequence of decreasingly lower values starting with an initial value and ending with a final value that is lower than the initial value as the electrode lead is inserted into the cochlea. Data representative of the recorded evoked response signal can be stored by processing facility 304 in storage facility 302 and / or in any other suitable storage medium that can serve a particular implementation.

[0032] Additionally or alternatively, the processing facility 304 can direct the acoustic stimulus generator to apply acoustic stimuli having a plurality of stimulus frequencies to a recipient of a cochlear implant during an insertion procedure in which an electrode lead communicatively coupled to the cochlear implant is inserted into the cochlea of the recipient, direct the cochlear implant to record a plurality of evoked response signals during the insertion procedure using electrodes disposed on the electrode lead, the evoked response signals each corresponding to a different stimulus frequency included in the plurality of stimulus frequencies, and plot a graph of the evoked response signals via the display device in substantially real-time as the insertion procedure is being performed by switching between each of the evoked response signals included in the plurality of evoked response signals such that, at any given time, only a single evoked response having the highest amplitude compared to the other evoked responses in the plurality of evoked response signals is displayed by the display device. These and other operations that can be performed by the processing facility 304 are described in greater detail herein.

[0033] The diagnostic system 300 can be implemented in any suitable manner. For example, Figure 4 An example configuration arrangement 400 is shown in which the diagnostic system 300 is implemented by a computing system 402 configured to be communicatively coupled to the sound processor 104. As shown, the computing system 402 can include an acoustic stimulus generator 404 communicatively coupled to a speaker 406. The computing system 402 is also communicatively coupled to a display device 408.

[0034] The computing system 402 can be implemented by any suitable combination of hardware (e.g., one or more computing devices) and software. For example, the computing system 402 can be implemented by a computing device programmed to perform one or more fitting operations for a recipient of a cochlear implant. To illustrate, the computing system 402 can be implemented by a desktop computer, a mobile device (e.g., a laptop computer, a smartphone, a tablet computer, etc.), and / or any other suitable computing device that can serve a particular implementation.

[0035] The acoustic stimulus generator 404 can be implemented by any suitable combination of components configured to generate acoustic stimuli. In some examples, the acoustic stimuli can include one or more tones having one or more stimulus frequencies. Additionally or alternatively, the acoustic stimuli can include any other type of acoustic content having at least one particular stimulus frequency of interest. The speaker 406 can be configured to deliver the acoustic stimuli generated by the acoustic stimulus generator 404 to the recipient. For example, the speaker 406 can be implemented by an ear mold configured to be fitted in or near the entrance of the ear canal of the recipient.

[0036] The display device 408 can be implemented by any suitable device configured to display graphical content generated by the computing system 402. For example, the display device 408 can display one or more graphs of evoked responses recorded by electrodes disposed on the electrode lead 110. In some alternative embodiments, the display device 408 is integrated into the computing system 402.

[0037] Figure 5 Another example configuration 500 is shown in which the diagnostic system 400 is implemented by the computing system 402. In the configuration 500, the acoustic stimulus generator 404 is included in the sound processor 104. For example, the sound processor 104 can be implemented by a bimodal sound processor (i.e., a sound processor configured to direct the cochlear implant 108 to apply electrical stimulation to the recipient and to direct the acoustic stimulus generator 404 to apply acoustic stimulation to the recipient). In some examples, the loudspeaker 406 can be implemented by an audio ear hook connected to the sound processor 104.

[0038] Figures 6A-6F An example insertion procedure is illustrated in which the electrode lead 600 is inserted into the cochlea 602 of a recipient. For illustrative purposes, the cochlea 602 is depicted in Figures 6A-6F as "uncoiled" rather than its actual, curved, spiral shape. The lead 600 can be similar to the lead 110 and can include a plurality of electrodes disposed thereon (e.g., electrodes 604-1 through 604-16). The electrode 604-1 is the distal-most electrode on the lead 600, and the electrode 604-16 is the proximal-most electrode on the lead 600.

[0039] Various characteristic frequency locations within the cochlea 602 are depicted in each of Figures 6A-6F . As shown, a first characteristic frequency location is associated with 4 kHz. Thus, electrical stimulation applied by an electrode positioned at this characteristic frequency location can cause the recipient to perceive a sound having 4 kHz. Figures 6A-6F Characteristic frequency locations associated with 2 kHz, 1 kHz, 500 Hz, and 250 Hz are also depicted. As shown, the frequencies associated with each characteristic frequency location are arranged in a tonotopic topology, with relatively higher frequencies positioned toward the entrance (or base) of the cochlea 602 and relatively lower frequencies positioned toward the distal end (or apex) of the cochlea 602.

[0040] Figure 6A The electrode lead 600 is shown entering the cochlea 602. In this figure, the electrode 604-1 is just inside the cochlea 602. Figure 6B The electrode lead 600 is shown after the electrode lead 600 has been further advanced into the cochlea 602 such that the electrode 604-1 is positioned at a characteristic frequency location corresponding to 4 kHz.Figures 6C-6F The electrode lead 600 is shown after the electrode 604-1 has been advanced further into the cochlea 602 such that the electrode 604-1 is located at a characteristic frequency location corresponding to 2 kHz Figure 6C ), then 1 kHz Figure 6D ), then 500 Hz Figure 6E ), and then 250 Hz Figure 6F ).

[0041] The diagnostic system 300 can determine that the electrode 604-1 passed a particular characteristic frequency location in any suitable manner. For example, the diagnostic system 300 can determine that the electrode 604-1 passed a particular characteristic frequency location by performing an excitation spread measurement (e.g., a cross impedance measurement) with respect to the electrode 604-1 and at least one other electrode disposed on the electrode lead 600. Based on the excitation spread measurement, the diagnostic system 300 can determine a number of electrodes disposed on the electrode lead 300 that are located within the cochlea 602. From the determined number of electrodes within the cochlea 602, the diagnostic system 300 can determine (e.g., estimate) a location of the electrode 604-1 within the cochlea 602.

[0042] For example, if the diagnostic system 300 determines that three electrodes are within the cochlea 602, the diagnostic system 300 can determine that the electrode 604-1 is located at a characteristic frequency location corresponding to 4 kHz. As another example, if the diagnostic system 300 determines that six electrodes are within the cochlea 602, the diagnostic system 300 can determine that the electrode 604-1 is located at a characteristic frequency location corresponding to 2 kHz. The relationship between the number of electrodes within the cochlea 602 and the location of the electrode 604-1 can be determined and / or defined in any suitable manner. In some examples, the diagnostic system 300 maintains data representative of the relationship (e.g., in the form of a lookup table).

[0043] As used herein, an "excitation diffusion measurement" can refer to any measurement configured to determine a range over which an excitation (e.g., an electrical pulse) applied by one electrode at one location can diffuse or propagate (e.g., through fluid and / or tissue at and around the location) to such that it can be detected (e.g., as a voltage) by another electrode at another location. Thus, an excitation diffusion measurement as implemented by the systems and methods described herein can be similar to a conventional impedance measurement in which an excitation is applied by one electrode and then detected by the same electrode (e.g., with reference to a ground electrode, with reference to another separate excitation electrode, etc.). However, unlike a conventional impedance measurement, an excitation diffusion measurement as implemented by the systems and methods described herein can apply an excitation using an electrode that is different and distinct from the electrode used to record (e.g., detect) the excitation (e.g., a voltage resulting from the application of the excitation) as it diffuses. Thus, in some examples, an excitation diffusion measurement can also be referred to as a "cross-impedance" measurement, etc.

[0044] As one example of how an excitation diffusion measurement can be implemented, the diagnostic system 300 can direct a first electrode (e.g., electrode 604-1) to generate an electrical pulse, and in response to the generation of the electrical pulse, the diagnostic system can detect a voltage between a second electrode (e.g., another one of the electrodes 604 or a ground electrode) and a reference (e.g., a ground electrode, a housing ground of the cochlear implant, etc.), where both the second electrode and the reference are distinct from the first electrode. Based on the excitation diffusion measurement, the diagnostic system 300 can determine whether at least one of the first electrode and the second electrode is located within the cochlea 602.

[0045] In certain implementations, the diagnostic system 300 can implement one or more of the above-described operations for each electrode 604. In this way, the diagnostic system 300 can detect sufficient information to determine not only a location for each electrode 604, but also an insertion depth of the electrode lead 600 as a whole. For example, at a point in time during the insertion process, the diagnostic system 300 can determine that the electrode lead 600 is located in a position in which a first X number of electrodes 604 have been inserted into the cochlea 602, while a remaining Y number of electrodes 604 remain outside the cochlea (where X and Y sum to the total number of electrodes disposed on the electrode lead).

[0046] Examples of excitation diffusion measurements are provided with respect to Figure 7 In particular, Figure 7FIGURE illustrates exemplary aspects of an electrode lead 700 and patient anatomy while the insertion procedure is being performed. The electrode lead 700 can be similar to any of the electrode leads described herein. In particular, as shown, the electrode lead 700 includes a proximal portion 702 beginning at a proximal end 704 and a distal portion 706 terminating at a distal end 708. The electrode lead 700 is provided with a plurality of electrodes 710, including a plurality of stimulating electrodes 710-S (e.g., stimulating electrodes 710-S1 through 710-S5 and 710-S16, as well as additional stimulating electrodes 710-S6 through 710-S15, which are not explicitly labeled but are referred to herein) on the distal portion 706 and including a ground electrode 710-G (e.g., a ring electrode) on the proximal portion 702. Figure 7

[0047] Figure 7 FIGURE illustrates a particular position of the electrode lead 700 during the insertion procedure, in which the electrode lead 700 (and, in particular, the distal portion 706) is being inserted into the cochlea 714 of the patient from the middle ear 712 through the round window 716 associated with the cochlea 714. For example, a goal of the insertion procedure can be to continue to insert the distal portion 706 into the cochlea 714 toward the apex 718 of the cochlea 714 until the distal portion 706 (and, in particular, the stimulating electrodes 710-S included therein) has passed through the round window 716 and is located within the cochlea 714.

[0048] In Figure 7 For purposes of illustration, various aspects of the electrode lead 700 and the illustrated features of the patient's anatomy are simplified. For example, although the cochlea 714 is "unrolled" in Figure 7 the cochlea 714 has a curved, spiral structure, as illustrated in Figure 2 the cochlea 714 has a curved, spiral structure, as illustrated in

[0049] However, Figure 7 ​The figures illustrate at least one aspect in which the diagnostic system 300 enables excitation spread measurements in a patient's anatomy. As shown, on the cochlear side of the round window 716, the cochlea 714 contains a conductive fluid ("fluid") that is different from the gaseous fluid (e.g., air) on the other side of the round window 716, which is conductive to electrical current applied to the fluid. In certain examples, the diagnostic system 300 can distinguish between different fluids within the cochlea 714 (e.g., perilymph in the vestibular and tympanic scala, endolymph in the medial scala, etc.) based on the different conductivities of the different fluids. In this way, the diagnostic system 300 can not only distinguish between electrodes located in the fluid of the cochlea 714 and electrodes still located in the air of the middle ear 712, but can also further distinguish between electrodes located in different parts of the cochlea 714 (e.g., located within one of the vestibular or tympanic scala, located within the medial scala, etc.).

[0050] The fluid within the cochlea 714 can carry electrical current and provide a range of current-conducting paths for an electrical pulse (e.g., a pulse provided by a current or voltage source) to spread between electrodes 710-S that have been inserted into the cochlea 714 (i.e., surrounded by the fluid). Thus, for example, if an electrical pulse is generated at one particular electrode 710-S, such as 710-Si, the fluid can provide a conductive path from the electrode 710-Si to other electrodes 710-S included within the cochlea 714 (i.e., surrounded by the fluid at the time illustrated in the figure, 710-S2 through 710-S10) and to tissue surrounding the cochlea 714. The electrical pulse can be generated by a cochlear implant or other device communicatively coupled to the proximal end 704. Thus, a return path for the electrical current associated with the electrical pulse can extend from the electrode 710-Si, through the fluid of the cochlea 714, through tissue associated with the cochlea 714 and the middle ear 712, through the ground electrode 710-G, back to a voltage or current source included in the cochlear implant or other device that generated the electrical pulse. Figure 7

[0051] Because the fluid within the cochlea 714 can conduct electrical current while the air outside of the cochlea 714 (i.e., the air in the middle ear 712 on the other side of the round window 716) cannot effectively conduct electrical current, only electrodes 710-S that have passed through the round window 716 into the cochlea 714 and are surrounded by the fluid of the cochlea 714 will be able to detect the excitation spread of the electrical pulse generated by the electrode 710-Si in the above example. Electrodes 710-S that have not been inserted through the round window 716 (e.g., electrodes 710-S11 through 710-S16 at the time illustrated in the figure) can thus not have a viable conductive path connecting them to the electrode 710-Si, and can thus be unable to detect the excitation spread of the electrical pulse generated at the electrode 710-Si. Figure 7

[0052] ​​As described above, the excitation spread measurement can be implemented in such a way that an electrical pulse is generated at a first electrode (e.g., electrode 710-S1 in the example above) and then detected between a second electrode (e.g., one of electrodes 710-S2 through 710-S16 or 710-G) and a reference (e.g., ground electrode 710-G, a housing ground of the cochlear implant, etc.) (i.e., how the electrical pulse has spread). For example, both the second electrode and the reference can be separate from the first electrode, which is in stark contrast to the way impedance measurements are conventionally implemented. Since it is known how much current or voltage is applied at the first electrode (e.g., by a current or voltage source that generates the electrical pulse) and how much current or voltage is detected at the second electrode, the extent to which the electrical pulse is able to spread (e.g., through the fluids and / or tissue of cochlea 714) between the first electrode and the second electrode can be determined (e.g., with Ohm's law and / or other similar principles). Accordingly, by determining that the electrical pulse has spread to at least some extent from the first electrode to the second electrode via an excitation spread measurement involving electrodes that are known to be inserted into cochlea 714, diagnostic system 300 can determine that both electrodes are inserted into cochlea 714. However, when the electrical pulse is determined not to have spread from the first electrode to the second electrode via an excitation spread measurement involving electrodes that are known to be inserted into cochlea 714 (i.e., when the electrical pulse fails to be detected at the second electrode because, for example, one of the electrodes is disposed in the air of middle ear 712 such that no conductive path exists between the first electrode and the second electrode), diagnostic system 300 can determine that one of the electrodes has not entered into cochlea 714.

[0053] Furthermore, by determining in this way whether each of electrodes 710-S is located within or outside of cochlea 714, the insertion depth of the entire electrode lead 700 can be determined. For example, by determining that electrodes 710-S1 through 710-S10 are located in the fluids of cochlea 714 and that electrodes 710-S11 through 710-S16 are located in the air of middle ear 712, diagnostic system 300 can determine that electrode lead 700 has entered into cochlea 714 about half way but still needs to be inserted further, as shown.

[0054] While the above examples describe excitation spread measurements in which electrical pulses are generated at an electrode known to be inserted into the cochlea 714 (i.e., electrode 710-S1), the same principles of excitation spread measurements would work if an electrode known to be inserted into the cochlea 174 (i.e., electrode 710-S1) is used to detect electrical pulses generated at a subject electrode 710-S. For example, the diagnostic system 300 can determine whether, for example, electrode 710-S5 is located in the cochlea 714 (i.e., whether electrode 710-S5 has a fluidic conduction path with electrode 710-S1) by generating an electrical pulse at electrode 710-S1 and attempting to detect the electrical pulse at electrode 710-S5, or vice versa, by generating an electrical pulse at electrode 710-S5 and attempting to detect the electrical pulse at electrode 710-S1. Accordingly, the diagnostic system 300 can include or have control over the pulse generation and detection circuitry to flexibly implement excitation spread measurements in these different ways.

[0055] Further details and examples of excitation spread measurements are provided in PCT Patent Publication No. WO / 2019 / 045747, the entirety of which is incorporated herein by reference.

[0056] The diagnostic system 300 can additionally or alternatively determine that the electrode 604-1 passes through the particular characteristic frequency location by detecting that the amplitude of the evoked response signal recorded by the electrode 604-1 decreases by at least an amplitude threshold amount and the phase of the evoked response signal recorded by the electrode 604-1 changes by at least a phase threshold amount over a predetermined period of time.

[0057] To illustrate, Figure 8 FIGURE 1 illustrates an example lead insertion procedure in which the electrode lead 600 is advanced into the cochlea 602. The reference numerals PI through P5 indicate the position of the electrode lead 600. For example, at position PI, the electrode lead 600 is at a first position in which the electrode 604-1 is approaching a characteristic frequency location corresponding to 4 kHz. At position P2, the electrode lead 600 is at a second position in which the electrode 604-1 is at the characteristic frequency location corresponding to 4 kHz. At positions P3-P5, the electrode lead 600 is in third, fourth, and fifth positions, respectively, in which the electrode 604-1 has advanced past the characteristic frequency location corresponding to 4 kHz.

[0058] Figure 8Also shown are graph 802 showing the amplitude of the evoked response signal recorded by electrode 604-1 during the lead insertion process and graph 804 showing the phase of the evoked response signal recorded by electrode 604-1 during the lead insertion process. In this example, the evoked response signal is generated in response to an acoustic stimulus with a stimulus frequency of 4 kHz. Therefore, as shown in graph 802, as electrode lead 600 moves toward the characteristic frequency position corresponding to 4 kHz, the amplitude of the evoked response signal increases and reaches a peak when electrode lead 600 is positioned at position P2. As electrode lead 600 passes the characteristic frequency position corresponding to 4 kHz, the amplitude of the evoked response decreases until it stabilizes at a steady-state value. As shown in graph 804, as electrode lead 600 moves toward the characteristic frequency position corresponding to 4 kHz, the phase of the evoked response remains at a relatively high level. However, when electrode lead 600 passes the characteristic frequency position corresponding to 4 kHz, the phase suddenly changes to a relatively low level.

[0059] like Figure 8 As shown, the decrease in the amplitude of the evoked response and the change in phase from a high level to a low level occur at approximately the same time, and both occur when electrode 604-1 passes through a characteristic frequency position corresponding to 4 kHz. Therefore, the diagnostic system 300 can determine the position of electrode 604-1 passing through a characteristic frequency position corresponding to 4 kHz by detecting a decrease in amplitude of the evoked response signal recorded by electrode 604-1 by at least an amplitude threshold amount and a change in phase of the evoked response signal recorded by electrode 604-1 by at least a phase threshold amount within a predetermined time period. The predetermined time period, amplitude threshold amount, and / or phase threshold amount can each be set by the diagnostic system 300 to any suitable value. For example, the predetermined time period can be set to a relatively short period (e.g., less than a few milliseconds) to ensure that the amplitude change and phase change correspond to each other. In some examples, the diagnostic system 300 can set the predetermined time period, amplitude threshold amount, and / or phase threshold amount in response to user input (e.g., via a graphical user interface). Alternatively, the diagnostic system 300 may also automatically set the predetermined time period, amplitude threshold, and / or phase threshold based on one or more factors such as hearing loss, stimulation frequency, and receptor characteristics (e.g., age, gender, etc.).

[0060] Figures 802 and 804 assume the stimulation frequency remains at 4 kHz, even after electrode 604-1 has passed the characteristic frequency position corresponding to 4 kHz. However, the flat lines shown after the amplitude and phase stabilize in a steady state are not helpful for the user to perform the insertion procedure in some examples.

[0061] Accordingly, in response to determining that electrode 604-1 passes through a characteristic frequency location corresponding to one of a sequence of decreasingly lower values of the stimulation frequency, system 300 can decrease the stimulation frequency to the next lower value included in the sequence of decreasingly lower values, in accordance with the systems and methods described herein. For example, with reference to Figure 8 , system 300 can decrease the stimulation frequency to 2 kHz in response to electrode 604-1 passing through a characteristic frequency location corresponding to 4 kHz. In doing so, the amplitude of the evoked response signal recorded by electrode 604-1 again increases until electrode 604-1 is positioned at a characteristic frequency location corresponding to 2 kHz. As electrode lead 600 passes through the characteristic frequency location corresponding to 2 kHz, the evoked response amplitude decreases in a manner similar to that shown in Figure 8 . The phase of the evoked response signal similarly changes in a manner similar to that shown in Figure 8 . This process can repeat as electrode 604-1 passes through other characteristic frequency locations within cochlea 602.

[0062] Figure 9 A graph 902 of the amplitude of the evoked response signal recorded by electrode 604-1 is shown as diagnostic system 300 sequentially steps through the stimulation frequency values of 4 kHz, 2 kHz, 1 kHz, and 500 kHz as described above. Figure 9 A graph 904 of the phase of the evoked response signal recorded by electrode 604-1 is also shown as diagnostic system 300 sequentially steps through the stimulation frequency values of 4 kHz, 2 kHz, 1 kHz, and 500 kHz as described above. As shown in graph 902, the amplitude of the evoked response signal includes a series of peaks 906 (e.g., 906-1 through 906-4) that are aligned in time with the times at which electrode 604-1 passes through a characteristic frequency location corresponding to a stimulation frequency value. Similarly, as shown in graph 904, the phase of the evoked response signal alternates between high and low values in a periodic manner, with the alternations occurring in time with the times at which electrode 604-1 passes through a characteristic frequency location corresponding to a stimulation frequency value.

[0063] Diagnostic system 300 can direct a display device (e.g., display device 408) to display a graph of the evoked response signal recorded by electrode 604-1. In some examples, diagnostic system 300 can direct the display device to display the graph substantially contemporaneously with the insertion procedure being performed.

[0064] To illustrate, Figure 10An exemplary graphical user interface 1000 is shown that can be displayed by a display device under the direction of the diagnostic system 300. As shown, the graphical user interface includes a graph 902 and a graph 904. In alternative embodiments, only one of the graphs 902 and 904 can be displayed within the graphical user interface 1000.

[0065] By displaying a graph of evoked response signals recorded by the electrode 604-1 during the insertion procedure, the diagnostic system 300 can provide real-time feedback to a user (e.g., a surgeon) performing the insertion procedure. This feedback can be used by the user to ensure that the electrode lead 600 is properly seated within the cochlea 602 and / or for any other purpose that can serve a particular implementation.

[0066] For example, the diagnostic system 300 can detect that the amplitude of the evoked response signal decreases by at least an amplitude threshold amount within a predetermined period of time without a change in the phase of the evoked response signal by at least a phase threshold amount. This can indicate that trauma to the cochlea 602 can have occurred. Such trauma can result from the electrode lead 600 puncturing the wall of the cochlea 602, being inadvertently seated within the wrong canal of the cochlea 602, and / or in any other suitable manner. In response, the diagnostic system 300 can provide a notification to the user indicating that trauma can have occurred.

[0067] To illustrate, Figure 11 A graphical user interface 1000 is shown after the amplitude of the evoked response signal decreases without a corresponding change in phase. As shown, a notification 1100 is included within the graphical user interface 1000. The notification 1100 indicates that trauma can have occurred. In response to seeing the notification 1100 appear within the graphical user interface 1000, the user can stop the insertion procedure and / or take other remedial action (e.g., by pulling the electrode lead back out of the cochlea, changing the electrode insertion angle, etc.). Any other type of notification (e.g., an audible or visual notification) can additionally or alternatively be presented to the user as can serve a particular implementation.

[0068] The sequence of decreasingly reduced stimulation frequency values described in the examples provided herein is merely exemplary. Additional or alternative stimulation values can also be included in the sequence as can serve a particular implementation. In some examples, an initial value included in the sequence is greater than 2 kHz and a final value is less than 2 kHz. To illustrate, a sequence of decreasingly reduced values can include an initial value between 4.5 kHz and 2.5 kHz, a second value between 2.5 kHz and 1.5 kHz, a third value between 1.5 kHz and 750 Hz, a fourth value between 750 Hz and 375 Hz, and a final value between 375 Hz and 0 Hz.

[0069] As noted, the diagnostic system 300 can additionally or alternatively also direct the acoustic stimulus generator to apply the acoustic stimulus having the plurality of stimulus frequencies to the recipient of the cochlear implant concurrently during an insertion procedure in which an electrode lead of the cochlear implant is inserted into the cochlea of the recipient. The diagnostic system 300 can direct the cochlear implant to use the electrode 604-1 to record the plurality of evoked response signals during the insertion procedure. The evoked response signals each correspond to a different stimulus frequency included in the plurality of stimulus frequencies.

[0070] For example, Figure 12 FIG. 13 illustrates an example configuration in which the acoustic stimulus includes stimulus frequencies of 4 kHz, 2 kHz, 1 kHz, and 500 Hz. Figure 12 A graph 1202 of the amplitudes of the plurality of evoked response signals 1204 (e.g., evoked response signals 1204-1 through 1204-4) recorded by the electrode 604-1 during the lead insertion procedure and a graph 1206 of the plurality of phase signals 1208 corresponding to the evoked response signals 1204 are also shown. Each evoked response signal 1204 and phase signal 1208 corresponds to a different stimulus frequency. For example, the evoked response signal 1204-1 and phase signal 1208-1 correspond to 4 kHz, the evoked response signal 1204-2 and phase signal 1208-2 correspond to 2 kHz, the evoked response signal 1204-3 and phase signal 1208-3 correspond to 1 kHz, and the evoked response signal 1204-4 and phase signal 1208-4 correspond to 500 Hz.

[0071] In practice, the graphs 1202 and 1206 can be difficult for a user to interpret, especially in real-time during the insertion procedure. This is because all of the signals 1204 and 1208 are plotted simultaneously. Accordingly, the diagnostic system 300 can plot the graph of the evoked response signals in substantially real-time as the insertion procedure is being performed by the display device in such a way that the display device displays only a single evoked response signal having the highest amplitude relative to the other evoked response signals in the plurality of evoked response signals at any given time by switching between displaying each evoked response signal included in the plurality of evoked response signals. This can result in the same graph being displayed as if the acoustic stimulus had only a single stimulus frequency value at any given time (as described above) being displayed. For example, by switching between displaying each evoked response signal in such a way, the graph 902 and / or the graph 904 are displayed by the display device as shown in FIGS. 10 and 11, respectively. Figure 10

[0072] Figure 13 FIG. 13 illustrates an example method 1300. Figure 13 The operations shown in FIG. 13 can be implemented by the diagnostic system 300 and / or any implementation thereof. Although Figure 13 ​FIGURE 1 illustrates an example system for diagnosing a cochlear implant, in accordance with one embodiment. However, other embodiments can omit, add to, reorder, and / or modify the operations shown in FIGURE 1. Figure 13 Any of the operations described herein.

[0073] In operation 1302, the diagnostic system directs an acoustic stimulus generator to apply an acoustic stimulus having a stimulus frequency to a recipient of a cochlear implant during an insertion procedure in which an electrode lead communicatively coupled to the cochlear implant is inserted into the recipient's cochlea. Operation 1302 can be implemented in any of the ways described herein.

[0074] In operation 1304, the diagnostic system directs the cochlear implant to record, using electrodes disposed on the electrode lead, evoked response signals representative of amplitudes of a plurality of evoked responses occurring within the recipient's body in response to the acoustic stimulus applied to the recipient during the insertion procedure. Operation 1304 can be implemented in any of the ways described herein.

[0075] In operation 1306, the diagnostic system incrementally steps the stimulus frequency through a sequence of decreasingly lower values starting with an initial value and ending with a final value lower than the initial value as the electrode lead is inserted into the cochlea. Operation 1306 can be implemented in any of the ways described herein.

[0076] In some examples, a non-transitory computer-readable medium storing computer-readable instructions can be provided in accordance with the principles described herein. The instructions, when executed by a processor of a computing device, can direct the processor and / or computing device to implement one or more operations including one or more of the operations described herein. Such instructions can be stored and / or transmitted using any of a variety of known computer-readable media.

[0077] A non-transitory computer-readable medium as referred to herein can include any non-transitory storage medium that participates in providing data (e.g., instructions) that can be read and / or executed by a computing device (e.g., by a processor of the computing device). For example, a non-transitory computer-readable medium can include, but is not limited to, any combination of non-volatile storage media and / or volatile storage media. Exemplary non-volatile storage media include, but are not limited to, read-only memory, flash memory, solid-state drives, magnetic storage devices (e.g., hard disks, floppy disks, magnetic tapes, etc.), ferroelectric random-access memory ("RAM"), and optical discs (e.g., compact discs, digital video discs, Blu-ray discs, etc.). Exemplary volatile storage media include, but are not limited to, RAM (e.g., dynamic RAM).

[0078] Figure 14 FIGURE 14 illustrates an example computing device 1400 that can be specially configured to implement one or more of the processes described herein. As Figure 14As shown in FIG. 14, computing device 1400 can include a communication interface 1402, a processor 1404, a storage device 1406, and an input / output ("I / O") module 1408 communicatively connected to each other via a communication infrastructure 1410. Although an exemplary computing device 1400 is shown in FIG. 14, the Figure 14 However, the components illustrated in FIG. 14 are not intended to be limiting. Figure 14 Additionally or alternatively, components can be used in other embodiments. The components of the computing device 1400 shown in FIG. 14 will now be described in additional detail. Figure 14 The components of the computing device 1400 shown in FIG. 14 will now be described in additional detail.

[0079] The communication interface 1402 can be configured to communicate with one or more computing devices. Examples of communication interface 1402 include, but are not limited to, a wired network interface (such as a network interface card), a wireless network interface (such as a wireless network interface card), a modem, an audio / video connection, and any other suitable interface.

[0080] The processor 1404 generally represents any type or form of processing unit capable of processing data and / or interpreting, executing, and / or directing execution of one or more of the instructions, processes, and / or operations described herein. The processor 1404 can perform operations by executing computer-executable instructions 1412 (e.g., applications, software, code, and / or other executable data) stored in the storage device 1406.

[0081] The storage device 1406 can include one or more data storage media, devices, or configurations and can employ any type, form, and combination of data storage media and / or device. For example, the storage device 1406 can include, but is not limited to, any combination of the non-volatile media and / or volatile media described herein. Electronic data, including the data described herein, can be temporarily and / or permanently stored in the storage device 1406. For example, data representative of the computer-executable instructions 1412 configured to direct the processor 1404 to perform any of the operations described herein can be stored within the storage device 1406. In some examples, the data can be arranged in one or more databases residing in the storage device 1406.

[0082] The I / O module 1408 can include one or more I / O modules configured to receive user input and provide user output. The I / O module 1408 can include any hardware, firmware, software, or combination thereof supportive of input and output functionality. For example, the I / O module 1408 can include hardware and / or software for capturing user input, including, but not limited to, a keyboard or keypad, a touchscreen component (e.g., touchscreen display), a receiver (e.g., an RF or infrared receiver), a motion sensor, and / or one or more input buttons.

[0083] The I / O module 1408 can include one or more devices for presenting output to a user, including but not limited to a graphics engine, a display (e.g., a display screen), one or more output drivers (e.g., display drivers), one or more audio speakers, and one or more audio drivers. In certain embodiments, the I / O module 1408 is configured to provide graphical data to a display for presentation to a user. The graphical data can be representative of one or more graphical user interfaces and / or any other graphical content that can serve a particular implementation.

[0084] In some examples, any of the systems, computing devices, and / or other components described herein can be implemented by the computing device 1400. For example, the storage facility 302 can be implemented by the storage device 1406, and the processing facility 304 can be implemented by the processor 1404.

[0085] In the foregoing description, various exemplary embodiments have been described. It will be evident, however, that various modifications and changes can be made thereto without departing from the scope of the application as set forth in the appended claims. For example, certain features of one embodiment described herein can be combined with features of another embodiment described herein or substituted for features of another embodiment described herein. Furthermore, the description and drawings are to be regarded in an illustrative rather than a restrictive sense.

Claims

1. A system for optimizing evoked response signal generation during an electrode lead insertion procedure, comprising: a memory storing instructions; a processor communicatively coupled to the memory and configured to execute the instructions to: direct an acoustic stimulus generator to apply an acoustic stimulus having a stimulus frequency to a recipient of a cochlear implant during an insertion procedure in which an electrode lead communicatively coupled to the cochlear implant is inserted into a cochlea of the recipient; direct the cochlear implant to record, using an electrode disposed on the electrode lead, an evoked response signal during the insertion procedure, the evoked response signal representing amplitudes of a plurality of evoked responses occurring within the recipient in response to the acoustic stimulus applied to the recipient; and incrementally step the stimulus frequency through a sequence of decreasingly lower values as the electrode lead is inserted into the cochlea, the sequence of decreasingly lower values beginning with an initial value and ending with a final value lower than the initial value; wherein: the processor is further configured to execute the instructions to, when the stimulus frequency has the initial value, determine that the electrode passes through a characteristic frequency location within the cochlea and corresponding to the initial value; and incrementally stepping the stimulus frequency includes, in response to determining that the electrode passes through the characteristic frequency location, decreasing the stimulus frequency from the initial value to a next lower value included in the sequence of decreasingly lower values.

2. The system of claim 1, wherein, Determining that the electrode passes through the characteristic frequency location includes: performing an excitation spread measurement for the electrode and at least one other electrode disposed on the electrode lead; and determining, based on the excitation spread measurement, a number of electrodes disposed on the electrode lead that are located within the cochlea.

3. The system of claim 1, wherein, Determining that the electrode passes through the characteristic frequency location includes detecting, over a predetermined time period, that the amplitude of the evoked response signal decreases by at least an amplitude threshold amount and that the phase of the evoked response signal changes by at least a phase threshold amount.

4. The system of claim 1, wherein: the processor is further configured to execute the instructions to, when the stimulus frequency has the next lower value, determine that the electrode passes through a second characteristic frequency location within the cochlea and corresponding to the next lower value; and incrementally stepping the stimulus frequency includes, in response to determining that the electrode passes through the second characteristic frequency location, decreasing the stimulus frequency from the next lower value to a further next lower value included in the sequence of decreasingly lower values.

5. The system of claim 1, wherein, the processor is further configured to execute the instructions to: detect, over a predetermined time period, that the amplitude of the evoked response signal decreases by at least an amplitude threshold amount without the phase of the evoked response signal changing by at least a phase threshold amount; and in response to the detection, provide a notification indicating that trauma to the cochlea is likely to have occurred.

6. The system of claim 1, wherein, the initial value is greater than 2 kHz and the final value is less than 2 kHz.

7. The system of claim 1, wherein, the sequence of decreasingly lower values includes: an initial value between 4.5 kHz and 2.5 kHz; a second value between 2.5 kHz and 1.5 kHz; a third value between 1.5 kHz and 750 Hz; a fourth value between 750 Hz and 375 Hz; and a final value between 375 Hz and 0 Hz.

8. The system of claim 1, wherein, The processor is further configured to execute instructions to direct the display device to display a graph of the evoked response signal.

9. The system of claim 8, wherein, Directing the display device to display the graph of the evoked response signal includes directing the display device to display the graph of the evoked response signal substantially in real time as the insertion procedure is being performed.

10. The system of claim 8, wherein, Directing the display device to display the graph of the evoked response signal includes directing the display device to display: a first graph representative of a magnitude of the evoked response signal; and a second graph representative of a phase of the evoked response signal.

11. The system of claim 1, wherein, The electrode is a distal-most electrode disposed on the electrode lead.

12. A computer program product comprising computer executable instructions that, when executed by a processor, cause the processor to: direct an acoustic stimulus generator to apply an acoustic stimulus having a stimulus frequency to a recipient of a cochlear implant during an insertion procedure in which an electrode lead communicatively coupled to the cochlear implant is inserted into a cochlea of the recipient; direct the cochlear implant to record, using an electrode disposed on the electrode lead, an evoked response signal during the insertion procedure, the evoked response signal representative of a magnitude of a plurality of evoked responses occurring within the recipient's body in response to the acoustic stimulus applied to the recipient; and as the electrode lead is inserted into the cochlea, incrementally step the stimulus frequency through a sequence of decreasingly lower values, the sequence of decreasingly lower values beginning with an initial value and ending with a terminal value lower than the initial value, wherein, incrementally stepping the stimulus frequency includes, when the stimulus frequency has the initial value, determining that the electrode passes through a characteristic frequency location within the cochlea and corresponding to the initial value, and in response to determining that the electrode passes through the characteristic frequency location, decreasing the stimulus frequency from the initial value to a next lower value included in the sequence of decreasingly lower values.

13. The computer program product of claim 12, wherein, Determining that the electrode passes through the characteristic frequency location includes: performing an excitation spread measurement for the electrode and at least one other electrode disposed on the electrode lead; and based on the excitation spread measurement, determining a number of electrodes disposed on the electrode lead that are located within the cochlea.

14. The computer program product of claim 12, wherein, Determining that the electrode passes through the characteristic frequency location includes detecting, over a predetermined time period, that the magnitude of the evoked response signal decreases by at least a magnitude threshold amount and that the phase of the evoked response signal changes by at least a phase threshold amount.

15. The computer program product of claim 12, further comprising computer executable instructions that, when executed by the processor, cause the processor to: when the stimulus frequency has the next lower value, determine that the electrode passes through a second characteristic frequency location within the cochlea and corresponding to the next lower value; and incrementally decreasing the stimulus frequency includes, in response to determining that the electrode passes through the second characteristic frequency location, decreasing the stimulus frequency from the next lower value to a further next lower value included in the sequence of decreasingly lower values.

16. The computer program product of claim 12, further comprising computer executable instructions that, when executed by the processor, cause the processor to: detect, over a predetermined time period, that the magnitude of the evoked response signal decreases by at least a magnitude threshold amount without the phase of the evoked response signal changing by at least a phase threshold amount; and In response to the detection, a notification is provided indicating that trauma to the cochlea can have occurred.

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