An implantable medical device is provided for the suppression or prevention of pain, movement disorders, epilepsy, cerebrovascular diseases, autoimmune diseases, sleep disorders, autonomic disorders, abnormal metabolic states, disorders of the muscular system, and neuropsychiatric disorders in a patient. The implantable medical device can be a neurostimulator configured to be implanted on or near a cranial nerve to treat headache or other neurological disorders. One aspect of the implantable medical device is that it includes an electronics enclosure, a substrate integral to the electronics enclosure, and a monolithic feed-through integral to the electronics enclosure and the substrate. In some embodiments, the implantable medical device can include a fixation apparatus for attaching the device to a patient.