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OBJECTIVE Advances in image-guided stereotactic surgery, microelectrode recording techniques, and stimulation technology have been the driving forces behind a resurgence in the use of functional neurosurgery for the treatment of movement disorders. Despite the dramatic effects of deep brain stimulation (DBS) techniques in ameliorating the symptoms of Parkinson's disease, many critical questions related to the targeting, effects, and mechanisms of action of DBS remain unanswered. In this report, we describe the methods used to localize the subthalamic nucleus (STN) and we present the characteristics of encountered cells. METHODS Twenty-six patients with idiopathic Parkinson's disease underwent simultaneous, bilateral, microelectrode-refined, DBS electrode implantation into the STN. Direct and indirect magnetic resonance imaging-based anatomic targeting was used. Cellular activity was analyzed for various neurophysiological parameters, including firing rates and interspike intervals. Physiological targeting confirmation was obtained by performing macrostimulation through the final DBS electrode. RESULTS The average microelectrode recording time for each trajectory was 20 minutes, with a mean of 5.2 trajectories/patient. Typical trajectories passed through the anterior thalamus, zona incerta/fields of Forel, STN, and substantia nigra-pars reticulata. Each structure exhibited a characteristic firing pattern. In particular, recordings from the STN exhibited an increase in background activity and an irregular firing pattern, with a mean rate of 47 Hz. The mean cell density was 5.6 cells/mm, with an average maximal trajectory length of 5.3 mm. Macrostimulation via the DBS electrode yielded mean sensory and motor thresholds of 4.2 and 5.7 V, respectively. CONCLUSION The principal objectives of microelectrode recording refinement of anatomic targeting are precise identification of the borders of the STN and thus determination of its maximal length. Microelectrode recording also allows identification of the longest and most lateral segment of the STN, which is our preferred target for STN DBS electrode implantation. Macrostimulation via the final DBS electrode is then used primarily to establish the side effect profile for postoperative stimulation. Microelectrode recording is a helpful targeting adjunct that will continue to facilitate our understanding of basal ganglion physiological features.

OBJECTIVE: Cerebral Nocardia abscesses are rare, accounting for approximately 1 to 2% of all cerebral abscesses. Prompt aggressive surgical treatment involving craniotomy and excision of these lesions has been advocated by many authors, because these lesions have significantly higher morbidity and mortality rates than do most other cerebral abscesses. We report an atypical presentation of cerebral nocardiosis localized to the choroid plexus of the lateral ventricle. CLINICAL PRESENTATION: A 56-year-old man presented with a 3-week history of fever, cough, and progressive headache and an ensuing 3-day history of progressive lethargy, confusion, and gait ataxia. Radiographic studies demonstrated a loculated contrast-enhancing left lateral ventricular lesion with significant perilesional parenchymal edema that was thought preoperatively to be a neoplasm. INTERVENTION: The patient underwent a craniotomy for resection of the lesion. Intraoperatively, a reddish gray lesion with purulent exudate was encountered within the left lateral ventricle intimately adherent to the choroid plexus as well as to the ependyma and subependymal veins. A frozen section demonstrated an organizing abscess wall. The lesion was resected in its entirety, and multiple cultures were sent for analysis. CONCLUSION: Microbiology cultures grew Nocardia asteroides. A course of intravenous antibiotics was started, which included trimethoprimsulfamethoxazole, amikacin, and ceftriaxone. Two weeks after surgery, at the time of discharge, the patient's neurological status had improved considerably. Although Nocardia abscesses have been documented to occur throughout the central nervous system, the presentation of a lesion confined to the choroid plexus of the lateral ventricle with significant parenchymal edema is unusual and demonstrates that Nocardia abscesses must be considered in the differential diagnosis of a contrast-enhancing intraventricular mass lesion involving the choroid plexus.

BACKGROUND Chronic occipital and suboccipital headache is a common symptom in patients with Chiari I malformation. These headaches may persist despite appropriate surgical treatment of the underlying pathology via suboccipital decompression, duraplasty, and cerebrospinal fluid diversion. Occipital nerve stimulation has been shown to be effective in the treatment of a variety of occipital headache/pain syndromes. OBJECTIVE To review retrospectively our experience with occipital nerve stimulation in patients with a primary diagnosis of Chiari malformation and a history of chronic occipital pain intractable to medical and surgical therapies. METHODS We present a retrospective analysis of our series of 22 patients with Chiari malformation and persistent occipital headaches who underwent occipital neurostimulator trials and, after successful trials, permanent stimulator placement. A trial was considered successful with >50% pain relief as assessed with a standard Visual Analog Scale score. Patients with a successful trial underwent permanent placement approximately 1 to 2 weeks later. Patients were assessed postoperatively for pain relief via the Visual Analog Scale. RESULTS Sixty-eight percent of patients (15 of 22) had a successful stimulator trial and proceeded to permanent implantation. Of those implanted, 87% (13 of 15) reported continued pain relief at a mean follow-up of 18.9 months (range, 6-51 months). Device-related complications requiring additional surgeries occurred in 40% of patients. CONCLUSION Occipital stimulation may provide significant long-term pain relief in selected Chiari I malformation patients with persistent occipital pain. Larger and longer-term studies are needed to further define appropriate patient selection criteria and to refine the surgical technique to minimize device-related complications.

BACKGROUND: Placement of spinal cord stimulating paddle leads has traditionally been performed under local anesthesia with intravenous sedation to allow intraoperative confirmation of appropriate placement. It may be difficult to maintain appropriate sedation in certain patients because of medical comorbidities. Furthermore, patients undergoing lead revision frequently have extensive epidural scarring, requiring multilevel laminectomies to place the electrode appropriately. OBJECTIVE: To report our technique of neurophysiologic monitoring that allows these procedures to be performed under general anesthesia. METHODS: Data from 78 patients who underwent electromyography during laminectomy for paddle lead placement were retrospectively reviewed. Seventy patients presented for first-time permanent system placement after a successful trial, and 8 were referred for revision or replacement of previously functioning systems. Surgeries were performed under general anesthesia with fluoroscopic guidance. Electromyography was used to help define the physiological midline of the spinal cord and to guide appropriate lead placement. Somatosensory evoked potentials were used as an adjunct to minimize the possibility of neural injury. RESULTS: Immediately postoperatively, 75 of 78 patients reported that the paresthesia coverage was as good as (or better than) that of the spinal cord stimulation trial. At the long-term follow-up, 1 system was removed for infection, and 6 systems were explanted for lack of efficacy. A total of 64 of the 78 implanted patients reported continued pain relief with stimulator use. Revision surgery was performed in 9 patients. CONCLUSION: The use of intraoperative electrophysiology for the placement of spinal cord stimulation paddle leads under general anesthesia is a safe and efficacious alternative to awake surgery.