Diaa Bahgat

Deep brain stimulation entrains local neuronal firing in human globus pallidus internus

Deep brain stimulation (DBS) in the internal segment of the globus pallidus (GPi) relieves the motor symptoms of Parkinsons disease, yet the mechanism of action remains uncertain. To address the question of how therapeutic stimulation changes neuronal firing in the human brain, we studied the effects of GPi stimulation on local neurons in unanesthetized patients. Eleven patients with idiopathic Parkinsons disease consented to participate in neuronal recordings during stimulator implantation surgery. A recording microelectrode and a DBS macroelectrode were advanced through the GPi in parallel until a single neuron was isolated. After a baseline period, stimulation was initiated with varying voltages and different stimulation sites. The intra-operative stimulation parameters (1-8 V, 88-180 Hz, 0.1-ms pulses) were comparable with the postoperative DBS settings. Stimulation in the GPi did not silence local neuronal activity uniformly, but instead loosely entrained firing and decreased net activity in a voltage-dependent fashion. Most neurons had decreased activity during stimulation, although some increased or did not change firing rate. Thirty-three of 45 neurons displayed complex patterns of entrainment during stimulation, and burst-firing was decreased consistently after stimulation. Recorded spike trains from patients were used as input into a model of a thalamocortical relay neuron. Only spike trains that occurred during therapeutically relevant voltages significantly reduced transmission error, an effect attributable to changes in firing patterns. These data indicate that DBS in the human GPi does not silence neuronal activity, but instead disrupts the pathological firing patterns through loose entrainment of neuronal activity.

Motor cortex stimulation for trigeminal neuropathic or deafferentation pain: an institutional case series experience.

Background: Trigeminal neuropathy is a rare, devastating condition that can be intractable and resistant to treatment. When medical treatment fails, invasive options are limited. Motor cortex stimulation (MCS) is a relatively recent technique introduced to treat central neuropathic pain. The use of MCS to treat trigeminal neuropathic or deafferentation pain is not widespread and clinical data in the medical literature that demonstrate efficacy are limited. Method: We retrospectively reviewed patients with trigeminal neuropathic or trigeminal deafferentation pain who were treated at the Oregon Health & Science University between 2001 and 2008 by 1 neurosurgeon using MCS. Results: Eight of 11 patients (3 male, 8 female) underwent successful permanent implantation of an MCS system. All 8 patients reported initial satisfactory pain control. Three failed to experience continued pain control (6 months of follow-up). Five continued to experience long-term pain control (mean follow-up, 33 months). Average programming sessions were 2.2/year (all 8 patients) and 1.55/year (5 patients who sustained long-term pain control). Patients with anesthesia dolorosa or trigeminal deafferentation pain who had previously undergone ablative trigeminal procedures responded poorly to MCS. We encountered no perioperative complications. Conclusion: MCS is a safe and potentially effective therapy in certain patients with trigeminal neuropathy.

Trigeminal neuralgia in young adults

OBJECT Trigeminal neuralgia (TN) is a form of facial pain that can be debilitating if left untreated. It typically affects elderly adults and is thought to be related to neurovascular compression. It is uncommon in people younger than 30 years of age, with only 1% of cases reportedly occurring in those younger than 20 years of age. The most common cause of compression in young adults is thought to be venous nerve compression either alone or in association with arterial nerve compression. The objective of this study was to review data in cases of TN in which patients were 25 years of age or younger and to identify TN disease characteristics, demographics, clinical features, operative findings, and outcome. METHODS The authors retrospectively reviewed the clinical records, surgical treatment, and long-term outcome in patients 25 years of age or younger with TN who underwent surgery performed by the senior author (K.J.B.) at Oregon Health & Science University between 1995 and 2008. RESULTS Seven patients (2 males and 5 females) met the inclusion criteria. The average age at symptom onset was 19.6 ± 3.4 years (± SD) and the average age at surgery was 22.9 ± 1.7 years. Six patients had right-sided symptoms and 1 had left-sided symptoms. Pain distribution was the V2 in 3 cases, V2-3 in 3 cases, and V3 in 1 case, with no cases of V1 affliction. A total of 11 procedures were performed in 7 patients, and 4 patients underwent a second procedure. Surgery and imaging revealed venous compression in all cases. The average follow-up period was 35.5 ± 39.9 months (median 12 months). Three patients reported a good outcome (no pain with or without medications) and 4 reported a poor outcome (either no pain relief or mild pain relief after surgery). CONCLUSIONS Trigeminal neuralgia is uncommon in young adults. Patients tend to present with symptoms similar to those in adults: long periods of pain and venous compression, but outcome unfortunately is not as good as that reported in the older population.

Thalamotomy as a Treatment Option for Tremor after Ineffective Deep Brain Stimulation

Background: As the number of deep brain stimulation (DBS) surgeries increases, complications from malpositioned electrodes, tolerance to stimulation and loss of efficacy have also increased. Our objective was to assess thalamotomy as a salvage treatment option after ineffective DBS. Methods: A retrospective chart analysis of patients who underwent ipsilateral stereotactic thalamotomy after an ineffective ventrointermediate nucleus DBS procedure was undertaken. Patient outcome was based on follow-up visit chart notes, and a nonvalidated patient telephone questionnaire to assess patients’ perception of tremor and functional ability after thalamotomy. Results: Six patients with essential tremor and 1 with tremor-predominant Parkinson’s disease met our inclusion criteria. Thalamotomies were undertaken for ineffective DBS due to dysarthria and paresthesias with programming in 2 patients, tremor that failed to respond to increased DBS despite a lack of side effects in 2 patients, malpositioned electrode in 2 patients, and sudden loss of DBS efficacy following eye surgery in 1 patient. Following thalamotomy, 3 patients reported improvement in symptoms and function, 3 patients reported improvement in symptoms that were not reflected in functional improvement, and 1 patient reported no improvement in symptoms or function. Conclusion: Thalamotomy may provide a viable salvage solution in patients who fail to respond to DBS due to complications such as malpositioned electrodes, tolerance to stimulation or loss of efficacy.

Surgical outcome and improvement in quality of life after microvascular decompression for hemifacial spasms: A case series assessment using a validated disease-specific scale

Background: Hemifacial spasm (HFS) is a movement disorder characterized by intermittent, involuntary clonic or tonic-clonic contractions of muscles innervated by the ipsilateral facial nerve. Recent studies have documented change in quality of life after HFS management with botulinum toxin injection. However, we failed to locate any study that documented change in quality of life after surgical management with retrosigmoid microvascular decompression (MVD). Methods: Our study objectives were 3-fold. Firstly, to use a disease-specific, validated quality of life assessment scale to document any change in quality of life after MVD for HFS. Secondly, to determine the time period in which the majority of patients undergoing MVD could be expected to benefit from surgery. Finally, to determine factors affecting the postoperative quality of life following MVD. A retrospective analysis of HFS patients treated with MVD at a single institution by a single surgeon (K.J.B.) between January 2000 and December 2007 was undertaken. A modification of a previously developed validated disease-specific quality of life assessment scale that included the addition of a parameter for difficulty in sleep was used to assess quality of life before and after surgery. Results: A total of 21 patients (14 female and 7 male) underwent treatment as specified. Eighty-five percent (17/20) of the patients reported prolonged remission of symptoms (mean follow-up period = 4.15 years). Five percent (1/20) reported occasional recurrence of twitches. The overall mean quality of life score improved from 11.1 preoperatively to 2.2 postoperatively. Conclusions: MVD offers significant and prolonged improvement in quality of life for the HFS patients we studied, as measured using a disease-specific, validated quality of life assessment scale. Postoperative quality of life, however, was strongly influenced by both the success of surgery in resolving the symptoms and the absence of any permanent complications of surgery.

Lesioning and Stimulation in Tremor-Predominant Movement Disorder Patients: An Institutional Case Series and Patient-Reported Outcome

Background: In certain movement disorder cases, a combined stimulation and lesioning approach in the same patient could be the ideal beneficial option. Objectives: The object of this study was to retrospectively examine the indications, outcome and complications in patients who had undergone both a lesioning (thalamotomy) and deep brain stimulation (DBS) procedure (bilateral or unilateral) for a tremor-predominant movement disorder performed by a single surgeon at one institution over a 15-year period. Methods: A retrospective review of patient records was undertaken. Patient outcome was based on follow-up visit chart notes and on a non-validated patient telephone questionnaire. Results: Thirty patients required a combined stimulation and lesioning approach to control tremor. Twelve patients had either unilateral or bilateral DBS as the first procedure followed by thalamotomy; two patients required a third procedure. Eighteen patients had thalamotomy as the first procedure followed by contralateral DBS either as the second or the third procedure. Eight patients required three procedures, which included either a repeat thalamotomy or a repeat DBS. We were able to contact 22 of 30 (15 male and 15 female, average age 70.7 ± 15.4 years) tremor-predominant movement disorder patients, retrospectively. Patient-reported outcome as assessed by a non-validated telephone questionnaire was: improvement in both symptoms and function in 59%, symptom but not function improvement in 32% and no improvement in either symptom or function or worsening in 9%. In comparison, based on retrospective chart review, 77% of patients had improved symptoms and functions, 20% of patients had improved symptoms with no effect on function and 3% of patients had no improvements of symptoms or functions. Conclusions: Lesioning, which has to a great extent fallen out of favor, still has a valuable role to play in the treatment of tremor-predominant movement disorders; it can still be applied in combination with stimulation with outcome results similar to that of bilateral stimulation.

Contents Vol. 88, 2010

A. Abosch, Minneapolis, Minn. M.L.J. Apuzzo, Los Angeles, Calif. T. Aziz, Oxford N.M. Barbaro, San Francisco, Calif. A.L. Benabid, Grenoble G. Broggi, Milan B.P. Brophy, Adelaide K.J. Burchiel, Portland, Oreg. J.W. Chang, Seoul G.R. Cosgrove, Providence, R.I. E.N. Eskandar, Boston, Mass. W.A. Friedman, Gainesville, Fla. R.E. Gross, Atlanta, Ga. T. Hori, Tokyo M.G. Kaplitt, New York, N.Y. Y. Katayama, Tokyo P.J. Kelly, New York, N.Y. D.S. Kondziolka, Pittsburgh, Pa. J.K. Krauss, Hannover A. Lozano, Toronto, Ont. L.D. Lunsford, Pittsburgh, Pa. V. Rajshekhar, Vellore J. Regis, Marseille A.R. Rezai, Columbus, Ohio M. Schulder, Manhassett, N.Y. M.P. Sindou, Lyon K.V. Slavin, Chicago, Ill. Z. Tian, Beijing F. Velasco Campos, Mexico City O. Vilela Filho, Goiânia Offi cial Journal of the World Society for Stereotactic and Functional Neurosurgery