Neurosurgery Blog

Neurosurg Rev (2013) 36:297–302

The postoperative course of microvascular decompression (MVD) for hemifacial spasm (HFS) is variable, and the optimal time for assessing the results is unclear.

From April 1997 to October 2007, MVD for HFS was performed in 801 patients. Patients were divided into two groups (cured or failed) according to subjective patient assessments over a 3-year period. We analyzed patient characteristics and surgical findings to determine prognostic factors. Medical records were analyzed retrospectively over the 3-year follow-up period.

Of the 801 patients who underwent surgery, 743 (92.8 %) appeared to be cured, 70 (8.7 %) had residual or recurrent spasms more than 1 year after surgery, 11 (1.3 %) had gradual improvement over 3 years, and 1 (0.1 %) had delayed improvement more than 3 years after surgery. Fifty-eight patients (7.2 %) had residual or recurrent spasms more than 3 years after surgery, of which 19 (2.4 %) had recurrence after initial relief. The mean time to spasm recurrence was 18.9 months. Intraoperative resolution of the lateral spread response (LSR) after decompression (p=0.048) and severe indentation (p=0.038) were significant predictors of good long-term outcome after MVD for HFS.

In our series, 70 patients (8.7 %) had residual or recurrent spasms more than 1 year after surgery, of which 12 (17.1 %) improved gradually after 1 year. If the surgeon can confirm intraoperative resolution of the LSR and severe indentation, reoperation can be delayed until 3 years after MVD.

Neurosurgery 72:555–565, 2013

Functional magnetic resonance imaging (fMRI) has become part of routine brain mapping in patients with epilepsy or tumor undergoing resective surgery. However, robust localization of crucial functional areas is required.

OBJECTIVE: To establish a simple, short fMRI task that reliably localizes crucial language areas in individual patients who undergo respective surgery.

METHODS: fMRI was measured during an 8-minute auditory semantic decision task in 28 healthy controls and 35 consecutive patients who had focal epilepsy or a brain tumor. Nineteen underwent resective surgery. Group and individual analyses were performed. Results in patients were compared with postsurgical language outcome and electrocortical stimulation when available.

RESULTS: fMRI activations concordant with the anterior and posterior language areas were found in 96% and 89% of the controls, respectively. The anterior and posterior language areas were both activated in 93% of the patients. These results were concordant with electrocortical stimulation results in 5 patients. Transient postsurgical language deficits were found in 2 patients in whom surgery was performed in the vicinity of the fMRI activations or who had postsurgical complications implicating areas of fMRI activations.

CONCLUSION: The proposed fast fMRI language protocol reliably localized the most relevant language areas in individual subjects. It appears to be a valuable complementary tool for surgical planning of epileptogenic foci and of brain tumors.

Neurosurg Focus 34 (3):E8, 2013

Glossopharyngeal neuralgia (GPN) is an uncommon facial pain syndrome often misdiagnosed as trigeminal neuralgia. The rarity of this condition and its overlap with other cranial nerve hyperactivity syndromes often leads to a significant delay in diagnosis.

The surgical procedures with the highest rates of pain relief for GPN are rhizotomy and microvascular decompression (MVD) of cranial nerves IX and X. Neurovascular conflict at the level of the root exit zone of these cranial nerves is believed to be the cause of this pain syndrome in most cases. Vagus nerve rhizotomy is usually reserved for cases in which vascular conflict is not evident.

A review of the literature reveals that although the addition of cranial nerve X rhizotomy may improve the chances of long-term pain control, this maneuver also increases the risk of permanent dysphagia and vocal cord paralysis. The risks of this procedure have to be carefully weighed against its benefits.

Based on the authors’ experience, careful patient selection with a thorough exploratory operation most often leads to identification of the site of vascular conflict, obviating the need for cranial nerve X rhizotomy.

J Neurosurg 118:491–497, 2013

Obsessive-compulsive disorder (OCD) is a common and disabling psychiatric illness, and in a significant proportion of patients with OCD the disease is refractory to conventional pharmacotherapy and psychotherapy. For more than half a century, patients with severe, treatment-resistant OCD have been treated with stereotactic limbic system lesions, including dorsal anterior cingulotomy. The authors present their results describing the efficacy and durability of limbic system surgery for OCD, characterizing a large cohort of patients treated at a single institution with a mean follow-up of more than 5 years.

Methods. The authors identified 64 consecutive patients undergoing cingulotomy for refractory OCD at the Massachusetts General Hospital between 1989 and 2009. Changes in OCD and major depressive disorder symptom severity were assessed at both the initial and most recent postoperative follow-up by using the Yale-Brown Obsessive Compulsive Scale and the Beck Depression Inventory, respectively. Full and partial OCD symptom responses were defined as Yale-Brown Obsessive Compulsive Scale score reductions of ≥ 35% and 25%–34%, respectively.

Results. Regarding OCD symptom improvement, at the first postoperative follow-up (mean 10.7 months), 35% of patients demonstrated a full response and 7% were partial responders. Thirty patients had a subsequent procedure (repeat cingulotomy or subcaudate tractotomy). By the most recent follow-up (mean 63.8 months), rates climbed to 47% and 22% for full and partial responses, respectively. Of the 24 patients with at least a partial response at initial follow-up, 20 (83%) retained at least a partial response at final follow-up. Comorbid major depressive disorder severity decreased by 17% at the most recent follow-up.

Conclusions. Limbic system surgery based on initial cingulotomy offers a durable and effective treatment option for appropriately selected patients with severe OCD who have not responded to conventional pharmacotherapy or psychotherapy.

Neurosurgery 72:353–366, 2013

Stereoelectroencephalography (SEEG) methodology, originally developed by Talairach and Bancaud, is progressively gaining popularity for the presurgical invasive evaluation of drug-resistant epilepsies.

OBJECTIVE: To describe recent SEEG methodological implementations carried out in our center, to evaluate safety, and to analyze in vivo application accuracy in a consecutive series of 500 procedures with a total of 6496 implanted electrodes.

METHODS: Four hundred nineteen procedures were performed with the traditional 2- step surgical workflow, which was modified for the subsequent 81 procedures. The new workflow entailed acquisition of brain 3-dimensional angiography and magnetic resonance imaging in frameless and markerless conditions, advanced multimodal planning, and robot-assisted implantation. Quantitative analysis for in vivo entry point and target point localization error was performed on a sub–data set of 118 procedures (1567 electrodes).

RESULTS: The methodology allowed successful implantation in all cases. Major complication rate was 12 of 500 (2.4%), including 1 death for indirect morbidity. Median entry point localization error was 1.43 mm (interquartile range, 0.91-2.21 mm) with the traditional workflow and 0.78 mm (interquartile range, 0.49-1.08 mm) with the new one (P < 2.2 · 10*16). Median target point localization errors were 2.69 mm (interquartile range, 1.89-3.67 mm) and 1.77 mm (interquartile range, 1.25-2.51 mm; P< 2.2 · 10*16), respectively.

CONCLUSION: SEEG is a safe and accurate procedure for the invasive assessment of the epileptogenic zone. Traditional Talairach methodology, implemented by multimodal planning and robot-assisted surgery, allows direct electrical recording from superficial and deep-seated brain structures, providing essential information in the most complex cases of drug-resistant epilepsy.

J Neurosurg 118:329–336, 2013

Patients with trigeminal neuralgia due to multiple sclerosis (TN-MS) and idiopathic TN (ITN) who underwent glycerol rhizotomy (GR) and radiofrequency thermocoagulation with glycerol rhizotomy (RFTC-GR) were compared to investigate the effectiveness of these percutaneous ablative procedures in the TN-MS population.

Methods. Between 1998 and 2010, 822 patients with typical TN were evaluated; 63 (8%) had TN-MS and 759 (92%) had ITN. Pain relief comparisons were made between 22 GR procedures in patients with TN-MS and 470 GR procedures in patients with ITN; 50 RFTC-GR procedures in patients with TN-MS and 287 RFTC-GR procedures in patients with ITN were compared. Analysis of time to recurrence included only procedures that achieved complete pain relief without medications.

Results. After 15 of the GR procedures (68%) in patients with TN-MS and 315 of the procedures (67%) in those with ITN, the patients were pain free without medications (p = 0.736). After 36 of the RFTC-GR procedures (72%) in patients with TN-MS and 210 of the procedures (73%) in those with ITN, the patients were pain free without medications (p = 0.657). The difference in pain relief between GR and RFTC-GR for patients with TN-MS was not significant (p = 0.447). The median time to failure of GR was 20 months in patients with TN-MS compared with 25 months in those with ITN (p = 0.403). The median time to failure of RFTC-GR was 26 months in the TN-MS population compared with 21 months in the ITN population (p = 0.449). Patients with TN-MS experienced similar times to recurrence whether they were treated with GR or RFTC-GR (p = 0.431).

Conclusions. Pain relief and durability of relief outcomes of GR and RFTC-GR were similar in patients with TN-MS and ITN, reinforcing their use as preferred treatments of TN-MS. The GR and RFTC-GR achieved comparable outcomes in patients with TN-MS, suggesting that both can be used to good effect.

DOI: 10.3171/2012.11.JNS12389

Obsessive-compulsive disorder (OCD) is a common and disabling psychiatric illness, and in a significant proportion of patients with OCD the disease is refractory to conventional pharmacotherapy and psychotherapy. For more than half a century, patients with severe, treatment-resistant OCD have been treated with stereotactic limbic system lesions, including dorsal anterior cingulotomy.

The authors present their results describing the efficacy and durability of limbic system surgery for OCD, characterizing a large cohort of patients treated at a single institution with a mean follow-up of more than 5 years.

Methods. The authors identified 64 consecutive patients undergoing cingulotomy for refractory OCD at the Massachusetts General Hospital between 1989 and 2009. Changes in OCD and major depressive disorder symptom severity were assessed at both the initial and most recent postoperative follow-up by using the Yale-Brown Obsessive Compulsive Scale and the Beck Depression Inventory, respectively. Full and partial OCD symptom responses were defined as Yale-Brown Obsessive Compulsive Scale score reductions of ≥ 35% and 25%–34%, respectively.

Results. Regarding OCD symptom improvement, at the first postoperative follow-up (mean 10.7 months), 35% of patients demonstrated a full response and 7% were partial responders. Thirty patients had a subsequent procedure (repeat cingulotomy or subcaudate tractotomy). By the most recent follow-up (mean 63.8 months), rates climbed to 47% and 22% for full and partial responses, respectively. Of the 24 patients with at least a partial response at initial follow-up, 20 (83%) retained at least a partial response at final follow-up. Comorbid major depressive disorder severity decreased by 17% at the most recent follow-up.

Conclusions. Limbic system surgery based on initial cingulotomy offers a durable and effective treatment option for appropriately selected patients with severe OCD who have not responded to conventional pharmacotherapy or psychotherapy.

Neurosurgery 71:1089–1095, 2012

Accurate localization of the subthalamic nucleus (STN) is critical to the success of deep brain stimulation surgery for Parkinson disease. Recent developments in high-field-strength magnetic resonance imaging (MRI) have made it possible to visualize the STN in greater detail. However, the relationship of the MR-visualized STN to the anatomic, electrophysiological, or atlas-predicted STN remains controversial.

OBJECTIVE: To evaluate the size of the STN visualized on 3-T MRI compared with anatomic measurements in cadaver studies and to compare the predictions of 3-T MRI and those of the Schaltenbrand-Wahren (SW) atlas for intraoperative STN microelectrode recordings.

METHODS: We evaluated the STN by 3-T MRI and intraoperative microelectrode recordings in 20 Parkinson disease patients undergoing deep brain stimulation surgery. We compared our findings with anatomic cadaver studies and with the individually scaled SW atlas-based predictions for each patient.

RESULTS: The dimensions of the 3-T MR-visualized STN were very similar to those of the largest anatomic study (MRI length, width, and height: 9.8 6 1.6, 11.5 6 1.6, and 3.7 6 0.7 mm, respectively; n = 40; cadaver length, width, and height: 9.3 6 0.7, 10.6 6 0.9, and 3.1 6 0.5 mm, respectively; n = 100). The amount of STN traversed during intraoperative microelectrode recordings was better correlated to the 3-T MR-visualized STN than the SW atlas-predicted STN (R = 0.38 vs R = 20.17).

CONCLUSION: The STN as visualized on 3-T MRI corresponds well with cadaveric anatomic studies and intraoperative electrophysiology. STN visualization with 3-T MRI may be an improvement over SW atlas-based localization for STN deep brain stimulation surgery in Parkinson disease.

Neurosurgery 71:1170–1184, 2012

Glioma surgery in eloquent areas remains a challenge because of the risk of postoperative motor deficits.

OBJECTIVE: To prospectively evaluate the efficiency of using a combination of diffusion tensor imaging (DTI) tractography functional neuronavigation and direct subcortical stimulation (DsCS) to yield a maximally safe resection of cerebral glioma in eloquent areas.

METHODS: A prospective cohort study was conducted in 58 subjects with an initial diagnosis of primary cerebral glioma within or adjacent to the pyramidal tract (PT). The white matter beneath the resection cavity was stimulated along the PT, which was visualized with DTI tractography. The intercept between the PT border and DsCS site was measured. The sensitivity and specificity of DTI tractography for PT mapping were evaluated. The efficiency of the combined use of both techniques on motor function preservation was assessed.

RESULTS: Postoperative analysis showed gross total resection in 40 patients (69.0%). Seventeen patients (29.3%) experienced postoperative worsening; 1-month motor deficit was observed in 6 subjects (10.3%). DsCS verified a high concordance rate with DTI tractography for PT mapping. The sensitivity and specificity of DTI were 92.6% and 93.2%, respectively. The intercepts between positive DsCS sites and imaged PTs were 2.0 to 14.7 mm (5.262.2 mm). The 6-month Karnofsky Performance Scale scores in 50 postoperative subjects were significantly increased compared with their preoperative scores.

CONCLUSION: DTI tractography is effective but not completely reliable in delineating the descending motor pathways. Integration of DTI and DsCS favors patient-specific surgery for cerebral glioma in eloquent areas.

Acta Neurochir (2012) 154:2063–2068

The impact of brain shift on deep brain stimulation surgery is considerable. In DBS surgery, brain shift is mainly caused by CSF loss. CSF loss can be estimated by post-surgical intracranial air. Different approaches and techniques exist to minimize CSF loss and hence brain shift. The aim of this survey was to investigate the extent and dynamics of CSF loss during DBS surgery, analyze its impact on final electrode position, and describe a simple and inexpensive method of burr hole closure.

Methods Sixty-six patients being treated with deep brain stimulation were retrospectively analyzed for this treatise. During surgery, CSF loss was minimized using bone wax as a burr hole closure. Intracranial air volume was calculated based on early post-surgery stereotactic 3D CT and correlated with duration of surgery and electrode deviations derived from post-surgery image fusion.

Results Median early post-surgery intracranial air was 2.1 cm3 (range 0–35.7 cm3, SD 8.53 cm3). No correlation was found between duration of surgery and CSF-loss (R0 0.078, p00.534), indicating that CSF loss mainly occurs early during surgery. Linear regression analysis revealed no significant correlations regarding volume of intracranial air and electrode displacement in any of the three principal axes. No significant difference regarding electrode deviations between first and second side of surgery were observed.

Conclusions CSF loss mainly occurs during the early phase of DBS surgery. CSF loss during a later phase of surgery can be effectively averted by burr hole closure. Postoperative intracranial air volumes up to 35 cm3 did not result in significant electrode displacement in our series. Comparing our results to studies previously published on this subject, burr hole closure using bone wax is highly effective.

J Neurosurg 117:955–961, 2012

The authors undertook this study to investigate the incidence, cause, and clinical influence of short circuits in patients treated with deep brain stimulation (DBS).

Methods. After the incidental identification of a short circuit during routine follow-up, the authors initiated a policy at their institution of routinely evaluating both therapeutic impedance and system impendence at every outpatient DBS follow-up visit, irrespective of the presence of symptoms suggesting possible system malfunction. This study represents a report of their findings after 1 year of this policy.

Results. Implanted DBS leads exhibiting short circuits were identified in 7 patients (8.9% of the patients seen for outpatient follow-up examinations during the 12-month study period). The mean duration from DBS lead implantation to the discovery of the short circuit was 64.7 months. The symptoms revealing short circuits included the wearing off of therapeutic effect, apraxia of eyelid opening, or dysarthria in 6 patients with Parkinson disease (PD), and dystonia deterioration in 1 patient with generalized dystonia. All DBS leads with short circuits had been anchored to the cranium using titanium miniplates. Altering electrode settings resulted in clinical improvement in the 2 PD cases in which patients had specific symptoms of short circuits (2.5%) but not in the other 4 cases. The patient with dystonia underwent repositioning and replacement of a lead because the previous lead was located too anteriorly, but did not experience symptom improvement.

Conclusions. In contrast to the sudden loss of clinical efficacy of DBS caused by an open circuit, short circuits may arise due to a gradual decrease in impedance, causing the insidious development of neurological symptoms via limited or extended potential fields as well as shortened battery longevity. The incidence of short circuits in DBS may be higher than previously thought, especially in cases in which DBS leads are anchored with miniplates. The circuit impedance of DBS should be routinely checked, even after a long history of DBS therapy, especially in cases of miniplate anchoring.

J Neurosurg 117:831–838, 2012

Patients with gliomas frequently have cognitive deficits, and surgery can exacerbate these deficits. Preoperative assessment is therefore crucial in patients undergoing surgery for glioma in eloquent areas, because the proximity of functional areas increases the risk of permanent postoperative cognitive disturbances. Although pre- and postoperative language and motor function in patients with glioma have been investigated frequently, data on good cognition studies are scarce. Most studies have focused on clinical neurological functioning or have only used brief neurological instruments. The authors investigated whether surgery for glioma in eloquent areas influences cognition early after surgery, by using an elaborate test protocol.

Methods. Twenty-eight patients with gliomas of the left hemisphere in language and nonlanguage areas were assessed before and 3 months after surgery with a comprehensive neuropsychological test protocol. The authors performed a correlation analysis between change in cognitive performance and tumor characteristics (that is, location, volume, pathological features, and histological grade) and between cognitive change and treatment-related factors (the extent of the resection and postoperative treatment with chemo- and radiotherapy).

Results. Both pre- and postoperatively, the mean performance of the patients was worse than the performance of the normal population in the language domain, the memory domain, and the executive functions (p < 0.05). Postoperatively, a decline was found in the language domain (t = 2.34, p = 0.027) and in the executive functions (t = 2.45, p = 0.022). However, cognitive change postsurgery was influenced by the location of the tumor; the decrease of cognitive score in the language domain was only observed in patients with tumors in or close to language areas (t = 2.33, p = 0.029). No effect on cognitive change was found for the other tumor characteristics and treatment-related factors.

Conclusions. This study underlines the importance of the use of a neuropsychological test protocol before and after surgery in patients with glioma, because several tasks in the domains of language, memory, and executive functions appeared to deteriorate after surgery. Tumor resection in language areas increases the risk of cognitive deficits in the language domain postoperatively.

Acta Neurochir (2012) 154:2075–2081

Transcranial magnetic stimulation (TMS) is being used in the pre-operative diagnostics of patients with tumors in or near the motor cortex. Although the main purpose of TMS in such patients is to map the functional areas of the motor cortex in spatial relation to the tumor, TMS also provides some numerical neurophysiological measurements of the functional status of the patient’s motor system. The aim of this paper is to provide reference values for these neurophysiological measurements from a large and varied clinical sample.

Methods TMS was used in the pre-operative work-up of patients with various types of tumors in or near the motor cortex during a 3-year period. Data was collected prospectively in 100 patients, yet this is a post hoc report.

Results Patient characteristics had no influence on the neurophysiological parameters. The response latency time was almost never different in the tumorous versus healthy hemisphere, so clinicians should be suspicious if they find interhemispheric differences for latency. A high interhemispheric ratio of resting motor threshold (RMT) or a low interhemispheric ratio of motor evoked potential (MEP) amplitude appear to suggest immanent deterioration of the patient’s motor status.

Conclusion In addition to topographic cortical mapping, TMS also serves as a neurophysiological assessment of the functional status of the patient’s motor system. The results presented here provide clinicians with a set of reference values to contextualize findings in their own tumor patients. Further research is still needed to better understand the full clinical relevance of these neurophysiological parameters.

J Neurosurg 117:839–843, 2012 

Disturbance of the arcuate fasciculus in the dominant hemisphere is thought to be associated with language- processing disorders, including conduction aphasia. Although the arcuate fasciculus can be visualized in vivo with diffusion tensor imaging (DTI) tractography, its involvement in functional processes associated with language has not been shown dynamically using DTI tractography. In the present study, to clarify the participation of the arcuate fasciculus in language functions, postoperative changes in the arcuate fasciculus detected by DTI tractography were evaluated chronologically in relation to postoperative changes in language function after brain tumor surgery.

Methods. Preoperative and postoperative arcuate fasciculus area and language function were examined in 7 right-handed patients with a brain tumor in the left hemisphere located in proximity to part of the arcuate fasciculus. The arcuate fasciculus was depicted, and its area was calculated using DTI tractography. Language functions were measured using the Western Aphasia Battery (WAB).

Results. After tumor resection, visualization of the arcuate fasciculus was increased in 5 of the 7 patients, and the total WAB score improved in 6 of the 7 patients. The relative ratio of postoperative visualized area of the arcuate fasciculus to preoperative visualized area of the arcuate fasciculus was increased in association with an improvement in postoperative language function (p = 0.0039).

Conclusions. The role of the left arcuate fasciculus in language functions can be evaluated chronologically in vivo by DTI tractography after brain tumor surgery. Because increased postoperative visualization of the fasciculus was significantly associated with postoperative improvement in language functions, the arcuate fasciculus may play an important role in language function, as previously thought. In addition, postoperative changes in the arcuate fasciculus detected by DTI tractography could represent a predicting factor for postoperative language-dependent functional outcomes in patients with brain tumor.

J Neurosurg 117:839–843, 2012

Disturbance of the arcuate fasciculus in the dominant hemisphere is thought to be associated with language-processing disorders, including conduction aphasia. Although the arcuate fasciculus can be visualized in vivo with diffusion tensor imaging (DTI) tractography, its involvement in functional processes associated with language has not been shown dynamically using DTI tractography. In the present study, to clarify the participation of the arcuate fasciculus in language functions, postoperative changes in the arcuate fasciculus detected by DTI tractography were evaluated chronologically in relation to postoperative changes in language function after brain tumor surgery.

Methods. Preoperative and postoperative arcuate fasciculus area and language function were examined in 7 right-handed patients with a brain tumor in the left hemisphere located in proximity to part of the arcuate fasciculus. The arcuate fasciculus was depicted, and its area was calculated using DTI tractography. Language functions were measured using the Western Aphasia Battery (WAB).

Results. After tumor resection, visualization of the arcuate fasciculus was increased in 5 of the 7 patients, and the total WAB score improved in 6 of the 7 patients. The relative ratio of postoperative visualized area of the arcuate fasciculus to preoperative visualized area of the arcuate fasciculus was increased in association with an improvement in postoperative language function (p = 0.0039).

Conclusions. The role of the left arcuate fasciculus in language functions can be evaluated chronologically in vivo by DTI tractography after brain tumor surgery. Because increased postoperative visualization of the fasciculus was significantly associated with postoperative improvement in language functions, the arcuate fasciculus may play an important role in language function, as previously thought. In addition, postoperative changes in the arcuate fasciculus detected by DTI tractography could represent a predicting factor for postoperative language-dependent functional outcomes in patients with brain tumor.

Neurosurgery 71:804–814, 2012 

Deep brain stimulation (DBS) of the subthalamic nucleus is an effective treatment for Parkinson disease. However, DBS is not responsive to an individual’s disease state, and programming parameters, once established, do not change to reflect disease state. Local field potentials (LFPs) recorded from DBS electrodes are being investigated as potential biomarkers for the Parkinson disease state. However, no patient data exist about what happens to LFPs over the lifetime of the implant.

OBJECTIVE: We investigated whether LFP amplitude and response to limb movement differed between patients implanted acutely with subthalamic nucleus DBS electrodes and patients implanted 2 to 7 years previously.

METHODS: We recorded LFPs at DBS surgery time (9 subjects), 3 weeks after initial placement (9 subjects), and 2 to 7 years (median: 3.5) later during implanted programmable generator replacement (11 sides). LFP power-frequency spectra for each of 3 bipolar electrode derivations of adjacent contacts were calculated over 5-minute resting and 30-second movement epochs. Monopolar impedance data were used to evaluate trends over time.

RESULTS: There was no significant difference in b-band LFP amplitude between initial electrode implantation (OR) and 3-week post-OR times (P = .94). However, b-band amplitude was lower at implanted programmable generator replacement times than in OR (P = .008) and post-OR recordings (P = .039). Impedance measurements declined over time (P < .001).

CONCLUSION: Postoperative LFP activity can be recorded years after DBS implantation and demonstrates a similar profile in response to movement as during acute recordings, although amplitude may decrease. These results support the feasibility of constructing a closed-loop, patient-responsive DBS device based on LFP activity.

Neurosurgery 71:815–825, 2012

The primary motor cortex, which is part of the corticobasal ganglia loops, may be an alternative option for the surgical treatment of Parkinson disease.

OBJECTIVE: To report on the 1-year safety and efficacy of unilateral extradural motor cortex stimulation in Parkinson disease.

METHODS: A quadripolar electrode strip was extradurally implanted over the motor cortex. Stimulation was continuously delivered through the electrode paddle contralateral to the most affected clinical side. Subjects were prospectively evaluated by the Unified Parkinson’s Disease Rating Scale (UPDRS) and the Parkinson’s Disease Quality of Life Questionnaire. In addition, an extensive cognitive and behavioral assessment and electroencephalogram recording were performed.

RESULTS: Nine patients were included in this study. No surgical complications or adverse events occurred. Moreover, no cognitive or behavioral changes were observed. Under the off-medication condition, the UPDRS III at baseline was decreased by 14.1%, 23.3%, 19.9%, and 13.2%, at 1, 3, 6, and 12 months, respectively. The motor effects were bilateral, appeared after 3 to 4 weeks of stimulation, and outlasted the stimulation itself for 3 to 4 weeks in 1 case of stimulator accidental switching off. The UPDRS IV was decreased by 40.8%, 42.1%, and 35.5% at 1, 3, and 12 months, respectively. The scores on the Parkinson’s Disease Quality of Life Questionnaire were increased at months 3, 6, and 12.

CONCLUSION: Extradural motor cortex stimulation is a safe procedure. After 12 months, the patients demonstrated a moderate improvement of motor symptoms (particularly axial symptoms) and quality of life.

Neurosurgery 71:224–238, 2012 DOI: 10.1227/NEU.0b013e31825972ab

Obesity is a growing health problem worldwide and is responsible for a significant proportion of health expenditures in developed nations. It is also notoriously difficult to treat. Prior attempts at pharmacological or neurological modulation, including deep brain stimulation, have primarily targeted homeostatic mechanisms of weight control centered in the hypothalamus. To date, these attempts have had limited success. Multiple lines of independent data suggest that dysregulated reward circuitry in the brain underlies behaviors leading to obesity.

Here, we review the existing data and related neurocircuitry, as well as the scope of obesity and currently available treatments. Finally, we suggest a neuromodulation strategy geared toward regulating these dysfunctional circuits, primarily by alteration of frontolimbic circuits.

Neurosurgery 70:911–920, 2012 DOI: 10.1227/NEU.0b013e318237a807 

For neuroepithelial tumors, the surgical goal is maximum resection with preservation of neurological function. This is contributed to by intraoperative magnetic resonance imaging (iMRI) combined with multimodal navigation.

OBJECTIVE: We evaluated the contribution of diffusion tensor imaging (DTI)-based fiber tracking of language pathways with 2 different algorithms (tensor deflection, connectivity analysis [CA]) integrated in the navigation on the surgical outcome.

METHODS: We evaluated 32 patients with neuroepithelial tumors who underwent surgery with DTI-based fiber tracking of language pathways integrated in neuronavigation. The tensor deflection algorithm was routinely used and its results intraoperatively displayed in all cases. The CA algorithm was furthermore evaluated in 23 cases. Volumetric assessment was performed in pre- and intraoperative MR images. To evaluate the benefit of fiber tractography, language deficits were evaluated pre- and postoperatively and compared with the volumetric analysis.

RESULTS: Final gross-total resection was performed in 40.6% of patients. Absolute tumor volume was reduced from 55.33 ± 63.77 cm3 to 20.61 ± 21.67 cm3 in first iMRI resection control, to finally 11.56 ± 21.92 cm3 (P < .01). Fiber tracking of the 2 algorithms showed a deviation of the displayed 3D objects by <5 mm. In long-term followup only 1 patient (3.1%) had a persistent language deficit.

CONCLUSION: Intraoperative visualization of language-related cortical areas and the connecting pathways with DTI-based fiber tracking can be successfully performed and integrated in the navigation system. In a setting of intraoperative high-field MRI this contributes to maximum tumor resection with low postoperative morbidity.

Neurosurgery 70:840–846, 2012 DOI: 10.1227/NEU.0b013e318236a809

The ventrolateral thalamus (ventral intermediate nucleus [Vim]) is the traditional target for neurosurgical treatment of essential tremor. The target, however, has varied substantially among different neurosurgeons.

OBJECTIVE: To evaluate the effect of deep brain stimulation in the thalamus and posterior subthalamic area (PSA) in relation to electrode location.

METHODS: Thirty-six (17 Vim/19 PSA) patients with 44 deep brain stimulation electrodes were included in this retrospective study. The effect of stimulation was evaluated with standardized settings for each contact using items from the Essential Tremor Rating Scale.

RESULTS: When each contact was evaluated in terms of the treated hand with standardized stimulation, the electrode contact providing the best effect in the individual patient was located in the zona incerta or radiation prelemniscalis in 54% and the Vim in 12%. Forty contacts provided a tremor reduction of . 90%. Of these, 43% were located in the PSA and 18% in the Vim according to the Schaltenbrand atlas. Of these 40 contacts, 37 were found in the PSA group.

CONCLUSION: More contacts yielding an optimal effect were found in the PSA group than in the Vim. Many patients operated on in the Vim got the best effect from a contact located in the PSA. This might suggest that the PSA is a more efficient target than the Vim.