Category: Functional

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The impact of brain shift in deep brain stimulation surgery

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.

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Short circuit in deep brain stimulation

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.

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Cognitive functioning early after surgery of gliomas in eloquent areas

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.

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Assessing the functional status of the motor system in brain tumor patients using transcranial magnetic stimulation

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.

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Arcuate fasciculus in brain tumor surgery

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.

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Correlation between language function and the left arcuate fasciculus detected by diffusion tensor imaging tractography after brain tumor surgery

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.

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Long-term Recordings of Local Field Potentials From Implanted Deep Brain Stimulation Electrodes

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.

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Unilateral Extradural Motor Cortex Stimulation Is Safe and Improves Parkinson Disease at 1 Year

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.

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Obesity and Brain Addiction Circuitry: Implications for Deep Brain Stimulation

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.

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Intraoperative Visualization of Fiber Tracking Based Reconstruction of Language Pathways in Glioma Surgery

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.

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Thalamic and Subthalamic Deep Brain Stimulation for Essential Tremor: Where Is the Optimal Target?

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.

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Limbic and Motor Function Comparison of Deep Brain Stimulation of the Zona Incerta and Subthalamic Nucleus

Neurosurgery 70[ONS Suppl 1]:ons125–ons131, 2012 DOI: 10.1227/NEU.0b013e318232fdac

Psychiatric and neuropsychological side effects of subthalamic nucleus (STN) stimulation have been increasingly recognized. Most programming regimens focus on contacts 0 and 1, whereas contact 3, which often is located near or in the zona incerta (ZI), is usually not used. The question of whether ZI stimulation may limit limbic effects has not been answered.

OBJECTIVE: To examine the effects of short-term stimulation near or in the ZI (contact 3) compared with stimulation of the STN using standard trajectories and targeting as measured by limbic and motor functions.

METHODS: Motor and limbic functions of 11 patients with STN DBS were assessed with the Unified Parkinson Disease Rating Scale-3, structured gait video analysis, Visual Analog Scale mood scales, task testing of impulsivity, and facial recognition under routine STN programming and under stimulation in or near the ZI. Postoperative magnetic resonance imaging confirmed the location of contact 3 near or in the ZI.

RESULTS: Data analysis with repeated-measures analysis of variance revealed that motor scores remained stable with both stimulation settings, with specific improvements in finger taps (P = .02) and rapid alternating movements (P = .03) in ZI stimulation. Stimulation near or in the ZI led to a decrease in self- reported anxiety and depression (P = .03 for both) and an improvement in fear recognition (P = .02).

CONCLUSION: We provide preliminary evidence that stimulation in or near the ZI results in maintained motor function while improving self-reported depression and anxiety in patients with bilateral STN DBS. Stimulation in or near the ZI may provide a useful programming setting for patients prone to psychiatric side effects.

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Memory Enhancement and Deep-Brain Stimulation of the Entorhinal Area

N Eng J Med, Vol 366(6), 9 February 2012, p 502–509. DOI: 10.1056/NEJMcibr1113400

The medial temporal structures, including the hippocampus and the entorhinal cortex, are critical for the ability to transform daily experience into lasting memories. We tested the hypothesis that deep-brain stimulation of the hippocampus or entorhinal cortex alters memory performance.

METHODS: We implanted intracranial depth electrodes in seven subjects to identify seizure-onset zones for subsequent epilepsy surgery. The subjects completed a spatial learning task during which they learned destinations within virtual environments. During half the learning trials, focal electrical stimulation was given below the threshold that elicits an afterdischarge (i.e., a neuronal discharge that occurs after termination of the stimulus).

RESULTS: Entorhinal stimulation applied while the subjects learned locations of landmarks enhanced their subsequent memory of these locations: the subjects reached these landmarks more quickly and by shorter routes, as compared with locations learned without stimulation. Entorhinal stimulation also resulted in a resetting of the phase of the theta rhythm, as shown on the hippocampal electroencephalogram. Direct hippocampal stimulation was not effective. In this small series, no adverse events associated with the procedure were observed.

CONCLUSIONS: Stimulation of the entorhinal region enhanced memory of spatial information when applied during learning.

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Brain stimulation for the treatment of epilepsy

Neurosurg Focus 32 (3):E13, 2012

The treatment of patients with refractory epilepsy has always been challenging. Despite the availability of multiple antiepileptic medications and surgical procedures with which to resect seizure foci, there is a subset of epilepsy patients for whom little can be done. Currently available treatment options for these unfortunate patients include vagus nerve stimulation, the ketogenic diet, and electric stimulation, both direct and indirect, of brain nuclei thought to be involved in epileptogenesis.

Studies of electrical stimulation of the brain in epilepsy treatment date back to the early 20th century, beginning with research on cerebellar stimulation. The number of potential targets has increased over the years to include the hippocampus, subthalamic nucleus, caudate nucleus, centromedian nucleus, and anterior nucleus of the thalamus (ANT).

Recently the results of a large randomized controlled trial, the electrical Stimulation of the Anterior Nucleus of Thalamus for Epilepsy (SANTE) trial, were published, demonstrating a significant reduction in mean seizure frequency with ANT stimulation. Soon after, in 2011, the results of a second randomized, controlled trial—the NeuroPace RNS trial—were published. The RNS trial examined closed-loop, responsive cortical stimulation of seizure foci in patients with refractory partial epilepsy, again finding significant reduction in seizure frequency.

In the present review, the authors examine the modern history of electrical stimulation of the brain for the treatment of epilepsy and discuss the results of 2 important, recently published trials, the SANTE and RNS trials.

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Multicenter study on subcallosal cingulate DBS for depression

J Neurosurg 116:315–322, 2012. DOI: 10.3171/2011.10.JNS102122

Deep brain stimulation (DBS) has been recently investigated as a treatment for major depression. One of the proposed targets for this application is the subcallosal cingulate gyrus (SCG). To date, promising results after SCG DBS have been reported by a single center. In the present study the authors investigated whether these findings may be replicated at different institutions. They conducted a 3-center prospective open-label trial of SCG DBS for 12 months in patients with treatment-resistant depression.

Methods. Twenty-one patients underwent implantation of bilateral SCG electrodes. The authors examined the reduction in Hamilton Rating Scale for Depression (HRSD-17) score from baseline (RESP50).

Results. Patients treated with SCG DBS had an RESP50 of 57% at 1 month, 48% at 6 months, and 29% at 12 months. The response rate after 12 months of DBS, however, increased to 62% when defined as a reduction in the baseline HRSD-17 of 40% or more. Reductions in depressive symptomatology were associated with amelioration in disease severity in patients who responded to surgery.

Conclusions. Overall, findings from this study corroborate the results of previous reports showing that outcome of SCG DBS may be replicated across centers.

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Localization of Primary Language Areas by Arcuate Fascicle Fiber Tracking

Neurosurgery 70:56–65, 2012 DOI: 10.1227/NEU.0b013e31822cb882

To reduce the risk of disabling postoperative functional deficit in patients with lesions in the dominant hemisphere, information about the localization of eloquent language areas is mandatory.

OBJECTIVE: To demonstrate the feasibility of arcuate fascicle (AF) tractography for proper localization of eloquent language areas in the superior temporal (STG) and inferior frontal gyrus (IFG).

METHODS: Between January and June 2010, we performed surgery in 13 patients with highly eloquent lesions with close spatial relationship to the primary language areas. All of them received preoperative diffusion tensor imaging for AF tractography. The STG and IFG were delineated at the ends of the AF. Five patients underwent functional magnetic resonance imaging of the primary language areas. The results were compared with tractography.

RESULTS: Tractography of the AF without prior knowledge of the localization of the STG and IFG was feasible in all cases. In the cases with functional magnetic resonance imaging, the activation maps matched the tractography results. In all but 1 patient, preservation of the primary language areas was possible, proven by the good neurological outcome. One patient suffered from a language dysfunction caused by a lesion in the medial and inferior temporal gyrus along the surgical pathway.

CONCLUSION: Tractography of the AF is a useful tool for identification of parts of the main primary language areas. Using tractography as a localization procedure to determine the primary language areas aids in the delineation of the STG and IFG and thus may help reduce the risk of postoperative permanent neurological deficit.

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Transcranial magnetic resonance imaging–guided focused ultrasound: noninvasive central lateral thalamotomy for chronic neuropathic pain

Neurosurgical Focus Jan 2012 / Vol. 32 / No. 1 / Page E1. DOI: 10.3171/2011.10.FOCUS11248

Recent technological developments open the field of therapeutic application of focused ultrasound to the brain through the intact cranium. The goal of this study was to apply the new transcranial magnetic resonance imaging–guided focused ultrasound (tcMRgFUS) technology to perform noninvasive central lateral thalamotomies (CLTs) as a treatment for chronic neuropathic pain.

METHODS

In 12 patients suffering from chronic therapy-resistant neuropathic pain, tcMRgFUS CLT was proposed. In 11 patients, precisely localized thermal ablations of 3–4 mm in diameter were produced in the posterior part of the central lateral thalamic nucleus at peak temperatures between 51°C and 64°C with the aid of real-time patient monitoring and MR imaging and MR thermometry guidance. The treated neuropathic pain syndromes had peripheral (5 patients) or central (6 patients) origins and covered all body parts (face, arm, leg, trunk, and hemibody).

RESULTS

Patients experienced mean pain relief of 49% at the 3-month follow-up (9 patients) and 57% at the 1-year follow-up (8 patients). Mean improvement according to the visual analog scale amounted to 42% at 3 months and 41% at 1 year. Six patients experienced immediate and persisting somatosensory improvements. Somatosensory and vestibular clinical manifestations were always observed during sonication time because of ultrasound-based neuronal activation and/or initial therapeutic effects. Quantitative electroencephalography (EEG) showed a significant reduction in EEG spectral overactivities. Thermal ablation sites showed sharply delineated ellipsoidal thermolesions surrounded by short-lived vasogenic edema. Lesion reconstructions (18 lesions in 9 patients) demonstrated targeting precision within a millimeter for all 3 coordinates. There was 1 complication, a bleed in the target with ischemia in the motor thalamus, which led to the introduction of 2 safety measures, that is, the detection of a potential cavitation by a cavitation detector and the maintenance of sonication temperatures below 60°C.

CONCLUSIONS

The authors assert that tcMRgFUS represents a noninvasive, precise, and radiation-free neurosurgical technique for the treatment of neuropathic pain. The procedure avoids mechanical brain tissue shift and eliminates the risk of infection. The possibility of applying sonication thermal spots free from trajectory restrictions should allow one to optimize target coverage. The real-time continuous MR imaging and MR thermometry monitoring of targeting accuracy and thermal effects are major factors in optimizing precision, safety, and efficacy in an outpatient context.

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Hardware-related infections after deep brain stimulation surgery: review of incidence, severity and management in 212 single-center procedures in the first year after implantation

Acta Neurochir (2011) 153:2337–2341. DOI 10.1007/s00701-011-1130-2

Device-related infection is a common occurrence after deep brain stimulation (DBS) surgery, and may result in additional interventions and a loss of efficacy of therapy. This retrospective review aimed to evaluate the incidence, severity and management of device-related infections in 212 DBS procedures performed in our institute.

Methods Data on 106 patients, in whom 212 DBS procedures were performed between 2001 and 2011 at our institute by a single neurosurgeon (M.P.), were reviewed to assess the incidence, severity, management and clinical characteristics of infections in the first year after the implantation of a DBS system.

Results Infections occurred in 8.5% of patients and 4.2% of procedures. Of the nine infections, eight involved the neurostimulator and extensions, and one the whole system. The infections occurred 30.7 days after implantation: 7 within 30 days and 2 within 6 months. Infected and uninfected patients were comparable in terms of age, sex, indication for DBS implantation and neurostimulator location. In eight cases, the system components involved were removed and re-implanted after 3 months, while in one case the complete hardware was removed and not re-implanted.

Conclusion The overall incidence of postoperative infections after DBS system implantation was 4.2%; this rate decreased over time. All infections required further surgery. Correct and timely management of partial infections may result in successful salvage of part of the system.

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Accuracy of Frame-Based Stereotactic Magnetic Resonance Imaging vs Frame-Based Stereotactic Head Computed Tomography Fused With Recent Magnetic Resonance Imaging for Postimplantation Deep Brain Stimulator Lead Localization

Neurosurgery 69:1299–1306, 2011 DOI: 10.1227/NEU.0b013e31822b7069

Introduction of the portable intraoperative CT scanner provides for a precise and cost-effective way of fusing head CT images with high-tesla MRI for the exquisite definition of soft tissue needed for stereotactic targeting.

OBJECTIVE: To evaluate the accuracy of stereotactic electrode placement in patients undergoing deep brain stimulation (DBS) by comparing frame-based postimplantation intraoperative CT (iCT) images fused to a recent 3T-MRI with frame-based postimplantation intraoperative MRI (iMRI) alone.

METHODS: Frame-based DBS surgeries of 46 targets performed from February 8, 2007 to April 28, 2008 in 26 patients with the use of immediate postimplantation iMRI for target localization were compared with frame-based immediate postimplantation iCT fused with a recent 3T brain MRI for DBS localization of 50 targets performed from August 13, 2008 to February 18, 2010 in 26 patients. Pre- and postoperative mid anterior commissure-posterior commissure line coordinates and XYZ coordinates for preoperatively calculated DBS targets (intended target) and for the permanent DBS lead tips were determined. The differences between preoperative DBS target and postoperative permanent DBS lead-tip coordinates based on postimplantation intraoperative MRI for the MRI-alone group and based on postimplantation intraoperative CT fused to recent preoperative MRI in the CTMRI group were measured. The t test and Yuen test were used for comparison.

RESULTS: No statistically significant differences were found between the 2 groups when comparing the pre- and postperative changes in mid anterior commissure-posterior commissure line coordinates and XYZ coordinates.

CONCLUSION: Postimplantation DBS lead localization and therefore targeting accuracy was not significantly different between frame-based stereotactic 1.5T-MRI and framebased stereotactic head CT fused with recent 3T-MRI.

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Discrepancies between the MRI and the electrophysiologically defined subthalamic nucleus

Acta Neurochir (2011) 153:2307–2318. DOI 10.1007/s00701-011-1081-7

The aim of our study was to evaluate discrepancies between the electrophysiologically and MRI-defined subthalamic nucleus (STN) in order to contribute to the ongoing debate of whether or not microelectrode recording (MER) provides additional information to imageguided targeting in deep brain stimulation.

Methods: Forty-four STNs in 22 patients with Parkinson’s disease were investigated. The three-dimensional MRI-defined STN was derived from segmentations of axial and coronal T2-weighted images. The electrophysiological STNs were generated from intraoperative MERs in 1,487 locations. The stereotactical coordinates of positive and negative STN recordings were re-imported to the planning software, where a three-dimensional reconstruction of the electrophysiological STN was performed and fused to the MRI data set. The estimated borders of the MRI- and MERSTN were compared. For statistical analysis Student’s t, Mann-Whitney rank sum and Fisher’s exact tests were used.

Results: MER-STN volumes, which were found outside the MRI-STN, ranged from 0 mm3 to 87 mm3 (mean: 45 mm3). A mean of 44% of the MER-STN volumes exceeded the MRI-STN (maximum: 85.1%; minimum: 15.1 %); 53.4% (n=793) of the microelectrode recordings were concordant and 46.6% (n=694) discordant with the MRI-defined anatomical STN. Regarding the dorsal borders, we found discrepancies between the MER- and MRI-STN of 0.27 mm (= mean; SD: 0.51 mm) on the first operated side and 1.51 mm (SD: 1.5 mm) on the second (p=0.010, t-test).

Conclusions: MER provides additional information to highresolution anatomical MR images and may help to detect the amount and direction of brain shift.

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