Implantable Subdural Cortical Stimulation for Chronic Intractable Pain Treatment-The Mayo Experience and Review of Literature.

OBJECTIVES: Motor cortex stimulation (MCS) is an effective technique in treating chronic intractable pain for some patients. However, most studies are small case series (n < 20). Heterogeneity in technique and patient selection makes it difficult to draw consistent conclusions. In this study, we present one of the largest case series of subdural MCS. MATERIALS AND METHODS: Medical records of patients who underwent MCS at our institute between 2007 and 2020 were reviewed. Studies with at least 15 patients were summarized for comparison. RESULTS: The study included 46 patients. Mean age was 56.2 ± 12.5 years (SD). Mean follow-up was 57.2 ± 41.9 months. Male-to-female ratio was 13:33. Of the 46 patients, 29 had neuropathic pain in trigeminal nerve territory/anesthesia dolorosa; nine had postsurgical/posttraumatic pain; three had phantom limb pain; two had postherpetic pain, and the rest had pain secondary to stroke, chronic regional pain syndrome, and tumor. The baseline numeric rating pain scale (NRS) was 8.2 ± 1.8 of 10, and the latest follow-up score was 3.5 ± 2.9 (mean improvement of 57.3%). Responders comprised 67% (31/46)(NRS ≥ 40% improvement). Analysis showed no correlation between percentage of improvement and age (p = 0.352) but favored male patients (75.3% vs 48.7%, p = 0.006). Seizures occurred in 47.8% of patients (22/46) at some point but were all self-limiting, with no lasting sequelae. Other complications included subdural/epidural hematoma requiring evacuation (3/46), infection (5/46), and cerebrospinal fluid leak (1/46). These complications resolved with no long-term sequelae after further interventions. CONCLUSION: Our study further supports the use of MCS as an effective treatment modality for several chronic intractable pain conditions and provides a benchmark to the current literature.

Clinical implications of nervus intermedius variants in patients with geniculate neuralgia: Let anatomy be the guide.

Geniculate neuralgia (GN) is an uncommon, but severe, condition that is characterized by excruciating paroxysmal pain in the seventh cranial nerve's cutaneous distribution of general somatic afferent fibers carried through the nervus intermedius (NI). GN becomes a surgical disease in refractory cases of pain after exhaustive medical management. Surgical intervention in the form of microvascular decompression and nerve sectioning has been investigated with good patient outcomes. Despite this, there are limited guidelines on either technique's appropriateness in specific operative scenarios. In our 30-year experience in GNs surgical management, we have found that a detailed knowledge of the NIs anatomy, variants, and intraoperative surgical anatomic findings are the key to choosing the most appropriate intervention, and may provide the answer to why some patients fail to experience pain relief after surgery. These anatomic variants also may explain why many patients commonly do not experience side effects related to the visceral efferent and special afferent fibers after nerve sectioning.

In NPH, setting valve opening pressure close to lumbar puncture opening pressure decreases overdrainage.

BACKGROUND: The management of normal pressure hydrocephalus (NPH) can be difficult, partly because there are frequent treatment complications such as overdrainage which, when serious, may require surgical intervention. We previously reported a correlation between the difference of lumbar puncture opening pressure minus the valve opening pressure setting (LPOP-VOP) (which we refer to as the delta) and increased rates of overdrainage. This led to a modification in our practice, whereby we now set the VOP equal to, or close to, the LPOP, resulting in lower deltas. OBJECTIVE: In this new study, our aim was to compare the rate of overdrainage in our patients with higher and lower deltas and assess the significance of setting the VOP equal, or close, to the patient's LPOP. METHODS: 1. We reproduced the association between delta and overdrainage. 2. We compared the incidence of overdrainage in those whose VOP was set close to LPOP (low delta) versus those with VOP setting distant from the LPOP (higher delta). 3. We compared symptom improvement in those with a low versus higher delta. RESULTS: We confirmed the relation between high delta and an increased rate of overdrainage, lower rates of overdrainage in those whose VOP was set close to the LPOP (Delta Adjusted Practice), and better improvement of symptoms when the VOP was set closer to the LPOP. CONCLUSION: We propose that the initial VOP should be set as close as possible to the patient's LPOP to decrease overdrainage without compromising symptom improvement.

Outcomes of large vestibular schwannomas following subtotal resection: early post-operative volume regression and facial nerve function.

INTRODUCTION: Subtotal resection (STR) of vestibular schwannoma (VS) tumors remains controversial and little is known regarding post-operative volume changes. METHODS: Authors retrospective reviewed the medical records from January 1st 2002 to January 1st 2018, for all patients who had undergone primary STR of large VS at a single tertiary academic institution. RESULTS: Our series consists of 34 patients with a mean age of 53.9 (median 53; range 21-87) years that had STR of their VS tumor. The mean pre-operative tumor diameter and volume was 3.9 cm (median 3.0 cm; range 1.6-6.0 cm) and 11.7 cm3 (median 9.6 cm3; range 2.8-44.3 cm3), respectively, with a mean extent of resection of 86% (median 90%; range 53-99%). The mean radiographic and clinical follow-up was 40 months (range 6-120 months) and 51 months (range 7-141 months), respectively. 85% of patients had optimal House-Brackmann (HB) scores (Grade 1 & 2) immediately post-operatively, and 91% at 1 year; 94% of patients had normal (HB 1) at last follow-up. There was significant regression of residual tumor volume at 1 year (p = 0.006) and 2 years (p = 0.02), but not at 3 years (p = 0.08), when compared to the prior year. There was significant regression of size over time, with a mean slope estimate of - 0.70 units per year (p < 0.001). CONCLUSION: Excellent clinical facial nerve outcomes can be obtained with STR of large VS tumors. Maximal reduction in tumor size occurs at 2-year post-operatively. Thus, in patients undergoing surgery for large VS, STR and a "watch and wait" strategy is a reasonable treatment option that may optimize facial nerve outcomes.

The impact of stereotactic laser ablation at a typical epilepsy center.

PURPOSE: Stereotactic laser ablation (SLA) is a novel form of epilepsy surgery for patients with drug-resistant focal epilepsy. We evaluated one hundred consecutive surgeries performed for patients with epilepsy to address the impact of SLA on our therapeutic approach, as well as patient outcomes. METHODS: A retrospective, single center analysis of the last one hundred neurosurgeries for epilepsy was performed from 2013 to 2015. Demographics, surgical procedures, and postoperative measures were assessed up to 5years to compare the effect of SLA on outcome. Confidence intervals (CI) and comparative tests of proportions compared outcomes for SLA and resective surgery. Procedural categorical comparison used Chi-square and Kaplan-Meier curves. Student t-test was utilized for single variables such as age at procedure and seizure onset. RESULTS: One hundred surgeries for epilepsy yielded thirty-three SLAs and twenty-one resections with a mean of 21.7-month and 21.3-month follow-up, respectively. The temporal lobe was the most common target for SLA (92.6%) and resection (75%). A discrete lesion was present on brain magnetic resonance imaging (MRI) in 27/32 (84.4%) of SLA patients compared with 7/20 (35%) of resection patients with a normal MRI. Overall, 55-60% of patients became seizure-free (SF). Four of five patients with initial failure to SLA became SF with subsequent resection surgery. Complications were more frequent with resection although SF outcomes did not differ (Chi square; p=0.79). Stereotactic laser ablation patients were older than those with resections (47.0years vs. 35.4years, p=0.001). The mean length of hospitalization prior to discharge was shorter for SLA (1.18days) compared with open resection (3.43days; SD: 3.16 days) (p=0.0002). CONCLUSION: We now use SLA as a first line therapy at our center in patients with lesional temporal lobe epilepsy (TLE) before resection. Seizure-free outcome with SLA and resection was similar but with a shorter length of stay. Long-term follow-up is recommended to determine sustained SF status from SLA.

Surgical treatment of bilateral glossopharyngeal neuralgia.

Glossopharyngeal neuralgia (GPN) is a condition characterised by sudden, severe pain in the distribution of the glossopharyngeal nerve. It can be triggered by talking, yawning, coughing and swallowing. Classically, patients experience a unilateral lancinating and excruciating pain described as electrical shock-like pain in the areas around the ear, tongue, or the mandibular angle. Uncommon manifestations include cardiac arrhythmias and syncope during pain episodes. Surgery is indicated in refractory cases. Bilateral GPN is rare, and definitive surgical treatment for bilateral GPN has not yet been reported. In this case report, a young woman with bilateral GPN who underwent staged surgery bilaterally is described. She did not develop life-threatening cardiac abnormalities postoperatively.

Nonaneurysmal "Pseudo-Subarachnoid Hemorrhage" Computed Tomography Patterns: Challenges in an Acute Decision-Making Heuristics.

BACKGROUND: Acute aneurysmal subarachnoid hemorrhage (SAH) is a medical and neurosurgical emergency from ruptured brain aneurysm. Aneurysmal SAH is identified on brain computed tomography (CT) as increased density of basal cisterns and subarachnoid spaces from acute blood products. Aneurysmal SAH-like pattern on CT appears as an optical illusion effect of hypodense brain parenchyma and/or hyperdense surrounding cerebral cisterns and blood vessels termed as "pseudo-subarachnoid hemorrhage" (pseudo-SAH). METHODS: We reviewed clinical, laboratory, and radiographic data of all SAH diagnoses between January 2013 and January 2018, and found subsets of nonaneurysmal SAH, originally suspected to be aneurysmal in origin. We performed a National Library of Medicine search methodology using terms "subarachnoid hemorrhage," "pseudo," and "non-aneurysmal subarachnoid hemorrhage" singly and in combination to understand the sensitivity, specificity, and precision of pseudo-SAH. RESULTS: Over 5 years, 230 SAH cases were referred to our tertiary academic center and only 7 (3%) met the definition of pseudo-SAH. Searching the National Library of Medicine using subarachnoid hemorrhage yielded 27,402 results. When subarachnoid hemorrhage and pseudo were combined, this yielded 70 results and sensitivity was 50% (n = 35). Similarly, search precision was relatively low (26%) as only 18 results fit the clinical description similar to the 7 cases discussed in our series. CONCLUSIONS: Aneurysmal SAH pattern on CT is distinct from nonaneurysmal and pseudo-SAH patterns. The origin of pseudo-SAH terminology appears mostly tied to comatose cardiac arrest patients with diffuse dark brain Hounsfield units and cerebral edema, and is a potential imaging pitfall in acute medical decision-making.

Brain-responsive neurostimulation in patients with medically intractable mesial temporal lobe epilepsy.

OBJECTIVE: Evaluate the seizure-reduction response and safety of mesial temporal lobe (MTL) brain-responsive stimulation in adults with medically intractable partial-onset seizures of mesial temporal lobe origin. METHODS: Subjects with mesial temporal lobe epilepsy (MTLE) were identified from prospective clinical trials of a brain-responsive neurostimulator (RNS System, NeuroPace). The seizure reduction over years 2-6 postimplantation was calculated by assessing the seizure frequency compared to a preimplantation baseline. Safety was assessed based on reported adverse events. RESULTS: There were 111 subjects with MTLE; 72% of subjects had bilateral MTL onsets and 28% had unilateral onsets. Subjects had one to four leads placed; only two leads could be connected to the device. Seventy-six subjects had depth leads only, 29 had both depth and strip leads, and 6 had only strip leads. The mean follow-up was 6.1 ± (standard deviation) 2.2 years. The median percent seizure reduction was 70% (last observation carried forward). Twenty-nine percent of subjects experienced at least one seizure-free period of 6 months or longer, and 15% experienced at least one seizure-free period of 1 year or longer. There was no difference in seizure reduction in subjects with and without mesial temporal sclerosis (MTS), bilateral MTL onsets, prior resection, prior intracranial monitoring, and prior vagus nerve stimulation. In addition, seizure reduction was not dependent on the location of depth leads relative to the hippocampus. The most frequent serious device-related adverse event was soft tissue implant-site infection (overall rate, including events categorized as device-related, uncertain, or not device-related: 0.03 per implant year, which is not greater than with other neurostimulation devices). SIGNIFICANCE: Brain-responsive stimulation represents a safe and effective treatment option for patients with medically intractable epilepsy, including patients with unilateral or bilateral MTLE who are not candidates for temporal lobectomy or who have failed a prior MTL resection.

Brain-responsive neurostimulation in patients with medically intractable seizures arising from eloquent and other neocortical areas.

OBJECTIVE: Evaluate the seizure-reduction response and safety of brain-responsive stimulation in adults with medically intractable partial-onset seizures of neocortical origin. METHODS: Patients with partial seizures of neocortical origin were identified from prospective clinical trials of a brain-responsive neurostimulator (RNS System, NeuroPace). The seizure reduction over years 2-6 postimplantation was calculated by assessing the seizure frequency compared to a preimplantation baseline. Safety was assessed based on reported adverse events. Additional analyses considered safety and seizure reduction according to lobe and functional area (e.g., eloquent cortex) of seizure onset. RESULTS: There were 126 patients with seizures of neocortical onset. The average follow-up was 6.1 implant years. The median percent seizure reduction was 70% in patients with frontal and parietal seizure onsets, 58% in those with temporal neocortical onsets, and 51% in those with multilobar onsets (last observation carried forward [LOCF] analysis). Twenty-six percent of patients experienced at least one seizure-free period of 6 months or longer and 14% experienced at least one seizure-free period of 1 year or longer. Patients with lesions on magnetic resonance imaging (MRI; 77% reduction, LOCF) and those with normal MRI findings (45% reduction, LOCF) benefitted, although the treatment response was more robust in patients with an MRI lesion (p = 0.02, generalized estimating equation [GEE]). There were no differences in the seizure reduction in patients with and without prior epilepsy surgery or vagus nerve stimulation. Stimulation parameters used for treatment did not cause acute or chronic neurologic deficits, even in eloquent cortical areas. The rates of infection (0.017 per patient implant year) and perioperative hemorrhage (0.8%) were not greater than with other neurostimulation devices. SIGNIFICANCE: Brain-responsive stimulation represents a safe and effective treatment option for patients with medically intractable epilepsy, including adults with seizures of neocortical onset, and those with onsets from eloquent cortex.

Neuropsychological outcomes following stereotactic laser amygdalohippocampectomy.

OBJECTIVE: The objective was to analyze neuropsychological testing data from 15 patients before and after stereotactic laser ablation surgery for temporal lobe epilepsy and to describe the seizure outcomes after stereotactic laser ablation surgery. METHODS: A retrospective review of 15 patients who underwent stereotactic laser ablation and who also underwent neuropsychological testing before and after surgery was performed. Verbal and visual memory was assessed in all 15 patients using California Verbal Learning Test and Wechsler Memory Scale IV. Naming was assessed in 9 of 15 patients using the Boston Naming Test. Statistical analysis was performed to determine clinically significant changes using previously validated reliable change indices and proprietary Advanced Clinical Solutions software. Seizure outcome data were evaluated using Engel classification. RESULTS: Postsurgery neuropsychological evaluation demonstrated that all 15 patients experienced at least 1 clinically significant decline in either verbal or visual memory. Ten patients in this series, including five with dominant-hemisphere surgery, demonstrated decline in delayed memory for narrative information (Logical Memory II). By contrast, the Boston Naming Test demonstrated more favorable results after surgery. Two of nine patients demonstrated a clinically significant increase in naming ability, and only one of nine patients demonstrated a clinically significant decline in naming ability. With at least 6months of follow-up after surgery, 33% reported seizure freedom. CONCLUSION: Stereotactic laser ablation can result in clinically significant and meaningful decline in verbal and visual memory when comparing patients to their own presurgical baseline. Naming ability, conversely, is much less likely to be impacted by stereotactic laser ablation and may improve after the procedure.

Non-contiguous meningeal metastases of olfactory neuroblastoma.

Olfactory neuroblastoma (ONB) is a malignant neoplasm centered along the roof of the nasal cavity near the cribriform plate. Although metastasis of this tumor has been reported, non-contiguous spread to the dura is rare. Here, we report the largest series of intracranial meningeal metastases of ONBs from M.D. Anderson Cancer Center and the University of Toronto. The unique natural history and geographical distribution of these metastatic lesions suggest a common mechanism of tumor spread along the dural vascular arborization.

Deep brain stimulation for levodopa-refractory benign tremulous parkinsonism.

Benign tremulous parkinsonism (BTP) is characterized by prominent resting tremor combined with action and postural components, and with only subtle rigidity and bradykinesia. This tremor is frequently disabling and poorly responsive to therapy with levodopa. Thus, BTP could be considered either as a distinct clinical disorder or a variant of PD. We present a case of a 57-year-old man who had a 3-year history of severe and functionally disabling resting tremor with action and postural features bilaterally but with left dominant hand predominance. There was only very mild rigidity and bradykinesia and no postural instability. His tremor was refractory to dopaminergic therapy, including carbidopa/levodopa. The dopamine transporter (DAT) imaging showed reduced tracer uptake in the putamen bilaterally, more so on the right side. He was treated with deep brain stimulation (DBS) targeting the right ventral intermediate nucleus of the thalamus. His tremor resolved immediately after procedure. The DAT imaging abnormalities indicate the presynaptic dopamine deficiency. In some autopsied BTP cases classic alpha-synuclein pathology of PD was observed. Thus, despite the lack of levodopa responsiveness BTP likely represents a variant of PD and not a distinct neurodegenerative disorder. DBS should be considered for patients with BTP PD variant despite their poor responsiveness to levodopa treatment.

Lateralization of mesial temporal lobe epilepsy with chronic ambulatory electrocorticography.

OBJECTIVE: Patients with suspected mesial temporal lobe (MTL) epilepsy typically undergo inpatient video-electroencephalography (EEG) monitoring with scalp and/or intracranial electrodes for 1 to 2 weeks to localize and lateralize the seizure focus or foci. Chronic ambulatory electrocorticography (ECoG) in patients with MTL epilepsy may provide additional information about seizure lateralization. This analysis describes data obtained from chronic ambulatory ECoG in patients with suspected bilateral MTL epilepsy in order to assess the time required to determine the seizure lateralization and whether this information could influence treatment decisions. METHODS: Ambulatory ECoG was reviewed in patients with suspected bilateral MTL epilepsy who were among a larger cohort with intractable epilepsy participating in a randomized controlled trial of responsive neurostimulation. Subjects were implanted with bilateral MTL leads and a cranially implanted neurostimulator programmed to detect abnormal interictal and ictal ECoG activity. ECoG data stored by the neurostimulator were reviewed to determine the lateralization of electrographic seizures and the interval of time until independent bilateral MTL electrographic seizures were recorded. RESULTS: Eighty-two subjects were implanted with bilateral MTL leads and followed for 4.7 years on average (median 4.9 years). Independent bilateral MTL electrographic seizures were recorded in 84%. The average time to record bilateral electrographic seizures in the ambulatory setting was 41.6 days (median 13 days, range 0-376 days). Sixteen percent had only unilateral electrographic seizures after an average of 4.6 years of recording. SIGNIFICANCE: About one third of the subjects implanted with bilateral MTL electrodes required >1 month of chronic ambulatory ECoG before the first contralateral MTL electrographic seizure was recorded. Some patients with suspected bilateral MTL seizures had only unilateral electrographic seizures. Chronic ambulatory ECoG in patients with suspected bilateral MTL seizures provides data in a naturalistic setting, may complement data from inpatient video-EEG monitoring, and can contribute to treatment decisions.

Two-year seizure reduction in adults with medically intractable partial onset epilepsy treated with responsive neurostimulation: final results of the RNS System Pivotal trial.

OBJECTIVE: To demonstrate the safety and effectiveness of responsive stimulation at the seizure focus as an adjunctive therapy to reduce the frequency of seizures in adults with medically intractable partial onset seizures arising from one or two seizure foci. METHODS: Randomized multicenter double-blinded controlled trial of responsive focal cortical stimulation (RNS System). Subjects with medically intractable partial onset seizures from one or two foci were implanted, and 1 month postimplant were randomized 1:1 to active or sham stimulation. After the fifth postimplant month, all subjects received responsive stimulation in an open label period (OLP) to complete 2 years of postimplant follow-up. RESULTS: All 191 subjects were randomized. The percent change in seizures at the end of the blinded period was -37.9% in the active and -17.3% in the sham stimulation group (p = 0.012, Generalized Estimating Equations). The median percent reduction in seizures in the OLP was 44% at 1 year and 53% at 2 years, which represents a progressive and significant improvement with time (p < 0.0001). The serious adverse event rate was not different between subjects receiving active and sham stimulation. Adverse events were consistent with the known risks of an implanted medical device, seizures, and of other epilepsy treatments. There were no adverse effects on neuropsychological function or mood. SIGNIFICANCE: Responsive stimulation to the seizure focus reduced the frequency of partial-onset seizures acutely, showed improving seizure reduction over time, was well tolerated, and was acceptably safe. The RNS System provides an additional treatment option for patients with medically intractable partial-onset seizures.

Hemangioblastoma of spinal nerve: a report of six cases.

AIMS: Hemangioblastomas may arise sporadically or in the setting of Von Hippel-Lindau (VHL) disease. In either instance, it rarely occurs outside the central nervous system. By analysis of a large case series, we sought to further characterize the clinical, radiologic and pathologic features of hemangioblastomas involving nerve root. MATERIALS AND METHODS: The clinical resentations of 6 proximal nerve root hemangioblastomas (1 an aggressive tumor) were analyzed with emphasis on the neuroimaging, operative, and pathologic findings. The literature is fully reviewed and updated. RESULTS: Nerve hemangioblastoma usually affects proximal spinal roots. Peripheral nerve is rarely involved. Both clinically and radiologically, the diagnosis is usually not suspected before surgery. Profuse bleeding at resection may be the first indication of the nature of the lesion. These tumors may arise both sporadically and in association with VHL disease. CONCLUSION: Given their rarity, nerve root hemangioblastomas are not generally considered in the preoperative differential diagnosis of proximal nerve root lesions. Given their propensity to bleed profusely at surgery and the potential association with VHL disease, knowledge of this entity is important.

Complex transient epileptic amnesia.

Transient epileptic amnesia is a rare but probably underrecognized form of temporal lobe epilepsy, which typically manifests as episodic isolated memory loss. Consequently, transient epileptic amnesia may be readily misdiagnosed as a nonepileptic memory dysfunction in older individuals. When appropriately recognized, it has been described as a treatment-responsive syndrome amenable to antiepileptic drugs. We describe a patient with drug-resistant transient epileptic amnesia treated with unilateral temporal lobectomy. Prolonged postictal slowing in the mesial temporal structures was evident on invasive electroencephalography 5 hours after the occurrence of a brief focal seizure. These findings support the theory of a Todd phenomenon as the underlying pathophysiological mechanism in transient epileptic amnesia.

Crying with depressed affect induced by electrical stimulation of the anterior insula: A stereo EEG case study.

Stereo-EEG (sEEG) is an invasive recording technique used to localize the seizure-onset zone for epilepsy surgery in people with drug-resistant focal seizures. Pathological crying reflects disordered emotional expression and the anterior insula is known to play a role in empathy and socio-emotional processing. We describe a patient where electrical stimulation mapping (ESM) of the anterior insula during sEEG generated pathological crying and profound sadness that was time-locked to the electrical stimulus. We evaluated a 35-year-old left-handed female for repeat epilepsy surgery. The patient had drug resistant focal impaired awareness seizures despite a previous left temporal neocortical resection informed by an invasive study using subdural grid and strip electrodes seven years earlier. She was studied invasively with 10 sEEG electrodes sampling temporal, occipital, and insular targets. In the process of functional mapping, stimulation of the anterior insular cortex provoked tearful crying with sad affect, reproducible upon repeat stimulation. Our case is unique in demonstrating transitory pathological crying with profound sadness provoked by ESM of the left anterior insula. Furthermore we demonstrate repeated time-synched crying from electrical stimulation, which supports the hypothesis that the anterior insula in the brain plays an important role in the biology of emotion, as implicated by previous studies.

Left Radiofrequency Thalamotomy for Drug-Refractory Essential Tremor.

Essential tremor is an idiopathic movement disorder characterized by bilateral action tremor of the upper limbs with or without other neurologic symptoms.1 Pharmacologic management is the first-line treatment for this condition. Surgical treatment includes deep brain stimulation and thalamotomy procedures.2 Furthermore, thalamotomy can be achieved by magnetic resonance imaging-guided focused ultrasound, stereotactic radiosurgery, or radiofrequency.3 Advantages of modulation therapies include bilateral implementation, adjustability, and reversibility of the effect.2 Disadvantages include delayed response, increased infection risk, and cost. Within ablation therapies, focused ultrasound is costly and not available widely, while stereotactic radiosurgery has a delayed symptomatic relief. Radiofrequency represents a cost-effective, widely available option with immediate results.3 We present the case of a 91-year-old right-handed man with essential tremor refractory to medical management (Video 1). He was offered all available treatment modalities and opted for a radiofrequency thalamotomy. Preoperative planning included stereotactic head frame placement and computed tomography scan. A left thalamic target with coordinates 11.5 mm lateral to the wall of the third ventricle, 8 mm anterior to the posterior commissure, and at the rostrocaudal level of the anterior commissure-posterior commissure plane was chosen. A 1.1-mm diameter, 10-mm tip RF electrode was advanced to the target. A lateral radiograph was taken to verify the position of the electrode. After trial stimulation, 2 RF lesions were performed. No intraoperative complications occurred. Immediate postoperative MRI showed an enhancing focus in the left thalamic lobe corresponding to the left thalamotomy lesion. The patient had excellent relief of tremor during his last follow-up, 5 months postoperatively.

Functional Activation Patterns of Deep Brain Stimulation of the Anterior Nucleus of the Thalamus.

BACKGROUND: Deep brain stimulation (DBS) of the anterior nucleus of the thalamus (ANT) is a recently approved therapy for patients with drug-resistant epilepsy. To date, there is a poor understanding of the mechanism of action and lack of in vivo biomarkers. We propose a method for investigating the in vivo stimulation effects using blood-oxygen-level-dependent (BOLD) magnetic resonance imaging (MRI) and present the brain activation pattern associated with ANT DBS. METHODS: Two patients undergoing ANT DBS for epilepsy underwent BOLD MRI using a block design after the DBS was programmed to alternate ON/OFF in 30-second blocks. The scanner was triggered using surface electrophysiologic recordings to detect the DBS cycle. Nine total runs were obtained and were analyzed using a general linear model. RESULTS: Active ANT stimulation produced activation within several areas of the brain, including the thalamus, bilateral anterior cingulate and posterior cingulate cortex, precuneus, medial prefrontal cortex, amygdala, ventral tegmental area, hippocampus, striatum, and right angular gyrus. CONCLUSIONS: Using block-design BOLD MRI, we were able to show widespread activation resulting from ANT DBS. Overlap with multiple areas of both the default mode and limbic networks was shown, suggesting that these nodes may modulate the effect of seizure control with ANT DBS.

Outcomes following surgical management of vagus nerve stimulator-related infection: a retrospective multi-institutional study.

OBJECTIVE: Surgical site infection (SSI) is a rare but significant complication after vagus nerve stimulator (VNS) placement. Treatment options range from antibiotic therapy alone to hardware removal. The optimal therapeutic strategy remains open to debate. Therefore, the authors conducted this retrospective multicenter analysis to provide insight into the optimal management of VNS-related SSI (VNS-SSI). METHODS: Under institutional review board approval and utilizing an institutional database with 641 patients who had undergone 808 VNS-related placement surgeries and 31 patients who had undergone VNS-related hardware removal surgeries, the authors retrospectively analyzed VNS-SSI. RESULTS: Sixteen cases of VNS-SSI were identified; 12 of them had undergone the original VNS placement procedure at the authors' institutions. Thus, the incidence of VNS-SSI was calculated as 1.5%. The mean (± standard deviation) time from the most recent VNS-related surgeries to infection was 42 (± 27) days. Methicillin-sensitive staphylococcus was the usual causative bacteria (58%). Initial treatments included antibiotics with or without nonsurgical procedures (n = 6), nonremoval open surgeries for irrigation (n = 3), generator removal (n = 3), and total or near-total removal of hardware (n = 4). Although 2 patients were successfully treated with antibiotics alone or combined with generator removal, removal of both the generator and leads was eventually required in 14 patients. Mild swallowing difficulties and hoarseness occurred in 2 patients with eventual resolution. CONCLUSIONS: Removal of the VNS including electrode leads combined with antibiotic administration is the definitive treatment but has a risk of causing dysphagia. If the surgeon finds dense scarring around the vagus nerve, the prudent approach is to snip the electrode close to the nerve as opposed to attempting to unwind the lead completely.