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.

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.

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.

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.

Nine-year prospective efficacy and safety of brain-responsive neurostimulation for focal epilepsy.

OBJECTIVE: To prospectively evaluate safety and efficacy of brain-responsive neurostimulation in adults with medically intractable focal onset seizures (FOS) over 9 years. METHODS: Adults treated with brain-responsive neurostimulation in 2-year feasibility or randomized controlled trials were enrolled in a long-term prospective open label trial (LTT) to assess safety, efficacy, and quality of life (QOL) over an additional 7 years. Safety was assessed as adverse events (AEs), efficacy as median percent change in seizure frequency and responder rate, and QOL with the Quality of Life in Epilepsy (QOLIE-89) inventory. RESULTS: Of 256 patients treated in the initial trials, 230 participated in the LTT. At 9 years, the median percent reduction in seizure frequency was 75% (p < 0.0001, Wilcoxon signed rank), responder rate was 73%, and 35% had a ≥90% reduction in seizure frequency. We found that 18.4% (47 of 256) experienced ≥1 year of seizure freedom, with 62% (29 of 47) seizure-free at the last follow-up and an average seizure-free period of 3.2 years (range 1.04-9.6 years). Overall QOL and epilepsy-targeted and cognitive domains of QOLIE-89 remained significantly improved (p < 0.05). There were no serious AEs related to stimulation, and the sudden unexplained death in epilepsy (SUDEP) rate was significantly lower than predefined comparators (p < 0.05, 1-tailed χ2). CONCLUSIONS: Adjunctive brain-responsive neurostimulation provides significant and sustained reductions in the frequency of FOS with improved QOL. Stimulation was well tolerated; implantation-related AEs were typical of other neurostimulation devices; and SUDEP rates were low. CLINICALTRIALSGOV IDENTIFIER: NCT00572195. CLASSIFICATION OF EVIDENCE: This study provides Class IV evidence that brain-responsive neurostimulation significantly reduces focal seizures with acceptable safety over 9 years.

Variability Between Direct and Indirect Targeting of the Anterior Nucleus of the Thalamus.

BACKGROUND: Preoperative thalamic targeting methods have historically relied on indirect targeting techniques that do not fully account for variances in anatomy or for thalamic atrophy in epilepsy. We aimed to address variability noted between traditional indirect targeting and direct targeting methods for the anterior nucleus of the thalamus (ANT). METHODS: Fifteen consecutive patients undergoing ANT deep brain stimulator placement were evaluated (30 thalamic nuclei). Direct ANT targeting was performed using a fast gray matter acquisition T1 inversion recovery sequence and compared with standard stereotactic coordinates. Thalamic volumes were calculated for each patient, and degree of thalamic volume loss was assessed compared with matched control subjects. Vertex analysis was performed to assess shape changes in the thalamus compared with age- and sex-matched subjects. RESULTS: There was significant variation between direct and indirect targets in the y-axis and z-axis on both sides. On the left, the direct target was located at y = 2 ± 1.3 mm and z = 9.3 ± 1.8 mm (both P = 0.02). On the right, the direct target was located at y = 2.9 ± 1.8 mm and z = 9.2 ± 2 mm (both P ≤ 0.0003). There was no significant difference in the x-coordinate on either side (P > 0.5). Additionally, there was a correlation between thalamic volume and difference between direct and indirect targets in the y-axis and the z-axis. CONCLUSIONS: We showed a significant difference in direct and indirect targeting in the y-axis and z-axis when targeting the ANT for deep brain stimulation for epilepsy. This difference is correlated to thalamic volume, with a larger difference noted in patients with thalamic atrophy.

Wada testing and fMRI in a polyglot evaluated for epilepsy surgery.

Despite advancements in the neurophysiology of language and presurgical evaluation for epilepsy surgery, there is a paucity of information in the literature regarding presurgical evaluation of multilingual patients. We present a case of a 52-year-old right-handed woman with refractory epilepsy who was fluent in six languages and underwent subsequent trilingual presurgical evaluation which included neuropsychological testing, Wada testing, functional magnetic resonance imaging (fMRI), and electrocortical stimulation. These studies suggested a seizure focus in the left temporal lobe and language localization that was predominantly right-hemispheric; she subsequently underwent left temporal laser interstitial thermal therapy without clinical disturbance in language function while remaining seizure-free. A multidisciplinary effort was integral in providing an optimal outcome for this patient.

The reliability of Deep Brain Stimulation YouTube videos.

BACKGROUND: Deep Brain Stimulation (DBS) was approved by the FDA in the 1990s and is used to treat a variety of movement disorders. Patients are increasingly turning to the internet for information regarding their ailments. In this study, we aim to evaluate the accuracy and reliability of information presented in DBS-related YouTube videos. METHODS: Using the "Relevance-Based Ranking" strategy for analysis we assessed the first 3 pages of YouTube for each of the following keywords: "Deep Brain Stimulation", "DBS", "DBS for Parkinson's disease", "DBS for essential tremor", and "DBS for movement disorders". Four independent healthcare personnel evaluated the videos' education quality and informational material using the validated DISCERN tool. RESULTS: Our study found that only 24% of the 42 published videos analyzed scored above a 3 on the DISCERN scoring scale (considered a "good" video). The search term "Deep Brain Stimulation" had the highest percentage of good videos (DISCERN > 3) (32%). We also found that the duration of videos was longer for the "good" videos (Good = 25.6 min vs Unhelpful = 3.0 min, P = 0.01). CONCLUSION: YouTube is one of the largest video platforms; the uploaded videos lack reliability and institutional oversight by the experts. We believe that medical institutions should explore this way of communicating to patients by publishing evidence-based and informative videos on diseases and their management. As it is imperative that the medical field advance to combat medical misinformation.

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.

Results of surgical resection of carotid body tumors: A twenty-year experience.

This study examines whether surgical resection of carotid body tumors (CBTs) is acceptable in light of potential significant neurologic complications. This IRB-approved retrospective study analyzed data from 24 patients undergoing surgical treatment for CBTs between April 1998 and April 2017 at Mayo Clinic (Florida campus only). For patients who underwent multiple CBT resections, only data from the first surgery was used in this analysis. CBT resection occurred in 24 patients with the following demographics: fourteen patients (58.3%) were female, median age was 56.5 years, median BMI was 29. A prior history of neoplasm was found in ten patients (41.7%). A known family history of paraganglioma was present in five patients (20.8%). Two patients were positive for succinate dehydrogenase mutation (8.3%). Multiple paragangliomas were present in seven patients (29.2%). There was nerve sacrifice in three patients (12.5%) during resection. Carotid artery reconstruction and patch angioplasty occurred in one patient (4.2%). Complete resection occurred in 24 patients (100.0%). Postoperatively, one patient (4.2%) suffered stroke. No mortalities occurred within or beyond 30 days of surgery. Persistent cranial nerve injury occurred in two patients (8.3%) with vocal cord paralysis. There was no recurrence of CBT through last follow-up. Five patients (20.8%) were diagnosed with other neoplasms after resection, including basal cell carcinoma, contralateral carotid body tumor, glomus vagale, and glomus jugulare. There was 100% survival at 1 year in patients followed for that time (n = 17). Surgical treatment remains the first-line curative treatment to relieve symptoms and ensure non-recurrence. While acceptable, neurologic complications are significant and therefore detailed preoperative informed consent is mandatory.

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.

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.

Video-Assisted Bilateral Thoracoscopic Sympathotomy for Palmar Hyperhidrosis.

In this video, we demonstrate a case of a 21-year-old right-handed man who presented with palmar hyperhidrosis. His symptoms started at the age of 4 years and progressively worsened throughout his life. Multiple medical treatments were used without significant benefit. His symptoms worsened to the limit that it affected his work and lifestyle. The patient was taken to the operating room in a supine position with both arms abducted 90°. The right and left chest were prepped and draped in a sterile fashion. The skin incision was done on the left side first, the left lung was isolated, and two 5-mm thoracoports were placed in the sixth and third intercostal spaces, respectively. Carbon dioxide insufflation was used to a pressure of 6 mm Hg for exposure. The chest was visualized, and the sympathetic chain was identified. Ribs were counted and then cautery at a low setting was used. The sympathetic chain was transected at the level of the head of the second rib. Accessory nerves of Kuntz were identified and resected. Carbon dioxide was then evacuated from the left chest using a bronchial tube exchanger and Valsalva maneuver. The lung was completely reinflated and skin was closed in a normal fashion. The same procedure was repeated on the right side. A chest radiograph was obtained intraoperatively, and no pneumothorax was observed. At the end of the procedure, both upper extremity temperature probes showed a significant increase from baseline. Informed patient consent was obtained.

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.

A curious case of DBS radiofrequency programmer interference.

Deep brain stimulation (DBS) systems frequently rely on radiofrequency (RF) transmission for patient programming. The potential exists for other devices to interfere with communication between the internal pulse generator (IPG) and the programming device. In this paper, we are reporting a case of programming interference between the IPG and the WaveID device.

Benefits and risks of unilateral and bilateral ventral intermediate nucleus deep brain stimulation for axial essential tremor symptoms.

INTRODUCTION: Many experts assume bilateral deep brain stimulation (DBS) is necessary to improve axial tremor in essential tremor (ET). In the largest clinical trial of DBS for ET to date evaluating a non-directional, constant current device, we studied the effects of unilateral and staged bilateral DBS on axial tremor. METHODS: We included all participants from the original trial with unilateral ventral intermediate nucleus (VIM) DBS and 90-day follow up at minimum. Primary outcomes were changes in pooled axial subscores in the Clinical Rating Scale for Tremor (CRST) at 90 and 180 days after activation of unilateral VIM DBS compared to pre-operative baseline (n=119). Additionally, we performed within-subject analyses for unilateral versus bilateral DBS at 180 days in the cohort who underwent staged surgery to bilateral DBS (n=39). RESULTS: Unilateral VIM DBS improved midline tremor by 58% at 90 days (median[IQR]) (3[3] to 1[2], p<0.001) and 65% at 180 days (3[3] to 1[2], p<0.001) versus pre-op baseline. In the staged to bilateral DBS cohort, midline tremor scores further improved after bilateral DBS at 180 days by 63% versus unilateral DBS (3[3] to 1[3], p=0.007). There were, however, 35 additional DBS and surgery-related adverse events, 14 related to incoordination, gait impairment, or speech impairment, versus 6 after unilateral DBS. CONCLUSION: Unilateral VIM DBS for ET significantly improved associated axial tremor. Staged bilateral DBS was associated with additional axial tremor improvement but also additional adverse events. Unilateral VIM DBS may be sufficient to achieve a goal of contralateral limb and axial tremor attenuation.

Magnetic Resonance-Guided Laser Interstitial Thermal Therapy Versus Stereotactic Radiosurgery for Medically Intractable Temporal Lobe Epilepsy: A Systematic Review and Meta-Analysis of Seizure Outcomes and Complications.

INTRODUCTION: Magnetic resonance-guided laser interstitial thermal therapy (MRgLITT) and stereotactic radiosurgery (SRS) are 2 emerging minimally invasive procedures being increasingly used for surgical intervention in cases of medically intractable temporal lobe epilepsy (TLE). To date, no comparative analyses of these 2 procedures have been made. In the current study, we synthesized pooled data from existing studies in an attempt to present a systematic review and meta-analysis of seizure and clinical outcomes of the 2 procedures in patients with TLE. METHODS: The Population, Intervention, Comparator, and Outcome (PICO) approach and Preferred Reporting Items for Systematic Reviews and Meta-Analysis (PRISMA) guidelines were followed to perform an indirect meta-analysis of seizure and clinical outcomes between MRgLITT and SRS. Only studies reporting outcomes for patients with TLE were included in the current review. RESULTS: A total of 19 studies were included in the final analysis, giving a total of 415 TLE patients. Of those studies, 9 were on MRgLITT, with a total of 250 patients (60%), and 10 were on SRS, with a total of 165 patients (40%). We found that the overall seizure freedom rate was comparable between the 2 procedures (MRgLITT 50%, 95% confidence interval [CI] 44% to 56%, vs. SRS 42%, 95% CI 27% to 59%, P = 0.39). Similarly, among patients with lesional pathologic conditions only, the seizure freedom rate was comparable between the 2 procedures (MRgLITT 62%, 95% CI 48% to 74%, vs. SRS 50%, 95% CI 37% to 64%, P = 0.23). Compared with SRS, MRgLITT was associated with lower complication rates (MRgLITT 20%, 95% CI 14% to 26% vs. SRS 32%, 95% CI 20% to 46%, P = 0.06) but similar reoperation rates (15%, 95% CI 9% to 22% vs. 27%, 95% CI 12% to 46%, P = 0.31). CONCLUSIONS: As minimally invasive procedures continue to gain popularity for use in surgery for epilepsy, it is imperative to evaluate their efficacy and safety outcomes. In this study we pooled the data from existing studies to compare the seizure and clinical outcomes in patients with TLE undergoing MRgLITT and SRS. We found similar outcomes and complications between the 2 procedures.

De novo temporal intermittent rhythmic delta activity after laser interstitial thermal therapy for mesial temporal lobe epilepsy predicts poor seizure outcome.

OBJECTIVE: To evaluate EEG abnormalities, particularly development of temporal intermittent rhythmic delta activity (TIRDA) after laser interstitial thermal therapy (LITT) and assess the role of further surgery after LITT. METHODS: We retrospectively identified consecutive cases of LITT for the prevalence of post-operative TIRDA. We assessed baseline demographics, clinical variables including age of seizure onset, age at surgery, pre-operative and post-operative EEG changes. RESULTS: 40 patients underwent LITT for drug-resistant temporal lobe epilepsy (TLE), 29 met inclusion criteria. Median duration of follow-up was 15 months. Ten patients had post-LITT ipsilateral TIRDA, another two demonstrated post-operative TIRDA but they occurred contralateral to the side of ablation. None of the patients with TIRDA on their post-LITT EEG became seizure-free. Six out of 29 patients (21%) eventually required anterior temporal lobectomy (ATL), and of those 6 patients 4 (66%) had evidence of TIRDA on their post-LITT follow up EEG. The sensitivity and specificity of post-LITT TIRDA in predicting surgical failure was 57.14% and 100% respectively. CONCLUSIONS: Post-LITT TIRDA may serve as a biomarker to predict unsuccessful seizure outcome following LITT and be an early indicator for ATL. SIGNIFICANCE: The presence of TIRDA following LITT should prompt early consideration for reoperation.

Laser ablation for mesial temporal epilepsy: a multi-site, single institutional series.

OBJECTIVEAlthough it is still early in its application, laser interstitial thermal therapy (LiTT) has increasingly been employed as a surgical option for patients with mesial temporal lobe epilepsy. This study aimed to describe mesial temporal lobe ablation volumes and seizure outcomes following LiTT across the Mayo Clinic's 3 epilepsy surgery centers.METHODSThis was a multi-site, single-institution, retrospective review of seizure outcomes and ablation volumes following LiTT for medically intractable mesial temporal lobe epilepsy between October 2011 and October 2015. Pre-ablation and post-ablation follow-up volumes of the hippocampus were measured using FreeSurfer, and the volume of ablated tissue was also measured on intraoperative MRI using a supervised spline-based edge detection algorithm. To determine seizure outcomes, results were compared between those patients who were seizure free and those who continued to experience seizures.RESULTSThere were 23 patients who underwent mesial temporal LiTT within the study period. Fifteen patients (65%) had left-sided procedures. The median follow-up was 34 months (range 12-70 months). The mean ablation volume was 6888 mm3. Median hippocampal ablation was 65%, with a median amygdala ablation of 43%. At last follow-up, 11 (48%) of these patients were seizure free. There was no correlation between ablation volume and seizure freedom (p = 0.69). There was also no correlation between percent ablation of the amygdala (p = 0.28) or hippocampus (p = 0.82) and seizure outcomes. Twelve patients underwent formal testing with computational visual fields. Visual field changes were seen in 67% of patients who underwent testing. Comparing the 5 patients with clinically noticeable visual field deficits to the rest of the cohort showed no significant difference in ablation volume between those patients with visual field deficits and those without (p = 0.94). There were 11 patients with follow-up neuropsychological testing. Within this group, verbal learning retention was 76% in the patients with left-sided procedures and 89% in those with right-sided procedures.CONCLUSIONSIn this study, there was no significant correlation between the ablation volume after LiTT and seizure outcomes. Visual field deficits were common in formally tested patients, much as in patients treated with open temporal lobectomy. Further studies are required to determine the role of amygdalohippocampal ablation.