Cost of pre-surgical evaluation for epilepsy surgery: A single-center experience

OBJECTIVE: To estimate the cost and time taken to evaluate adults with drug-resistant focal epilepsy for potentially curative surgery. METHODS: We reviewed data on 100 consecutive individuals at a tertiary referral center evaluated for epilepsy surgery in 2017. The time elapsed between referral and either surgery or a definitive decision not to progress was measured. National Health Service tariffs applicable to our setting were used to estimate the total cost of evaluation for individuals following different routes through the pre-surgical pathway. After surgery, self-reported seizure freedom rates were obtained from each individual to assess the approximate cost of pre-surgical evaluation per additional person seizure-free. RESULTS: Of 100 individuals evaluated, 27 had surgery, 63 had a definitive decision not to have surgery, and ten were awaiting further investigations. The median duration of the pre-surgical evaluation was 29.7 months (IQR 18.6-44.1 months), with a median cost per person of £9138 (IQR £6984-£14,868). Those who proceeded to Stage Two investigations (including fluorodeoxyglucose positron emission tomography, ictal single-photon emission computerized tomography and intracranial electroencephalography) had a higher cost and extended evaluation length. After a median of 3.1 (IQR 2.3-3.7) years, 15/27 people who had surgery were seizure-free. This equated to an approximate cost of £123,500 spent per additional person seizure-free. CONCLUSION: Pre-surgical evaluation is long and costly, particularly for those who require icEEG. For those with drug-resistant focal epilepsy, surgery is, however, associated with a greater chance of seizure freedom. The suitability and risk-benefit ratio of surgery should be considered at each step of the pre-surgical pathway

Seizure outcomes in people with drug-resistant focal epilepsy evaluated for surgery but do not proceed

ObjectiveTo ascertain seizure outcomes in people with drug-resistant focal epilepsy considered for epilepsy surgery but who did not proceed.MethodsWe identified people discussed at a weekly presurgical epilepsy multi-disciplinary (MDT) meeting from January 2015 to December 2019 and in whom a decision not to proceed to surgery was made. Seizure outcomes were obtained from individuals, primary care physicians and attending neurologists at a minimum of 12 months following the not to proceed decision.ResultsWe considered 315 people who did not proceed to surgery after evaluation. Nine died, and 25 were lost to follow-up. We included 281 people with a median follow-up of 2.4 (IQR 1.5–4) years. In total, 83 (30%) people reported that seizures had improved or resolved since the MDT meeting. Thirteen (5%) were seizure-free over the last 12 months of follow-up, 70 (25%) had experienced more than 50% reduction in seizure frequency, 180 (64%) had no meaningful change, and 18 (6%) reported a doubling of seizure frequency. Of the 53 (16%) who had vagal nerve stimulation, 19/53 (37%) reported more than 50% reduction in frequency, including one seizure-free.SignificanceThe chances of seizure freedom with further medications and neurostimulation are low for people with drug-resistant focal epilepsy who have been evaluated for surgery and do not proceed, but improvement may still occur. Up to a quarter have a > 50% reduction in seizures, and one in twenty become seizure-free eventually. Trying additional anti-seizure medication and neurostimulation is worthwhile in this population

Hippocampal resection in Temporal Lobe epilepsy: do we need to resect the tail?

Introduction: Anteromesial temporal lobe resection is the most common surgical technique used to treat drug-resistant mesial temporal lobe epilepsy, particularly when secondary to hippocampal sclerosis. Structural and functional imaging data suggest the importance of sparing the posterior hippocampus for minimising language and memory deficits. Recent work has challenged the view that maximal posterior hippocampal resection improves seizure outcome. This study was designed to assess whether resection of posterior hippocampal atrophy was associated with improved seizure outcome. Methods: Retrospective analysis of a prospective database of all anteromesial temporal lobe resections performed in individuals with hippocampal sclerosis at our epilepsy surgery centre, 2013-2021. Pre- and post-operative MRI were reviewed by 2 neurosurgical fellows to assess whether the atrophic segment, displayed by automated hippocampal morphometry, was resected, and ILAE seizure outcomes were collected at 1 year and last clinical follow-up. Data analysis used univariate and binary logistic regression. Results: Sixty consecutive eligible patients were identified of whom 70% were seizure free (ILAE Class 1 & 2) at one year. There was no statistically significant difference in seizure freedom outcomes in patients who had complete resection of atrophic posterior hippocampus or not (Fisher’s Exact test statistic 0.69, not significant at p<.05) both at one year, and at last clinical follow-up. In the multivariate analysis only a history of status epilepticus (OR=0.2, 95%CI:0.042-0.955, p=.04) at one year, and pre-operative psychiatric disorder (OR=0.145, 95%CI:0.036-0.588, p=.007) at last clinical follow-up, were associated with a reduced chance of seizure freedom. Significance: Our data suggest that seizure freedom is not associated with whether or not posterior hippocampal atrophy is resected. This challenges the traditional surgical dogma of maximal posterior hippocampal resection in anteromesial temporal lobe resections and is a step further optimising this surgical procedure to maximise seizure freedom and minimise associated language and memory deficits

Automatic segmentation of stereoelectroencephalography (SEEG) electrodes post-implantation considering bending

The accurate and automatic localisation of SEEG electrodes is crucial for determining the location of epileptic seizure onset. We propose an algorithm for the automatic segmentation of electrode bolts and contacts that accounts for electrode bending in relation to regional brain anatomy. Co-registered post-implantation CT, pre-implantation MRI, and brain parcellation images are used to create regions of interest to automatically segment bolts and contacts. Contact search strategy is based on the direction of the bolt with distance and angle constraints, in addition to post-processing steps that assign remaining contacts and predict contact position. We measured the accuracy of contact position, bolt angle, and anatomical region at the tip of the electrode in 23 post-SEEG cases comprising two different surgical approaches when placing a guiding stylet close to and far from target point. Local and global bending are computed when modelling electrodes as elastic rods. Our approach executed on average in 36.17 s with a sensitivity of 98.81% and a positive predictive value (PPV) of 95.01%. Compared to manual segmentation, the position of contacts had a mean absolute error of 0.38 mm and the mean bolt angle difference of 0.59◦ resulted in a mean displacement error of 0.68 mm at the tip of the electrode. Anatomical regions at the tip of the electrode were in strong concordance with those selected manually by neurosurgeons, ICC(3, k) = 0.76, with average distance between regions of 0.82 mm when in disagreement. Our approach performed equally in two surgical approaches regardless of the amount of electrode bending. We present a method robust to electrode bending that can accurately segment contact positions and bolt orientation. The techniques presented in this paper will allow further characterisation of bending within different brain regions

Automatic segmentation of stereoelectroencephalography (SEEG) electrodes post-implantation considering bending

PURPOSE: The accurate and automatic localisation of SEEG electrodes is crucial for determining the location of epileptic seizure onset. We propose an algorithm for the automatic segmentation of electrode bolts and contacts that accounts for electrode bending in relation to regional brain anatomy. METHODS: Co-registered post-implantation CT, pre-implantation MRI, and brain parcellation images are used to create regions of interest to automatically segment bolts and contacts. Contact search strategy is based on the direction of the bolt with distance and angle constraints, in addition to post-processing steps that assign remaining contacts and predict contact position. We measured the accuracy of contact position, bolt angle, and anatomical region at the tip of the electrode in 23 post-SEEG cases comprising two different surgical approaches when placing a guiding stylet close to and far from target point. Local and global bending are computed when modelling electrodes as elastic rods. RESULTS: Our approach executed on average in 36.17 s with a sensitivity of 98.81% and a positive predictive value (PPV) of 95.01%. Compared to manual segmentation, the position of contacts had a mean absolute error of 0.38 mm and the mean bolt angle difference of [Formula: see text] resulted in a mean displacement error of 0.68 mm at the tip of the electrode. Anatomical regions at the tip of the electrode were in strong concordance with those selected manually by neurosurgeons, [Formula: see text], with average distance between regions of 0.82 mm when in disagreement. Our approach performed equally in two surgical approaches regardless of the amount of electrode bending. CONCLUSION: We present a method robust to electrode bending that can accurately segment contact positions and bolt orientation. The techniques presented in this paper will allow further characterisation of bending within different brain regions