Epilepsy with anterior temporal encephaloceles: Baseline characteristics, post-surgical outcomes, and comparison to mesial temporal sclerosis

OBJECTIVE

To review clinical and neuropsychological characteristics and natural history of a series of patients with temporal lobe epilepsy (TLE) and anterior temporal encephaloceles (ATE) and compare them to a similar series of TLE patients with mesial temporal sclerosis (MTS) to identify characteristics suggestive of ATE-related epilepsy.

METHODS

Patients with epilepsy and ATE were identified via clinic encounters and consensus epilepsy surgery conference at a Level 4 epilepsy center. The drug-resistant subset of these patients who underwent epilepsy surgery (twenty-two of thirty-five) were compared to age- and laterality-matched patients with MTS. Clinical, neuropsychological, electrophysiologic, and surgical data were abstracted through chart review.

RESULTS

In comparison with MTS, ATE patients were more often female, had significantly later onset of epilepsy, and did not have prior febrile seizures. In addition, ATE patients were more likely to have chronic headaches and other historical features consistent with idiopathic intracranial hypertension (IIH). Failure to identify ATE on initial imaging was common. Most patients had limited temporal cortical resections sparing mesial structures. Of the twenty ATE patients who had a long-term postsurgical follow-up, seventeen (85%) had International League Against Epilepsy (ILAE) Class 1 or 2 outcomes.

SIGNIFICANCE

A shorter duration of epilepsy, female gender, and lack of history of febrile seizures may suggest ATE as an etiology of refractory TLE in adults. Targeted encephalocele resections can result in seizure freedom, underscoring the importance of encephalocele identification.

Avoidance of Pitfalls and Complications During Surgery for Temporal Lobe Epilepsy

Anterior temporal lobectomy with amygdalohippocampectomy is the most common epilepsy surgery, which, in cases of mesial temporal lobe epilepsy caused by mesial temporal sclerosis, usually leads to improvements in seizure control, cognitive function, and quality of life. Nevertheless, while the primary goal of intervention is achieved in a large majority of patients, a small number of them, unfortunately, encounter complications. Some morbidity is nonspecific and may be noted after any craniotomy (e.g., surgical site infections, meningitis, bone flap osteomyelitis, and operative site or craniotomy-related hematomas). On the other hand, certain complications are specifically associated with surgery for temporal lobe epilepsy and can be discussed from the etiological standpoint: mechanical injuries of the brain; injury of eloquent neuronal structures; arterial and venous injuries; cerebral venous thrombosis; remote cerebellar hemorrhage; and postoperative hydrocephalus, seizures, and psychiatric disorders. In many cases, these complications are manifested in the early postoperative period by alterations of consciousness and a focal neurological deficit, and it may require immediate decisions on their appropriate management.

Apparent diffusion coefficient is associated with seizure outcome after magnetic resonance-guided laser interstitial thermal therapy for mesial temporal lobe epilepsy

BACKGROUND

Magnetic resonance-guided laser interstitial thermal therapy (MRgLiTT) is becoming a first-line surgical therapy for mesial temporal lobe epilepsy (mTLE) due to good seizure control and low complication risk. However, seizure outcomes after MRgLiTT remain highly variable and there is a need to improve patient selection and post-operative prognostication. In this retrospective study, we investigated whether the pre-operative MRI-derived apparent diffusion coefficient (ADC), used as a marker of tissue pathology in the mesial temporal structures could help predict seizure outcome.

METHODS

Thirty-five patients who underwent MRgLiTT at our institution between 2014 and 2019 were included in the study. Demographic and clinical data were retrospectively collected. Seizure outcome was defined as good (ILAE Class I-II) and poor (ILAE Class III-VI). Volumetrics were performed on pre-ablation hippocampus and amygdala. Ablation volumes, and the proportion of ablated hippocampus and amygdala calculated via their respective mean voxel-wise ADC intensities were quantified from pre-operative and intra-operative post-ablation MRIs and statistically compared between the two outcome cohorts. Univarate and multivariate regression analysis was performed to identify demographic, clinical, and radiographic predictors of seizure outcome.

RESULTS

Mean age at LiTT was 36 years and 14 (40 %) were female. Mean follow-up duration was 1.90 ± 0.17 years. Twenty-seven (77 %) patients had mesial temporal sclerosis. There was no significant difference in the ablation volumes and proportion of ablated volume of hippocampus and amygdala between the two outcome groups. Patients with good seizure outcome had significantly higher normalized ADC intensities in the ablated mesial temporal structures compared to those with poor outcome (0.01 ± 0.08 vs.-0.29 ± 0.06; p = 0.015).

CONCLUSIONS

mTLE patients with higher ADC intensities in the ablated regions of the hippocampus and the amygdala are more likely to have good seizure outcome following MRgLiTT. Our results suggest that pre-operative ADC analysis may improve both patient selection and epileptogenic zone targeting during MRgLiTT. Further investigation with large, prospective cohorts is needed to validate the clinical utility of ADC in improving seizure outcome following MRgLiTT.

Neuroimaging in pediatric temporal lobe epilepsy: Does neuroimaging accurately predict pathology and surgical outcome?

Temporal lobe epilepsy (TLE) in children is considered different from that in adults. As such, characterizing the structural lesions present in pediatric patients with TLE and their association with long-term seizure control is important. Here, we aimed to assess the concordance between preoperative imaging and postoperative histopathological diagnoses and their associations with seizure outcomes in pediatric patients with TLE undergoing temporal lobe surgery. We retrospectively reviewed the charts of pediatric patients with TLE who underwent surgical treatment between 1988 and 2020 as a part of the Comprehensive Epilepsy Program at the University of Alberta. Demographic, age at seizure onset, age at surgery, preoperative electroencephalography (EEG), long-term video EEG, imaging (magnetic resonance imaging [MRI] and computed tomography), neuropathology, and long-term seizure outcome data were acquired and analyzed. One hundred and seventeen patients underwent surgery for refractory TLE; the preoperative MRI diagnosis was concordant with the histopathological diagnosis in 76 % of cases. Tumors were identified with high accuracy (91 %). Mesial temporal sclerosis (MTS) was strongly associated with an excellent outcome after surgery (94 %). Patients with normal imaging results or non-specific pathologies were more likely to experience poor seizure outcomes after surgery (50 %). The radiological identification of lesions was associated with good long-term seizure outcomes, whereas normal MRI results were associated with significantly poorer long-term seizure outcomes. An accurate preoperative MRI is essential to epilepsy surgery since it impacts all stages of management; these results will thereafter help inform practitioners' efforts to predict seizure outcome.

Usefulness of magnetic resonance spectroscopy in mesial temporal sclerosis: a systematic review

BACKGROUND

Magnetic resonance spectroscopy (MRS) provides non-invasive information about metabolic features in different regions of the brain affected by mesial temporal sclerosis (MTS).

PURPOSE

To review articles analyzing the most common alterations in biochemical parameters in MTS and the applications of MRS in presurgical assessment.

METHODS

We undertook a systematic literature search for MRS in MTS in PubMed, SCOPUS, and Cochrane based on the MESH terms ""Magnetic Resonance Spectroscopy", "Proton Magnetic Resonance Spectroscopy", "Carbon-13 Magnetic Resonance Spectroscopy", "1H-MRS", "31P-MRS", "mesial temporal sclerosis", "hippocampal sclerosis", "mesial temporal seizure", and "mesial temporal epilepsy".

RESULTS

Of the initial 134 articles found, 30 were selected after the exclusion process. Of these, 13 detected a decrease in N-acetylaspartate (NAA), 9 showed a decreased in the ratio NAA/Cho+Cr, and 8 demonstrated a decreased in the ratio NAA/Cr, all of them in the ipsilateral hippocampus. Nine studies also found reduced NAA levels in extrahippocampal regions.

CONCLUSIONS

The main findings were a decrease in NAA in the ipsilateral hippocampus. In addition, NAA levels were low outside the hippocampus so MTS could be a more extensive disease. Patients without MTS also presented a decrease in NAA in the ipsilateral hippocampus although NAA was even lower in the MTS patients. Thus, MRS could be useful in the presurgical evaluation to locate the epileptogenic focus, but not specific for the diagnosis of MTS.

Lateralizing magnetic resonance imaging findings in mesial temporal sclerosis and correlation with seizure and neurocognitive outcome after temporal lobectomy

BACKGROUND

Mesial temporal sclerosis (MTS) is the most common cause of temporal lobe epilepsy (TLE). While MTS is associated with a high cure rate after temporal lobectomy (TL), postoperative neurocognitive deficits are common, and a subset of patients may continue to have refractory seizures.

OBJECTIVE

To use magnetic resonance (MR) volumetry to identify features of the mesial temporal lobe in patients with MTS that correlate with seizure and neurocognitive outcome after temporal lobectomy.

METHODS

Thirty-five patients with unilateral MTS, high-resolution MR imaging, and at least one year of postoperative assessments were retrospectively examined. Volumetric analysis of the hippocampus, parahippocampal gyrus (PHG) and FLAIR hyperintensity of the affected temporal lobe was performed. TL resections were manually segmented, and resection heat maps reflecting seizure outcome were produced. The degree of preoperative atrophy of the affected mesial structures relative to the unaffected side were related to preoperative and postoperative component scores of verbal and visuospatial memory as well as confrontation naming.

RESULTS

Greater FLAIR hyperintense volume was associated with favorable seizure outcome at one year and last follow-up. Resections extending most medial and posteriorly were associated with favorable seizure outcome. In patients with left MTS, less atrophy of the affected PHG was predictive of higher preoperative naming scores and greater postoperative naming deficit, while less hippocampal atrophy was predictive of higher preoperative verbal memory component scores.

CONCLUSION

Greater hippocampal FLAIR volume is associated with favorable surgical outcome. Hippocampal volume correlates with preoperative verbal memory, while PHG volume is implicated in confrontation naming ability.

Magnetic Resonance Imaging-Guided Laser Interstitial Thermal Therapy for Epilepsy: Systematic Review of Technique, Indications, and Outcomes

BACKGROUND

For patients with focal drug-resistant epilepsy (DRE), surgical resection of the epileptogenic zone (EZ) may offer seizure freedom and benefits for quality of life. Yet, concerns remain regarding invasiveness, morbidity, and neurocognitive side effects. Magnetic resonance-guided laser interstitial thermal therapy (MRgLITT) has emerged as a less invasive option for stereotactic ablation rather than resection of the EZ.

OBJECTIVE

To provide an introduction to MRgLITT for epilepsy, including historical development, surgical technique, and role in therapy.

METHODS

The development of MRgLITT is briefly recounted. A systematic review identified reported techniques and indication-specific outcomes of MRgLITT for DRE in human studies regardless of sample size or follow-up duration. Potential advantages and disadvantages compared to available alternatives for each indication are assessed in an unstructured review.

RESULTS

Techniques and outcomes are reported for mesial temporal lobe epilepsy, hypothalamic hamartoma, focal cortical dysplasia, nonlesional epilepsy, tuberous sclerosis, periventricular nodular heterotopia, cerebral cavernous malformations, poststroke epilepsy, temporal encephalocele, and corpus callosotomy.

CONCLUSION

MRgLITT offers access to foci virtually anywhere in the brain with minimal disruption of the overlying cortex and white matter, promising fewer neurological side effects and less surgical morbidity and pain. Compared to other ablative techniques, MRgLITT offers immediate, discrete lesions with real-time monitoring of temperature beyond the fiber tip for damage estimates and off-target injury prevention. Applications of MRgLITT for epilepsy are growing rapidly and, although more evidence of safety and efficacy is needed, there are potential advantages for some patients.

Evaluation of patients with late-onset and medically refractory temporal lobe epilepsy with mesial temporal sclerosis

OBJECTIVES

Our study aims to compare demographics, clinical features and postsurgical outcomes between early and late-onset patients with medically refractory temporal lobe epilepsy (TLE) related to mesial temporal sclerosis (MTS).

PATIENTS AND METHODS

Seventy-one patients admitting to the Epilepsy Clinic of Istanbul University-Cerrahpasa, Cerrahpasa Faculty of Medicine between 1995-2015, who were diagnosed with refractory TLE related to MTS, were included in our study. All of these patients were resistant to medical treatment, and thus candidates for, or underwent surgery, and had no pathology other than MTS in their cranial magnetic resonance imaging (MRI). Based on previous studies, those patients were divided into two categories as "early-onset" and "late-onset", according to the age-onset of afebrile recurrent seizures, where the cutoff was determined as 20 years. Demographics, clinical features, and postsurgical outcomes were compared between both groups.

RESULTS

Fifty-three patients included in our study had early-onset MTS-TLE, and 18 patients had late-onset MTS-TLE. Demographics, clinical features, characteristics of electroencephalography (EEG), MRI, PET MRI/CT, neuropsychometric test (NPT) and postsurgical outcomes were similar in both groups.

CONCLUSION

In both the early-onset and late-onset groups, the presence of similar demographics, clinical features, and postoperative outcomes have suggested that the course of the disease and the success of surgical treatment were not associated with the age-onset of seizures in TLE related to MTS.

Prediction of Memory Impairment in Epilepsy Surgery by White Matter Diffusion

OBJECTIVE

To analyze the relationship between cognitive performance and white matter integrity in patients with temporal lobe epilepsy (TLE) to establish radiologic criteria to help with patient selection for surgery.

METHODS

The study included 19 adults with temporal lobe epilepsy. A tractography analysis of fractional anisotropy and mean diffusivity (MD) of the following fascicles was performed: arcuate fascicle, cingulum, fornix, inferior fronto-occipital fascicle, inferior longitudinal fascicle, parahippocampal fibers of the cingulum, and uncinate fascicle. The Wechsler Memory Scale-Third Edition neuropsychological test was performed to evaluate short- and long-term verbal (Logical Memory I and II subtests) and nonverbal (Visual Reproduction I and II subtests) memory. Relationships between memory scores and diffusion were calculated.

RESULTS

Lower Logical Memory I subtest scores were correlated with lower MD of the right inferior fronto-occipital fascicle, while lower Logical Memory II subtest scores were related to higher values of fractional anisotropy in bilateral cingulum, right uncinate, and right parahippocampal fibers of the cingulum and lower MD in left cingulum fascicle. Finally, lower values in Visual Reproduction I subtest scores were associated with lower values in MD in right cingulum and inferior fronto-occipital fascicles.

CONCLUSIONS

Structural changes of some white matter tracts were associated with deterioration of both short- and long-term memory. These alterations were more associated with verbal memory than with nonverbal memory. These changes mainly consist of an increase in fractional anisotropy and a decrease in MD, which could be interpreted as reorganization phenomena. Diffusion tensor imaging could be a useful tool for cognitive assessment in surgical candidates with temporal lobe epilepsy who are not suitable for neuropsychological testing or in whom their results do not lead to definitive conclusions.

Zygomatic-Meatal Perpendicular Projection Lines: Bony Landmarks for Early Identification of the Temporal Horn of the Lateral Ventricle

OBJECTIVE

Localization of the temporal horn of the lateral ventricle (TH) may be required during temporal lobe and ambient cistern surgery. Most available anatomic landmarks for TH localization are based on adjacent cortical landmarks that are inherently variable or subtle. This study aimed to localize the anterior tip of the TH relative to adjacent bony landmarks.

METHODS

The TH was exposed on 21 sides of 11 cadaveric heads via removal of the middle temporal gyrus. Two lines were defined: (1) a perpendicular line to the zygomatic arch projected from the anterior concavity of the posterior zygomatic root (line A), and (2) a parallel line passing through the anterosuperior corner of the external auditory canal (line B). Sagittal distances from lines A and B to a parallel line passing through the anterior recess of the TH (line H) were measured.

RESULTS

Mean (standard deviation) distances from lines A and B to line H were 13.3 (2.5) mm and 11.9 (2.2) mm, respectively. Line H was at 53% (8%) of the line A-line B interval measured from line A. The best way to search for the TH was to start approximately 15 mm posterior to line A and progress posteriorly such that a more posteriorly located TH tip would not be missed.

CONCLUSIONS

The zygomatic-meatal landmark is a reliable tool to localize TH during various approaches. It is independent from the approach trajectory. This landmark may be used as an ancillary tool in conjunction with other cortical landmarks and image guidance.

An image processing algorithm to aid diagnosis of mesial temporal sclerosis in children: a case-control study

BACKGROUND

Mesial temporal sclerosis (MTS) is an important cause of intractable epilepsy. Early and accurate diagnosis of MTS is essential to providing curative and life-changing therapy but can be challenging in children in whom the impact of diagnosis is particularly high. Magnetic resonance imaging (MRI) plays an important role in the diagnosis of MTS, and image processing of MRI is a recently studied strategy to improve its accuracy.

OBJECTIVE

In a retrospective case-control study, we assessed the performance of an image processing algorithm (Correlative Image Enhancement [CIE]) for detecting MTS-related hippocampal signal abnormality in children.

MATERIALS AND METHODS

Twenty-seven pediatric MTS cases (9 males, 18 females; mean age: 16±standard deviation [SD] 6.7 years) were identified from a pathology database of amygdylo-hippocampectomies performed in children with epilepsy. Twenty-seven children with no seizure history (9 males, 18 females; mean age: 13.8±SD 2.8 years), and with normal brain MRI, were identified for the control group. Blinded investigators processed the MRI coronal FLAIR (fluid-attenuated inversion recovery) images with CIE, saved the processed images as a separate series, and made equivalent region of interest measurements on the processed and unprocessed series to calculate contrast-to-noise ratio. Six blinded reviewers then rated the randomized series for hippocampal signal abnormality and MTS disease status.

RESULTS

CIE increased signal intensity and contrast-to-noise ratio in 26/27 hippocampi with pathologically confirmed MTS (96.3%) with the mean (SD) contrast-to-noise ratio of cases increasing from 14.9 (11.1) to 77.7 (58.7) after processing (P<0.001). Contrast-to-noise ratio increased in 1/54 normal control hippocampi (1.9%), with no significant change in the mean contrast-to-noise ratio of the control group after processing (P=0.57). Mean (SD) reader sensitivity for detecting abnormal signal intensity increased from 83.3% (14.2) to 94.8% (3.3) after processing. Mean specificity for abnormal signal intensity increased from 94.4% (7.3) to 96.3% (0). While sensitivity improved after processing for detection of MTS disease status in 4/6 readers, the mean reader sensitivity and specificity for MTS detection increased only minimally after processing, from 79.6% to 80.7% and from 95.7% to 96.3%, respectively.

CONCLUSION

The CIE image processing algorithm selectively increased the contrast-to-noise ratio of hippocampi affected by MTS, improved reader performance in detecting MTS-related hippocampal signal abnormality and could have high impact on pediatric patients undergoing work-up for seizures.

Probing circuit of Papez with stimulation of anterior nucleus of the thalamus and hippocampal evoked potentials

PURPOSE

Despite documented clinical effectiveness, deep brain stimulation (DBS) therapy for drug-resistant epilepsy rarely yields long-term seizure free outcomes.

METHODS

This pilot study in five patients investigated circuit of Papez evoked potentials (EPs) using hippocampal sensing during anterior nucleus of the thalamus (ANT) electrical stimulation. We hypothesize that hippocampal EP is a potential biomarker that could be useful for ANT electrode targeting and improving seizure reduction. We obtained bilateral circuit of Papez EPs in five patients with bilateral temporal lobe epilepsy (TLE). The circuit of Papez EPs were measured and assessed by signal amplitude. Volumetric analysis of relevant mesial temporal structures and ANT stimulation analysis was performed on immediate post-implantation images.

RESULTS

The patient with the most favorable seizure outcome, which meant long-term seizure reduction greater than 50 % compared to baseline, had strong bilateral EPs and normal hippocampal structure. Conversely, those without clinical benefit with ANT DBS had absent or weak bilateral EPs as well as MRI findings consistent with mesial temporal sclerosis (MTS).

CONCLUSION

The data support the hypothesis that hippocampal EPs with ANT stimulation may be used to as a surrogate marker to probe circuit of Papez and predict ANT DBS efficacy.

Are psychogenic nonepileptic seizures risk factors for a worse outcome in patients with refractory mesial temporal epilepsy submitted to surgery? Results of a retrospective cohort study

OBJECTIVE

The objective of this study was to verify if the presence of psychogenic nonepileptic seizures (PNES) could be a risk factor precluding corticoamygdalohippocampectomy (CAH) in patients with refractory temporal lobe epilepsy (TLE) and mesial temporal sclerosis (MTS) (TLE-MTS).

METHODS

This retrospective cohort study analyzed medical data of patients with refractory TLE-MTS accompanied in a Brazilian epilepsy surgery center. Presurgical psychiatric evaluations were performed using the Diagnostic and Statistical Manual of Mental Disorders (DSM-5) criteria. Engel's I classification two years after surgery was considered as a favorable outcome.

RESULTS

Of the 81 patients initially included (65 females; 56.5%), 49 (60.5%) had TLE-MTS without PNES, 24 (29.7%) with TLE-MTS and PNES, and eight (9.8%) with PNES only, who were excluded from further statistical comparisons. Nine patients with PNES (37.5%) underwent CAH versus 35 (71.4%) without PNES (p = 0.005). Five patients (55.5%) with PNES versus 26 (74.3%) without PNES presented Engel I (p = 0.54). The relative risk (RR) was of 1.90 for patients without PNES to undergo CAH and of 1.33 to be at Engel I.

CONCLUSIONS

In this study, PNES were associated with less CAH. There were no differences, however, regarding favorable postsurgical outcomes. These results highlight that the sole presence of PNES should not preclude CAH in patients with TLE-MTS, despite the necessity of careful presurgical psychiatric evaluation.

Evaluation of dual pathology among drug-resistant epileptic patients with hippocampal sclerosis

PURPOSE

Dual pathology (DP) is defined as simultaneous presence of hippocampal sclerosis (HS) and any other pathology in the brain. Since this is a less probed concept, we aimed to evaluate the frequency and characteristics of DP among drug-resistant epileptic patients with HS.

METHODS

This is a cross-sectional study conducted during 2007-2016 in Kashani Comprehensive Epilepsy Center, Isfahan, Iran. Patients with diagnosis of drug-resistant epilepsy and HS were enrolled in the study, and demographic data, seizure semiology, EEG findings, and MRI findings were collected. We compared these variables between three groups of DP, unilateral HS, and bilateral HS.

RESULTS

Of the 200 enrolled cases, 29 patients (14.5%) had DP and 21 patients (10.5%) had bilateral HS; the remaining patients had unilateral HS. The average age of patients with DP was 30.03, and 65.5% of them were male. Patients with DP had more EEG discharges from regional and multi-focal sites compared to unilateral HS (P value < 0.001). Also, complex partial seizure (CPS) was more commonly presented in patients with unilateral HS (96.8%). Comparison of disease characteristics between DP and bilateral HS showed no difference in most categories (P > 0.05).

CONCLUSIONS

We found DP among 14.5% of our drug-resistant epileptic patients with HS. DP patients mostly presented with CPS and had high proportion of ictal and interictal EEG discharges from regional and multi-focal areas. Gliosis and focal cortical dysplasia were the most common pathologies among DP patients. Patients with DP showed a similar behavior to bilateral HS in many features.

Widespread white matter DTI alterations in mesial temporal sclerosis independent of disease side

PURPOSE

The aim of this study was to evaluate white matter (WM) integrity in vivo in patients with unilateral mesial temporal sclerosis (MTS).

METHODS

Diffusion tensor imaging (DTI) findings from patients with left-sided MTS (L-MTS; N = 14) and right-sided MTS (R-MTS; N = 13), all taking antiepileptic medication, were compared with those from gender- and age-matched controls; DTI was performed along 30 noncollinear directions in a 1.5-T scanner. Tract-based spatial statistics (TBSS) analysis was performed by creating a WM skeleton; 5000-permutation-based inference (threshold, p < 0.05) was used to identify fractional anisotropy (FA) abnormalities. Mean (MD), radial (RD), and axial diffusivities (AD) were projected onto the mean FA skeleton.

RESULTS

Compared with the control groups, patients with MTS had decreased FA affecting widespread WM tracts as well as extensive areas with increased RD, bilaterally and independent of the disease side. Areas with decreased FA and increased RD overlapped substantially. There were no significant differences in DTI parameters between L-MTS and R-MTS patients.

CONCLUSION

Diffusion tensor imaging abnormalities were observed within and beyond the temporal lobe in patients with MTS. Patients with R- and L-MTS had extensive bilateral abnormalities in comparison to controls. These findings suggest that MTS pathobiology involves diffuse dysfunction of WM tracts, even in areas with no direct connections to the hippocampus.

Enhancing contrast to noise ratio of hippocampi affected with mesial temporal sclerosis: A case-control study in children undergoing epilepsy surgeries

OBJECTIVE

Detection of mesial temporal sclerosis (MTS) in children with epilepsy is important. We assessed whether an image-processing algorithm (Correlative Image Enhancement, CIE) could facilitate recognition of hippocampal signal abnormality in the presence of MTS by increasing contrast to noise ratio between affected hippocampus and normal gray matter.

PATIENTS AND METHODS

Baseline coronal FLAIR images from brain MRIs of 27 children with epilepsy who underwent hippocampal resection were processed using CIE. These included 19 hippocampi with biopsy proven MTS and 8 biopsy proven normal hippocampi resected in conjunction with hemispherotomy. We assessed the effect of processing on contrast to noise ratio (CNR) between hippocampus and normal insular gray matter, and on assessment of hippocampal signal abnormality by two masked neuroradiologists.

RESULTS

Processing resulted in a significant increase in mean CNR (from 3.9 ± 5.3 to 25.3 ± 25.8; P < 0.01) for hippocampi with MTS, with a substantial (>100%) increase from baseline seen in 15/19 (78.9%) cases. Baseline CNR of 1.7 ± 5.3 for normal hippocampi did not change significantly after processing (1.8 ± 5.3; P = 1.00). For one reader, baseline sensitivity (14/19; 73.6%) was unaffected but the specificity improved from 62.5% (5/8) to 100%. An increase in both sensitivity (from 73.6% to 78.9%) and specificity (from 62.5% to 75%) was seen for the second reader.

CONCLUSION

By enhancing CNR for diseased hippocampi while leaving normal hippocampi relatively unaffected, CIE may improve the diagnostic accuracies of radiologists in detecting MTS-related signal alteration within the affected hippocampus.

Anxiety is common and independently associated with clinical features of epilepsy

OBJECTIVE

The objective of this study was to assess for independent association of anxiety symptoms with epilepsy localization and other epilepsy-related and demographic factors in a large tertiary care adult epilepsy population.

METHODS

Among 540 adults, anxiety was measured by the Symptom Checklist 90-R (SCL-90R) anxiety subscale, and detailed demographics, epilepsy localization, and depression scores (SCL-90R) were collected. High anxiety was defined by SCL-90R anxiety T-score ≥ 60. Stepwise multiple logistic regression was carried out to assess for independent association of high anxiety scores with demographic and clinical factors.

RESULTS

High anxiety symptoms were present in 46.1% of participants (N = 250). Focal or unknown epilepsy type and depression scores were independently associated with high anxiety (adjusted odds ratios (OR): 2.89 (95% confidence interval [CI] = 1.33-6.29, p = 0.007) and 2.12 (95% CI = 1.83-2.45, p < 0.001), respectively; depression odds per 5-point increase in scale). Among the focal epilepsy subpopulation, mesial temporal sclerosis was also independently associated with high anxiety, with adjusted OR: 2.12 (95% CI = 1.11-4.04, p = 0.023). Lower education, non-white race/ethnicity, Spanish native language, prior head trauma, antiseizure drug polytherapy, and left focus or bilateral foci (in focal epilepsy) were associated with high anxiety in simple logistic regression, but these associations were not independent. A total of 46 individuals (18.4% of those with high anxiety) scored high for anxiety but not depression. Only 26% of those with high anxiety symptoms were taking a potentially anxiolytic medication.

CONCLUSION

Anxiety symptoms, often without concomitant depression, were highly prevalent in this epilepsy sample and independently associated with focal/unknown epilepsy and mesial temporal sclerosis. These results strongly support the value of screening specifically for anxiety in the epilepsy clinic, to direct patients to appropriate treatment.

Urea cycle disorder presenting as bilateral mesial temporal sclerosis - an unusual cause of seizures: a case report and review of the literature

BACKGROUND

Urea cycle disorders are secondary to defects in the system converting ammonia into urea, causing accumulation of ammonia and other byproducts which are neurotoxic. Ornithine transcarbamylase deficiency is the most common of the urea cycle disorders and frequently presents with coma or seizures during hyperammonemia. However, seizures can also occur without metabolic decompensation.

CASE PRESENTATION

We describe a 23-year-old Chinese woman with urea cycle disorder who presented with confusion due to focal seizures arising from the left frontotemporal region. Interestingly, her ammonia levels remained normal during the seizures. Neuroimaging showed bilateral mesial temporal sclerosis. Her seizures were successfully controlled with two anti-epileptic medications.

CONCLUSIONS

This case adds evidence of the predisposition of the temporal lobe to injury in urea cycle disorder. Urea cycle disorder can lead to mesial temporal sclerosis which leads to increased susceptibility of patients to seizures regardless of their metabolic state.

Drug-resistant epilepsy development following stem cell transplant and cyclosporine neurotoxicity induced seizures: Case report in an adult and analysis of reported cases in the literature

Introduction

Drug-resistant epilepsy (DRE) occurs in 20–30% of all patients who develop epilepsy and can occur from diverse causes. Cyclosporine-A (CSA) is an immunosuppressive drug utilized to prevent graft-versus-host disease (GvHD) in transplant patients and is known to cause neurotoxicity, including seizures. In some cases, however, patients can develop DRE. Only a limited number of cases have been reported in which DRE has developed after CSA exposure — all in children. Here we present a rare case of an adult developing DRE after post-transplant CSA neurotoxicity. In addition, we provide a comprehensive review and analysis of all reported cases in the literature.

Case report

A 29-year-old man with Non-Hodgkin's Lymphoma underwent an allogenic hematopoietic stem cell transplant and experienced a CSA-induced seizure at 7.5 months' post-transplant. The patient was discontinued on CSA and began a low dose tacrolimus regimen. At 33 months' post-transplant, he had seizure recurrence and developed DRE. Imaging revealed right mesial temporal sclerosis (MTS) and video EEG localized ictal activity to the right anterior temporal lobe. He was successfully treated with a right anterior temporal lobectomy and amygdalohippocampectomy.

Literature review

Seven peer-reviewed studies described 15 patients who underwent transplantation with post-transplant CSA administration and subsequently developed DRE following an initial CSA-induced seizure. All 15 patients were children suggesting that young age is a risk factor for DRE after CSA-induced seizures. Initial CSA-induced seizures occurred at an average of 1.6 ± 1.1 months after transplant and seizure recurrence 9.2 ± 8.0 months after transplant. All reported CSA routes of administration (n = 6) were intravenous and 7 of 9 (78%) reported CSA blood levels above the therapeutic range. The incidence of MTS (40%) in these 15 patients was significantly higher than the incidence in the general DRE population (24%) and was most effectively treated via epilepsy surgery.

Conclusions

The use of cyclosporine for GvHD prophylaxis and treatment following transplantation may cause seizures and be associated with DRE. Although discontinuation and dose decrease of CSA often reverse adverse neurological events, initial CSA-induced seizures may be associated with MTS that and subsequent greater risk of DRE development.

Prognostic significance of postoperative spikes varied in different surgical procedures for mesial temporal sclerosis

PURPOSE

We conducted this study to compare the occurrence and prognostic significance of early postoperative interictal epileptiform discharges (IEDs) on seizure outcomes between corticoamygdalohippocampectomy (CAH) and selective amygdalohippocampectomy (SAH).

METHODS

We reviewed our database of patients who had epilepsy surgery with hippocampus atrophy or signal changes on brain MRIs and pathology of mesial temporal sclerosis. One hundred and seventy-seven CAH and 39 SAH patients were enrolled. Postoperative EEG within 30days, other preoperative variables and seizure outcome 2years after surgery were obtained for analysis. Engel's IA and IB were defined as seizure-free.

RESULTS

There was no significant difference in the seizure-free rate between the two procedures (127 (71.8%) of CAH vs 30 (76.9%) of SAH, p=0.51). Postoperative IEDs were more frequently seen in the SAH group (64.1%) than in the CAH group (29.9%), p<0.001. The IEDs in the SAH group did not show correlation with the seizure outcome 2 years after surgery. In the CAH group, patients who had no postoperative IEDs showed a higher seizure-free rate compared to those with IEDs (78.2% vs 56.6%, p=0.003; OR 2.267, 95% CI 1.09-4.73, p=0.029 in multivariate logistic regression).

CONCLUSIONS

Early postoperative IEDs are more frequently seen in SAH than in CAH. Unlike in patients with CAH, the presence of IEDs after SAH was not a predictor of seizure recurrence. The type of surgery should be considered while utilizing postoperative IEDs for evaluating the prognosis.

Epilepsy in neurofibromatosis type 1

OBJECTIVES

To describe the characteristics of epilepsy in patients with Neurofibromatosis type 1 (NF1).

METHODS

Analysis of a cohort of consecutive NF1 patients seen in our NF1 clinic during a three-year period.

RESULTS

Of the 184 NF1 patients seen during that period, 26 had epilepsy and three had febrile seizures. Of the 26, 17 (65%) had localization-related epilepsy, seven of whom (41%) were drug resistant. Six (23%) had apparently primary generalized epilepsy (0/6 drug resistant), two (8%) Lennox-Gastaut syndrome, and one (4%) West syndrome (all three were drug-resistant). As compared to the patients with no epilepsy, those with epilepsy were more likely to have MRI findings of mesial temporal sclerosis (MTS) (23% vs. 5%, p=0.0064), and cerebral hemisphere tumors (31% vs. 10%, p=0.0079), but not of the other MRI findings including neurofibromatosis bright objects, or optic gliomas. Three of the six patients with MTS underwent temporal lobectomy with subsequent control of their seizures with confirmation of MTS on pathology in 3/3 and presence of coexisting focal cortical dysplasia (FCD) in 2/3. We also have observed three additional patients outside the above study with the association of NF1, MTS, and intractable epilepsy.

SIGNIFICANCE

Epilepsy is relatively common in NF1, often occurs in patients with brain tumors or with MTS which can coexist with FCD, can be associated with multiple types of epilepsy syndromes, and when localization-related is often drug-resistant. Patients with NF1 and MTS can respond to medial temporal lobectomy and may have coexisting medial temporal lobe cortical dysplasia.

Epileptologist's view: Laser interstitial thermal ablation for treatment of temporal lobe epilepsy

A procedure called laser interstitial thermal ablation has been utilized to treat drug resistant epilepsy. With this technique, a probe is stereotactically inserted into a target structure responsible for seizures, such as mesial temporal lobe, hypothalamic hamartoma, or a small malformation of cortical development, and the tip is then heated by application of laser energy to ablate structures adjacent to the probe tip. This procedure has the advantage of selectively targeting small lesions responsible for seizures, and is far less invasive than open surgery with shorter hospitalization, less pain, and rapid return to normal activities. Initial results in mesial temporal lobe epilepsy are promising, with perhaps half of patients becoming free of seizures after the procedure. Neuropsychological deficits appear to be reduced because of the smaller volume of ablated cortex in contrast to large resections. More research must be done to establish optimal targeting of structures for ablation and selection of candidates for surgery, and more patients must be studied to better establish efficacy and adverse effect rates.

Surgical outcome in adolescents with mesial temporal sclerosis: Is it different?

There are extensive studies evaluating mesial temporal sclerosis (MTS) in adults and limited studies in children, with adolescents being included within both patient populations. Our aim was to evaluate predictors of surgical outcome solely in adolescent patients with MRI- and pathology -proven MTS. The Yale Epilepsy Surgery Database was reviewed from 1987 to 2012 for adolescent patients with confirmed MTS on MRI and pathology who underwent temporal lobectomy and had greater than two-year postsurgical follow-up. Clinical and electrographic data were reviewed. Eighteen patients were identified. Eleven patients (61%) were seizure-free. All seven patients (39%) who were not seizure-free free were found to have lateralized ictal onset within one hemisphere involving two or more lobes on scalp EEG (p<0.001). Of the 7 patients who were not seizure-free, 4 had a history of status epilepticus (compared to 1/11 seizure-free patients; p=0.047), and 4 had lateralized hypometabolism involving two or more lobes within a hemisphere seen on PET (compared to 0/8 seizure-free patients; p=0.002). A novel finding in our study was that lateralized (rather than localized) ictal onset on scalp EEG, lateralized hypometabolism on PET, and history of status epilepticus were risk factors for not attaining seizure freedom in adolescents with MTS who underwent temporal lobectomy.

Incomplete Circle of Willis: A risk factor for mesial temporal sclerosis?

OBJECTIVE

The aim of this study was to investigate whether there may be a correlation between the anatomical variants of Circle of Willis (CoW) and presence/laterality of mesial temporal sclerosis (MTS).

METHODS

We retrospectively identified the CoW variants on Wada angiograms in 71 patients with pathologically proven MTS. Angiograms were interpreted by two radiologists independently and blinded to clinical data. We divided the anterior and posterior components of the CoW into functionally complete and functionally incomplete groups. We then sought its correlation with the presence and laterality of MTS.

RESULTS

No statistically significant relationship was found between the functional status of the anterior circulation and the laterality of the MTS (p=0.657). Relationship of the posterior incomplete circle to MTS was statistically significant on both sides (p=0.023 for the left, p=0.04 for the right), with an effect size moderate to large for the left side and moderate for the right side. Although the fetal variant appeared to be related to the ipsilateral MTS, it did not reach to a level of statistical significance (p=0.15).

SIGNIFICANCE

The study demonstrates a statistically significant association of the incomplete posterior circulation of the CoW to the presence of ipsilateral MTS. Further studies in larger patient populations may be needed to seek whether an incomplete circulation may facilitate development of MTS, especially affecting the watershed zones.

Factors predicting the outcome following surgical treatment of mesial temporal epilepsy due to mesial temporal sclerosis

BACKGROUND

Mesial temporal sclerosis (MTS) is the most common disease found in an epilepsy surgery series. Early age of onset, a history of febrile convulsions, epileptiform discharges on EEG, duration of epilepsy, number of generalized seizures and severity of psychiatric disorders are possible prognostic factors in patients with MTS.

OBJECTIVE

The aim of this study is to review the clinical, semiotic, psychological, electrophysiological and neuroradiological researches and relate their findings to the prognosis of patients with MTS who underwent anteromedial temporal lobectomy (ATL).

METHODS

Of 1,214 patients evaluated for surgery in the epilepsy Center of Faculdade de Medicina de São Jose do Rio Preto (FAMERP), a tertiary Brazilian epilepsy center, 400 underwent ATL for MTS. Examinations and clinical data were analyzed and compared with the Engel Outcome Classification.

RESULTS

Of all the items analyzed, the MRI showed the greatest influence on patient outcome. As for the clinical evaluation and pathological antecedents, age at surgery, epilepsy duration, perinatal insults, family history of epilepsy, febrile seizures, neuropsychological abnormalities and presence of generalized tonic-clonic seizure all had statistical significance.

CONCLUSION

In order to identify the most appropriate candidates for ATL, it is very important to consider the prognostic factors associated with a favorable outcome for counseling patients in daily practice.

Benign mesial temporal lobe epilepsy: A clinical cohort and literature review

OBJECTIVE

We present a single-center retrospective study of benign mesial temporal lobe epilepsy (bMTLE) between 1995 and 2014.

METHODS

Hospital records and clinic charts were reviewed. The clinical, Eelectroencephalographic (EEG), imaging features, and response to treatment with antiepileptic drugs (AEDs) were documented. Patients were included in this study if they were seizure-free for a minimum of 24months with or without an AED.

RESULTS

Twenty-seven patients were identified. There were 19 (70%) females, mean age at first seizure was 32.2 (range: 15-80years). In all patients, seizures were mild, and seizure freedom was readily achieved with the initiation of AED therapy. Sixteen patients (59%) had mesial temporal sclerosis (MTS). In three patients, we attempted to discontinue AED therapy after a prolonged period of remission (5-8years), but all had seizure recurrence within 2 to 4weeks.

SIGNIFICANCE

Not all temporal lobe epilepsy is refractory to medication, despite the presence of MTS. Until clinical trials indicate otherwise, surgery is not indicated but life-long medical treatment is advocated.

Anterior temporal lobectomy for older adults with mesial temporal sclerosis

OBJECTIVE

To compare postoperative seizure-free survival between older and younger adults.

METHODS

A retrospective cohort of 107 temporal lobe epilepsy patients with a diagnosis of mesial temporal sclerosis (MTS) received anterior temporal lobectomy (ATL) between 1993 and 2014. We divided the lower three quartiles (younger) and top quartile (older, all 47+ years) of patients, then reviewed patient registry and electronic medical records to determine time to first self-reported seizure after ATL, the primary outcome (mean=3.5years of follow-up, SD=3.6). We also assessed Engel classifications, intraoperative and postoperative treatment complications, and social disability. We used Cox proportional hazard models to assess the association between individual traits and time of seizure recurrence.

RESULTS

During follow-up, 35/107 (32.7%) patients had post-operative seizure(s). After adjustment for potential confounders there were no significant differences in the probability of post-operative seizures between the older and younger groups, though we had limited precision (hazard ratio of 0.67 [0.28-1.59]), (p=0.36). There were more treatment complications and disability in older patients (18% vs. 1.3% for any complications, 84.62% vs. 58.23% for driving disability, and 84.6% vs. 60.7% for work disability, p<0.05).

CONCLUSION

Older patients appear to have more complications after ATL, compared with younger patients. Age, however, does not appear to have a large independent association with seizure recurrence.

Usefulness of repeat review of head magnetic resonance images during presurgical epilepsy conferences

Surgical epilepsy conferences are an important part of the process of determining whether a patient is a candidate for resective epilepsy surgery. At these conferences, repeat review (re-review) of the magnetic resonance images (MRIs) of the patient's head often occurs. This study assessed how often radiologic re-review at a presurgical epilepsy conference resulted in a changed interpretation of the head MRI. Charts were reviewed for 239 patients who had been presented at presurgical epilepsy conferences between 2008 and 2012. Of the 233 patients whose MRIs were re-reviewed, resective surgery was performed in 94 patients (40.3%). Forty-one patients (17.6%) had a previously undiagnosed finding, and 18 of the 41 (43.9%) underwent resective surgery. For 4 of the 41 patients (9.8%) with a previously undiagnosed pertinent finding, re-review detected abnormalities that were not amenable to surgical resection (autoimmunity or significant bilateral pathology).

Differential gene expression in dentate granule cells in mesial temporal lobe epilepsy with and without hippocampal sclerosis

OBJECTIVE

Hippocampal sclerosis is the most common neuropathologic finding in cases of medically intractable mesial temporal lobe epilepsy. In this study, we analyzed the gene expression profiles of dentate granule cells of patients with mesial temporal lobe epilepsy with and without hippocampal sclerosis to show that next-generation sequencing methods can produce interpretable genomic data from RNA collected from small homogenous cell populations, and to shed light on the transcriptional changes associated with hippocampal sclerosis.

METHODS

RNA was extracted, and complementary DNA (cDNA) was prepared and amplified from dentate granule cells that had been harvested by laser capture microdissection from surgically resected hippocampi from patients with mesial temporal lobe epilepsy with and without hippocampal sclerosis. Sequencing libraries were sequenced, and the resulting sequencing reads were aligned to the reference genome. Differential expression analysis was used to ascertain expression differences between patients with and without hippocampal sclerosis.

RESULTS

Greater than 90% of the RNA-Seq reads aligned to the reference. There was high concordance between transcriptional profiles obtained for duplicate samples. Principal component analysis revealed that the presence or absence of hippocampal sclerosis was the main determinant of the variance within the data. Among the genes up-regulated in the hippocampal sclerosis samples, there was significant enrichment for genes involved in oxidative phosphorylation.

SIGNIFICANCE

By analyzing the gene expression profiles of dentate granule cells from surgically resected hippocampal specimens from patients with mesial temporal lobe epilepsy with and without hippocampal sclerosis, we have demonstrated the utility of next-generation sequencing methods for producing biologically relevant results from small populations of homogeneous cells, and have provided insight on the transcriptional changes associated with this pathology.

Temporal lobe volume predicts Wada memory test performance in patients with mesial temporal sclerosis

The Wada test is widely used in the presurgical evaluation of potential temporal lobectomy patients to predict postoperative memory function. Expected asymmetry (EA), defined as Wada memory lateralized to the nonsurgical hemisphere, or a higher score after injection of the surgical hemisphere would be considered favorable in terms of postoperative memory outcome. However, in some cases, nonlateralized memory (NM) results, with no appreciable asymmetry, may occur because of impaired scores after both injections, often leading to denial of surgery. The reason for such nonlateralized Wada memory in patients with intractable temporal lobe epilepsy (TLE) remains unclear. Given that quantitative morphometric magnetic resonance imaging studies in TLE patients have shown bilateral regional atrophy in temporal and extratemporal structures, we hypothesized that the volume loss in contralateral temporal structures could contribute to nonlateralized Wada memory performance. To investigate this, we examined the relationship between the volume changes of temporal structures and Wada memory scores in patients with intractable TLE with mesial temporal sclerosis (MTS) using an age- and gender-matched control group. Memory was considered nonlateralized if the absolute difference in the total correct recall scores between ipsilateral and contralateral injections was <11%. Among 21 patients, Wada memory was lateralized in 15 and nonlateralized in 6 patients, with all the nonlateralized scores being observed in left TLE. The recall scores after ipsilateral injection were significantly lower in patients with an NM profile than an EA profile (23 ± 14% vs. 59 ± 18% correct recall, p ≤ 0.001). However, the recall scores after contralateral injection were low but similar between the two groups (25 ± 17% vs. 25 ± 15% correct recall, p=0.97). Compared to controls, all the patients showed greater volume loss in the temporal regions. However, patients with a NM profile showed significantly more volume loss than those with a lateralized memory profile in both contralateral and ipsilateral temporal regions (p<0.05). Left hemispheric Wada memory performance correlated positively with the size of the left mesial and neocortical temporal structures (r=0.49-0.63, p=0.005-0.04). Our study suggests that volume loss in the nonsurgical temporal structures is associated with nonlateralized Wada memory results in patients with intractable TLE.

Radiosurgery for Medial Temporal Lobe Epilepsy Resulting from Mesial Temporal Sclerosis

Medial temporal lobe epilepsy associated with mesial temporal sclerosis (MTS) is perhaps the most well-defined epilepsy syndrome that is responsive to structural interventions such as surgery. Several minimally invasive techniques have arisen that provide additional options for the treatment of MTS while potentially avoiding many of open surgery's associated risks. By evading these risks, they also open up treatment options to patients who otherwise are poor surgical candidates. Radiosurgery is one of the most intensively studied of these alternatives and has found a growing role in the treatment of medial temporal lobe epilepsy.

The Role of Stereotactic Laser Amygdalohippocampotomy in Mesial Temporal Lobe Epilepsy

Stereotactic laser amygdalohippocampotomy (SLAH) uses laser interstitial thermal therapy guided by magnetic resonance thermography. This novel intervention can achieve seizure freedom while minimizing collateral damage compared to traditional open surgery, in patients with mesial temporal lobe epilepsy. An algorithm is presented to guide treatment decisions for initial and repeat procedures in patients with and without mesial temporal sclerosis. SLAH may improve access by medication-refractory patients to effective surgical treatments and thereby decrease medical complications, increase productivity, and minimize socioeconomic consequences in patients with chronic epilepsy.

Decrease in CA3 inhibitory network activity during Theiler's virus encephalitis

Viral infections of the central nervous system are often associated with seizures, and while patients usually recover from the infection and the seizures cease, there is an increased lifetime incidence of epilepsy. These viral infections can result in mesial temporal sclerosis, and, subsequently, a type of epilepsy that is difficult to treat. In previous work, we have shown that Theiler's murine encephalomyelitis virus (TMEV) infections in C57B/6 mice, an animal model of virus-induced epilepsy, results in changes in excitatory currents of CA3 neurons both during the acute infection and two months later, at a time when seizure thresholds are reduced and when spontaneous seizures can occur. The changes in the excitatory system differ at these two time points, suggesting different mechanisms for seizure generation. In the present paper, we examine GABAergic mediated inhibition in CA3 pyramidal cells at these two time points following TMEV infection. We found that amplitudes of sIPSCs and mIPSCs were reduced during the acute infection, but recovered at the two-month time point. These observations are consistent with previous measurements of excitatory currents suggesting different mechanisms of seizure generation during the acute infection and during chronic epilepsy.

Surgical treatment for medically refractory focal epilepsy in a patient with fragile X syndrome

RATIONALE

Medication resistant temporal lobe epilepsy occurs in a small population of patients with fragile X syndrome. We present the case of a 24-year-old man with medically refractory temporal lobe epilepsy and fragile X syndrome who underwent left anterior temporal lobectomy resulting in cessation of seizures.

METHODS

Our patient was diagnosed with fragile X syndrome with a fully mutated, fully methylated FMR1 gene resulting in 572 CGG repeats. He developed seizures initially controlled with Depakote monotherapy, but progressed to become medically refractive to combination treatment with Depakote, lamotrigine and zonisamide. Prolonged video EEG monitoring revealed interictal left temporal sharp waves and slowing as well as subclinical and clinical seizures, each with left temporal onset. 3T MRI was consistent with left mesial temporal sclerosis. After discussing the case in our multidisciplinary surgical epilepsy conference, he was referred for presurgical evaluation including neuropsychological testing and Wada testing.

RESULTS

He underwent an asleep left anterior temporal lobectomy, sparing the superior temporal gyrus. Pathology showed neuronal loss and gliosis in the hippocampus and amygdala. Twelve months after surgery, the patient has not experienced a seizure. He is described by his parents as less perseverative and less restless.

CONCLUSIONS

We have presented the case of a 24 year-old-man with fragile X syndrome who underwent successful left anterior temporal lobectomy for the treatment of medically refractory epilepsy who is now seizure free without further functional impairment. This case report demonstrates the feasibility of surgical treatment for a patient with comorbid fragile X syndrome and mesial temporal sclerosis.

Morphological changes after radiosurgery for mesial temporal lobe epilepsy

Background

To review our experience with morphological developments during the long-term follow-up of patients treated by Gamma Knife radiosurgery for mesial temporal lobe epilepsy.

Method

Between 1995 and 1999, we treated 14 patients with marginal doses of 24 Gy (n = 6) and 18–20 Gy (n = 8). Nine of these were operated on for insufficient seizure control. We reviewed seizure outcome and magnetic resonance images in both operated and unoperated patients and also re-examined histopathology specimens.

Results

Of the nine operated patients, two were Engel IIIA, one was IVA, five were IVB, and one was Engel IVC prior to surgery. At their final visit, five cases had become Engel class IA, one patient was ID, and two were IIC. In one patient the follow-up was not long enough for classification. Of the five unoperated patients, one was Engel class IB, one was IIIA, one IIB and one IVB at their final visit. Radionecrosis developed in 11 patients, occurring more often and earlier in those treated with higher doses. Collateral edema reached outside the temporal lobe in six patients, caused uncal herniation in two and intracranial hypertension in three. During longer follow-up, postnecrotic pseudocysts developed in 9 patients, and postcontrast enhancement persisted for 2.5–16 years after GKRS in all 14 patients. In five of them we detected its progression between 2 and 16 years after treatment. Signs of neoangiogenesis were found in two patients and microbleeds could be seen in five. Histopathology revealed blood vessel proliferation and macrophage infiltration.

Conclusions

Early delayed complications and morphological signs suggesting a risk of development of late delayed complications are frequent after radiosurgery for mesial temporal lobe epilepsy. Together with its unproven antiseizure efficacy, these issues should be taken into account when planning future studies of this method.

Electronic supplementary material

The online version of this article (doi:10.1007/s00701-015-2525-2) contains supplementary material, which is available to authorized users.

Machine learning classification of mesial temporal sclerosis in epilepsy patients

BACKGROUND AND PURPOSE

Novel approaches applying machine-learning methods to neuroimaging data seek to develop individualized measures that will aid in the diagnosis and treatment of brain-based disorders such as temporal lobe epilepsy (TLE). Using a large cohort of epilepsy patients with and without mesial temporal sclerosis (MTS), we sought to automatically classify MTS using measures of cortical morphology, and to further relate classification probabilities to measures of disease burden.

MATERIALS AND METHODS

Our sample consisted of high-resolution T1 structural scans of 169 adults with epilepsy collected across five different 1.5T and four different 3T scanners at UCLA. We applied a multiple support vector machine recursive feature elimination algorithm to morphological measures generated from FreeSurfer's automated segmentation and parcellation in order to classify Epilepsy patients with MTS (n=85) from those without MTS (N=84).

RESULTS

In addition to hippocampal volume, we found that alterations in cortical thickness, surface area, volume and curvature in inferior frontal and anterior and inferior temporal regions contributed to a classification accuracy of up to 81% (p=1.3×10(-17)) in identifying MTS. We also found that MTS classification probabilities were associated with a longer duration of disease for epilepsy patients both with and without MTS.

CONCLUSIONS

In addition to implicating extra-hippocampal involvement of MTS, these findings shed further light on the pathogenesis of TLE and may ultimately assist in the development of automated tools that incorporate multiple neuroimaging measures to assist clinicians in detecting more subtle cases of TLE and MTS.

Triple pathological findings in a surgically amenable patient with mesial temporal lobe epilepsy

Mesial temporal sclerosis (MTS) is a well-recognized cause of intractable epilepsy; however, coexistence with focal cortical dysplasia (FCD) is less common. Middle fossa epidermoid cysts are rare and may involve the temporal lobe. Most epidermoids are clinically silent, slow-growing, and seldom associated with overt symptomatology, including seizures. We describe a patient with multiple comorbidities including left MTS and a large epidermoid cyst involving the left quadrigeminal plate cistern compressing upon the cerebellar vermis and tail of the left hippocampus, resulting in refractory left temporal lobe epilepsy. The patient underwent left anterior temporal lobectomy. The surgical pathology demonstrated a third pathological finding of left temporal FCD type Ia. The patient has been seizure-free since the surgery. This case provides additional information with regard to the understanding of epileptogenicity and surgical planning in patients with MTS and epidermoid cysts.

The evolution of epilepsy surgery between 1991 and 2011 in nine major epilepsy centers across the United States, Germany, and Australia

OBJECTIVE

Epilepsy surgery is the most effective treatment for select patients with drug-resistant epilepsy. In this article, we aim to provide an accurate understanding of the current epidemiologic characteristics of this intervention, as this knowledge is critical for guiding educational, academic, and resource priorities.

METHODS

We profile the practice of epilepsy surgery between 1991 and 2011 in nine major epilepsy surgery centers in the United States, Germany, and Australia. Clinical, imaging, surgical, and histopathologic data were derived from the surgical databases at various centers.

RESULTS

Although five of the centers performed their highest number of surgeries for mesial temporal sclerosis (MTS) in 1991, and three had their highest number of MTS surgeries in 2001, only one center achieved its peak number of MTS surgeries in 2011. The most productive year for MTS surgeries varied then by center; overall, the nine centers surveyed performed 48% (95% confidence interval [CI] -27.3% to -67.4%) fewer such surgeries in 2011 compared to either 1991 or 2001, whichever was higher. There was a parallel increase in the performance of surgery for nonlesional epilepsy. Further analysis of 5/9 centers showed a yearly increase of 0.6 ± 0.07% in the performance of invasive electroencephalography (EEG) without subsequent resections. Overall, although MTS was the main surgical substrate in 1991 and 2001 (proportion of total surgeries in study centers ranging from 33.3% to 70.2%); it occupied only 33.6% of all resections in 2011 in the context of an overall stable total surgical volume.

SIGNIFICANCE

These findings highlight the major aspects of the evolution of epilepsy surgery across the past two decades in a sample of well-established epilepsy surgery centers, and the critical current challenges of this treatment option in addressing complex epilepsy cases requiring detailed evaluations. Possible causes and implications of these findings are discussed.

Memory outcome following left anterior temporal lobectomy in patients with a failed Wada test

PURPOSE

This study aimed to compare the memory outcome following left anterior temporal lobectomy (ATL) between patients with a failed Wada test and patients who passed the Wada test.

METHODS

From 1996 to 2002, we performed the Wada test on all patients with unilateral left mesial temporal lobe epilepsy with hippocampal sclerosis (MTLE-HS) and concordant electroclinical data before ATL. We used a 12-item recognition paradigm for memory testing and awarded a score of +1 for each correct response and -0.5 for each incorrect response. No patient was denied surgery on the basis of Wada scores. We assessed cognitive and memory functions using the Wechsler Adult Intelligence Scale and the Wechsler Memory Scale preoperatively and at one year after ATL. We compared the number of patients who showed decline in memory scores, as per the published reliable change indices, between the patients with a failed Wada test and the patients who passed the Wada test.

RESULTS

Out of the 116 eligible patients with left MTLE-HS, 88 underwent bilateral Wada test, while 28 underwent ipsilateral Wada test. None of them developed postoperative amnesia. Approximately, one-third of patients with a failed Wada memory test when the failure was defined as a contralateral score of <4, as an ipsilateral score of >8, and as an asymmetry score of <0. The patients with Wada memory failure had a longer pre-ATL duration of epilepsy (p<0.003). The memory and quality-of-life outcomes did not differ between the group with a failed Wada memory test and the group who passed the Wada memory test. The results remained the same when analyses were repeated at various other cutoff points.

CONCLUSION

The patients with left MTLE-HS with concordant electroclinical, MRI, and neuropsychological data should not be denied ATL solely on the basis of Wada memory test results.

Predictors of spontaneous transient seizure remission in patients of medically refractory epilepsy due to mesial temporal sclerosis (MTS)

PURPOSE

To analyze the predictors of spontaneous transient seizure remission for ≥1 year in patients with drug-resistant epilepsy (DRE) due to mesial temporal sclerosis (MTS).

METHODS

This analysis included 38 patients with DRE (M:F = 20:18, age: 31.7 ± 10.9 years) diagnosed with unilateral MTS (right:left = 16:22). Group I ('remission' group) comprised of patients with seizure remission (M:F = 10:8, age: 32.8 ± 12.3 years, mean seizure free period: 2.2 ± 1.1 years; median: 2.1 years). Group II ('non-remission' group) comprised of age and gender matched 20 patients (M:F = 10:10, age: 30.7 ± 9.7 years) with unilateral MTS who never had seizure remission and subsequently underwent epilepsy surgery. Groups I and II were compared to find the predictors associated with transient seizure remission.

RESULTS

The age at onset of seizures in group I was 13.2 ± 11.8 years and in group II was 12.0 ± 7.6 years. The duration of seizure was: group I - 19.7 ± 12.5 years and group II - 19.3 ± 7.7 years. Past history of seizure remissions (p < 0.001), frequent periods of remissions (p < 0.001), first remission within a year of onset of seizures (p = 0.04) and normal EEG (p = 0.04) were the important clinical predictors associated with seizure remission in this cohort. Fifteen patients in group I (83.3%) experienced remission following either change in AED (p ≤ 0.001) or increase in AED dosages (p < 0.001). There was no difference between the two groups regarding the type of semiology (partial vs. secondarily generalized) (p = 0.50), family history of seizures (p = 1.0), side of the lesion (p = 0.34), history of febrile seizures (p = 1.0) and the number of AEDs used (p = 0.53).

CONCLUSION

The present study unfolds, some of the clinically relevant predictors associated with transient seizure remission in patients with DRE and MTS. Future molecular and network studies are required to understand its mechanism.

Factors predicting the outcome following medical treatment of mesial temporal epilepsy with hippocampal sclerosis

PURPOSE

There is a lack of information from South America regarding factors that predict the clinical outcomes of patients treated medically for mesial temporal lobe epilepsy with hippocampal sclerosis (MTLE-HS). This study was conducted to determine which of these factors are the most important.

METHODS

This study included 110 South American patients with MTLE-HS treated with antiepileptic drugs. The factors considered included age, gender, age of epilepsy onset, interval between the lesion and the first seizure, central nervous system infection, traumatic brain injury, perinatal asphyxia, febrile convulsion, history of status epilepticus, types of seizures, site of hippocampal sclerosis (HS), extrahippocampal pathology, and electroencephalogram (EEG) abnormalities. The patients were divided into two groups based on the response to treatment: Group I, seizure free for at least two years; and Group II, not seizure free.

RESULTS

On the multivariate analysis, the factors associated with a poor prognosis in terms of seizure frequency and control following treatment included the presence of an early onset of seizure, more than 10 seizures per month before treatment, and EEG abnormalities.

CONCLUSION

The recognition of risk factors, such as early onset of seizures, more than 10 seizures per month before treatment, and EEG abnormalities, could lead to the identification of risk groups among patients with MTLE-HS and refractory epilepsy, possibly designating these individuals as candidates for early epilepsy surgery.

Hippocampal volume loss following childhood convulsive status epilepticus is not limited to prolonged febrile seizures

Purpose

Childhood convulsive status epilepticus (CSE), in particular prolonged febrile seizures (PFS), has been linked with mesial temporal sclerosis (MTS). Previous studies have shown that hippocampal injury occurs in the acute phase immediately following CSE, but little is known about the longer term evolution of such injury. This study aimed to investigate the longer term outcome of childhood CSE with sequential magnetic resonance imaging (MRI) looking for progressive hippocampal injury during the first year post-CSE.

Methods

Eighty children (0.18–15.5 years) underwent brain MRI 1 month post-CSE, 50 with a repeat MRI at 6 months and 46 with repeat MRI at 12 months post-CSE. Thirty-one control subjects without neurologic problems had a single brain MRI for comparison. Hippocampal volumes were measured from each MRI scan by two independent observers, and hippocampal growth rates were estimated in each patient with suitable imaging.

Key Findings

Hippocampal volume loss was found in 20–30% of patients and was not associated with the etiology or clinical features of CSE, including seizure duration or focality. A borderline association was found between a history of previous seizures (p = 0.063) and the number of previous febrile seizures (p = 0.051), suggesting that multiple insults may be important in the pathogenesis of progressive hippocampal injury.

Significance

It is apparent that progressive hippocampal damage can occur after CSE of any etiology and is not limited to PFS. Repeated seizures may play an important role, but further follow-up is needed to determine any other risk factors and proportion of children showing initial volume loss progress to clinical MTS and temporal lobe epilepsy.

EEG-fMRI findings in late seizure recurrence following temporal lobectomy: A possible contribution of area tempestas

Late seizure relapses following temporal lobectomy for drug-resistant temporal lobe epilepsy occur in 18–30% of operated-on cases, and recent evidence suggests that a significant proportion of them are due to maturation and activation of proepileptic tissue having defied initial resection and located at the vicinity of or at a short distance from its borders, usually over the posterior medial, basal temporal-occipital, and lateral temporal regions. Experimental studies in animals and functional imaging studies in humans suggest that the area tempestas, a particular region of the basal-frontal piriform cortex, is critical for kindling and initiation and propagation of seizure activity arising from different cortical foci, especially limbic ones. This case report of a patient with late seizure relapse, three years following an initially successful right temporal lobectomy for ipsilateral medial temporal sclerosis, is the first one in the literature to demonstrate interictal EEG–fMRI evidence of significant BOLD signal changes over the inferior, basal and lateral temporal and temporooccipital cortices posterior to the resection margin, plus a significant BOLD signal change over the ipsilateral basal frontal region, closely corresponding to the piriform cortex/area tempestas. Our case study provides further functional imaging evidence in support of maturation/activation of proepileptic tissue located at the vicinity of the initial temporal lobe resection in cases of late seizure relapses and suggests, in addition, a possible role for the piriform cortex/area tempestas in the relapsing process.

Distinguishing language and race disparities in epilepsy surgery

This study aimed to identify whether race/ethnicity and limited English proficiency impact the likelihood of pursuing surgical treatment for medically refractory epilepsy. We conducted a retrospective cohort study of 213 patients with medically refractory epilepsy and mesial temporal sclerosis who were being considered for temporal lobectomy between January 1, 1993 and December 31, 2010 with follow-up through December 31, 2012. Demographic and clinical factors potentially associated with surgical utilization, including self-reported race/ethnicity and preferred language, were gathered from the medical record. Patients of Asian/Pacific Islander or African American race were significantly less likely to pursue surgical treatment of epilepsy compared with non-Hispanic whites in a multivariate logistic regression model (adjusted for nonconcordant ictal EEG, age, and limited English proficiency) (OR 0.20, p=0.003; OR 0.15, p=0.001, respectively). Limited English proficiency was also significantly associated with lower odds of surgery (OR 0.38, p=0.034). Both race and limited English proficiency contribute to disparities in the surgical management of medically refractory epilepsy, especially among Asian/Pacific Islanders and African Americans. Culturally sensitive patient-physician communication and patient education materials might aid in surgical decision-making among minority groups.

Low prevalence but high specificity of material-specific memory impairment in epilepsy associated with hippocampal sclerosis

PURPOSE

Material-specific memory impairment is used as a lateralizing tool in the evaluation of temporal lobe epilepsy. Lateralizing ability of material-specific memory deficits in temporal lobe epilepsy remains controversial.

METHODS

We studied memory impairment profiles of verbal and nonverbal memory deficits with eight memory subtests of four neuropsychological instruments (two verbal and two nonverbal) in 87 right-handed patients with epilepsy associated with unilateral mesial temporal sclerosis (MTS; 44 right - R, 43 left - L) and 42 controls, with an IQ >70, at least 8 years of education, and without comorbidities.

KEY FINDINGS

Selective verbal memory impairment was noted in 11 of 43 or 25.6% of left MTS cases, with 82.2% specificity, whereas selective nonverbal memory impairment was noted in 11 of 42 or 26.2% of right MTS cases, with 92% specificity. Nonlateralizing profiles of memory performance were seen in the remaining 65 of 87 patients. Approximately half (46/87 or 52.9%) of the patients had intact memory function in both modalities, equally distributed between patients with right MTS (23/44) and left MTS (23/43). Global impairment of both memory types was seen in 12 of 87 or 13.8% of patients, equally distributed between the two groups (7/43 left and 5/44 right).

SIGNIFICANCE

Lateralizing profiles of selective verbal and nonverbal memory deficits are highly specific for left and right MTS, although infrequently encountered in our patients. Nonlateralizing profiles predominated in this population. These findings suggest hemispheric asymmetry memory function, with complex functional interaction of the hippocampi, and possible compensatory mechanisms in the setting of a unilateral lesion.

Expression analysis and clinical correlation of aquaporin 1 and 4 genes in human hippocampal sclerosis

Mesial temporal sclerosis (MTS) is the most frequent cause of drug resistant symptomatic partial epilepsy. The mechanism and genetic background of this unique pathology are not well understood. Aquaporins (AQP) are regulators of water homeostasis in the brain and are expressed in the human hippocampus. We explored the role of AQP genes in the pathogenetic mechanisms of MTS through an evaluation of gene expression in surgically removed human brain tissue. We analyzed AQP1 and 4 mRNA levels by quantitative real-time polymerase chain reaction and normalized to ABL and cyclophilin genes, followed by immunohistochemistry for AQP4. Relative expressions were calculated according to the delta Ct method and the results were compared using the Mann-Whitney U test. Brain specimens of 23 patients with epilepsy who had undergone surgery for MTS and seven control autopsy specimens were investigated. Clinical findings were concordant with previous studies and 61% of the patients were seizure-free in the postoperative period. AQP1 and 4 gene expression levels did not differ between MTS patients and control groups. Immunofluorescence analysis of AQP4 supported the expression results, showing no difference. Previous studies have reported contradictory results about the expression levels of AQP in MTS. To our knowledge, only one study has suggested upregulation whereas the other indicated downregulation of perivascular AQP4. Our study did not support these findings and may rule out the involvement of AQP in human MTS.

Mesial temporal sclerosis is linked with more widespread white matter changes in temporal lobe epilepsy

Temporal lobe epilepsy patients with unilateral mesial temporal sclerosis (TLE + uMTS) have been demonstrated to have extensive white matter abnormalities both ipsilateral and contralateral to the seizure onset zone. However, comparatively less is known about the white matter integrity of TLE patients without MTS (non-lesional TLE, nl-TLE). The purpose of the study was to investigate the diffusion properties of thirteen major white matter tracts in patients with TLE + uMTS and nl-TLE. Diffusion tensor imaging (DTI) was performed on 23 TLE + uMTS (15 left MTS and 8 right MTS), 15 nl-TLE and 21 controls. Thirteen tracts were delineated by tractography and their diffusion parameters compared for the two TLE groups relative to controls, with left and right hemispheres combined per tract. A subgroup analysis investigated left and right MTS separately. Compared to controls, reduced anisotropy was detected in ten tracts for TLE + uMTS, but only the parahippocampal cingulum and tapetum for nl-TLE. Right MTS subgroup showed reduced anisotropy in 7 tracts bilaterally (3 limbic, 3 association, 1 projection) and 2 tracts ipsilaterally (1 association, 1 projection) and the body of the corpus callosum whereas the left MTS subgroup showed reduced anisotropy in 4 tracts bilaterally (2 limbic, 1 association, 1 projection) and 2 tracts ipsilaterally (1 limbic, 1 association). Diffusion abnormalities in tracts were observed within and beyond the temporal lobe in TLE + uMTS and were more widespread than in nl-TLE. Patients with right MTS had more extensive, bilateral abnormalities in comparison to left MTS. These findings suggest different dysfunctional networks in TLE patients with and without MTS.