Seizure onset patterns predict outcome after stereo-electroencephalography-guided laser amygdalohippocampotomy.

OBJECTIVE: Stereotactic laser amygdalohippocampotomy (SLAH) is an appealing option for patients with temporal lobe epilepsy, who often require intracranial monitoring to confirm mesial temporal seizure onset. However, given limited spatial sampling, it is possible that stereotactic electroencephalography (stereo-EEG) may miss seizure onset elsewhere. We hypothesized that stereo-EEG seizure onset patterns (SOPs) may differentiate between primary onset and secondary spread and predict postoperative seizure control. In this study, we characterized the 2-year outcomes of patients who underwent single-fiber SLAH after stereo-EEG and evaluated whether stereo-EEG SOPs predict postoperative seizure freedom. METHODS: This retrospective five-center study included patients with or without mesial temporal sclerosis (MTS) who underwent stereo-EEG followed by single-fiber SLAH between August 2014 and January 2022. Patients with causative hippocampal lesions apart from MTS or for whom the SLAH was considered palliative were excluded. An SOP catalogue was developed based on literature review. The dominant pattern for each patient was used for survival analysis. The primary outcome was 2-year Engel I classification or recurrent seizures before then, stratified by SOP category. RESULTS: Fifty-eight patients were included, with a mean follow-up duration of 39 ± 12 months after SLAH. Overall 1-, 2-, and 3-year Engel I seizure freedom probability was 54%, 36%, and 33%, respectively. Patients with SOPs, including low-voltage fast activity or low-frequency repetitive spiking, had a 46% 2-year seizure freedom probability, compared to 0% for patients with alpha or theta frequency repetitive spiking or theta or delta frequency rhythmic slowing (log-rank test, p = .00015). SIGNIFICANCE: Patients who underwent SLAH after stereo-EEG had a low probability of seizure freedom at 2 years, but SOPs successfully predicted seizure recurrence in a subset of patients. This study provides proof of concept that SOPs distinguish between hippocampal seizure onset and spread and supports using SOPs to improve selection of SLAH candidates.

Transient headache and neurological deficits with cerebrospinal fluid lymphocytosis syndrome: A comprehensive systematic review of 93 patients from 57 studies.

BACKGROUND: Headache with neurologic deficits and cerebrospinal fluid lymphocytosis, previously also termed pseudomigraine with temporary neurologic symptoms and lymphocytic pleocytosis, is a self-limiting syndrome characterized by moderate to severe headache associated with focal neurological deficits occurring in the context of lymphocytosis in the cerebrospinal fluid. As a consequence of its rarity, data regarding headache with neurologic deficits and cerebrospinal fluid lymphocytosis is sparse. Therefore, we conducted this review to analyze data related to 93 patients of headache with neurologic deficits and cerebrospinal fluid lymphocytosis, to characterize their demographics, clinical manifestations, investigations and treatment options. METHODS: We performed a systematic review of cases reported through PubMed and Google scholar database, using Preferred Reporting Items for Systematic Reviews and Meta-Analyses protocol. Keywords used were 'Headache with Neurologic Deficits and cerebrospinal fluid lymphocytosis', 'Headache with neurologic deficits and cerebrospinal fluid lymphocytosis syndrome'. The quality of the included studies was assessed using the Joanna Briggs Institute Critical Appraisal Tool. RESULTS: We analyzed a total of 93 cases of headache with neurologic deficits and cerebrospinal fluid lymphocytosis with a mean age of 28.8 years at onset. Seventy patients (75.2%) were adults, while 23 (24.7%) belonged to the pediatric age group. Comparing these groups, mean age at onset was 32.5 years and 14.3 years, respectively. The average duration of follow-up was 11.08 months. Thirty percent of patients experienced relapsing episodes of headache with neurologic deficits and cerebrospinal fluid lymphocytosis symptoms. The most common type of headache reported was unilateral severe throbbing episodic headache. Other associated symptoms included sensory deficit (60%) and motor deficits (54.8%). The least common symptoms were nystagmus and agraphia, which were reported in one patient each. Antiviral agents were a common treatment option in the acute phase (n = 23 patients [23.6%]), while Flunarizine was the most commonly used agent in the chronic setting (n = 3 patients [3.2%]). While most of the patients had normal brain magnetic resonance imaging, 20 patients had magnetic resonance imaging abnormalities, including (but not limited to) non-specific white matter lesions (eight patients) and meningeal enhancement (six patients). The most common electroencephalographic findings included diffuse and focal slowing. The mean cerebrospinal fluid opening-pressure was 240.5 mmH2O. Cerebrospinal fluid protein was elevated in 59 (63.4%) patients, with a mean value of 114 mg/dL. Two patients in our cohort were found to have cerebrospinal fluid oligoclonal bands. CONCLUSION: Headache with neurologic deficits and cerebrospinal fluid lymphocytosis tends to affect young individuals with a slight male predominance. Unilateral severe throbbing episodic headache with associated hemi-paresthesia and hemiparesis were the most common symptoms based on our review. Elevated cerebrospinal fluid opening-pressure can be seen in headache with neurologic deficits and cerebrospinal fluid lymphocytosis syndrome. Early recognition of the syndrome is paramount. Antivirals were found to be among the most widely used treatments in the acute setting. Magnetic resonance imaging of the brain is mostly normal. Diffuse and focal slowing were among the most common electroencephalographic findings. Cerebral flow abnormalities on perfusion scans are not uncommon in headache with neurologic deficits and cerebrospinal fluid lymphocytosis. Prospective studies with a larger sample size are needed to validate our findings and guide the clinical care of these patients.

Source localization of ictal SEEG to predict postoperative seizure outcome.

OBJECTIVE: Stereo-electroencephalography (SEEG) is inherently-three-dimensional and can be modeled using source localization. This study aimed to assess the validity of ictal SEEG source localization. METHODS: The dominant frequency at ictal onset was used for source localization in the time and frequency domains using rotating dipoles and current density maps. Validity was assessed by concordance with the epileptologist-defined seizure onset zone (conventional SOZ) and the surgical treatment volume (TV) of seizure-free versus non-seizure-free patients. RESULTS: Source localization was performed on 68 seizures from 27 patients. Median distance to nearest contact in the conventional SOZ was 7 (IQR 6-12) mm for time-domain dipoles. Current density predicted ictal activity with up to 86 % (60-87 %) accuracy. Distance from time-domain dipoles to the TV was smaller (P = 0.045) in seizure-free (2 [0-4] mm) versus non-seizure-free (12 [2-17] mm) patients, and predicted surgical outcome with 91 % sensitivity and 63 % specificity. Removing near-field data from contacts within the TV negated outcome prediction (P = 0.51). CONCLUSIONS: Source localization of SEEG accurately mapped ictal onset compared with conventional interpretation. Proximity of dipoles to the TV predicted seizure outcome when near-field recordings were analyzed. SIGNIFICANCE: Ictal SEEG source localization is useful in corroborating the epileptogenic zone, assuming near-field recordings are obtained.

Digital reconstruction of infraslow activity in human intracranial ictal recordings using a deconvolution-based inverse filter.

Infraslow activity (ISA) is a biomarker that has recently become of interest in the characterization of seizure recordings. Recent data from a small number of studies have suggested that the epileptogenic zone may be identified by the presence of ISA. Investigation of low frequency activity in clinical seizure recordings, however, has been hampered by technical limitations. EEG systems necessarily include a high-pass filter early in the measurement chain to remove large artifactual drifts that can saturate recording elements such as the amplifier. This filter, unfortunately, attenuates legitimately seizure-related low frequencies, making ISA difficult to study in clinical EEG recordings. In this study, we present a deconvolution-based digital inverse filter that allows recovery of attenuated low frequency activity in intracranial recordings of temporal lobe epilepsy patients. First, we show that the unit impulse response (UIR) of an EEG system can be characterized by differentiation of the system's step response. As proof of method, we present several examples that show that the low frequency component of a high-pass filtered signal can be restored by deconvolution with the UIR. We then demonstrate that this method can be applied to biologically relevant signals including clinical EEG recordings obtained from seizure patients. Finally, we discuss how this method can be applied to study ISA to identify and assess the seizure onset zone.

Hippocampal spikes have heterogeneous scalp EEG correlates important for defining IEDs.

OBJECTIVE: To identify scalp EEG correlates of hippocampal spikes in patients with mesial temporal lobe epilepsy (mTLE). METHODS: We recorded scalp and intracranial EEG simultaneously in 20 consecutive surgical candidates with mTLE. Hippocampal spikes were identified from depth electrodes during the first hour of sleep on the first night of recording in the epilepsy monitoring unit, and their scalp EEG correlates were identified. RESULTS: Hippocampal spiking rates varied widely from 101 to 2187 (556 ± 672, mean ± SD) spikes per hour among the subjects. Of the 16,398 hippocampal spikes observed in this study, 492 (3.0%) of hippocampal spikes with extensive involvement of lateral temporal cortex were associated with scalp interictal epileptiform discharges (IEDs) including spikes and sharp waves; 198 (1.2%) of hippocampal spikes with limited involvement of lateral temporal cortex were associated with sharp transients or sharp slow waves, and 78 (0.05%)of hippocampal spikes with no lateral temporal involvement were associated with small sharp spikes (SSS). SSS were not correlated with independent temporal neocortical spikes. CONCLUSIONS: There are morphologically heterogeneous scalp EEG correlates of hippocampal spikes including SSS, sharp transients, sharp slow waves, spikes, and sharp waves. SSS correlate with hippocampal spikes and are likely an EEG marker for mTLE. These findings have important clinical implications for the diagnosis and localization of mTLE, and provide new perspectives on criteria for defining scalp IEDs.

SEEG in 3D: Interictal Source Localization From Intracerebral Recordings.

BACKGROUND: Stereo-electroencephalography (SEEG) uses a three-dimensional configuration of depth electrodes to localize epileptiform activity, but traditional analysis of SEEG is spatially restricted to the point locations of the electrode contacts. Interpolation of brain activity between contacts might allow for three-dimensional representation of epileptiform activity and avoid pitfalls of SEEG interpretation. OBJECTIVE: The goal of this study was to validate SEEG-based interictal source localization and assess the ability of this technique to monitor far-field activity in non-implanted brain regions. METHODS: Interictal epileptiform discharges were identified on SEEG in 26 patients who underwent resection, ablation, or disconnection of the suspected epileptogenic zone. Dipoles without (free) and with (scan) gray matter restriction, and current density (sLORETA and SWARM methods), were calculated using a finite element head model. Source localization results were compared to the conventional irritative zone (IZ) and the surgical treatment volumes (TV) of seizure-free vs. non-seizure-free patients. RESULTS: The median distance from dipole solutions to the nearest contact in the conventional IZ was 7 mm (interquartile range 4-15 mm for free dipoles and 4-14 mm for scan dipoles). The IZ modeled with SWARM predicted contacts within the conventional IZ with 83% (75-100%) sensitivity and 94% (88-100%) specificity. The proportion of current within the TV was greater in seizure-free patients (P = 0.04) and predicted surgical outcome with 45% sensitivity and 93% specificity. Dipole solutions and sLORETA results did not correlate with seizure outcome. Addition of scalp EEG led to more superficial modeled sources (P = 0.03) and negated the ability to predict seizure outcome (P = 0.23). Removal of near-field data from contacts within the TV resulted in smearing of the current distribution (P = 0.007) and precluded prediction of seizure freedom (P = 0.20). CONCLUSIONS: Source localization accurately represented interictal discharges from SEEG. The proportion of current within the TV distinguished between seizure-free and non-seizure-free patients when near-field recordings were obtained from the surgical target. The high prevalence of deep sources in this cohort likely obscured any benefit of concurrent scalp EEG. SEEG-based interictal source localization is useful in illustrating and corroborating the epileptogenic zone. Additional techniques are needed to localize far-field epileptiform activity from non-implanted brain regions.

Laser interstitial thermal therapy for NPRL3-related epilepsy with multiple seizure foci: A case report.

Introduction: NPRL3 gene mutations cause autosomal dominant familial focal epilepsy of variable foci (FFEVF) and is characterized by focal epilepsy arising from different brain regions including temporal, frontal, parietal and occipital lobes. About 50% of patients with NPRL3 related epilepsy are resistant to medical treatment. Method: We present a case of 27 years old man with NPRL3 related focal drug-resistant epilepsy. Stereotactic EEG showed two independent seizure foci, namely, left hippocampus and left orbitofrontal cortices. He underwent laser interstitial thermal therapy for ablating both foci in the same procedure that led to seizure cessation. Conclusion: laser interstitial thermal therapy can be an effective treatment for drug resistant NPRL3 related focal epilepsy with better tolerance and less morbidity as compared to open surgical resection, particularly in those with multiple seizure foci.