Frontopolar ictal epileptiform discharges on scalp electroencephalogram in temporal lobe epilepsy

The Utility of Limited-Montage Electroencephalography for Seizure Detection in Children

BACKGROUND

The primary objective of this study was to investigate the utility of limited-montage electroencephalography (EEG) for seizure detection in children. We also aimed to determine whether the detection rate differed among different montage patterns.

METHODS

This study was carried out between November 2019 and October 2020 at a tertiary children's hospital in Japan. The subjects were inpatients in the pediatric intensive care unit who had an epileptic seizure during EEG monitoring. Each patient's EEG record, consisting of a 15-minute recording during an epileptic seizure and a 15-minute recording in the absence of an epileptic seizure, was extracted from the medical charts. The EEG data were then analyzed using six, limited-montage coverage patterns: (1) Fp1-C3, Fp2-C4, (2) Fp1-O1, Fp2-O2, (3) Fp1-T3, Fp2-T4, (4) C3-O1, C4-O2, (5) C3-T3, C4-T4, and (6) O1-T3, O2-T4. The sensitivity and specificity of each montage for seizure detection was analyzed.

RESULTS

One hundred thirty-two EEG data points from 11 patients were examined. Sensitivity and specificity were the highest for Fp1-O1 and Fp2-O2 at 73% and 91%, respectively. Overall, the montage covering the frontopolar area had the highest detection rate, followed by the montage covering the occipital, central, and temporal areas.

CONCLUSION

Limited-montage EEG identified seizures in children hospitalized in the intensive care unit, but the detection rate differed by montage coverage. The detection rate was highest in the montage covering the frontopolar area.

Endovascular Neuromodulation: Safety Profile and Future Directions

Endovascular neuromodulation is an emerging technology that represents a synthesis between interventional neurology and neural engineering. The prototypical endovascular neural interface is the Stentrode^TM, a stent-electrode array which can be implanted into the superior sagittal sinus via percutaneous catheter venography, and transmits signals through a transvenous lead to a receiver located subcutaneously in the chest. Whilst the Stentrode^TM has been conceptually validated in ovine models, questions remain about the long term viability and safety of this device in human recipients. Although technical precedence for venous sinus stenting already exists in the setting of idiopathic intracranial hypertension, long term implantation of a lead within the intracranial veins has never been previously achieved. Contrastingly, transvenous leads have been successfully employed for decades in the setting of implantable cardiac pacemakers and defibrillators. In the current absence of human data on the Stentrode^TM, the literature on these structurally comparable devices provides valuable lessons that can be translated to the setting of endovascular neuromodulation. This review will explore this literature in order to understand the potential risks of the Stentrode^TM and define avenues where further research and development are necessary in order to optimize this device for human application.

[A case series of 4 epilepsy patients with promnesia]

Promnesia is a feeling of familiarity and foreknowledge and is a manifestation of simple partial seizures (focal aware seizures). It is similar to déjà vu and has been reported to be a rare symptom in patients with temporal lobe epilepsy. Here, we investigated the clinical characteristics in 4 patients with partial epilepsy presenting promnesia. Three out of 4 patients showed abnormal electroencephalography (EEG) and/or MRI findings in the temporal lobe. Furthermore, in 2 patients, promnesia was the only aura. It is important to actively obtain medical history of patients about promnesia because this is useful for identifying the epileptic focus. Further cases need to be analyzed to evaluate the sensitivity and specificity of promnesia for diagnosis and therapy of partial epilepsy.

The contribution of 18F-FDG PET in preoperative epilepsy surgery evaluation for patients with temporal lobe epilepsy

OBJECTIVE

To assess the predictive diagnostic added value of positron emission tomography (PET) in preoperative epilepsy surgery evaluation for patients with temporal lobe epilepsy (TLE).

METHODS

A meta-analysis of publications from 1992 to 2006 was performed. Forty-six studies were identified that met inclusion criteria presenting detailed diagnostic test results and a classified postoperative outcome. Studies exclusively reporting on patients with brain tumors or on children were excluded.

RESULTS

The analyses were complicated by significant differences in study design and often by lack of precise patient data. Ipsilateral PET hypometabolism showed a predictive value of 86% for good outcome. The predictive value was 80% in patients with normal MRI and 72% in patients with non-localized ictal scalp EEG. In a selected population of 153 TLE patients with a follow-up of >12 months PET correlated well with other non-invasive diagnostic tests, but none of the odds ratios of any test combination was significant.

CONCLUSION

Our data confirm that ipsilateral PET hypometabolism may be an indicator for good postoperative outcome in presurgical evaluation of drug-resistant TLE, although the actual diagnostic added value remained questionable and unclear. PET does not appear to add value in patients localized by ictal scalp EEG and MRI. Prospective studies limited to non-localized ictal scalp EEG or MRI-negative patients are required for validation.

Fibers from the dorsal premotor cortex elicit motor-evoked potential in a cortical dysplasia

OBJECTIVE

To identify the fibers originating from the dorsal premotor cortex (dorsal PMC) that contribute to motor-evoked potentials (MEP), we have applied integrated functional neuronavigation and awake surgery during removal of an epileptic cortical dysplasia located in the right premotor cortex.

METHODS

Chronic subdural electrodes were employed for functional mapping during a routine invasive evaluation for intractable epilepsy. After the fibers originating from the dorsal PMC were plotted into the tractography-integrated functional neuronavigation, subcortical MEPs and clinical symptoms were examined during resection of the epileptogenic dorsal PMC.

RESULTS

During removal of the epileptogenic area, MEPs were elicited by electrical stimulation of the fibers originating from the dorsal PMC, which were separated from the pyramidal tracts from the precentral gyrus. Resection of the dorsal PMC and its fibers caused a transient dysmetric movement of the left toe without motor weakness.

CONCLUSION

Functional corticospinal tract fibers originating from the dorsal PMC can be defined and removed safely under local anesthesia with the aid of integration of functional neuronavigation and subcortical electrical stimulation.

A step-by-step resection guided by electrocorticography for nonmalignant brain tumors associated with long-term intractable epilepsy

To delineate a surgical strategy for long-term intractable epilepsy associated with nonmalignant brain tumor, we developed a protocol for 25 patients whereby removal of tumor alone and additional irritative peritumoral tissue between sulci (gyrectomy), as well as further resectioning, was performed based on intraoperative electrocorticogram results. In five patients, no irritative zones were observed that required resectioning following complete removal of tumors. Additional gyrectomy was indicated in 18 patients who demonstrated gliosis or cortical dysplasia in the peritumoral residual irritative zone. Remote irritative zone observed in two patients was correlated with long-term and frequent seizures. During a follow-up period of at least 5 years, seizure outcome was Engel category I in 92%, and all patients have remained tumor-free. Peritumoral gyrectomy as a means of removing likely epileptic tissue following tumor resection appears to be a useful method for treating long-term intractable tumoral epilepsy. Further resectioning of remote tissue should be considered in patients with severely intractable seizures.

Surgical resection of an epileptogenic cortical dysplasia in the deep foot sensorimotor area

Epileptogenic foci in the foot/leg motor area of cortex are rarely resected, due to the risks of the surgical procedures. A 31-year-old right-handed man with cortical dysplasia deep in the central sulcus suffered from disturbances in walking due to frequent daily seizures. Following subdural electrode implantation to define the epileptogenic area and assess cortical function, limited regions of cortex were removed from the foot/leg primary motor and sensory areas under local anesthesia until the epileptiform discharges disappeared. Postoperative motor weakness and sensory disturbances completely resolved within 2 weeks and 2 months, respectively; the patient has been free from seizures for more than a year and a half postsurgery. Intraoperative examination demonstrated that small and moderate cortical dysplasia in the depths of the central sulcus exhibits both intrinsic epileptogenicity and function. Focused resection of the lower extremity of the sensorimotor area may be a surgical strategy for intractable epilepsy if resolution of clinical symptoms with minimal dysfunction due to the limited size of the resection is expected to follow surgery.

Focal extratemporal epilepsy: clinical features, EEG patterns, and surgical approach

The objective of this review is a summary of the clinical and electrographic findings in those forms of epilepsy to which the term 'extratemporal' (ExT) can be applied. They form a group that differs in many ways from the better known temporal lobe epilepsies. Seizure foci are difficult to localize by clinical semiology alone but modern imaging now often allows a precise definition of the epileptogenic area. The most common causes of ExT epilepsy are tumors and cortical dysgenesis. The concept of 'dual pathology' implies the coexistence of two or more distinct lesions, typically mesial temporal sclerosis and cortical dysplasia. Electroencephalography (EEG) and electrocorticography (ECoG) are valuable tests in the definition of the epileptogenic area beyond the structural lesion, and surgical removal must be guided by the nature of the lesion and the extent of the epileptogenic zone.