Frequency of unilateral and bilateral mesial temporal sclerosis in primary and secondary epilepsy: a forensic autopsy study

Surgical Technique and Outcome of Extensive Frontal Lobectomy for Treatment of Intracable Non-lesional Frontal Lobe Epilepsy

Although extensive frontal lobectomy (eFL) is a common surgical procedure for intractable frontal lobe epilepsy (FLE), there have been very few reports regarding surgical techniques for eFL. This article provides step-by-step descriptions of our surgical technique for non-lesional FLE. Sixteen patients undergoing eFL were included in this study. The goals were to maximize gray matter removal, including the orbital gyrus and subcallosal area, and to spare the primary motor and premotor cortexes and anterior perforated substance. The eFL consists of three steps: (1) positioning, craniotomy, and exposure; (2) lateral frontal lobe resection; and (3), resection of the rectus gyrus and orbital gyrus. Resection ahead of bregma allows preservation of motor and premotor area function. To remove the orbital gyrus preserving anterior perforated substance, it is essential to visualize the olfactory trigone beneath the pia. It is important to observe the surface of the contralateral medial frontal lobe for complete removal of the subcallosal area of the frontal lobe. Thirteen patients (81.25%) became seizure-free and three patients (18.75%) continued to have seizures. None of the patients showed any complications. The eFL is a good surgical technique for the treatment of intractable non-lesional FLE. For treatment of epilepsy by eFL, it is important to resect the non-eloquent area of the frontal lobe as much as possible with preservation of the eloquent cortex.

Temporal lobectomy with delayed amnesia following a new lesion on the other side

PURPOSE

To describe a delayed severe complication of temporal lobectomy for intractable epilepsy.

METHOD

A case of amnesia occurring 24 years after surgery is described and five similar cases from the literature reviewed.

RESULTS

Mean age at surgery (5 right) was 40 years (19-62 years), 3 female. Four of five tested had impaired visual and verbal memory preoperatively but not sufficient to contraindicate surgery. Pathology was mesial temporal sclerosis in 3, 1 cavernoma, 1 dysembryoplastic neuroepithelial tumor (DNET) and 1 normal. Postoperatively, four were seizure free 3-12 years off medication and two continued with seizures. There was no unexpected postoperative memory change until incapacitating anterograde amnesia developed 1-24 years after surgery. In five patients, including ours, this followed definite or possible status epilepticus with new mesial temporal sclerosis on the opposite side in the four that were investigated by MRI. One patient developed a glioblastoma in the opposite temporal lobe.

CONCLUSION

Continuing or late recurrence of seizures from the remaining temporal lobe after temporal lobectomy can result in incapacitating amnesia if status epilepticus occurs. Other new lesions on the opposite side to surgery can have the same effect.

Failed epilepsy surgery for mesial temporal lobe sclerosis: a review of the pathophysiology

Object

The object of the current study was to review the electrophysiology and pathological substrate of failed temporal lobe surgery in patients with mesial temporal sclerosis.

Methods

A systematic review of the literature was performed for the years 1999–2010 to assess the cause of failure and to identify potential reoperation candidates.

Results

Repeat electroencephalographic evaluation documenting ipsilateral temporal lobe onset was the most frequent cause for recurrent epileptogenesis, followed by contralateral temporal lobe seizures. Less frequently, surgical failures demonstrated an electroencephalogram that was compatible with extratemporal localization. The generation of occult or new epileptogenic zones as well as residual epileptogenic tissue could explain these findings.

Conclusions

The outcome of temporal lobe surgery for epilepsy is challenged by a somewhat consistent failure rate. Reoperation results in improved seizure control in properly selected patients. A detailed knowledge of the pathophysiology is beneficial for the reevaluation of these patients.

Failure of temporal lobe resection for epilepsy in patients with mesial temporal sclerosis: results and treatment options

OBJECT

The purpose of this study was to identify the causes of failed temporal lobe resection in patients with mesial temporal sclerosis (MTS) and the role of repeat surgery for seizure control.

METHODS

This is a retrospective study of 105 patients who underwent temporal lobe resection for MTS with unilateral electroencephalographic findings. The mean follow-up duration was 36 months (range 24-84 months). Surgeries were all performed by the senior author (F.L.V.).

RESULTS

Following initial surgical intervention, 97 patients (92%) improved to Engel Class I or II (Group A), and 8 (8%) did not have significant improvement (Engel Class III or IV; Group B). These 8 patients were restudied using video-electroencephalography (EEG) and MR imaging. All major surgical failures occurred within 1 year after initial intervention. Reevaluation demonstrated 3 patients (37.5%) with contralateral temporal EEG findings. Five patients (62.5%) had evidence of ipsilateral recurrent discharges. Four patients underwent extended neocortical resection along the previous resection cavity. Their outcomes ranged from Engel Class I to Class III. Only 1 patient (12.5%) who failed to improve after initial surgery was found to have incomplete resection of mesial structures. This last patient underwent reoperation to complete the resection and improved to Engel Class I.

CONCLUSIONS

Failure of temporal lobe resection for MTS is multifactorial. The cause of failure lies in the pathological substrate of the epileptogenic area. Complete seizure control cannot be predicted solely by conventional preoperative workup. Initial surgical failures from temporal lobe resection often benefit from reevaluation, because reoperation may be beneficial in selected patients. Based on this work, the authors have proposed a management and treatment algorithm for these patients.

Neuronal dysfunction in children with newly diagnosed temporal lobe epilepsy

We sought to determine whether neuronal dysfunction throughout the temporal lobes of children with temporal lobe epilepsy (TLE) is already as severe at the time of diagnosis as it is in patients with long-standing intractable TLE (INT-TLE). Proton magnetic resonance spectroscopic imaging was used to measure N-acetylaspartate/creatine (NAA/Cr) ratios in the temporal lobes of five consecutive children with newly diagnosed TLE (ND-TLE), five with INT-TLE, and 30 normal control subjects. The median age of those with ND-TLE and those with INT-TLE did not significantly differ (P = 0.92). All five patients with ND-TLE had bilateral reductions in the NAA/Cr ratio. Two of the five patients with INT-TLE had bilateral reductions in the NAA/Cr ratio; three had unilateral reductions in the NAA/Cr ratio. In the three patients with lesions the NAA/Cr ratio decrease extended outside these lesions. No significant differences were detected in any temporal lobe region between the ND-TLE and INT-TLE groups. The severity of the neuronal dysfunction in the children with ND-TLE was at least as severe as in those with INT-TLE and was not restricted to one temporal lobe, implying that the neuronal abnormalities observed in patients with TLE occur before the clinical manifestations.

[11C]Flumazenil PET in patients with epilepsy with dual pathology

PURPOSE

Coexistence of hippocampal sclerosis and a potentially epileptogenic cortical lesion is referred to as dual pathology and can be responsible for poor surgical outcome in patients with medically intractable partial epilepsy. [11C]Flumazenil (FMZ) positron emission tomography (PET) is a sensitive method for visualizing epileptogenic foci. In this study of 12 patients with dual pathology, we addressed the sensitivity of FMZ PET to detect hippocampal abnormalities and compared magnetic resonance imaging (MRI) with visual as well as quantitative FMZ PET findings.

METHODS

All patients underwent volumetric MRI, prolonged video-EEG monitoring, and glucose metabolism PET before the FMZ PET. MRI-coregistered partial volume-corrected PET images were used to measure FMZ-binding asymmetries by using asymmetry indices (AIs) in the whole hippocampus and in three (anterior, middle, and posterior) hippocampal subregions. Cortical sites of decreased FMZ binding also were evaluated by using AIs for regions with MRI-verified cortical lesions as well as for non-lesional areas with visually detected asymmetry.

RESULTS

Abnormally decreased FMZ binding could be detected by quantitative analysis in the atrophic hippocampus of all 12 patients, including three patients with discordant or inconclusive EEG findings. Decreased FMZ binding was restricted to only one subregion of the hippocampus in three patients. Areas of decreased cortical FMZ binding were obvious visually in all patients. Decreased FMZ binding was detected visually in nonlesional cortical areas in four patients. The AIs for these nonlesional regions with visual asymmetry were significantly lower than those for regions showing MRI lesions (paired t test, p = 0.0075).

CONCLUSIONS

Visual as well as quantitative analyses of FMZ-binding asymmetry are sensitive methods to detect decreased benzodiazepine-receptor binding in the hippocampus and neocortex of patients with dual pathology. MRI-defined hippocampal atrophy is always associated with decreased FMZ binding, although the latter may be localized to only one sub-region within the hippocampus. FMZ PET abnormalities can occur in areas with normal appearance on MRI, but FMZ-binding asymmetry of these regions is lower when compared with that of lesional areas. FMZ PET can be especially helpful when MRI and EEG findings of patients with intractable epilepsy are discordant.