Temporal lobe meningoencephaloceles – The Bethel experience

Introduction: Temporal lobe meningoencephaloceles are identified as potential epileptogenic lesions during presurgical workup. Surface EEG and invasive EEG monitoring are used to prove their epileptogenicity. The extent of surgical resection required to achieve seizure freedom is still unclear.

Objectives: To clarify the diagnostic value of invasive EEG monitoring for the detection of epileptogenicity and its significance for an individually adapted extent of surgical resection in patients with temporal meningoencephaloceles.

Results: We present the clinical, diagnostic and outcome data of 20 patients who underwent resective neurosurgery for temporal meningoencephalocele at our center.

Half of the patients (10/20) were directed straight to surgical treatment based on EEG-data in agreement with imaging findings . Resection was performed as a circumscribed lesionectomy in 8/10 and as an apical partial temporal lobe resection (resection of the pole and corpus amygdaloideum while sparing mesial structures) in 2/10. 6/8 patients in group 1 (circumscribed lesionectomy) were seizure-free and none of the two in group 2.

An invasive depth electrode assessment was performed in 10/20. 1 patient received a circumscribed lesionectomy, 5 patients an apical partial temporal lobe resection, 1 patient a modified apical partial temporal lobe resection (additional removal of hippocampal head), 3 patients an anterior TLR (including removal of mesial structures).

In the invasive group, 7/8 patients with long running outcome data were seizure-free postoperatively. Two patients had recently undergone surgery, as a matter of fact they had been also seizure-free for 1 and 2 months respectively. Only one patient was not seizure free (he had received an anterior partial temporal lobe resection).

After circumscribed lesionectomy (both groups) seizure freedom was achieved in 7/9 patients and after extended lesionectomy in the sense of an apical TLR in 5/7 patients, in addition 1 modified apical partial temporal lobe resection remained seizure free (operated on just 2 months ago). After anterior partial temporal lobe resection 2/3 patients were seizure-free (all oft hem invasively examined).

Summary:

In patients with temporal lobe meningoencephaloceles and a complex constellation of findings (e.g. bilateral findings) invasive EEG-monitoring with depth electrodes helps to determine the epileptogenicity and extent of neurosurgical resection and therefore improves the outcome.