Abstracts

Since MRI is such a sensitive tool at detecting hippocampal atrophy (HA), many epilepsy centers use MRI as a screening test to select anteromesial temporal lobectomy candidates likely to have mesial temporal sclerosis (MTS). There is controversy about the need for or extent of video-EEG monitoring in patients with MTS and there is financial pressure to minimize the associated expenses. Previous investigators have retrospectively analyzed surgical cases to determine if video-EEG made a difference in the surgical decision. In our series of cases with mesial temporal sclerosis (MTS) based on MRI revealing HA, the results of video-EEG monitoring were reviewed to determine the types of events recorded during long term monitoring since this more closely mimics the way patients are evaluated.
We queried a prospectively maintained relational database for all EEG studies in patients age 14 years and older evaluated at a large metropolitan county hospital. We analyzed video-EEG reports in 1458 unique patients seen during a 5-year period from 1998 to 2003. We reviewed data in 122 patients with MRI showing evidence for MTS on T2 and/or FLAIR image sequences and their 922 events recorded in the epilepsy-monitoring unit, excluding events where we saw no EEG changes, clinical symptoms or signs. Seizure types recorded and epilepsy classification were determined for each case.
Unsuspected bitemporal independent seizures were recorded in 5 patients (4%). Psychogenic nonepileptic seizures (PNES) occurred in 6 patients (5%) with 10 seizures. Epileptic seizures were also recorded in 5/6 cases with PNES. Unusual events occurred in 24 patients (20%) 46 times; there were no EEG changes and the events were not clinically epileptic or psychogenic. The family or patient often thought these events were seizures, but they usually represented sleep, arousals, hypnic starts, atypical feelings or other nonepileptic phenomena. Subclinical electrographic seizures occurred 32 times in 6 patients (5%). Isolated somatosensory auras occurred in 3 patients and 5 seizures and were not suspected at first in two of these patients from the initial history since both also had more typical temporal lobe auras.
In patients with MRI documented MTS, video EEG can show that a substantial minority of medically refractory patients have nonepileptic events, bitemporal independent seizures, or seizures that suggest an extratemporal localization. The video-EEG monitoring results allowed physicians to optimize medical and psychological care and avoid potentially risky epilepsy surgery in poor surgical candidates. While some argue that patients with a good history and appropriate neuroimaging findings do not require video-EEG monitoring, these data suggest that this type of presurgical evaluation can be justified.
[Supported by: Parkland Health and Hospital System, Dallas County, Texas, USA]