Abstracts

RATIONALE: Neuropathologic examination of tissue following anterior temporal lobectomy (ATL) for treatment of complex partial seizures (CPS) reveals histologic substrates that correlate with postoperative seizure control. Mesial temporal sclerosis (MTS) is the most common pathology in patients undergoing surgery for CPS, accounting for approximately 50% of patients. Within MTS several different patterns of neuronal loss and gliosis have been described, including Ammon[scquote]s horn sclerosis (AHS) and Atypical sclerosis (Atypical). The category of Atypical sclerosis includes: end folium (CA4) sclerosis; sclerosis of the dentate gyrus and CA4; and sclerosis of CA1 alone. We evaluated the influence of the underlying neuropathology of AHS and Atypical sclerosis on clinical seizure outcome following ATL.
METHODS: Neuropathologic examination revealed that of 150 patients who underwent ATL from 1980 to 1999, 77 patients were classified as AHS, while 20 patients were classified as Atypical. All patients underwent neurologic and neurophysiologic evaluations prior to ATL. Seizure control was evaluated at least 6 months postsurgery using a standard seizure outcome scale of a reduction in seizures: 1) [gt]95%, 2) 75-95%, 3) 50-74%, 4) [lt]50%, and 5) none.
RESULTS: The AHS and Atypical groups did not differ preoperatively on gender, birth weight, handedness, age at surgery, educational attainment, and age of seizure onset. 66% of AHS patients reported febrile seizures, in contrast to 19% of Atypical patients. The AHS group tended to report more seizures per month preoperatively than the Atypical group. At the mean follow-up of 8.1 years, 82% of the AHS and 30% of Atypical patients reported a greater than 95% reduction in seizure frequency (P=.001). Furthermore, 32% of AHS patients discontinued AEDs following ATL compared to only 5% of the Atypical patients (P=.008).
CONCLUSIONS: AHS patients demonstrated better seizure control following ATL than the Atypical sclerosis patients. We postulated that the latter group may have a more widely disseminated pathology that is less amenable to resection. The current findings highlight the need to counsel patients on the probable degree of control of seizures after ATL if their radiological and neurological findings are not entirely consistent with the classic pattern of AHS. The differentiation in the patterns of clinical and demographic findings following ATL raises the question of whether the classical AHS and the Atypical sclerosis groups comprise two distinct syndromes. These findings highlight the need for future research to investigate these pathology groups as separate entities.
Support: Funding supported by a NIH Postdoctoral Medical Rehabilitation Research Training Grant HDO7465 and the Peter Kellaway, Ph.D. Endowment for Research.