Bilateral reductions of hippocampal volume, glucose metabolism, and Wada hemispheric memory performance are related to the duration of mesial temporal lobe epilepsy

In refractory temporal lobe epilepsy (TLE) temporal lobe structures and fun ctions are continuously or intermittently affected by abnormal brain electr ical events, noxious neurochemical agents, and metabolic disturbances. Ther e is conflicting evidence regarding the relationship between the duration o f refractory mesial TLE and quantitative measures of temporal lobe function s and volumes of the hippocampi. Twenty patients (aged 28 +/- 7 years, 14 m ales) with an initial precipitating injury before the age of 5 years were s ubjected to high-resolution magnetic resonance imaging, fluoro-2-deoxy-D-gl ucose positron-emission tomography (PET), and the Wada test. We investigate d whether the duration of unilateral refractory TLE (12 left, 8 right) affe cts hippocampal volume, glucose metabolism, or Wada hemispheric memory perf ormance. Ipsilateral to the epileptogenic zone the hippocampal volume, meta bolism, and Wada hemispheric memory performance were reduced compared to th e corresponding contralateral measures. The duration of epilepsy controlled for age at investigation, side of seizure origin, underlying cause, and se x were negatively correlated with ipsi- and contralateral hippocampal volum e, hippocampal metabolism, and Wada hemispheric memory performance. Moreove r, ipsilateral Wada hemispheric memory performance and contralateral hippoc ampal glucose metabolism were correlated with the frequency of habitual sei zures. Refractory TLE seems to be associated with a slow but ongoing bilate ral temporal lobe damage. These cross-sectional results require verificatio n by longitudinal studies carried out over a period of more than two decade s.