Hippocampal T(2) abnormalities correlate with antecedent events and help predict seizure intractability.

Abstract

We performed hippocampal T(2) relaxometry as part of a routine magnetic resonance imaging (MRI) examination in 50 normal controls and 127 consecutive patients referred because of suspected seizures.On the basis of T(2) values in controls (100.2 +/- 4.2 ms) we defined normal as <110 ms (<mean + 2 SD), borderline as 110-113 ms (mean + 2 SD to mean + 3 SD) and abnormal as >113 ms (>mean + 3 SD).After detailed investigation, 103 of these 127 patients had epilepsy and 24 did not. In the nonepilepsy group, none had abnormal hippocampal T(2) values. Twenty-seven of the 103 patients in the epilepsy group had abnormal values, 7 were borderline and 69 were normal. Only 5 patients with abnormal T(2) values did not have temporal lobe epilepsy: 1 had extratemporal lobe epilepsy, 1 had generalized epilepsy and 3 had unclassified epilepsy. Twenty-two of 27 (81%) patients with abnormal hippocampal T(2) values had intractable epilepsy [compared with 32 of 69 (46%) patients with normal values; p < 0.05, chi(2) test]. Two thirds of patients with abnormal values had a history of a major antecedent event (compared to only 7% of those with normal values, p < 0.05, chi(2) test).Abnormal T(2) relaxometry is significantly associated with intractable epilepsy as well as with major antecedent events.