MR DETECTION OF HIPPOCAMPAL DISEASE IN EPILEPSY - FACTORS INFLUENCINGT2 RELAXATION-TIME

PURPOSE: To assess the reproducibility and stability of hippocampal T2 relaxation times and examine the effects of patients' age, seizures, and duration of epilepsy on this measure. METHODS: Hippocampal T2 rela xation times were measured in 63 patients with chronic epilepsy (55 wi th partial and 8 with idiopathic generalized seizures) using a Carr-Pu rcell-Meiboom-Gill sequence, echo times 22 to 262 millisecond, on a 1. 5-T clinical MR imaging system. Twenty-three patients on stable medica tion regimens underwent repeated T2 relaxometry after an interval of b etween 115 and 331 days. In 4 patients with partial seizures, hippocam pal T2 relaxation times were measured interictally and again within 45 minutes of seizures. RESULTS: In the 55 patients with partial epileps y, hippocampal T2 relaxation times did not correlate with seizure freq uency, duration of epilepsy, or age, but they were significantly more abnormal in those patients with a history of prolonged (more than 30 m inutes) early childhood seizures than in those without. Eight patients with idiopathic generalized epilepsy had normal MR and hippocampal T2 relaxation times. In the 23 patients who underwent repeated T2 relaxo metry there was no evidence of qualitative changes in T2-weighted imag es of the hippocampi or systematic changes of hippocampal T2 relaxatio n times with time. In 4 patients recent complex partial or secondary g eneralized seizures did not acutely alter hippocampal T2 relaxation ti mes. CONCLUSION: Hippocampal T2 relaxation time is a precise, reliable , stable, noninvasive measurement sensitive to hippocampal disease. Th ese results do not suggest progression of hippocampal disease in patie nts with intractable partial seizures during periods of up to 331 days .