Water diffusion in the human hippocampus in epilepsy

The hippocampus plays a central role in the generation and propagation of s eizures in patients with complex partial seizures. Hippocampal sclerosis (I IS) is a common structural abnormality in patients with refractory epilepsy . The aim of this study was to quantify diffusion in the hippocampus in pat ients with epilepsy to evaluate the diffusion changes associated with HS. W e scanned 20 subjects (14 patients and 6 controls) with a 1.5T magnetic res onance (MR) system using a cardiac-gated, navigated spin-echo diffusion-wei ghted sequence. Hippocampal ADC measurements were performed on maps of the ADC measured in three orthogonal directions labeled x, y, and z. The mean A DC (ADC(av)) and an anisotropy index (AI) were calculated, Hippocampi which fulfilled the MR criteria for HS had a higher ADC(av) (p < 0.001) and a lo wer AI (p = 0.04) than normal appearing hippocampi in patients and hippocam pi in controls. These results imply a loss of structural organization in sc lerotic hippocampi and an expansion of the extracellular space. Quantitativ e measurements of diffusion can be used as an independent parameter for the identification and characterization of abnormal hippocampi in epilepsy. (C ) 1998 Elsevier Science Inc.