Utility of short tau inversion recovery sequence in the diagnosis of hippocampal sclerosis

Abstract

Objective To evaluate the utility of short tau inversion recovery (STIR) sequence in the diagnosis of hippocampal sclerosis (HS). Methods Twenty-one patients with medial temporal lobe epilepsy without neoplasm lesions or injuries by conventional MRI sequence including T1WI, T2WI and FLAIR were included in this study. STIR imaging in axial, coronal and sagittal sequences was performed on these patients. Diagnosis of HS was based on the findings of hippocampal atrophy, alteration signal, disturbed internal structure and enlargement of the inferior horn. The findings shown on conventional MRI were compared with those on STIR sequence. Furthermore, the correlation of radiologic and histological findings was investigated in 6 patients operated for refractory seizures. Results On conventional MRI sequence, 14 patients (66.7%) were confirmed with unilateral HS and 4 patients were suspected with unilateral HS. In contrast, all these 18 patients (85.7%) were confirmed with unilateral HS by STIR. Particularly, STIR sequence delineated the internal structure of hippocampus more clearly than conventional MRI sequences did. “C” shaped contour in subiculum-CA1-CA2 was revealed in normal hippocampus on STIR sequence and disappeared in HS, correlated to the pathology finding of loss of neuron in CA1 in resected tissues in 6 operated patients. The patients with HS also showed areas of hypodensity in CA4 on STIR, in accordance with pathologic findings of gliosis in this area in the 6 operated patients. Conclusion STIR sequence could depict the internal anatomical structure of hippocampus with high resolution superior to conventional MRI sequences, and can be of great value in the diagnosis of HS. Key words: Hippocampus; Sclerosis; Epilepsy; temporal lobe; Diagnostic imaging; Short tau inversion recovery