PROPELLER MRI visualizes detailed pathology of hippocampal sclerosis

Purpose: Hippocampal sclerosis (HS) is the most common cause of refractory temporal lobe epilepsy. Histopathologically, HS is characterized by neuron loss and gliosis. HS can be identified on MRI by signal increase on T-2-weighted images and volume loss on T-1-weighted volume images. The Periodically Rotated Overlapping Parallel Lines with Enhanced Reconstruction ("PROPELLER") sequence has excellent contrast between grey and white matter and compensates for subjects moving during the scan. The aim of the current report was to explore PROPELLER image quality of the hippocampus compared to routine sequences. Methods: Routine sequences (T-1 volume, T-2-weighted, PD and FLAIR images) and PROPELLER images were acquired in four presurgical patients with HS using a GE 3T Excite HD scanner (General Electric). Resected tissue was stained with LFB, and for GFAP, NeuN and dynorphin immunohistochemistry. Hippocampal sections were compared with PROPELLER images. Results: PROPELLER images were T-2-weighted and had superior tissue contrast compared to routine sequences. PROPELLER images showed the internal hippocampal structures and tissue changes associated with HS. This corresponded to changes seen on histopathological sections confirming that the sequence could distinguish between different strata and subfields of the hippocampus. Discussion: The PROPELLER sequence shows promise for detailed in vivo imaging of the hippocampus in patients who did not move overtly, negating the inevitable subtle movements during scans. More detailed in vivo studies of the hippocampal formation, investigating subtle abnormalities such as end folium sclerosis, and the neocortex are now possible and may increase the diagnostic yield of MRI.