Epilepsia, 49(1):33–39, 2008 doi: 10.1111/j.1528-1167.2007.01277.x FULL-LENGTH ORIGINAL RESEARCH PROPELLER MRI visualizes detailed pathology of hippocampal sclerosis Soﬁa H. Eriksson, Maria Thom, Philippa A. Bartlett, Mark R. Symms, Andrew W. McEvoy, Sanjay M. Sisodiya, and John S. Duncan Department of Clinical and Experimental Epilepsy, Institute of Neurology, University College London, London, and National Society for Epilepsy, Chalfont St. Peter, United Kingdom SUMMARY 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 T2-weighted images and volume loss on T1-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 mov- ing 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 (T1 volume, T2-weighted, PD and FLAIR images) and PRO- PELLER 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. Hippocam- pal sections were compared with PROPELLER images. Results: PROPELLER images were T2-weighted and had superior tissue contrast compared to rou- tine sequences. PROPELLER images showed the in- ternal 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 hip- pocampus in patients who did not move overtly, negating the inevitable subtle movements during scans. More detailed in vivo studies of the hip- pocampal formation, investigating subtle abnor- malities such as end folium sclerosis, and the neo- cortex are now possible and may increase the diag- nostic yield of MRI. KEY WORDS: Epilepsy, Magnetic Resonance Imaging, PROPELLER, Hippocampal sclerosis, Histopathology. INTRODUCTION Hippocampal sclerosis (HS) is the most common cause of refractory temporal lobe epilepsy. Histopathologically, HS is characterized by neuronal loss and gliosis. The neu- ron loss in classical HS is greatest in CA1 and the hilar re- gion (including CA4) with accompanying gliosis (Bruton, 1988). In severe HS there can be almost total neuronal loss Accepted July 26, 2007; Online Early publication September 18, 2007. Address correspondence and reprint requests to SM Sisodiya, Depart- ment of Clinical and Experimental Epilepsy, Institute of Neurology, UCL, Queen Square, Box 29, London WC1N 3BG, United Kingdom. E-mail: sisodiya@ion.ucl.ac.uk Blackwell Publishing, Inc. C 2008 International League Against Epilepsy in all hippocampal subfields. There may also be dispersion of the dentate granule cell layer, making this appear broad- ened (Houser, 1990). In addition, sprouting of excitatory mossy fibers may be demonstrated using the Timms histo- chemical method (Sutula et al., 1989). There are also milder forms of nerve cell loss, such as “end folium sclerosis” (Bruton, 1988) in which the cell loss appears to be restricted to the hilus. These cases are not readily identified on MRI, epilepsy onset is later and out- come after surgery is worse than in cases with classical HS (van Paesschen and Revesz, 1997). More recently a new classification system for HS has been proposed based on the pattern of nerve cell loss within the hippocampus seen histopathologically with different clinical phenotypes for the different groups (Blumcke et al., 2007). To date, these 33