Postmortem Examination of H.M.'s Brain: Autopsied Brain, In Situ MRI, and Ex Vivo MRI

H.M.’s first in vivo MRI scans occurred in 1992 at Brigham and Women’s Hospital and in 1993 at Massachusetts General Hospital. He underwent several additional in vivo imaging sessions in subsequent years. These scans revealed that the bilaterally symmetrical lesion damaged most of the amygdaloid complex, the entorhinal cortex, part of the ventrocaudal perirhinal cortex, the uncal and rostral portions of the hippocampal complex, and part of the parahippocampal cortex.  Some of the ventral perirhinal and parahippocampal cortex was intact.  Approximately 2 cm of caudal hippocampal tissue was also spared, but it appeared atrophic and was likely deafferented due to removal of the entorhinal cortex.  The subcortical white matter associated with the most anterior portions of the superior, middle, and inferior temporal gyri may have been compromised by the resection.  The cerebellar atrophy was dramatic, but the cortical surface appeared normal for H.M.’s age.

H.M. died on December 2, 2008.  That night, we conducted a wide variety of in situ MRI scans in a 3 Tesla scanner at the Massachusetts General Hospital Martinos Center.  The next morning, H.M.’s body was transported to the Massachusetts General Hospital Morgue, where Dr. Matthew Frosch performed an autopsy.  Photographs taken immediately afterward provided the first documentation of H.M.’s lesions in his fresh brain.  After approximately 10 weeks of tissue fixation, we obtained structural ex vivo data at ultra-high resolution using 3 Tesla and 7 Tesla magnets.  The postmortem research had two goals—to document the specific structures that were removed and spared in H.M.’s brain, based on the gross examination of the fresh brain and analysis of the MRI images, and to relate the behavioral dissociations documented during H.M.’s life to the precisely established sparing and loss of brain tissue.  Here, we briefly introduce the anatomical structures that define the medial temporal lobe region and then describe the findings from H.M.’s autopsy and in situ and ex vivo MRI studies.