Hippocampal dentate gyrus dysplasia and the risk of sudden unexpected death

Hippocampal dentate gyral dysplasia is well-described in temporal lobe epilepsy and may be a risk factor for sudden, unexpected death in several populations: infants (sudden infant death syndrome [SIDS], sudden unexpected infant death [SUID]), toddlers (sudden unexpected death of a child [SUDC]), and epileptics (sudden unexpected death in epilepsy [SUDEP]). We examined reports and histopathological slides from autopsies performed at our institution from 2008 through 2016 to determine whether the presence or absence of any of the described forms of such dysplasias (duplications, hyperconvolutions, and granule cell dispersion, including bilamination), correlated with the causes of death. From well over 4000 autopsies, we identified 949 autopsies with a neuropathology examination by a neuropathologist. Of these, 205 cases (21.6%) had 1 or more of the described abnormalities of 1 or both dentate gyri; 87 (42.4%) of the individuals in this group of 205 autopsies had died suddenly and unexpectedly, including 29/90 (32.2%) cases of SUDEP, 17/31 (54.8%) cases of SUDC, and 51/104 (49.0%) cases of infants with SIDS or SUID. We conclude that these changes are readily recognizable by experienced neuropathologists and that because they are overrepresented in an autopsy population that died suddenly and unexpectedly, they may represent a risk factor for such outcomes.