Hippocampal sclerosis
Hippocampal sclerosis (HS) or mesial temporal sclerosis (MTS) is a neuropathological condition with severe neuronal cell loss and gliosis in the hippocampus. Neuroimaging tests such as magnetic resonance imaging (MRI) and positron emission tomography (PET) may identify individuals with hippocampal sclerosis. Hippocampal sclerosis occurs in 3 distinct settings: mesial temporal lobe epilepsy, adult neurodegenerative disease and acute brain injury. In 1825, Bouchet and Cazauvieilh described palpable firmness and atrophy of the uncus and medial temporal lobe of brains from epileptic and non-epileptic individuals. In 1880, Wilhelm Sommer investigated 90 brains and described the classical Ammon's horn sclerosis pattern, severe neuronal cell loss in hippocampal subfield cornum Ammonis 1 (CA1) and some neuronal cell loss in hippocampal subfield CA4. a finding later confirmed by Bratz. In 1927, Spielmeyer described cell loss of all hippocampal subfields, the total Ammon's horn sclerosis pattern, and in 1966, Margerison and Corsellis described cell loss primarily involving the CA4 subfield, the end folium sclerosis pattern. In 1935. Stauder linked mesial temporal lobe seizures to hippocampal sclerosis. Hippocampal sclerosis was later found to occur in older adults with neurodegenerative diseases such as frontotemporal lobar degeneration and amyotrophic lateral sclerosis. In 2006, researchers determined that amyotrophic lateral sclerosis and frontotemporal lobar degeneration are often TAR DNA-binding protein 43 (TDP-43) proteinopathies. In 2009, researchers recognized that about 10-20% of individuals with frontotemporal lobar degeneration not caused by tau proteinopathy occurred because of a RNA-binding protein FUS (FUS) proteinopathy; hippocampal sclerosis often accompanied the FUS proteinopathy. In 1994, Dickson et al. described hippocampal sclerosis occurring in elderly demented individuals > 80 years old with disproportionately greater impaired memory.
