Hippocampal sclerosis
Neuropathological condition with hippocampal cell loss and gliosis.
Hippocampal sclerosis (HS), also called mesial temporal sclerosis (MTS), is a neuropathological condition marked by severe loss of neurons and gliosis within the hippocampus. It arises in three main contexts: mesial temporal lobe epilepsy, adult neurodegenerative disease, and acute brain injury. Imaging techniques like magnetic resonance imaging (MRI) and positron emission tomography (PET) can help detect it.
In 1825, Camille Bouchet and Jean-Baptiste Cazauvieilh noted firmness and shrinkage of the uncus and medial temporal lobe in both epileptic and non-epileptic brains. Wilhelm Sommer, in 1880, examined 90 brains and identified the classic Ammon's horn sclerosis pattern: heavy neuronal loss in the CA1 hippocampal subfield and some loss in CA4, later confirmed by Emil Bratz. Walther Spielmeyer, in 1927, described loss across all hippocampal subfields—total Ammon's horn sclerosis. In 1966, James H. Margerison and John Arthur Nicholas Corsellis reported loss mainly in CA4, termed end folium sclerosis. Karl Heinz Stauder, in 1935, linked mesial temporal lobe seizures to hippocampal sclerosis.
Later, hippocampal sclerosis was found in older adults with neurodegenerative diseases like frontotemporal lobar degeneration and amyotrophic lateral sclerosis. In 2006, researchers established that these two conditions are often TAR DNA-binding protein 43 (TDP-43) proteinopathies. By 2009, they recognized that about 10–20% of frontotemporal lobar degeneration cases not due to tau proteinopathy stem from a FUS proteinopathy, often accompanied by hippocampal sclerosis. In 1994, Dickson and colleagues described hippocampal sclerosis in demented individuals over 80 with disproportionately severe memory impairment. In 2007, researchers identified this as Limbic-predominant age-related TDP-43 encephalopathy (LATE), a TDP-43 proteinopathy.
For mesial temporal lobe epilepsy, the typical sample comes from epilepsy surgery. The International League Against Epilepsy (ILAE) defines three HS types: predominant loss in CA1 and CA4 (type 1), CA1 alone (type 2), and CA4 alone (type 3). Classic and total Ammon's horn sclerosis match type 1. Type 1 is most common; type 2 occurs in 5–10% of cases; type 3 in 4–7.4%. Type 3 often appears with dual pathology like focal cortical dysplasia or brain tumors. Mossy fiber sprouting is frequent.
Quick Facts
- Field
- Neurology
Facts from the source article.
Lore & Background
In 1825, Camille Bouchet and Jean-Baptiste Cazauvieilh described palpable firmness and atrophy of the uncus and medial temporal lobe in brains from epileptic and non-epileptic individuals. In 1880, Wilhelm Sommer investigated 90 brains and described the classical Ammon's horn sclerosis pattern, with severe neuronal cell loss in hippocampal subfield CA1 and some loss in CA4, later confirmed by Emil Bratz. In 1927, Walther Spielmeyer described cell loss of all hippocampal subfields, and in 1966, James H. Margerison and John Arthur Nicholas Corsellis described cell loss primarily involving the CA4 subfield. In 1935, Karl Heinz Stauder linked mesial temporal lobe seizures to hippocampal sclerosis.
Hippocampal sclerosis was later found in older adults with neurodegenerative diseases such as frontotemporal lobar degeneration and amyotrophic lateral sclerosis. In 2006, researchers determined that these conditions are often 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 FUS proteinopathy, often accompanied by hippocampal sclerosis. In 1994, Dickson et al. described hippocampal sclerosis in elderly demented individuals over 80 with disproportionately greater impaired memory, later identified as limbic-predominant age-related TDP-43 encephalopathy (LATE).
Reader's Guide
Hippocampal sclerosis is significant as the most common brain abnormality in those with temporal lobe epilepsy, with about 70% of those evaluated for epilepsy surgery having it. The International League Against Epilepsy defines three HS types based on neuronal cell loss patterns, with type 1 being most prevalent. In mesial temporal lobe epilepsy, surgical removal of the hippocampus that spares neighboring structures leads to improved seizure control in many instances. In adult neurodegenerative disease, hippocampal sclerosis is often associated with TDP-43 proteinopathy, as in LATE, where MRI shows asymmetrical hippocampal atrophy and PET shows reduced glucose metabolism in the medial temporal lobe. The condition's presence influences prognosis and treatment, with about 70% of those with intractable mesial temporal lobe epilepsy and hippocampal sclerosis becoming seizure-free after surgery. The recognition of hippocampal sclerosis in different settings has advanced understanding of epilepsy and dementia, though its relationship to febrile seizures remains unclear.
Did You Know?
- Hippocampal sclerosis occurs in three distinct settings: mesial temporal lobe epilepsy, adult neurodegenerative disease, and acute brain injury.
- HS ILAE type 1, the most prevalent type, corresponds to the classic and total Ammon's horn sclerosis pattern.
- In LATE, TDP-43 immunochemistry will determine if TDP-43 proteinopathy caused hippocampal sclerosis.
- About 70% of those evaluated for temporal lobe epilepsy surgery have hippocampal sclerosis.
More in Disorders causing seizures 1-24
Spotted an error? Know more?
Reader corrections go straight into our review queue. Suggest an edit · How this site is sourced