Epilepsy and Neuron Loss in the Hippocampus

Abstract

Quantitation of hippocampal neurons was performed in 20 patients with generalized epilepsy. Twelve suffered from partial seizures. The neuronal numbers were compared with the control series of patients without epilepsy. It was established that there were fewer neurons in the hippocampi from patients with epilepsy than from those of controls. The neuron loss was particularly marked in the endfolium (field H3), the granule cells (fascia dentata), and particularly in the caudal (anterior) part of the structure. Frequent, generalized epileptic seizures and long duration of the epileptic disorder influenced the neuron loss. In some parts of the pyramidal band (field H1), the neuron loss appeared at a younger age, which leads one to suspect its particular involvement in the seizure mechanism. The neuron loss was not related to the different types of seizures investigated. The results support the hypothesis of neuron loss as an ongoing process in patients with epilepsy, whatever the type of epilepsy, when tonic-clonic seizures, as is very common, are present.

Apoptosis and proliferation of dentate gyrus neurons after single and intermittent limbic seizures

“…The finding of apoptosis in a similar pattern in these two different models of temporal lobe epilepsy indicates that early death of specific granular and hilar neurons through apoptosis might constitute one of the primary events in seizure-induced hippocampal pathology. Postmortem analysis of humans with chronic idiopathic epilepsy suggests that neuronal damage is cumulative and related to the frequency of seizures and duration of the disease (50). This implies that even if the cell loss induced by each brief seizure episode may be modest, as demonstrated here, the apoptosis of dentate gyrus neurons following repeated seizures over several years could lead to severe pathological changes, possibly also hippocampal sclerosis in patients.…”

Updating hippocampal representations: CA2 joins the circuit

“…CA2 is more resistant to cell loss following clinical or experimentally-induced seizures relative to other subfields [120,121], potentially because of its expression of adenosine A1 receptors [50] and their anticonvulsant properties [122]. Some species of rodent may even be seizure-resistant due to unique CA2 cytoarchitecture [123].…”

Muscarinic Receptor Loss and Preservation of Presynaptic Cholinergic Terminals in Hippocampal Sclerosis

“…The hippocampal formation (HF) is most consistently and severely affected in medically refractory temporal lobe epilepsy, and the term hippocampal sclerosis (HS) is used to describe the neuronal loss and gliosis in this structure. Quantitative studies demonstrated that neuronal cell counts are decreased in all regions of the HF and are diminished maximally in the CA1 region in HS (2)(3)(4). The striking tendency of the HF to sustain neuronal cell loss led to extensive investigation of this structure in an attempt to understand better the pathogenesis of partial epilepsy.…”