Update on Cysticercosis Epileptogenesis: the Role of the Hippocampus

Abstract

Neurocysticercosis (NCC) is the most common helminthic infection of the nervous system and a frequent cause of reactive seizures and epilepsy worldwide. In many cases, multiple episodes of focal seizures related to an identifiable parenchymal brain cyst (and likely attributable to local damage) continue for years after the cyst resolves. However, cases where seizure semiology, interictal EEG abnormalities, and parasites location do not correlate raise concerns about the causal relationship between NCC and either reactive seizures or epilepsy, as well as the epileptogenic potential of parasites. Neurosurgical series of patients with intractable epilepsy and cross-sectional population-based studies have shown a robust association between NCC and hippocampal sclerosis (HS), which might contribute to the above-referred inconsistencies. Current information does not allow to define whether in patients with NCC, HS could result from recurrent seizure activity from a local or distant focus or from chronic recurrent inflammation. In either case, HS may become the pathological substrate of subsequent mesial temporal lobe epilepsy (MTLE). Longitudinal clinical- and population-based cohort studies are needed to evaluate the causal relationship between NCC and HS and to characterize this association with the occurrence of MTLE. If a cause-and-effect relationship between NCC and HS is demonstrated, NCC patients could be assessed to examine neuronal mechanisms of hippocampal epileptogenesis in comparison with animal models, to identify biomarkers of hippocampal epileptogenesis, and to develop novel interventions to prevent epilepsy in NCC and perhaps in other forms of acquired epilepsy.

The Association Between Neurocysticercosis and Hippocampal Atrophy is Related to Age

“…[4][5][6][7] However, it is not yet clear whether this association is related to repetitive seizure activity or to mechanisms of local or remote inflammation. [8][9][10] We recently reported the association between calcified NCC and hippocampal atrophy in a population of 248 older adults living in rural Ecuador. 11 This report expands the studied population to 663 individuals, including 318 aged 40-59 years, to explore whether this association persists at a younger age.…”

Hippocampal sclerosis in a child with multiple neurocysticercosis

“…[12] This case wherein follow-up neuroimaging studies have revealed the development of HS 2 years after the diagnosis of NCC lends support to the hypothesis that NCC can be a causative factor in the development of HS and potential mechanism seems to be inflammation-mediated and not recurrent seizures. Another unusual finding, in this case, has been nondevelopment of refractory epilepsy despite the presence of HS.…”

Antiparasitic treatment of neurocysticercosis - The effect of cyst destruction in seizure evolution

“…Additionally, multiple reports suggest that NCC may lead to mesial temporal sclerosis as a secondary epileptogenic focus. 56–59 Repeated focal seizures along years or even decades in patients with NCC suggest a structural damage and formation of epileptogenic circuits, independent of the contributory effect of transient episodes of inflammation.…”