The relationship between neurocysticercosis and epilepsy: an endless debate

Abstract

Neurocysticercosis (NC), or cerebral infection with Taenia solium, is an important public health problem worldwide. Among the neurological sequelae of NC, seizures have been described as the most common symptom. Acute symptomatic seizures often result from degeneration of a viable cyst; however, not all of these patients with acute or provoked seizures will develop epilepsy (i.e., recurrent unprovoked seizures). Because of the high prevalence of epilepsy and NC, a causal, as well as incidental relationship between the two may exist. The epileptogenicity of calcified cysts as well as the potential association between NC and hippocampal sclerosis necessitates future research. Antihelminthic treatment of NC results in disappearance of viable cysts in about one-third of patients with parenchymal disease, but a reduction in seizure recurrence has not been demonstrated in randomized controlled trials. Prevention is critical to reduce the burden of seizure and epilepsy related to NC.Keywords: cysticercosis, Taenia solium, seizure, parasitic. RESUMOA neurocisticercose (NC) ou infecção cerebral pela Taenia solium é importante problema de saúde pública em todo o mundo. Entre as sequelas neurológicas da NC, as crises convulsivas têm sido descritas como os sintomas mais frequentes. Crises convulsivas sintomáticas agudas resultam, muitas vezes, da degeneração de cistos viáveis; entretanto, nem todos os pacientes com NC e crises agudas ou provocadas desenvolvem epilepsia (i.e., crises recorrentes não provocadas). Pode haver uma relação entre epilepsia e NC, causal ou incidental, devido à alta prevalência de ambas. O potencial epileptogênico dos cistos calcificados assim como a possível associação entre NC e esclerose hipocampal ainda necessitam de futuras pesquisas. O tratamento anti-helmíntico da NC resulta no desaparecimento de cistos viáveis em cerca de 1/3 dos pacientes com a doença parenquimatosa, mas não foi demonstrada redução nas taxas de recorrência das crises convulsivas em estudos randomizados controlados. A prevenção é crítica para reduzir o contingente de crises convulsivas e epilepsia relacionadas à NC.

Neurocysticercosis, familial cerebral cavernomas and intracranial calcifications: differential diagnosis for adequate management

“…Although there are evidences supporting seizures as the most common manifestation of NCC in the symptomatic patients 7 NC can be asymptomatic in some cases and seropositiveness through enzyme-linked immune transfer blot assay (EITB) does not always indicate active disease nor CNS involvement 8 . Carpio detected that the proportion of the seropositivity in epileptic NCC patients was the same reported in the general population in the same geographic areas 3 . On the other hand there is a chance of dual disease, like temporal lobe epilepsy with hippocampal sclerosis and NCC, in endemic regions, being involved in the pathogenesis of epilepsy in patients diagnosed with NC and the differential diagnosis will only be reached by means of special neurophysiological testing 9 .…”

“…as the leading cause of epilepsy in endemic regions, although the distinction of seizures occurrence and epilepsy related to NCC has not achieved complete elucidation 3 . With cerebral cyst degeneration there is a contrast enhancement of the lesion surrounded by edema on CT as well as high signal images on MRI T2 sequences and gadolinium enhancement on T1 images supposedly due to inflammatory reactions 4,5 .…”

Inflammation is a key risk factor for persistent seizures in neurocysticercosis

“…Previous studies of the association between disease burden and seizure severity in NCC patients have had mixed results,4, 31 and thus it is possible that other factors can modify the strength of this association. Our study results suggest that the degree of the inflammatory response to the parasite may be one of these factors.…”

“…Seizures in subjects with calcified lesions could be caused by a neurotoxic effect of calcium or, as some authors have suggested, might be unrelated to calcifications 4. The role of inflammation as a contributing factor to seizures in subjects with calcified lesions has not been well studied, as these lesions have traditionally been thought to be immunologically inert.…”

“…These seizures are thought to be caused by perilesional gliosis, inflammation, and/or neurotoxicity from calcified lesions1, 4, 5, 6, 7 and may lead to epilepsy (a disease of chronic recurrent seizures). NCC is the most common cause of acquired adult epilepsy worldwide 4, 7, 8, 9, 10, 11, 12, 13. Epilepsy due to NCC can lead to severe health consequences as seizures are associated with an increased risk of sudden death14, 15, 16, 17 and 20–30% of NCC patients with epilepsy continue to have seizures despite treatment 9…”