Evaluating the Association of Calcified Neurocysticercosis and Mesial Temporal Lobe Epilepsy With Hippocampal Sclerosis in a Large Cohort of Patients With Epilepsy

Abstract

Background: Neurocysticercosis (NCC) is a parasitic infection of the central nervous system that has been associated with mesial temporal lobe epilepsy with hippocampal sclerosis (MTLE-HS). However, this association has not been completely established.

Objective: To evaluate the prevalence of calcified NCC (cNCC), its characteristics and a possible association between cNCC and MTLE-HS in a cohort of 731 patients with epilepsy.

Methods: We review clinical, EEG and neuroimaging findings of 731 patients with epilepsy. From these, 659 had CT-scans and 441 patients had complete neuroimaging with CT-scans and MRI. In these patients, we review the prevalence and characteristic of epilepsy in cNCC and in MTLE-HS patients.

Results: Forty-two (6.4%) of the 659 patients studied with CT-scans had cNCC. cNCC lesions were more frequent in women than in men (n = 33-78.6% vs. n = 09-21.4%, respectively; OR = 3.64;(95%CI = 1.71-7.69); p < 0.001). cNCC was more often in patients who developed epilepsy later in life, in older patients, in patients who had a longer history of epilepsy, and in those with a lower educational level. MTLE-HS was observed in 93 (21.1%) of 441 patients that had complete neuroimaging, and 25 (26.9%) of these 93 patients also had cNCC. Calcified NCC was observed in only 17 (4.9%) of the remaining 348 patients that had other types of epilepsy rather than MTLE-HS. Thus, in our cohort, cNCC was more frequently associated with MTLE-HS than with other forms of epilepsy, O.R. = 11.90;(95%CI = 6.10-23.26); p < 0.0001).

Conclusions: As expected, in some patients the epilepsy was directly related to cNCC lesional zone, although this was observed in a surprisingly lower number of patients. Also, cNCC lesions were observed in other forms of epilepsy, a finding that could occur only by chance, with epilepsy probably being not related to cNCC at all. In this cohort, cNCC was very commonly associated with MTLE-HS, an observation in agreement with the hypothesis that NCC can contribute to or directly cause MTLE-HS in many patients. Given the broad world prevalence of NCC and the relatively few studies in this field, our findings add more data suggesting a possible and intriguing frequent interplay between NCC and MTLE-HS, two of the most common causes of focal epilepsy worldwide.

Keywords: epileptogenesis; gender differences in epilepsy; hippocampal sclerosis; inflammation in epilepsy; initial precipitating injury (IPI); neurocysticercosis.

Figure 1

Design of the study. Data of all 731 patient were collected. From these, 659 patients had CT-scans and 42 of them had imaging compatible with cNCC. Complete neuroimaging was available for reviewing in 441patients. The Tables showing main analysis done are included in this figure making easy to follow the steps of this study.

Figure 2

CT-scans of four different patients showing small calcifications (1–10 mm in diameter), single or multiple, located in brain parenchyma. These lesions are typically observed in patients with calcified neurocysticercosis and can be easily observed using CT-scan.

Figure 3

(A) CT-scan showing a single calcification (black arrow) highly suggestive of cNCC. (B) MRI FLAIR coronal imaging showing findings of hippocampal sclerosis (white arrow), typically observed in patients with mesial temporal lobe epilepsy associated with hippocampal sclerosis.

Figure 4

The map is showing countries at risk for neurocysticercosis in the world, according to World Health Organization (/WHO). at:http://apps.who.int/iris/bitstream/10665/153237/1/9789241508452_eng.pdf?ua = 1. [Last accessed November, 2021]. The map is also showing places were main of the original clinical work evaluating the association of neurocysticercosis and mesial temporal lobe epilepsy associates with hippocamapal sclerosis were done. Numbers are references to these works, as detailed in Table 6.