Epilepsy-associated neurocognitive disorders (EAND) in an onchocerciasis-endemic rural community in Cameroon: A population-based case–control study

Abstract

Background: Epilepsy affects at least 50 million individuals worldwide, especially in sub-Saharan Africa (sSA). Cognitive impairment is common in people with epilepsy (PWE) yet, little is known on the burden of cognitive impairment in people with epilepsy in sSA. This study was thus designed to assess cognitive impairment in PWE or epilepsy-associated neurocognitive disorders (EAND) in a rural population in Cameroon. Methods: This was a case-control study including PWE and age/sex-matched healthy controls from July to September 2017 in Bilomo, a village in the Mbam and Kim Division. The Montreal Cognitive Assessment (MoCA), International HIV Dementia Scale (IHDS), Dubois' Five Word testing, Frontal Assessment Battery (FAB), Isaac's Set Test and the Clock drawing test were administered to the study participants to evaluate global and specific cognitive functions. Results: Eighty participants were included (40 cases and 40 controls) with a mean age of 25.78 years. Using the MoCA, 87.5% of cases had cognitive impairment, against 37.5% of controls (p < 0.001; OR 11.67; CI 3.40-45.09). Using the IHDS, the prevalence of global cognitive impairment was 84.6% among the cases against 40% for the controls (p = <0.001; OR 7.07; CI 2.29-29.19). Specifically, executive function deficits (92.5% of cases vs 40.0% of controls p = <0.001 OR = 18.50 CI; 4.48-105.08) and decreased verbal fluency (100% of cases against 45% of controls p < 0.001) were the most affected cognitive domains. Longer duration of epilepsy and higher seizure frequency were associated with global cognitive impairment. Low level of education was associated with both decreased verbal fluency and executive dysfunction while a longer stay in Bilomo correlated with poor results on the Isaac's Set Test. Conclusion:The prevalence of cognitive impairment appears to be much higher in PWE in the Mbam valley, particularly decreased executive function and verbal fluency, than in people without epilepsy. Longer disease duration, higher seizure frequency, low level of education and length of stay in Bilomo are associated with poorer cognitive performance. More studies are needed to refine evaluation tools to better characterize and manage EAND in sSA.

Epilepsy in the Sanaga‐Mbam valley, an onchocerciasis‐endemic region in Cameroon: electroclinical and neuropsychological findings

“…The second important finding of our study is the confirmation of the finding of severe CI in PWE in the Mbam valley by Njamnshi et al 31 who reported 92.5% reduction of performance in executive function tests and 100% impairment of verbal fluency. In our study participants, 66% had severe frontal CI, while 29% showed severe global CI and 28% had severe episodic memory impairment.…”

“…CI might thus be a consequence of repeated seizures, and this is consistent with the fact that EEG abnormalities are mainly in the frontal and temporal lobe. However, the role of ASM and onchocerciasis infection in CI in our study subjects cannot be ruled out, especially given that the case‐control study in Bilomo 31 reported CI in controls, although the issue of using culturally sensitive neuropsychological tests remains to be resolved. ASM might have contributed to CI as phenobarbital use was associated with a lower cognitive score than carbamazepine, suggesting a potentiation of the cognitive disorders by phenobarbital, known for its long‐term side effects on attention mechanisms 37 …”

“…5,18,24 We detected a specific EEG pattern consisting of bifrontotemporal slow waves and/or 1.5-to 2-Hz spikes and waves among 36 (72.2%) PWE with abnormal EEGs and related cognitive deficits mostly in frontal cognition. Interestingly, a case-control study conducted in 2017 in Bilomo, a village in the Mbam valley using a verbal and nonverbal neuropsychological battery, demonstrated a higher prevalence of cognitive impairment in PWE than in controls, particularly a significant decrease in executive function and verbal fluency, 31 suggesting underlying frontal and temporal dysfunction.…”

Association Between Ov16 Seropositivity and Neurocognitive Performance Among Children in Rural Cameroon: a Pilot Study

“…Based on these results, it appears that infection with O. volvulus may impact executive functions more than motor functions. In line with these observations, a recent study conducted in the onchocerciasis-endemic village of Bilomo in Cameroon found a high prevalence of both executive function deficits (92.5% among PWE vs 40.0% among controls; p < 0.001) and decreased verbal fluency (100% among PWE vs 45% among controls; p < 0.001), with a longer duration of residence in the village being associated with poorer neurocognitive performance (Njamnshi et al, 2020). This suggests that exposure to O. volvulus may induce cognitive impairment which could be exacerbated by the development of epilepsy.…”

“…Indeed, previous studies revealed that persons with OAE often show signs of cognitive impairment (Colebunders et al, 2018a, b;Siewe Fodjo et al, 2019a, b, c). Furthermore, in a recent case-control study in onchocerciasisendemic communities in Cameroon in Cameroon, we found that cognitive impairment (assessed using a comprehensive neuropsychological test battery) was significantly more prevalent in persons with epilepsy (PWE) than in age-and sexmatched controls (Njamnshi et al, 2020). However, it is still unclear whether the cognitive symptoms observed in persons with OAE preceded seizure onset, or were solely consequences of the repeated epileptic episodes.…”