Neuropsychological Testing in Patients in Juvenile Myoclonic Epilepsy: Are They Required in Every Patient?

Dear Editor

We read with great interest the recently published article titled “Cognitive dysfunction in Juvenile Myoclonic Epilepsy (JME) – A tertiary care center study” by Chawla et al.[1] The authors have concluded that JME patients demonstrate both frontal and parieto-occipital lobe dysfunction. Hence, detailed higher mental function tests supplemented by functional neuroimaging studies should be done in JME patients for their comprehensive management. We wish to add certain points.

Not only the patients of JME, but patients with other idiopathic epilepsy or electroclinical syndromes also demonstrate some subclinical impairment in neuropsychological tests, but in most of these cases, it does not require any medication and does not change the management decisions of the clinicians.[2] The authors themselves have pointed out that idiopathic epilepsies do not show any apparent cognitive impairment and only sophisticated neuropsychological tests can bring out subclinical cognitive dysfunction in them. Thus, a detailed neuropsychiatric assessment might not be feasible for every case of JME in busy clinical settings and functional neuroimaging is also not available in many centers; neither it is feasible for all of them in resource-constrained settings. The results of these tests are less likely to change the treatment decisions of clinicians pertaining to comprehensive management and hence in our opinion should be preserved only to research settings. It would be better if the authors can provide a brief battery of neuropsychological tests addressing different domains of higher mental function and which can be completed successfully within few minutes in a busy outpatient setting like the revised Bhatia's short battery of performance test of intelligence for adults.

Secondly, the authors have included patients as young as 12 years in the study but utilized certain neuropsychological tests mainly validated for adults or >18 years of age like PGIMS is mainly validated for patients of a minimum age of 20 years. Younger patients might not have performed some components of PGIMS appropriately, which could have confounded the study results. It would have been better if the authors would have chosen appropriate neuropsychological scales for adolescents.

Thirdly, the authors have explored various probable factors affecting the cognitive performance of JME patients and performed univariate analysis to determine the presence of any association and positive/negative correlation between the dependent variable (cognitive function) and independent variables (age at enrollment, age at onset, EEG abnormality, and duration of epilepsy). However, it would have been more informative if the authors would have attempted to perform multivariate logistic regression analysis or at least ANCOVA to determine whether there is an association between the independent variables assumed by authors.[34] This is because the age of onset appears to be somewhat inversely correlated with the duration of epilepsy in the sample population. The authors should have considered some other more important determinants of cognitive function such as type and number of ASMs and family history of seizures in the univariate analysis, as included in the study by Kim et al.[5] The authors themselves have mentioned in the discussion section that valproate, levetiracetam, and topiramate have a contrasting effect on the cognitive function of patients. Moreover, some of the correlations found by the authors appear to be unexpected and in contradiction with findings from previous studies, for example, age of onset had a negative correlation with conflicting instructions and a positive correlation with thematic perception. It would have been more informative if the authors would have described the possible reasons for such contrasting findings in their study population.

Another notable fact is that the authors did not consider specific endophenotypes of JME while measuring cognitive dysfunction in JME patients. JME is a heterogeneous syndrome. Seizures can be precipitated by nonspecific factors, such as sleep deprivation and stress, and by specific stimuli, such as eye closure, photic stimuli, language, and praxis. This is probably because the presence of these reflex traits indicates the hyperexcitability of different cortical areas. This got reflected in their neuropsychological deficit profile in the study by de Carvalho et al.[6] The patients with these reflex traits performed worse on Trail Making Test, as compared to their counterparts, which are independent of other clinical variables.

Lastly, most of the previous studies exploring the cognitive function of JME patients also determined IQ, presence of subclinical depression and anxiety of the patients using standard psychometric scales like Raven's Progressive Matrices test, Wechsler Adult Intelligence Scale, Beck Depression Inventory, and Beck Anxiety Inventory.[7] It would be more informative if the authors would have performed psychometric tests for detecting subclinical abnormalities in these domains. This is because the previous studies have shown that subclinical anxiety and depression in these patients contributes to cognitive dysfunction in JME patients.

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