Literature Review

Antiepileptic drugs may not independently impair cognition


 

FROM NEUROLOGY

No antiepileptic drug (AED) is independently associated with cognitive dysfunction, according to research published online ahead of print Feb. 3 in Neurology. Optimizing AED therapy to reduce or prevent seizures is thus unlikely to affect cognition, according to the investigators.

Dr. Emma Foster of Monash University in Australia

Dr. Emma Foster

Patients who take AEDs commonly report cognitive problems, but investigations into the cognitive effects of AEDs have yielded inconsistent results. “We were also interested in this association, as we often treat complex patients taking multiple or high-dose AEDs, and our patients often report cognitive dysfunction,” said Emma Foster, MBBS, an epilepsy fellow at Alfred Health and the Royal Melbourne Hospital in Victoria, Australia. “We were particularly interested to examine how much AEDs affect cognition relative to other factors. We commonly see patients in our tertiary epilepsy care unit who have had severe epilepsy for a long time or who have psychiatric disorders, and these factors may also contribute to cognitive dysfunction.”

Researchers analyzed patients admitted for video EEG monitoring

For their study, Dr. Foster and colleagues prospectively enrolled patients admitted to the Royal Melbourne Hospital’s video EEG monitoring unit between January 2009 and December 2016. Patients were included in the study if they were age 18 years or older, had been admitted for diagnostic or surgical evaluation, and had complete data for the relevant variables. Patients were prescribed AED monotherapy or polytherapy.

The researchers based epilepsy diagnoses on the 2014 International League Against Epilepsy criteria. Diagnoses of psychogenic nonepileptic seizures (PNES) were based on a consensus of epileptologists at weekly multidisciplinary clinical meetings, which was supported by evaluation of all available data. Some patients received a diagnosis of comorbid epilepsy and PNES. If data were insufficient to support a diagnosis of epilepsy or PNES, the admission was considered nondiagnostic.

All participants underwent neuropsychologic and neuropsychiatric screening. Researchers assessed patients’ objective, global cognitive function using the Neuropsychiatry Unit Cognitive Assessment Tool (NUCOG), a validated instrument. Patients responded to the Quality of Life in Epilepsy inventory (QOLIE-89) to provide a measure of subjective cognitive function. They also responded to the Hospital Anxiety and Depression Scale (HADS) to screen for mood disorders.

Dr. Foster and colleagues measured seizure frequency through patient self-report. Patients averaged their seizure frequency during the 12-month period before admission to the video EEG unit. They categorized it according to a 12-point system in which 0 denotes patients who are seizure-free and not taking AEDs and 12 denotes patients in status epilepticus. Patients with PNES used the same scale to report event frequency, although the system was not designed for this purpose.

Almost half of patients were prescribed polypharmacy

The researchers included 331 patients in their analysis. The population’s mean age was 39.3 years, and about 62% of patients were female. Approximately 47% of patients had epilepsy, 25.7% had PNES, 6.6% had comorbid epilepsy and PNES, and 20.5% had a nondiagnostic outcome. Among patients with epilepsy, most (54.5%) had temporal lobe epilepsy, followed by extratemporal focal epilepsy (32.1%) and generalized epilepsy (13.5%). The mean number of AEDs prescribed on admission was 1.6, and mean seizure or event frequency score was 7.2, which indicated 1-3 seizures per month. Mean HADS depression score was within the normal range (5.7), and mean HADS anxiety score was in the borderline range (8.2).

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