Literature Review

Antiepileptic drugs may not independently impair cognition


 

FROM NEUROLOGY

Approximately 45% of patients were prescribed AED polypharmacy on admission, 25.1% were prescribed AED monotherapy, and 29.9% were prescribed no AED. Levetiracetam, valproate, and carbamazepine were the most frequently prescribed AEDs. Most patients with epilepsy (73.1%) were on polypharmacy, compared with 17.6% of patients with PNES, 63.6% of patients with epilepsy and PNES, and 8.8% of nondiagnostic patients.

Older age and greater seizure frequency predicted impaired objective cognitive function. Comorbid epilepsy and PNES appeared to predict impaired objective cognitive function as well, but the data were inconclusive. No AED was a significant predictor of objective cognitive function. Higher depression and anxiety scores and greater seizure frequency predicted impaired subjective cognitive function. No AED predicted subjective cognitive function.

Future studies could address particular cognitive domains

Previous studies have suggested that treatment with topiramate predicts objective or subjective cognitive function, but Dr. Foster and colleagues did not observe this result. The current findings suggest that topiramate may have a less significant effect on cognition than the literature suggests, they wrote. In addition, more evidence is needed to fully understand the effects of clobazam, valproate, phenytoin, and gabapentin because the analysis was underpowered for these drugs.

Although NUCOG assesses global cognitive function reliably, its ability to measure particular cognitive subdomains is limited. “We aim to conduct future research investigating the complex associations between different cognitive functions, including processing speed, and specific AEDs in this heterogeneous population,” said Dr. Foster.

Despite the study’s large sample size, the researchers could not explore potential interactions between various predictor variables. “Epilepsy may interact with the aging process or with other medical conditions associated with aging, such as hypertension and diabetes, and this may increase the risk of cognitive decline,” said Dr. Foster. “Older age may also be associated with reduced capacity to metabolize drugs, increased sensitivity to the cognitive and neurological effects of drugs, less cognitive reserve, and increased likelihood of taking multiple medications, which, along with AEDs, may exert a cognitive effect.”

The current findings may reduce concerns about the effects of AEDs on cognitive function and encourage neurologists to pursue the proper dosing for optimal seizure control, wrote the authors. “However, it is possible that some individuals may be more susceptible than others to AED-related cognitive dysfunction,” said Dr. Foster. “We do not have a robust way to predict who these patients will be, and it is still good practice to make patients aware that some people experience adverse cognitive effects from AEDs. However, it needs to be emphasized that it is unlikely to be the sole reason for their cognitive impairment. Other issues, such as poor seizure control or unrecognized or undertreated mood disorders, are even more important factors for impaired cognition.”

Patients who report cognitive problems should be screened for mood disorders, Dr. Foster continued. “It would also be important to consider whether the patients’ cognitive complaints arise from subtle clinical or subclinical seizure activity and subsequent postictal periods. To investigate this [question] further, clinicians may arrange for prolonged EEG monitoring. This [monitoring] could be done in an ambulatory setting or during an inpatient admission.”

The study was conducted without external funding. Dr. Foster and other investigators reported research funding from professional associations and pharmaceutical companies that was unrelated to the study.

SOURCE: Foster E et al. Neurology. 2020 Feb 3. doi: 10.1212/WNL.0000000000009061.

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