Diagnosing Cognitive Disorders in Older Adults with Temporal Lobe Epilepsy

Objective To characterize the nature and prevalence of cognitive disorders in older adults with temporal lobe epilepsy (TLE) and compare their cognitive profiles to non-epileptic patients with mild cognitive impairment (i.e., classic MCI; cMCI). Methods Seventy-eight older patients with TLE, 77 cMCI, and 69 normal aging controls (NAC), all 55-80 years, completed neuropsychological measures of memory, language, executive function and processing speed. An actuarial neuropsychological method designed to diagnose MCI was applied to individual patients to identify older adults with TLE who met diagnostic criteria for MCI (TLE-MCI). A linear classifier was performed to evaluate how well the diagnostic criteria differentiated patients with TLE-MCI from cMCI. In TLE, the contribution of epilepsy-related and vascular risk factors to cognitive impairment was evaluated using multiple regression. Results Forty-three TLE patients (60%) met criteria for TLE-MCI, demonstrating marked deficits in both memory and language. A classification model between TLE-MCI and cMCI correctly classified 81.1% (90.6% specificity, 61.3% sensitivity) of the cohort based on neuropsychological scores. Whereas TLE-MCI showed greater deficits in language relative to cMCI, patients with cMCI showed greater rapid forgetting on memory measures. Both epilepsy-related risk factors and the presence of leukoaraiosis on MRI contributed to impairment profiles in TLE-MCI. Interpretation Approximately 60% of older adults with TLE meet diagnostic criteria for a cognitive disorder associated with aging (i.e., MCI). The TLE-MCI phenotype may be secondary to an accumulation of epilepsy and vascular risk factors, signal the onset of a neurodegenerative disease, or represent a combination of both factors.