Cognitive impairment is one of the most common symptoms of anti-leucine rich glioma inactivated 1 (anti-LGI-1) encephalitis, but little is known about the cognitive profile of these patients. This study characterized the cognitive profile of patients with anti-LGI-1 encephalitis and compared patterns of impairment to healthy controls and other patient groups with known temporal lobe/limbic involvement.

A retrospective analysis of adult patients with anti-LGI-1 encephalitis who underwent neuropsychological assessment was conducted. Performance patterns of anti-LGI-1 patients were compared to patients deemed cognitively healthy (HC), as well as patients with amnestic mild cognitive impairment (aMCI) and temporal lobe epilepsy (TLE).

Among 10 anti-LGI encephalitis patients (60% male, median age 67.5 years) who underwent neuropsychological testing (median = 38.5 months from symptom onset), cognitive deficits were common, with 100% of patients showing impairment (≤1.5 SD below mean) on 1+ measures and 80% on 2+ measures. Patients with anti-LGI-1 encephalitis performed worse than controls on measures of basic attention, vigilance, psychomotor speed, complex figure copy, and aspects of learning/memory. Of measures which differed from controls, there were no differences between the anti-LGI-1 and TLE patients, while the anti-LGI-1 patients exhibited higher rates of impairment in basic attention and lower rates of delayed verbal memory impairment compared to the aMCI patients.

Long-term cognitive deficits are common in patients with anti-LGI-1 encephalitis and involve multiple domains. Future research in larger samples is needed to confirm these findings.