Electroencephalography and polysomnography as predictors of long‐term functional outcomes in anti‐ CASPR2 encephalitis: A multicenter cohort study

Abstract Objective The clinical manifestations of autoimmune encephalitis associated with contactin‐associated protein‐like 2 (CASPR2) were atypical and progressed slowly. We aimed to summarize the characteristics of video‐electroencephalography (V‐EEG) and video‐polysomnography (V‐PSG) to achieve early recognition and assess long‐term outcomes. Methods 27 patients with anti‐CASPR2 encephalitis were enrolled from four tertiary hospitals in China (2018–2022). All patients underwent 24‐h V‐EEG monitoring, and seven of them received additional overnight V‐PSG recording. We retrospectively analyzed the clinical and electrophysiological features, sleep features, treatments, prognostic factors, and clinical outcomes of these patients. The Clinical Assessment Scale in Autoimmune Encephalitis (CASE) was used to assess the initial severity and long‐term prognosis. Results There were 8 children and 19 adults enrolled, including 11 males and 16 females, respectively. 20 (74.1%) of them suffered from infrequent epileptic seizures, with ten having seizures at initial presentation and five experiencing status epilepticus. In addition to seizures, some developed psychiatric symptoms (14/27), sleep disorders (8/27), and Morvan syndrome (7/27). Twenty‐three (23/27) patients presented notable EEG abnormalities, including diffuse slow‐wave activities (DSWA, 7/23), intermittent slow‐wave activity (12/23), interictal focal/generalized spikes and spike‐and‐slow‐wave complexes (7/23). Median duration of follow‐up was 40 months (range: 12–78 months). Compared to those with normal background, patients with DSWA had worse clinical outcomes (CASE ≥10, χ 2 = 10.188, p = .005). The patients with poor prognosis in the study showed sleep fragmentation, reduced nonrapid eye movement stage 3 (N3), and rapid eye movement stage (REM). Three patients (3/7) exhibited complete absence of N3 sleep, which was linked to a negative prognosis. Significance Slow‐wave activities involving the frontal and temporal lobes, as well as reduced N3 and REM sleep, are commonly observed in patients with anti‐CASPR2 encephalitis. DSWA and the absence of N3 sleep may serve as predictors of a worse prognosis in anti‐CASPR2 encephalitis.