Sleep manifestations of voltage-gated potassium channel complex autoimmunity

Abstract

Objective: To identify the spectrum of sleep disorders associated with autoantibodies reactive with voltage-gated potassium channel (VGKC) complexes.

Design: Case series of all patients with neurologic disorders of VGKC autoimmunity evaluated in the Mayo Clinic Center for Sleep Medicine (Rochester, Minnesota) between January 1, 1994, and February 1, 2010.

Setting: Academic referral center.

Patients: Fifteen consecutive patients were identified with limbic encephalitis (n = 5), Morvan syndrome (n = 4), and overlapping features (n = 6).

Intervention: Ten patients received immunotherapy (corticosteroids, cyclophosphamide, or mycophenolate mofetil).

Main outcome measure: Response to immunotherapy.

Results: The median VGKC autoantibody value at presentation was 1.51 nmol/L (range, 0.09-4.86 nmol/L). Neoplasms were discovered in 5 patients (33%) (thymoma [n = 2], prostate adenocarcinoma, colon adenocarcinoma, and melanoma). In 14 patients (93%), serious sleep disturbances were identified (insomnia, dream enactment behavior, suspected nocturnal epilepsy, and hypersomnia). Severe insomnia occurred in 9 patients (60%), regardless of neurologic presentation. Polysomnography at presentation (7 patients) revealed a mean sleep efficiency of 19% (4 patients had complete absence of sleep). Dream enactment behavior occurred in 8 patients (53%), including 3 of 5 with limbic encephalitis and all 4 with Morvan syndrome. Two of 7 polysomnograms demonstrated loss of rapid eye movement sleep muscle atonia; absent or minimal rapid eye movement sleep precluded interpretation in 4 patients. Sleep disorders resolved completely or almost completely in 8 of 10 patients who received immunotherapy.

Conclusions: Sleep disorders are cardinal manifestations of VGKC complex autoimmunity in association with a spectrum of neurologic presentations. They may respond favorably to immunotherapy.