Abstract|Sleep Disorders 1| Volume 357, SUPPLEMENT 1, e96-e97, October 15, 2015

Quantitative analyses of REM sleep without atonia in patients with voltage gated potassium channel antibody syndrome

      Background: Voltage-gated potassium channel antibody syndrome (VGKC-AS) is an autoimmune disorder with prominent neurological and sleep disturbances, including limbic encephalitis (LE) and REM sleep behavior disorder (RBD). We analyzed REM sleep without atonia (RSWA) in VGKC-AS patients.
      Design: We comparatively analyzed RSWA between VGKC-AS patients (n = 18) with (n = 7) and without (n = 11) RBD, controls, and RBD (n = 18) without VGKC-AS. REM muscle activity was compared in the submentalis (SM) and anterior tibialis (AT) muscles, and the automated REM atonia index (RAI) was calculated. Statistical analyses involving group comparisons and regression were then performed. Analyses for Lgi-1 (Leucine-rich, glioma inactivated 1) and Caspr-2 (Contactin-associated protein-like 2) antibodies were also performed.
      Results: Seven (39%) VGKC-AS patients had RBD, including 5 (71%) men. VGKC-AS patients had intermediately higher RSWA, higher than controls but lower than traditional RBD patients (p < 0.05). LE patients had higher phasic muscle activity in AT (p = 0.03). VGKC-RBD patients had higher tonic muscle activity than those without dream enactment (p = 0.03). Only 3/18 (17%) VGKC patients were Lgi-1 positive and all 18 were Caspr2 negative. No associations between Lgi-1 and RSWA were found.
      Conclusions: VGKC patients had higher overall RSWA than controls, but lower than traditional RBD patients. VGKCAS-RBD patients had higher tonic RSWA than VGKC-AS patients without dream enactment, and LE patients had higher overall and leg phasic RSWA than other VGKC-AS patients. This data informs prompt diagnosis of VGKCAS-RBD, potentially enabling immunomodulation. Future prospective research is needed to analyze immunotherapy impact on VGKC-AS RSWA and clinical outcomes.