Strained face during sleep in multiple system atrophy: not just a bad dream.

Abstract

Patients with Parkinsons'Disease (PD) and Multiple System Atrophy (MSA) may be subject to sleep state dissociation. Motivated by the fortuitous observation of a prominent facial muscle activity during video-polysomnography (vPSG) in patients with MSA, we assessed facial motor activity and chin muscle tone during sleep in MSA compared to PD and controls. A sleep expert blinded to pathology and to sleep stage retrospectively analyzed facial activity in 62 vPSG (11 MSA,38 PD, and 13 controls). Facial movements were classified into six categories: "Eyes closing/opening", "Eyebrows frowning", "Raising eyebrows", "Smiling", "Other mouth movements", and "Strained face", an expression involving both the superior and inferior parts of the face. Chin EMG activity was quantified during REM and NREM sleep using the Atonia Index (AI), a validated algorithm. MSA patients had an increased number of all facial movements compared to controls during NREM. "Strained face" was significantly more frequent in MSA compared to PD, even after adjusting for the presence of RBD. AI was lower in MSA compared to controls and PD during REM and NREM sleep. This difference remained significant compared to PD in NREM sleep during N1 and N2 after adjusting for the presence of RBD. Facial movements during sleep are frequent in MSA, "strained face" appears to be a hallmark of this condition. The presence of increased facial activity and elevated muscle tone during all stages of sleep in MSA may be a manifestation of sleep state dissociation, reflecting a more severe neurodegeneration.