Genioglossus reflex responses to brief pulses of negative pharyngeal pressure in people with multiple sclerosis

Genioglossus reflex responses to brief pulses of negative pharyngeal pressure in people with multiple sclerosis





H. Hensen1,2, A.M. Osman3, J. Carberry3, S. Gandevia1, A. Krishnan4, D.J. Eckert1,3



1Neuroscience Research Australia, Randwick, Australia; 2School of Medical Sciences, University of New South Wales, Sydney, Australia; 3Adelaide Institute for Sleep Health, Flinders University, Adelaide, Australia; 4Prince of Wales Clinical School, Sydney, Australia



Introduction



Sleep apnoea is common in people with multiple sclerosis (MS). However, it is frequently undiagnosed and untreated as people with MS often do not fit the “typical” obstructive sleep apnoea (OSA) profile (i.e. non‐obese and female predominance). Accordingly, the causes of OSA may differ in people with MS such that non‐anatomical factors (e.g. impaired upper airway muscle function) might play an important role. The aim of this study was to determine if genioglossus reflex responses to brief pulses of negative pharyngeal pressure differ in people with sleep apnoea with versus without MS.



Methods



To date 10 people (6 females) with sleep apnoea (apnoea‐hypopnoea index >10 events/hr) and MS were recruited and matched to 6 controls (2 females) without MS, on age, sex and AHI severity. Participants were fitted with a nasal mask, pneumotachograph, two pressure‐tipped catheters in the upper airway and two fine‐wire intramuscular electrodes into the genioglossus muscle to measure muscle EMG activity. 55 to 100 brief (250 ms) negative pressure pulses (˜−12 cmH2O mask pressure) were delivered every 2–6 breaths at random during quite nasal breathing in wakefulness and supine position.



Results



In 7/10 MS and all control participants there was a short latency excitation reflex response of the genioglossus to negative pressure pulse stimuli. However, two people with MS had no discernible reflex response despite the presence of clear phasic genioglossus muscle activity during quiet breathing and another had predominant reflex suppression with minimal initial excitation (similar to previous observations in REM and people with tetraplegia and OSA).



Discussion



This is the first study to assess genioglossus reflex responses to negative pressure in people with MS. Consistent with recent findings in people with tetraplegia and OSA, the current preliminary findings suggest that altered genioglossus reflex responses in certain people with MS may contribute to the development of their sleep apnoea.