Keywords
neuromuscular disorders apnea hypopnea index strength level REM sleep NREM sleep
Introduction: Neuromuscular disorders (NMD) cover a range of genetic diseases that are usually
progressive and characterized by skeletal muscle weakness, including diaphragm. Skeletal
muscle weakness has a major responsibility on sleep breathing disorders (SBD), since
there are no validated questionnaires for children as a screening tool. The current
gold standard for SBD diagnosis is Polysomnography (PSG) with capnography, however,
little is known about the correlation between muscle strength and PSG variables, particularly
when it comes to the differentiation among REM and non-REM variables.
Objective: The main goal was to analyze the difference in polysomnographic and respiratory findings
among neuromuscular disorders´ patients with reduced muscle strength during NREM and
REM sleep.
Methods: We analyzed 30 patients with neuromuscular disorders and divided them into groups
according to muscle strength level and region (proximal and distal upper and lower
limbs and cervical region). We also divided apnea hypopnea index (AHI) and minimal
oxygen saturation (SaO2) between REM and NREM sleep and analyzed it by means of Mann-Whitney
U test. Then, we compared these features among the reduced muscle strength groups
by means of t Student test.
Results: Our sample was composed of 30 children and adolescents aged 4 to 19 years (10 ± 4).
20 of them were diagnosed with Duchenne Muscular Dystrophy (DMD) and 23 had reduced
proximal lower limbs muscle strength. This group presented medium NREM AHI of 4,31 ± 4,74
versus medium REM AHI of 12,72 ± 14,68 with statistical significance (p = 0,002).
The reduced distal lower limbs muscle strength group was composed of 14 individuals
and presented medium NREM AHI of 5,37 ± 5,36 against medium REM AHI of 13,85 ± 14,39
also with statistical significance (p = 0,01). In relation to minimal SaO2 we found
no difference statistically significant in this sample.
Conclusion: The measure of muscle strength is proving to be an anticipatory sign of SBD, as well
as its severity, emphasizing a huge concern about the REM sleep breathing pattern
and its consequences. The lower limbs correlation with worse AHI may be due to the
progression design of the most prevalent disease: DMD. Although our sample was small,
we believe that this data can be used as a tool to address respiratory disease progression.