Sleep-disordered breathing in neuromuscular disorders: a condition in search of recognition

The clinical usefulness of a self-administered questionnaire for sleep-disordered breathing in patients with neuromuscular disease

Background

Patients with neuromuscular disease (NMD) are at risk of developing sleep-disordered breathing (SDB) with hypercapnic respiratory failure. We hypothesised that a self-administered questionnaire (SiNQ-5 scores) may be useful to assess patients who are established on treatment for NMD with SDB.

Methods

Patients attending a tertiary referral centre filled in the SiNQ-5 (range 0-10 points, lower scores indicating fewer symptoms). The questionnaire contains five questions related to breathlessness, sleep and posture. Patients with NMD and treated SDB were compared to NMD without SDB, to sleep apnoea, chronic obstructive pulmonary disease (COPD) and heart failure (HF) patients' scores, as well as a group of patients without SDB. Results were compared using Kruskal-Wallis one-way analysis of variance, with Dunn/Bonferroni post-hoc tests if comparisons were found to be statistically significant.

Results

A total of 265 (156 male) patients completed the assessment, 40 had NMD with treated SDB [SiNQ-5 score 3.4 (3.0) points], 11 had NMD without SDB [2.7 (2.9) points], 120 patients had obstructive sleep apnoea (OSA) [4.1 (2.6) points], 16 had COPD [3.9 (3.0) points] and 9 had HF [3.2 (2.8) points], 69 patients had other conditions with no evidence of SDB [3.0 (2.4) points; P=0.077]. Patients with NMD without SDB and those with SDB who were on treatment did not differ in their responses (P=0.417). Question #1 allowed discrimination between patients with NMD with SDB [0.8 (0.8) points] and other disorders without respiratory involvement [0.3 (0.6) points; P=0.024].

Conclusions

The SiNQ-5 scores in neuromuscular patients with SDB who are established on treatment and NMD patients without SDB, as well as in patients with other conditions leading to SDB are similar.

Acute and chronic respiratory failure

Respiratory failure (RF) can be attributed to a plethora of neuromuscular diseases (NMDs) and manifests clinically in a multitude of overt or more subtle ways. The basic principles of pathophysiology, diagnosis and treatment of neurologic diseases and of RF apply concomitantly to this subset of patients. Various entities should be approached according to the latest evidence-based recommendations. Treatment follows the natural disease progression, from minimal respiratory assistance to mechanical ventilation (MV). A comprehensive treatment plan has to be formulated that takes into consideration the patient's wishes.

Sleep disorders in neuromuscular diseases

PURPOSE OF REVIEW

Patients with neuromuscular disorders (NMD) are especially vulnerable to sleep-related dysfunction. Sleep-disordered breathing often precedes diurnal respiratory failure in NMD patients, requiring timely recognition and management with noninvasive ventilation (NIV). This paper reviews the mechanisms, diagnostic evaluation, and management of sleep disorders in various neuromuscular diseases.

RECENT FINDINGS

The severity, duration, and type of NMD influence the pattern of sleep disturbance. Several investigators have addressed other clinical aspects including rating scales for sleep complaints, hypocretin-1 deficiency, excessive daytime somnolence, and relation of sleep disorder with length of CTG trinucleotide repeats in myotonic dystrophy. Benefits of NIV on quality of life and survival in adults and children with chronic NMD are well established, and recently have been documented even in patients with nocturnal hypoventilation and daytime normocapnia. In contrast, the timing for investigation with polysomnography and for initiation of NIV is debated.

SUMMARY

Patients with chronic NMD should be routinely assessed for sleep-disordered breathing and sleep complaints, because these are treatable complications in an otherwise progressive disease process. Further research is needed to establish the indications for polysomnography and to determine the optimal timing for initiating NIV to treat sleep-disordered breathing in patients with neuromuscular diseases.

Neuromuscular disorders and sleep

Neuromuscular disorders are caused by the primary involvement of the motor unit. In these patients, sleep-disordered breathing (SDB) due to respiratory muscle weakness is often encountered during sleep. Because there is a tendency to overlook this disorder, all patients with neuromuscular disorders should be questioned about SDB. Overnight polysomnography is the best investigation for SDB and nocturnal desaturations. In the management of these patients, noninvasive intermittent positive pressure ventilation results in improvement of SDB and breathing.

Sleep-disordered Breathing in Neuromuscular Disease

Patients with neuromuscular disorders involving respiratory muscles (upper airway muscles, respiratory accessory muscles, diaphragm, even abdominal muscles that stabilize the chest) have more significant problems with breathing during sleep, especially during REM sleep, than during wakefulness. There are means of appropriately treating sleep disordered breathing and improving the quality of life of these patients. Treatment helps to avoid daytime symptoms and additional autonomic nervous system dysfunction. The treatment involves support of breathing during sleep. It must be adjusted to the severity of the problem during sleep, which implies systematic investigation and treatment based on polygraphic recordings during sleep. Patients, even when stable, need to be monitored during sleep at least once a year and more often if symptomatic, ie, appearance of any daytime symptom or frequent upper respiratory infection or indication of daytime CO(2) retention.