Sleep and breathing disorders in myotonic dystrophy type 2

Area of Science:

• Neurology
• Pulmonology
• Sleep Medicine

Background:

• Sleep disorders and respiratory impairments are common in myotonic dystrophy type 1 (DM1).
• Limited polysomnography (PSG) and no phrenic compound motor action potential (CMAP) studies exist for myotonic dystrophy type 2 (DM2).

Purpose of the Study:

• To investigate sleep disorders and respiratory impairments in DM2 patients.
• To assess phrenic compound motor action potential (CMAP) in DM2.
• To compare findings in DM2 with healthy controls and DM1 patients.

Main Methods:

• Sixteen DM2 patients underwent respiratory symptom questionnaires, polysomnography (PSG), and arterial gas analyses (AGA).
• Respiratory functions and phrenic CMAPs were evaluated.
• Data were compared to 16 healthy controls and 25 DM1 patients.

Main Results:

• Daytime tiredness was the most frequent symptom in DM2 patients.
• Sleep architecture analysis showed increased stage 3 and REM sleep, and decreased stage 2 sleep compared to controls.
• DM2 patients exhibited reduced respiratory volumes, abnormal AGA, nocturnal oxygen desaturation, and elevated EtCO2, less pronounced than in DM1.
• 12% of DM2 patients had small CMAP amplitudes, correlating with poorer respiratory function and sleep quality.
• Obstructive sleep apnea was present in 38% of DM2 patients; hypoventilation was not detected by PSG.

Conclusions:

• Diaphragm weakness and sleep apnea may occur in DM2 patients.
• Regular screening for respiratory insufficiency symptoms and phrenic CMAP monitoring are recommended for DM2.
• PSG is indicated for DM2 patients with suggestive symptoms, abnormal AGA, or higher BMI.