Snoring or stridor? It could be a lifesaving distinction

Internal Medicine News, Feb 1, 2007

MONTREAL -- The distinction of nocturnal stridor from simple snoring can allow the initiation of potentially lifesaving therapy in patients with multiple system atrophy, according to Dr. Michael H. Silber.

"If you miss this diagnosis, the patient could die," stressed Dr. Silber, who is professor of neurology at the Mayo Clinic in Rochester, Minn., and codirector of the Sleep Disorders Center there.

Multiple system atrophy (MSA) is the most important cause of stridor in the setting of sleep disturbance, Dr. Silber said. The neurodegenerative condition causes contraction of the vocal cords and restriction of airflow through the larynx during inspiration.

Untreated stridor in MSA can be a cause of sudden nocturnal death, sometimes within days of diagnosis, he said at the Eighth World Congress on Sleep Apnea.

The strained, harsh, high-pitched, inspiratory sound of stridor should be easily distinguishable from snoring by trained sleep technicians--but only if they can hear it.

"If you don't have a microphone ... you may miss the stridor altogether. There is absolutely no way from simply looking at a polysomnogram that you can differentiate stridor from snoring," he said.

"It's also absolutely vital to question these patients and their bed partners about the presence of stridor--and I try to demonstrate the sound."

The potential for undiagnosed MSA and stridor should be recognized in any sleep clinic patient with parkinsonism, Dr. Silber said.

"Some come with undiagnosed parkinsonism, and others come with what they think is the more common Parkinson's disease," he said in an interview. "We pick up the presence of stridor, and that's a strong marker that probably they don't have ordinary Parkinson's disease but have MSA."

Other sleep disturbances are common in conjunction with MSA and stridor, he said, including sleep apnea. "A very high percentage of these patients also have REM sleep behavior disorder and act out their dreams--so there are a number of reasons why they may end up in a sleep center."

The diagnosis of MSA-related stridor is made simply by listening for its distinct sound. However, it should be followed by laryngoscopy to assess the state of the patient's vocal cords while he or she is awake, Dr. Silber said.

"If the vocal cords are fixed and don't move at all, that's a very serious issue and one would move toward recommending tracheostomy," he said.

If the vocal cords appear normal on examination while the patient is awake, the stridor is most likely being caused by the patient's paradoxical movement during sleep--in which case, continuous positive airway pressure may be the best approach to eliminate the stridor, he added.