The statement was published Oct. 1 in Neurology. In addition to reviewing the literature on the topic and providing recommendations, the authors described several areas for future research.
MSA is a rare neurodegenerative disorder that entails autonomic failure, cerebellar ataxia, and parkinsonism. Laryngeal stridor has a high positive predictive value in the diagnosis of MSA, but consensus about its definition and clinical implications had not been established previously. The Istituto di Ricovero e Cura a Carattere Scientifico (IRCCS) delle Scienze Neurologiche di Bologna (Italy) convened a consensus conference of experts in 2017 to determine diagnostic criteria for stridor in MSA, define its prognostic value, suggest treatment options, and indicate subjects for future research. The neurologists reviewed studies of any design that reported original data. They based their statements on 34 published articles, most of which were class III or IV.
The authors defined stridor in MSA as “a strained, high-pitched, harsh respiratory sound, mainly inspiratory, caused by laryngeal dysfunction leading to narrowing of the rima glottidis.” Stridor may occur exclusively during sleep or during sleep and wakefulness. It may be recognized during a clinical examination, through witness report, or through an audio recording. Neurologists may consider laryngoscopy to exclude mechanical lesions or functional vocal cord abnormalities related to other neurologic conditions, wrote the authors. Drug-induced sleep endoscopy and video polysomnography also may be considered.
Whether stridor, or certain features of stridor, affects survival in MSA is uncertain. “Stridor within 3 years of motor or autonomic symptom onset may shorten survival,” according to the statement. “However, identification of stridor onset may be difficult.” Moreover, stridor during wakefulness is considered to reflect a more advanced stage of disease, compared with stridor during sleep. Although stridor can be distressing for the patient and his or her caregivers, its influence on health-related quality of life has yet to be determined, according to the statement.
Continuous positive airway pressure (CPAP) during sleep can be a useful symptomatic treatment and should be considered a first-line therapy for stridor, wrote the authors. Tracheostomy, another effective symptomatic treatment, bypasses upper-airway obstruction at the larynx. “Persistent and severe stridor may require tracheostomy,” according to the statement. It is not certain whether CPAP improves survival in patients with MSA and stridor, and tracheostomy may improve survival. The literature contains insufficient evidence about whether minimally invasive procedures or botulinum toxin injections are effective symptomatic treatments for stridor, wrote the authors.
During their review of the literature, the authors identified what they considered to be several research gaps. The diagnosis of stridor remains challenging, and investigators should develop a questionnaire for detecting stridor, they wrote. A smartphone application also could be developed to recognize stridor automatically. “The relationship between stridor and other breathing disorders (i.e., central apneas and breathing rate abnormalities) and their respective contributions to disease prognosis and survival should be determined through a multicenter prospective study,” according to the statement. Finally, randomized controlled trials comparing CPAP and tracheostomy for various degrees of stridor could guide physicians’ choice of treatment.
The IRCCS funded the study. One of the authors is a section editor for Neurology, and other authors reported receiving honoraria from various companies such as Novartis, Sanofi, and UCB.