Incidence and risk factors for secondary extralaryngeal dystonia in patients with laryngeal dystonia.

BACKGROUND AND OBJECTIVES

Laryngeal dystonia (LD) is a focal dystonia affecting adductor and/or abductor muscles of the larynx. It can be isolated or may spread to extra laryngeal muscles. The aim of this study was to report the characteristics of LD over time in a large single-center study with a long follow-up.

METHODS

Retrospective review of patients with LD referred to our institution between 1991 and 2021. Demographic data, time to diagnosis, type of LD, follow-up and spread of dystonia [SD] were recorded. Risk factors for spread of dystonia during follow-up were analyzed.

RESULTS

Over the 30-year period, 516 patients (77.3 % female, median age 50 years, range 5-87 years) were analyzed. Three hundred and fifteen patients (61 %) had adduction laryngeal dystonia, 136 patients (26.4 %) had abduction laryngeal dystonia, 46 patients (8.9 %) had adductor respiratory laryngeal dystonia, 12 patients (2.3 %) had mixed laryngeal dystonia, and seven patients (1.4 %) had singer's laryngeal dystonia. A previous history of dystonia was found in 47 patients (9.1 %). A laryngeal tremor was found in 68 patients (13.2 %). Since the onset of symptoms, LD was diagnosed after a median of 3 years (IQR: 1.0, 7.0). SD occurred in 55 patients (10.7 %) after a median time of 4 year (IQR: 1.5, 13.0). Patients with mixed laryngeal dystonia had higher probability of SD (p = 0.018).

DISCUSSION

This study reports a large European study of LD, with a long follow-up. SD occurred in 10.5 % of patients. Patients with mixed laryngeal dystonia had a higher probability of SD. A close follow-up may be recommended for patients with mixed laryngeal dystonia.