Risk factors and demographics in patients with spasmodic dysphonia.

OBJECTIVES: Spasmodic dysphonia has been characterized as a functional, psychogenic, or movement disorder with no known etiology or cure. In the present study, risk factors associated with other movement disorders were evaluated in patients with spasmodic dysphonia. STUDY
DESIGN: Retrospective patient survey of 168 patients with a known diagnosis of spasmodic dysphonia who completed questionnaires at the time of interval botulinum toxin injection.
METHODS: Patients completed questionnaires on demographics, education level, work history, significant life events, medical, social, and family history. The results were compared with those of first-degree relatives as a control group with similar demographics. Data were analyzed using percentages calculated on the total number of responses and distribution of frequency of each. Statistical significance was estimated on t tests of chi2 values.
RESULTS: In the series of 168 patients, there was a female predominance of 79%. Age range at onset was 13 to 71 years with an average of age of 45 years. Sixty-five percent of patients had previously had the measles or mumps compared with the national average of 15% in a similar age group (P =.0001). Thirty percent of patients directly associated onset of spasmodic dysphonia symptoms to an upper respiratory tract infection, and 21% to a major life stress. There was no significant incidence of any other medical or neurological condition or symptomatology. There was no family history of spasmodic dysphonia. Twenty-six percent of patients had an essential tremor compared with 4% of first-degree relatives (P =.0001), and 11% had associated writer's cramp compared with 2% of relatives (P =.02). Less than 1% of patients described a history of toxic exposure or electrical injury.
CONCLUSIONS: The majority of patients with spasmodic dysphonia are girls and women. A significantly higher incidence of childhood viral illness was found in the patients with spasmodic dysphonia. Patients with spasmodic dysphonia had a significant incidence of both essential tremor and writer's cramp but no history of major illness or other neurological disorder. There appear to be no significant environmental or hereditary patterns in the etiology of spasmodic dysphonia. Stress or viral infection may induce the onset of symptoms of spasmodic dysphonia. Many features of the disorder are common to other movement disorders, and this knowledge may direct future research efforts.