Case-control study of risk factors for spasmodic dysphonia: a comparison with other voice disorders

Objectives: This epidemiology study examined risk factors uniquely associated with spasmodic dysphonia (SD). Study Design: Case-control. Methods: A questionnaire was administered to 150 patients with SD (with and without coexisting vocal tremor) and 136 patients with other structural, neurological, and functional voice disorders (excluding SD and vocal tremor). Questions included personal and family medical histories, environmental exposures, trauma, illnesses, voice use habits and the Short Form 36. Results: Several factors were uniquely associated with SD (α=0.05), including: (1) a personal history of cervical dystonia, sinus and throat illnesses, mumps, rubella, dust exposure and frequent volunteer voice use, (2) a family history of voice disorders, (3) an immediate family history of vocal tremor and meningitis, and (4) an extended family history of head and neck tremor, ocular disease, and meningitis. Vocal tremor coexisted with SD in 29% of cases. Measles and mumps vaccines were protective for SD. Conclusions: SD is likely multi-factorial, associated with several endogenous and exogenous factors. Certain viral exposures, voice use patterns, and familial neurological conditions may contribute to the onset of SD later in life.