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We were interested to see the sex prevalence results in the recent review of focal dystonia by Soland et al.1 They found that of 956 patients with dystonia, 558 (58.4%) were female, for a ratio of 1.4:1. All but the cases of writer’s cramp had more females than males. In their spasmodic dysphonia group the ratio was 2.6:1 female:male (n=36).
We have reviewed our database of the cases of spasmodic dysphonia seen at the Mayo Clinic, Scottsdale, between 1989 and 1996. There have been a total of 270 patients seen, 241 with adductor, and 29 with abductor spasmodic dysphonia. The overall ratio of females:males was 214:56 or 3.8:1. Thus females made up 79.3% of our population with spasmodic dysphonia. Broken down into subgroups, the female:male ratio was 4.1:1 for the adductors and 2.2:1 for the abductors. The mean age was 60 years for the men and 64.6 years for the women. Most (186) of these patients continue to be followed up for botulinum toxin injections.
Our results, in this much larger population of patients with spasmodic dysphonia, suggest a greater female predominance than most previous studies. The only other large magnitude study was by Blitzer and Brin2 who reported 260 patients with idiopathic spasmodic dysphonia with a female:male ratio of 1.4:1. They later separated out their patients with abductor spasmodic dysphonia (n=32) and found a female:male ratio of 0.5:1. The other studies have been smaller, 21 and 41 patients, with a female:male ratio of 2.85:13 and 3.5:1.4 Ludlow et al 5 had only 16 patients and all but one were females. Given the overall similarities (female predominance) among the published series, we do not think that the female predominance is due to ascertainment bias. Whether there are genetic, hormonal, or autoimmune factors causing this is unknown. Only one series of abductor spasmodic dysphonia showed a male predominance, although our series had a female predominance. Certainly further investigation is needed.
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