Spasmodic dysphonia (SD) is a rare disease and its epidemiological status is unclear. This review aimed to explore the current prevalence and clinical features of SD in Japan. Methods: We reviewed Japanese surveys of SD and compared them to surveys reported from other countries. We focused on SD prevalence, clinical features (SD type, sex and age), and treatment modalities. Results: The SD prevalence in Japan was 3.5-7.0/100,000, similar to that in Rochester (NY, USA) and Iceland. Adductor SD predominated (90-95%) and females were four-fold more likely to be affected than males. Mean age at onset was approximately 30 years in Japan. Several years elapsed from onset to diagnosis. The most frequent treatment was botulinum toxin injection, and surgical intervention, particularly type 2 thyroplasty is becoming more popular. Conclusions: Our review demonstrated some differences of clinical features of SD in Japan compared with other countries, such as a greater female predominance and younger age of onset. Many physicians and patients may be unfamiliar with the clinical features of SD leading to delayed of diagnosis. Therefore, we proposed diagnostic criteria to facilitate early diagnosis and an appropriate choice of treatment modalities.
Aims: To verify whether humming corrects supraglottic compression in muscle tension dysphonia (MTD) patients. Methods: We enrolled 23 MTD participants (13 male, 10 female) showing supraglottic compression. Each individual was instructed to perform 3 types of phonation under transnasal laryngofiberscopy: natural phonation, humming phonation without pitch change and subsequent um-hum phonation, i.e. humming with pitch glide up as if agreeing with someone. The degree of supraglottic compression was estimated with 2 parameters. The false vocal fold and anterior-posterior indices (the FVF and AP indices) were calculated by normalizing the lateral width and AP length of the visible vocal cords at phonation normalized to the mean vocal cord length at inspiration, respectively. These indices were compared among the tasks. Results: All the MTD participants but 5 females accomplished decreases in the vocal roughness scores upon the phonatory tasks. The whole MTD group showed significant increases in the FVF and AP indices even after humming without pitch change with a dominance of the AP index. The humming-responsive MTD subgroup showed greater increases in both indices than the humming-resistant subgroup. Conclusion: These data demonstrate that humming corrects both the lateral and AP components of supraglottic compression in most MTD patients.
Acoustic analysis was conducted to investigate symptomatic differences in decreased oral alternating motion rates (AMRs) between individuals with spastic and with ataxic dysarthria. The subjects were 6 individuals with spastic dysarthria, 6 with ataxic dysarthria and 6 normal speakers. Monosyllables /pa/ and /ta/ were used to examine alternating motions of the lips and tongue, respectively. In the decreased AMRs of the spastic group, the mean syllable durations were generally longer in the individuals where the mean total syllable durations were longer, and in the decreased AMRs of the ataxic group, the mean gap durations were generally longer in the individuals where the mean total syllable durations were longer. It was suggested that each syllable component could represent a separate function and contribute differently to the decreased AMRs in these dysarthric groups.
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