Spasmodic Dysphonia: Standardized Spanish Tool for Ambulatory Consult Diagnosis

Spasmodic dysphonia (SD) is a focal dystonia of the larynx where involuntary spasms of its intrinsic muscles are triggered by specific phonemes. The diagnosis is challenging and is performed by listening to the patient's voice, supported by nasolaryngoscopy. There is no diagnostic tool in Spanish for SD. The objective of our study is to establish phonetically studied vocal tasks in Spanish language to diagnose patients with SD.

This is a prospective study in three groups of patients: 11 with SD, 11 with another vocal disease, and 11 with no vocal disease, recruited in the Voice Unit of Hospital Clínico Universidad Católica. Of the patients with SD, 10 (90.9%) had adductor SD and 1 (9.1%) abductor SD. Vocal tasks phonetically studied by a speech language pathologist as laryngeal spasm triggers were recorded. The audio recordings were randomized and analyzed by nine evaluators: three experts and six otolaryngology residents. The correlation between the different professionals for the correct diagnosis was analyzed.

The audio recordings were analyzed and patients with SD presented irregular voice breaks that occurred during the trigger phonemes. Evaluators classified the audio recordings: the expert group presented 100% sensitivity, 95-100% specificity and individual consistency of κ=0.73-0.82. The interrater agreement was 81.8%. The resident group presented 55-100% sensitivity, 58-95% specificity, and individual consistency of κ=0.36-0.82. The interrater agreement was 67.0%.

We obtained a strong to almost perfect interrater agreement in experts and fair to almost perfect in residents. This study shows that the established list of phonetically studied and standardized words can be a useful tool for the diagnosis of SD.