A five‐year review of treatment and research on spasmodic dysphonia

Abstract

ABSTRACT This paper presents the experience of successful relief of vocal symptoms in patients suffering from spasmodic dysphonia (SD) through botulinum toxin (btx) injections offered at the National Hospital for Neurology and Neurosurgery as part of a research‐based trial. Over the past five years we have had over 200 referrals nationwide, with 150 patients now under regular review. The National Hospital is the main national centre offering btx injection treatment of SD. The methods of diagnosis, treatment and counselling offered by the speech and language therapist at the voice clinic are described. The treatment protocol has been closely monitored by the research team. A number of significant studies have clarified aspects of the management of SD patients, as focused in three main areas:(1) Differences in potency between the two forms of btx; (2) Efficacy of btx injections in the treatment of SD; (3) Psychological features of patient histories before and after btx treatment. SD patients receiving btx injections worldwide are treated with either the US or UK brand of toxin. Our investigations have indicated that the dosage and method of injection varies from clinic to clinic. We have determined that this can, in part, be attributed to differences in potency by comparing the dose effects of the two brands of toxin in a random controlled trial. A 3:1 difference in the level of potency by use of 3.75 units for injections has been found. Efficacy of treatment is being monitored continuously. Patients (N=31) had improved vocal characteristics as measured by objective and subjective means. Reduced variability of pitch was reflected in significantly decreased standard deviation of fundamental frequency. Patients' ‘voice diaries’ also reflect subjective impressions of improved voice quality in 96% (preliminary report (Whurr et al., 1993)). Our patient cohort repeatedly vocalised feelings of depression and despair at the effect the disorder has had on their lives and ability to function. The psychological aspects of SD are currently under investigation. Patients (N=46) were given several questionnaires to determine the frequency and level of psychoneurotic symptoms. Sixty‐five per cent of patients had normal ratings, whereas 30% had mild depression on the Beck scale. Of the 20 patients with psychological referring symptoms, 16 had lower depression scores six months after treatment. Only 17% had psycho‐neurotic symptoms on the Crown‐Crisp scale, and half of these were within normal limits after treatment (Whurr et al., 1994).