GENETIC ASPECTS OF FAMILIAL VOICE AND SPEECH DISORDERS

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The purpose of this project is to examine risk factors involved in the epigenesis of familial voice and speech disorders. Familial cases of voice disorders such as spasmodic dysphonia, voice tremor and idiopathic vocal fold paralysis have been reported in the literature. We have recently ascertained 4 families with abductor spasmodic dysphonia, each with 2 or more members having similar forms of abductor spasmodic dysphonia. In all, only women are affected. The disorder occasionally first appeared in childhood, earlier in life than is typical of sporadic cases of this disorder. In each of two of the families, two sisters were affected while in the other two families there is evidence of vertical transmission from grandmother to daughter to granddaughter. In some cases, one member is affected primarily by abductor vocal fold tremor while another has abductor spasmodic dysphonia. Other forms of focal dystonia, such as torticollis and blepharospasm, were reported in only one family. The pathophysiology of the vocal fold control disorder involves a lack of adductor muscle activation for speech tasks rather than hyperactivity of the abductor muscles causing speech breaks. In the last year we have been examining families with vocal fold paralysis. In some instances this is associated with a mild peripheral neuropathy. The type of peripheral neuropathy that would primarily affect the recurrent laryngeal nerves is of interest. We are examining speech processing factors that may be related to a risk for two speech disorders, stuttering and cluttering. For designing genetic studies it is important to determine whether those who recover from these developmental disorders differ from those who remain affected throughout their lifetime. The results will help us decide whether only those chronically affected should be identified as having the disorder. Both standardized assessment and experimental tests are being used to quantify the speech processing factors in contrast with controls. We are comparing speech learning for production and perception, speech perception and psychoacoustic skills and speech self monitoring in family members with and without familial stuttering or cluttering. The results will have a direct bearing upon the model for epigenesis of these disorders and will provide a theoretical basis for genetic studies of persons at risk for stuttering and cluttering.