GENETIC ASPECTS OF FAMILIAL VOICE AND SPEECH DISORDERS

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Summary of Work: The purpose of this project is to examine risk factors leading to 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. In the last year, we have concentrated on ascertainment of families with more than one member affected with the same voice disorder. We have identified 5 families, either with spasmodic dysphonia or vocal tremor. A recent report in the literature of low arylsulphatase A levels in persons with familial spasmodic dysphonia and voice tremor was re-examined. A series of 10 control subjects and 10 persons with adductor and 10 with abductor spasmodic dysphonia were tested. Urine assays of arylsulphatase A levels did not confirm this previous report either in familial or sporadic cases of spasmodic dysphonia. We are exploring the role of heredity in the etiology of two speech disorders, stuttering and cluttering. Our working hypothesis is that stuttering is a multifactoral disorder depending upon genetic factors altering brain development patterns rendering certain individuals more susceptible to developmental stuttering. As a result of the interaction between neural plasticity and behavioral development. Individuals who stutter may or may not recover from developmental dysfluency. We are examining this hypothesis by comparing speech learning, production and monitoring skills in persons with and without familial stuttering and their affected and unaffected family members. The familial pattern of cluttering, another speech disorder, is usually more evident and the disorder depends upon both perceptual and production phonological deficits which may interfere with fluent speech. Speech production, learning, self-monitoring and perceptual skills are being examined in both groups and control subjects. Both standardized assessment and experimental tests have been developed and are being used with family members who have and have not recovered from developmental dysfluency. 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.