Trial Information

Characteristics of Idiopathic Familial Voice Disorders

OBJECTIVE:

Our purpose is to examine for evidence of genetic risk factors associated with idiopathic
laryngeal motor control disorders. During the conception of the protocol, we were
interested in investigating the pattern of inheritance of familial voice disorders,
specifically spasmodic dysphonia and tremor. Interestingly, the initial search for families
revealed several large families with idiopathic vocal fold paralysis with some family
members experiencing symptoms of spasmodic dysphonia. During subsequent years, the research
has focused on inherited forms of vocal fold paralysis in an attempt to determine the
relationship between the laryngeal motor control disorder and other associated neuropathies,
and to determine the existence of a specific genetic abnormality. These idiopathic
laryngeal motor control disorders were one manifestation of peripheral neuropathies or may
be an isolated disorder with only laryngeal involvement. Subsequently, we have shifted our
emphasis back to the identification of genetic risk factors for spasmodic dysphonia.

Hypothesis 1) Familial risk factors for spasmodic dysphonia result in a particular phenotype
and genotype.

Hypothesis 2) Environmental risk factors may differentiate between affected and unaffected
members of families with spasmodic dysphonia.

Hypothesis 3) Whole genome screening will identify SNPs associated with the occurrence of
spasmodic dysphonia.

STUDY POPULATION:

Families with multiple members affected with spasmodic dysphonia, vocal fold paralysis, and
tremor will be ascertained.

DESIGN:

A pedigree will be developed via a questionnaire and voice history. Affected and unaffected
family members will be examined to determine the presence and extent of their laryngeal
motor control disorder. Affected family members will also undergo neurological examination
and nerve and muscle studies to determine the loci of their pathology. A genotype will be
developed for affected and unaffected family members, through DNA testing of blood samples.

OUTCOME MEASURES:

This is a natural history study characterizing the phenotype and genotype of idiopathic
laryngeal motor control disorders.