Abnormal interhemispheric inhibition in musician's dystonia – Trait or state?

• Interhemispheric inhibition is increased in professional musicians.
• A positive family history of dystonia results in less interhemispheric inhibition.
• Dystonia per se had no influence on interhemispheric inhibition.
• Interhemispheric inhibition is a possible endophenotypic marker of genetic determined dystonia.

IntroductionA clustering of relatives with dystonia has been reported in families with musician's dystonia suggesting a genetic contribution to this disease. The aim of the present study was to determine whether interhemispheric inhibition (IHI) measured with transcranial magnetic stimulation is impaired in healthy family members rendering it a suitable endophenotypic marker for musician's dystonia.MethodsPatients with musician's hand dystonia (n = 21), patients with sporadic writer's cramp (n = 15), their healthy family members (n = 27), healthy musicians (n = 12) and healthy non-musicians (n = 12) were included. An extended interview about the family history and musical activity was performed. IHI in both hemispheres was measured using transcranial magnetic stimulation.ResultsA stepwise regression analysis revealed musical activity (p = 0.001) and a family history of dystonia (p = 0.008) but not dystonia per se, age, handedness or gender as relevant factors modulating IHI.ConclusionThese data support the notion of a genetic background of musician's hand dystonia and suggests that reduced IHI is a possible endophenotypic marker of this disorder.