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Background: Previous family studies provided evidence that blepharospasm (BSP) can aggregate in families but did not give accurate and reliable information on the characteristics and degree of familial clustering. Aim: To evaluate the proportion of familial and non-familial BSP cases, the clinical expression of dystonia within families, the inheritance pattern, and the extent of penetrance. Methods: The study was based on the examination of the first degree relatives of 56 probands with primary BSP. Results: The 56 families produced a potential population of 436 first degree relatives of whom 296 were alive and 233 were examined. The proportion of index patients with at least one first degree relative affected by BSP, or adult onset dystonia other than BSP, was 27%. There was a remarkable degree of phenotypic variability of dystonia within families. Similar segregation ratios were calculated for probands' siblings and children. Under the assumption of autosomal dominant transmission of adult onset dystonia, penetrance was about 20%. Conclusions: The findings of this family study are relevant for accurately counselling the families of patients with BSP and may help identify the most appropriate study design to explore genetic susceptibility in BSP. [ABSTRACT FROM AUTHOR]

Objective: To study the reliability of the diagnosis of blepharospasm, oromandibular dystonia, cervical dystonia, and writer's cramp among neurologists.Methods: 12 patients with adult onset focal segmental dystonia were videotaped in a standardised way. The tape was sent to six neurologists who are involved in clinical practice without a specific interest in movement disorders (general neurologists), and to four neurologists expert in movement disorders. The observers had to recognise whether the patients were affected by dystonia and to distinguish among blepharospasm, oromandibular dystonia, cervical dystonia, and writer's cramp. Interobserver reliability was assessed by kappa statistics, and the degree of agreement was classified according to the Landis classification.Results: The 10 neurologists reached slight to moderate agreement on the diagnosis of these four disorders. When the observers were subdivided according with their professional experience in the field, a moderate to perfect agreement on the diagnosis was achieved by specialists in movement disorders, and a fair to moderate agreement by the general neurologists.Conclusions: Neurologists may have different ability to recognise adult onset focal dystonia, depending on their experience and on the type of dystonia. [ABSTRACT FROM AUTHOR]