Cerebellar ataxia with spasmodic cough: a new form of dominant ataxia.

BACKGROUND Although mentioned in most series, "pure" autosomal dominant cerebellar ataxias, except spinocerebellar ataxia type 6, are difficult to differentiate on clinical grounds. OBJECTIVE To describe Portuguese families with a peculiar pure form of dominant ataxia that, to our knowledge, has never been documented before and in which cerebellar signs are preceded by spasmodic cough. PATIENTS Through a population-based survey of hereditary ataxias in Portugal, we identified 19 patients in 6 families with this particular disorder. RESULTS The majority of patients had a pure late-onset ataxia with a benign evolution. In all of the families, attacks of spasmodic coughing preceded ataxia for 1 to 3 decades and were a reliable marker of the disease. In Portugal, this form of ataxia accounts for 2.7% of all of the dominant ataxias. CONCLUSIONS The families that we describe shared some relevant clinical and imagiological features with spinocerebellar ataxia type 5 and the recently described spinocerebellar ataxia type 20, allelic to spinocerebellar ataxia type 5. Spinocerebellar ataxia types 5 and 20 could be different phenotypic expressions of the same molecular disorder. The association of a dominant ataxia with spasmodic cough is rare but probably underdiagnosed.