The clinical features and classification of the late onset autosomal dominant cerebellar ataxias. A study of 11 families, including descendants of the 'the Drew family of Walworth'.

The clinical features of 11 families containing 73 individuals with dominantly inherited cerebellar ataxia of late onset are described. Many of the patients had physical signs in addition to cerebellar ataxia, which included dementia, supranuclear ophthalmoplegia, extrapyramidal dysfunction, optic atrophy, pigmentary retinal degeneration, myoclonus and deafness. These associated features were generally very variable within members of the same family. Intrafamilial correlation of age of onset and an analysis of clustering of clinical features within families using X2 tests suggested that there was little evidence of genetic heterogeneity in the eight kindreds where ophthalmoplegia, optic atrophy, dementia, or extrapyramidal signs were found in affected individuals. One of these families contained descendants of the 'Drew family of Walworth' described by Ferguson and Critchley in 1929. The three other families contained patients with clinically distinct syndromes which were: cerebellar ataxia with pigmentary retinal degeneration; a later onset (over 60 years) 'pure' cerebellar syndrome; and an ataxia disorder associated with myoclonus and deafness. A simple classification of the autosomal dominant cerebellar ataxias is proposed and discussed in relation to previous attempts to classify these disorders on clinical and pathological grounds.