Autosomal Dominant Cerebellar Ataxias

Autosomal dominant hereditary ataxias may be reviewed in three sections including a) spinocerebellar ataxias (SCA), b) episodic ataxias, and c) other autosomal dominant ataxias (dentatorubral-pallidoluysian atrophy, fragile X-associated tremor/ataxia syndrome) similar to SCA. Among autosomal dominant ataxias, SCAs are the most frequently observed group. Cerebellar ataxia is a progressive picture characterized by clumsiness and dysarthria. The disease generally starts at the third or fourth decade; however, it may also develop during childhood or old age. Cerebellum and brain stem atrophy are generally its most distinct features; however, it may involve other regions as well, causing different phenotypes. According to the pathogenetic classification conducted in recent years, SCA’s are divided into three groups: <em>(i)</em> SCAs with expanded polyglutamine due to CAG repeat, <em>(ii)</em> uncoded expanded SCAs when expansions are present in uncoded areas of genes, and <em>(iii)</em> classical mutation SCAs. Of episodic ataxias (EA), seven types were defined. Among the ones which are most frequently observed, EA type 1 develops as a result of the mutation of the genes which code the voltage-dependent potassium channel, whereas EA type 2 develops with the mutation of the voltage-dependent calcium channel gene. Episodic ataxias generally start during childhood. Fragile X-associated tremor/ataxia syndrome is observed in old males who are premutation carriers in fragile X mental retardation 1 gene. All of these patients are aged above 50 and develop progressive intention tremor and ataxia. Such symptoms may be accompanied by progressive cognitive difficulties and behavioral disorders including amnesia, executive function disorders, and anxiety.