Spinocerebellar Ataxia Type 2

This chapter focuses on Spinocerebellar Ataxia type 2 (. SCA2) genes. SCA2 was first described clinically as a distinct genetic entity in a large, homogeneous population of patients with dominantly inherited cerebellar ataxia from the Holguin province of Cuba. In this founder population, ataxic gait and other cerebellar findings are universal, and many patients have slow saccadic eye movements. Tendon reflexes are usually brisk during the first years of life, but absent several years later. SCA2 is also particularly common in India. Analysis of a large number of SCA2 pedigrees has indicated a wide range of phenotypic manifestations that make SCA2 indistinguishable from other SCAs in the individual patient, although some findings such as slow saccades, peripheral neuropathy, and dementia are particularly common in SCA2. Identification of the SCA2 gene has led to a definition of the phenotype that includes not only the typical ataxia phenotype, but also rarer parkinsonian phenotypes that may at times be indistinguishable from idiopathic Parkinson's disease.