**3.4 Mitochondrial ataxia**

Cerebellar and sensory ataxias, which are caused by defects in mitochondrial DNA, are frequently coupled with additional symptoms in mitochondrial ataxias [35]. These ataxias include maternally inherited hereditary ataxias caused by deletions or duplications of mitochondrial DNA or point mutations in the genes encoding for RNAs and respiratory chain components [35, 36]. A mutation in the mitochondrial DNA polymerase subunit gamma (POLG) gene results in mitochondrial recessive ataxia syndrome [35, 36]. With cerebellar and afferent/sensory ataxia, POLG-related ataxia is a mixed ataxia that manifests with a variety of non-ataxia symptoms, including sensory neuropathy, external ophthalmoplegia, ptosis, epilepsy, and hyperkinetic movement abnormalities [35, 36].
