**3.1 Primary ataxia**

Ataxias that affect the primary cerebellum can also be considered as sporadic and inherited. The latter includes episodic ataxias, X-linked cerebellar ataxias, mitochondrial ataxias, autosomal dominant cerebellar ataxias, also known as spinocerebellar ataxias (SCAs), and autosomal recessive cerebellar ataxias (ARCAs). The cerebellar variant of multiple system atrophy (MSA-C) and idiopathic late-onset cerebellar ataxias are examples of idiopathic degenerative cerebellar ataxias [24–31].

### **3.2 Congenital ataxia**

Cerebellar malformations or pontocerebellar hypoplasia can produce congenital ataxias, which manifest as cerebellar ataxias. The uncommon autosomal recessive condition, Joubert's syndrome, whose most well-known manifestation is the "molar tooth sign" on MRI, is defined by a congenital hind-brain abnormality. The clinical picture includes multiple organ involvement, cerebellar ataxia, respiratory dysregulation, ocular motor apraxia, and neonatal hypotonia. Till now, more than 20 causal genes have been found, the majority of which encode proteins for the main cilium, and an organelle found within cells that plays a key role in many cellular processes. The genetic condition known as ciliopathies, which is a new class, includes Joubert's syndrome (**Figure 1**) [32, 33].
