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Non-progressive cerebellar ataxia with previous acute cerebellar injury of undetermined origin: a puzzling neurological disorder.

C erebellar ataxias are a heterogeneous group of diseases and can be classified as primary and secondary, as well as hereditary and sporadic 1. Primary cerebellar ataxias are subdivided into sporadic and hereditary ataxias 1. The latter include congenital ataxias (such as Joubert' s syndrome); autosomal recessive cerebellar ataxias (ARCAs), including Friedreich' s ataxia and ataxia telangiectasia; autosomal dominant cerebel-lar ataxias, also known as spinocerebellar ataxias (SCAs), such as SCAs type 1, 2, 3, 6, 7 and 10); episodic ataxias; X-linked cerebellar ataxias; and mitochondrial ataxias. 1 Idiopathic sporadic degenerative cerebellar ataxias include the cerebellar form of multiple system atrophy (MSA-C) and idiopathic late-onset cerebellar ataxias (ILOCA) 1. Secondary, or acquired, ataxias result from a variety of exogenous or endogenous non-genetic causes, including those of a toxic (drug-induced cerebellar ataxia), paraneoplastic, immune-mediated, nutritional or infectious nature, as well as focal injury to the cerebellum 1. Non-progressive cerebellar ataxias are a very rare, chronic neurological condition with different etiologies, including congenital cerebellar malformations (such as Joubert' s syndrome) and inherited neurometabolic disorders (such as GLUT1 deficiency). They include sporadic cerebellar ataxias associated with infections (chick-enpox virus, Epstein-Barr virus) and toxic agents (previous drug exposure) and autoimmune cerebellar ataxias 2,3,4. A peculiar group of non-progressive cerebellar ataxias can be associated with previous acute or subacute cerebellar insult of unknown etiology 5. In this issue of Arquivos de Neuro-Psiquiatria, Pinto et al. report an interesting and puzzling non-progressive cerebellar ataxia with previous acute cerebellar injury of undetermined origin 5. The authors studied five adult patients with acquired non-progressive cerebellar ataxia (mean age of onset = 20.8 years) associated with cerebellar or olivopontocerebellar atrophy who presented with previous acute or subacute onset (mean value = 10 days) without a known etiology for the condition 5. They discuss in great detail various possible etiologies of this mysterious condition, including neuro-genic etiologies (either unidentified because of incomplete genetic investigation or associated with genetic diseases with mild phenotypes or formes frustes) and inborn errors of metabolism (undiagnosed because of incomplete screening), but failed to find a specific etiology in their series of patients 5. While most published cases of non-progressive ataxia are described in early childhood, have a congenital etiology (e.g., cerebellar hypoplasia) and are frequently accompanied by mental retardation, a significant number of cases are unclassifiable 2,3,4. In contrast, sporadic cerebellar ataxia with adult onset is associated with genetic, non-genetic and sporadic degenerative diseases 6,7. In …