Objective: Assess the prevalence and compare clinical features of SAOA, MSA and sporadic ataxia patients with a genetic diagnosis in ILOCA patients.

Background: Cerebellar ataxias are a heterogeneous group of disorders. The term Idiopathic Late Onset Cerebellar Ataxias (ILOCA) was introduced to designate the apparently non-hereditary and non-symptomatic adult onset ataxias. Some cases have Multiple System Atrophy (MSA), some genetic causes without family history and many remain without diagnosis: Sporadic Adult Onset Ataxia of unknown etiology (SAOA). The influence of alcohol consumption in the phenotype of these disorders remains debatable.

Methods: Retrospective study of demographic, clinical and imaging characteristic of all patients with progressive cerebellar syndrome with onset after 20 years, no family history of neurological disease and no established symptomatic cause of ataxia. Patients with past or active alcohol abuse were included. All were observed in our Movement Disorders outpatient clinic between January 1997 and July 2015.

Results: 38 ILOCA patients, 19 male, mean age at disease onset 54 (20-71). Besides cerebellar ataxia (100%), 63% had dysarthria, 63% oculomotor abnormalities, 45% pyramidal signs, and 18 % polyneuropathy. In 12 (32 %) patients, a diagnosis of possible or probable MSA was made. Nine (24%) had a history of alcohol abuse, 2 in the MSA group. Thirteen (50%) of the non-MSA patients underwent genetic tests: one tested postive for Friedereich Ataxia and another had a probable mitochondrial citopathy. Disautonomia, parkinsonism and RBD symptoms were more common in the MSA group (100% vs 17%, p<0.0001; 50% vs 12.5%, p=0,01; 42% vs 0% p=0,001, respectively). In the non-MSA group, alcohol abuse was associated with more polyneuropathy and less dysarthria (43% vs 6%, p=0.03, 29% vs 82%, p=0.01, respectively).

Conclusions: In our series only 39% of patients had a definitive diagnosis. Compared with other series, ours had a similar percentage of MSA cases but a lower prevalence of genetic ones. Besides disautonomia and parkinsonism (required criteria for MSA diagnosis) only RBD was statistically more prevalent in the MSA group. Our investigation supports the notion that ILOCA may have some clinical aspects that can help in differential diagnosis, like RBD in MSA, and polyneuropathy in alcohol abuse.

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MDS Abstracts - https://www.mdsabstracts.org/abstract/the-aetiology-of-idiopathic-late-onset-cerebellar-ataxia/