Demystifying the Etiology of ILOCA in the Genomic Era: A Narrative Review.

Background: Idiopathic Late-Onset Cerebellar Ataxia (ILOCA) is a challenging and heterogeneous disorder characterized by progressive cerebellar ataxia beginning after the age of 40 without a family history of cerebellar ataxia. Despite extensive investigations, many cases remain undiagnosed. The advent Next Generation Sequencing (NGS) has significantly advanced the identification of genetic causes associated with ILOCA.

Objective: This study aims to review the concept of ILOCA, its historical perspective, epidemiology, diagnostic criteria, and the impact of the new era of genetic diagnosis facilitated by NGS technologies.

Methods: A comprehensive literature review was conducted, focusing on the genetic advancements in diagnosing ILOCA.

Results: ILOCA accounts for a significant proportion of late-onset cerebellar ataxias. The prevalence of late-onset cerebellar ataxias ranges from 2.2 to 12.4 per 100,000 individuals, with genetic causes identified in up to 30-50% of cases using NGS. Key genetic findings include repeat expansion disorders such as Spinocerebellar Ataxia type 27 B, Cerebellar Ataxia, Neuropathy and Vestibular Areflexia Syndrome and Friedreich Ataxia. SCAs and Autosomal Recessive Cerebellar Ataxia caused by point mutations are also frequently observed in large cohorts. Advances in NGS have increased the diagnostic yield for ILOCA.

Conclusion: ILOCA represents a significant diagnostic challenge due to its heterogeneous nature and the overlap with other neurodegenerative and genetic conditions. The use of NGS technologies has revolutionized the diagnostic approach, uncovering genetic causes in a substantial number of previously undiagnosed cases. Routine investigation of specific genes associated with ILOCA is recommended to improve diagnostic accuracy and patient management.