Genetic and Clinical Predictors of Ataxia in Pediatric Primary Mitochondrial Disorders

Evaluation of ataxia in children is challenging in clinical practice. This is particularly true for highly heterogeneous conditions such as primary mitochondrial disorders (PMD). This study aims to explore cerebellar and brain abnormalities identified on MRI as potential predictors of ataxia in patients with PMD and, likewise, to determine the effect of the patient's genetic profile on these predictors as well as determination of the temporal relationship of clinical ataxia with MRI findings. We evaluated clinical, radiological, and genetic characteristics of 111 PMD patients younger than 21 years of age at The Children's Hospital of Philadelphia. Data was extracted from charts. Blinded radiological evaluations were carried out by experienced neuroradiologists. Multivariate logistic regression and generalized equation estimates were used for analysis. Ataxia was identified in 41% of patients. Cerebellar atrophy or putaminal involvement with mitochondrial DNA (mtDNA) mutations (OR 1.18, 95% CI 1.1-1.3, p < 0.001) and nuclear DNA mutation with no atrophy of the cerebellum (OR 1.14, 95% CI 1.0-1.3, p = 0.007) predicted an increased likelihood of having ataxia per year of age. Central tegmental tract predicted the presence of ataxia independent of age and pathogenic variant origin (OR 9.8, 95% CI 2-74, p = 0.009). Ataxia tended to precede the imaging finding of cerebellar atrophy. Cerebellar atrophy and putaminal involvement on MRI of pediatric-onset PMD may predict the presence of ataxia with age in patients with mtDNA mutations. This study provides predicted probabilities of having ataxia per year of age that may help in family counseling and future research of the population.