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103 A novel MRI biomarker for ataxia-telangiectasia: evaluating the lack of hypoin- tensity of the dentate nuclei

Background Ataxia-Telangiectasia (AT) is a rare autosomal recessive multisystemic disorder. Classic AT has a characteristic neurological phenotype but variant AT has a variable presentation leading to diagnostic delay. Early diagnosis is essential for cancer surveillance and but imaging biomarkers are currently lacking. The lack of hypointensity of the dentate nuclei (DN) in some inherited ataxias has been reported. We evaluate the DN hypointensity in our UK AT cohort. Methods 26 patients (age range 4-55 years) underwent MRI susceptibility-weight imaging (SWI) across two study sites (the National Paediatric and Adult AT clinics, UK). For the paediatric patients, 14 age-matched controls (age range 5-17 years) also underwent MRI SWI. Evaluation of hypodensity of the DN was made using a visual rating score by two independent investigators for each study site. Results The average DN visual rating score for patients 0.55 in paediatric cases (4-17 years, N = 11) and 0.64 in age- and sex-matched controls. In adults (18-55 years, N = 14), the average visual ranking score was 0.07. Conclusions We demonstrate failure of hypointensity in the DN in AT patients. We propose that lack of hypointensity in the dentate nuclei is a useful biomarker for AT and easily applicable for clinical practice.