To describe long-term follow-up brain MRI findings in patients with cerebrotendinous xanthomatosis (CTX) treated with chenodeoxycholic acid (CDCA). Of a cohort of 79 Dutch patients with CTX, we retrospectively reviewed brain MRI findings of patients at diagnosis (before the start of treatment) and after long-term follow-up (7-27 years) in 12 patients. In addition, we report on 2 families with remarkable brain MRI findings. MRI abnormalities showed progression in all 7 patients diagnosed at 24 years or older and only in 1 of 5 patients diagnosed younger than 24 years. MRI findings in the other patients diagnosed younger than 24 years were normal at baseline and remained normal even after follow-up of more than 25 years. The total MRI scores at baseline were 2 and 19 and at follow-up 4 and 37, respectively, for patients diagnosed before or after the age of 24 years, despite a comparable number of treatment years. MRI findings are fully in line with our long-term treatment effect article, emphasizing the importance of early diagnosis and treatment in CTX. Expanding the spectrum of brain MRI findings (including the finding of a posterior leukoencephalopathy) leads to a better understanding of the heterogeneity of this treatable disease.