1. A 62-year-old man with progressive action tremor and a 74-year-old man with progressive ataxia Teaching NeuroImages Neurology Resident and Fellow Section © 2014 American Academy of Neurology

2. First patient: 62-year-old man with progressive action tremor since 3 years Second patient: 74-year-old man with progressive ataxia since 5 months Clinical examination did not show other abnormalities Brain MRI revealed bilateral middle cerebellar peduncle hyperintensities associated with a hyperintensity of the inferior part of the splenium of the corpus callosum on FLAIR sequences. Patient 2 also showed a traumatic subdural hematoma due to a ataxia-related fall. © 2014 American Academy of Neurology Renard, et al Vignette

3. Imaging © 2014 American Academy of Neurology Renard, et al

4. Middle cerebellar peduncle and splenial hyperintensities Disorders associated with middle cerebellar peduncle hyperintensities include multiple system atrophy, multiple sclerosis, autosomal dominant spinocerebellar atrophy, leukodystrophy syndromes, anterior inferior cerebellar artery infarctions, and fragile X-associated tremor ataxia syndrome (FXTAS). FXTAS was genetically proven in both our patients. Causes of focal splenial hyperintensities include Marchiafava- Bignami disease, mild encephalitis with a reversible splenial lesion, multiple sclerosis, trauma, and leukodystrophy. Splenial hyperintensity has been recently reported as frequently encountered and proposed as an additional radiological diagnostic criterion in FXTAS. © 2014 American Academy of Neurology Renard, et al