Out of interest, what is Treacher-Collins syndrome?
Treacher Collins syndrome (also called mandibulofacial dysostosis) is a genetic abnormality due to bilateral malformation of 1st and 2nd branchial arches resulting in multiple facial anomalies.
What is the differential?
Cerebellitis (given the history) and Lhermitte-Duclos disease.
This demonstrates unilateral enlargement of the left cerebellar hemisphere, in particular the neocerebellum with evidence of hypointensity of the affected segment on T1 and hyperintensity on T2. The ipsilateral folia appear marginally enlarged with distortion of the fourth ventricle and deviation of the brainstem to the right. There is associated leptomeningeal enhancement. Both lateral, third, and temporal horns are dilated. No intraparenchymal abnormalities demonstrated.