Unusual MRI characteristics of Posterior Cranial Fossa Dermoid Cyst Associated with Klippel-Feil syndrome: A Case Report and Literature Review.

Intracranial dermoid cysts are rare inclusion cysts characterized as well-defined cystic lesions with typically distinct Magnetic Resonance Imaging (MRI) features. However, in rare cases, their imaging features can be atypical because of their variable components. This case report highlights unusual radiological findings of a posterior cranial fossa dermoid cyst that deviates from typical presentation patterns and reveals a rare association between these lesions and Klippel-Feil syndrome (KFS). We detail the case of a 50-year-old female patient who presented with progressive weakness, persistent headaches, and deteriorating vision. MRI of the brain displayed a 6X4.5 cm well-defined cystic lesion in the posterior fossa, showing hyperintensity on T1-weighted images (T1WI) and profound hypointensity on T2-weighted images (T2WI), along with cervical vertebrae fusion indicative of KFS. These atypical imaging findings of posterior cranial fossa dermoid cyst challenge conventional diagnostic patterns and underline the necessity for further exploration of these lesions to avoid misdiagnosis. Also presence of posterior cranial fossa dermoid cysts should be considered in a patient diagnosed with KFS.