Ruptured intracranial dermoid cyst with progressive spinal dissemination: illustrative case.

backgroundDissemination of an intracranial dermoid cyst to the cervical or thoracic spine is rare and can present treatment challenges. Dermoid cysts are typically benign and slow-growing, but ruptured contents can disseminate within the CNS. In rare cases, the disseminated fragments can migrate extensively and accumulate over time, leading to progressive neurological symptoms. OBSERVATIONS: The authors report the case of a 39-year-old woman who presented with extensive progression of disseminated dermoid cyst fragments. Initially identified as small intracisternal fat globules, these fragments migrated and extensively disseminated throughout the spinal canal, eventually leading to involvement of the cervical and thoracic spine. Symptom progression included left-hand weakness, numbness, and neck pain due to spinal cord compression. Surgical decompression at the foramen magnum alleviated cranial pressure and improved symptoms. LESSONS: While ruptured dermoid cyst contents are known to migrate intracranially, few cases of dissemination to the craniocervical junction or spinal cord have been reported. This case emphasizes the importance of serial imaging to document progression and the role of decompression in managing mass effect secondary to ruptured dermoid cyst contents at the craniocervical junction. https://thejns.org/doi/abs/10.3171/CASE25506.