With a histologically benign nature, spinal dermoid cysts represent 0.6% of all dermoid cysts and 22.9% of CNS dermoid cysts. However, in exceedingly rare instances, the rupture of a spinal dermoid cyst can lead to dissemination of fat droplets into the cerebrospinal fluid, which then migrate caudally into the intraventricular and subarachnoid spaces. This migration can result in atypical neurological symptoms including headache, aseptic meningitis, and obstructive hydrocephalus, underscoring the clinical complexity and warranting emergent investigation. 

Upon admission, the patient was afebrile and hemodynamically stable. He was intubated and sedated with a Glasgow Coma Scale score of 8. The initial noncontrast head CT raised concerns for pneumocephalus, but subsequent imaging revealed acute obstructive hydrocephalus secondary to fat deposition in the intraventricular and subarachnoid spaces. Emergent external ventricular drainage was promptly initiated. Further MRI of the lumbar spine identified a ruptured dermoid cyst with cephalad migration of fat and an associated tethered spinal cord. Notably, an earlier MRI from 12 years prior had indicated the presence of an intraspinal dermoid cyst with evidence of a minor rupture. Patient subsequently underwent placement of a right frontal ventriculoperitoneal shunt and recovered without further medical or neurological complications.