Dermoid Cyst
A dermoid cyst is a benign, slow-growing congenital lesion that develops from skin-related tissues trapped during early fetal development. Unlike many other cysts, dermoid cysts may contain fat, hair, skin glands, and other tissue elements. Inside the skull, these cysts most commonly occur near the midline of the brain and may be discovered incidentally on imaging or after symptoms develop due to their size or location. Although present from birth, they may not be identified until later in life.
What is it?
Dermoid cysts develop from embryonic skin-related cells that become trapped within the developing nervous system during fetal life. Over time, these cells continue producing skin-associated materials, resulting in a cyst that may contain fat, keratin, hair, and glandular tissue. This mixed composition gives dermoid cysts a characteristic and often complex appearance on imaging studies.
Intracranial dermoid cysts most commonly occur near the midline of the brain, including regions such as the suprasellar area, posterior fossa, and areas near the brainstem. They typically grow very slowly, and many remain stable for years without causing symptoms.
When symptoms occur, they are usually related to compression of nearby brain structures or, less commonly, rupture of the cyst. MRI is the preferred imaging test for evaluating dermoid cysts because the fatty components within the lesion produce characteristic MRI findings that help distinguish dermoid cysts from other developmental or cystic lesions. CT imaging can also be very useful because fat appears as a low-density area on CT scans.
If a dermoid cyst ruptures, MRI may reveal tiny fat droplets scattered within the cerebrospinal fluid spaces, a finding that strongly supports the diagnosis and may explain associated symptoms.
Important to Know
Most dermoid cysts are benign and slow growing. Small lesions without symptoms are often managed conservatively with periodic imaging follow-up.
When a cyst causes symptoms, enlarges significantly, or ruptures, surgical removal may be considered. Complete removal is not always possible because some cysts may be closely attached to important nerves, blood vessels, or brain structures. In these situations, partial removal may be safer.
A rare but important complication is rupture of the cyst, which releases fatty contents into surrounding cerebrospinal fluid spaces. This can trigger chemical meningitis, an inflammatory reaction that may cause severe headache, neck stiffness, fever-like symptoms, nausea, seizures, or worsening neurological symptoms. Rupture may occur spontaneously or following head trauma.
Red flag symptoms include sudden severe headache, neck stiffness, worsening neurological symptoms, vision changes, seizures, confusion, or loss of consciousness. These symptoms require prompt medical evaluation.