Coronal CT. 3rd ventricular colloid cyst in the antero-superior 3rd ventricle.
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Cysts (Arachnoid, Colloid, Dermoid, Epidermoid)
Arachnoid Cyst
- Arachnoid-lined cyst, associated with the meninges.
- Often arise from the middle cranial fossa (near the temporal lobes), suparasellar region, posterior fossa
- Typically asymptomatic but can cause compressive symptoms: headaches, seizures, obstruction, etc...
Colloid Cyst
3rd ventricular colloid cysts are benign epithelial-lined cysts (specifically in the anterior/superior 3rd ventricle*) that contain fat and cholesterol crystal and although they are generally asymptomatic, they will cause intermittent headaches (from intermittent obstructive hydrocephalus), if they obstruct CSF flow through the 3rd ventricle.
Patients present with intermittent headaches because the obstructive hydrocephalus is intermittent (it varies based on the intermittent obstruction of CSF outflow*).
- Importantly, if there is acute hydrocephalus, lumbar puncture (LP) is contraindicated, because it could lead to infratentorial herniation.
Dermoid Cyst
- Consist of keratinaceous material and derive from ectopic ectodermal tissue (like epidermoid cysts) BUT they are filled with hair follicles and other skin elements, including sebaceous and sweat glands; they are "pearly" white in appearance.
- Localize to multiple regions: posterior fossa, sellar, lumbosacral
- Typically occur in children
- Chemical meningitis can occur upon dermoid cyst rupture.
Epidermoid Cyst
- Consist of keratinaceous material and are lined with squamous-type epithelium; derive from ectopic ectodermal tissue..
- Localize to the cerebellopontine angle
- Typically occur in young adults
See Rathke's cleft cyst along with craniopharyngioma