arachnoid cyst
A fluid-filled sac located between the arachnoid membrane and brain surface, which may cause symptoms through mass effect or remain asymptomatic.
Full Definition
An arachnoid cyst is a benign, cerebrospinal fluid-filled sac that develops within the arachnoid membrane, one of the protective coverings of the brain and spinal cord. These cysts can be congenital (primary) or acquired (secondary) following trauma, infection, or surgery. Most arachnoid cysts are asymptomatic and discovered incidentally on brain imaging. However, larger cysts may cause symptoms through mass effect, including headaches, seizures, developmental delays, or focal neurological deficits depending on their location. Common locations include the middle cranial fossa, posterior fossa, and suprasellar region. Treatment is reserved for symptomatic cysts and may involve surgical drainage, fenestration, or cystoperitoneal shunting.
Usage
Usage note: Not to be confused with other types of intracranial cysts.
In Context
- "The large left temporal arachnoid cyst was causing midline shift and required surgical intervention." — Neurosurgical consultation
- "Incidental arachnoid cyst was noted on MRI but deemed clinically insignificant." — Radiology report