Intracranial arachnoid cyst

**Definition:** A fluid filled cavity within the arachnoid membrane which may be congenital or acquired. Acquired causes include trauma, infection and surgery. The most common site is the middle cranial fossa. Factors that influence whether the cyst causes symptoms include its size and location. Symptoms if present may include headache, dizziness, nausea and vomiting, seizures, developmental delay