A colloid cyst is a benign, fluid-filled sac typically located in the third ventricle of the brain. These cysts are made up of a gelatinous substance and are often asymptomatic, meaning they don’t cause symptoms in many cases. However, when they grow large enough, they can obstruct the flow of cerebrospinal fluid (CSF), leading to hydrocephalus (increased pressure within the brain) and neurological symptoms