3RD VENTRICLE COLLOID CYST 

Colloid cysts constitute about 3% of primary brain neoplasms and roughly about 1/5th  of intraventricular space occupying lesions. They are mostly located at the foramen of Monro 

They usually present in early middle age  and rarely in the paediatric population

They are mostly found incidentally . Owing to their critical position in the roof of the third ventricle they can on occasion dramatically present with sudden obstructive hydrocephalus and thunderclap headache or collapse and unconsciousness.