The most common type of brain cyst, arachnoid cysts can be congenital (present at birth) or caused by trauma.
Arachnoid cysts are the most common type of brain cyst (fluid-filled sacs). Experts believe that arachnoid cysts occur due to a split of the arachnoid membrane, which is one of the three layers of tissue surrounding and protecting the brain and spinal cord. Arachnoid cysts occur four times more often in males than in females.
There are two main types of arachnoid cysts:
Primary arachnoid cyst – These are congenital (present at birth) cysts.
Secondary arachnoid cyst – These are cysts that are caused by head injury or trauma sometime after birth.
Some arachnoid cysts never cause any complications. However, in other cases, the pressure on the brain can cause symptoms, such as: