What is a ball valve headache?
Some masses may be loosely based on a tissue pedicle, allowing for mobilization with positional changes. For example, this may occur in colloid cysts, which most commonly arise in the third ventricle and may account for the fluctuating symptoms with these masses, as they may swing back and forth with positional changes of the head. As the patient’s head moves to a new position, the cyst may shift and block the foramen of Monro and the outflow of CSF from the lateral ventricle, causing an acute increase in intracranial pressure. The on-and-off occlusion of the foramen of Monro causes episodic headache, which is termed the “ball-valve effect.”