Reversible diencephalic dysfunction: episodic hyperhidrosis due to a trapped third ventricle.

We present a patient with episodic hyperhidrosis (EH) who had 15 attacks per day for 3 years following placement of a lateral ventricular shunt. MRI revealed that she had an isolated third ventricle. Stereotactic shunting of the third ventricle resulted in immediate and complete resolution of her symptoms. We suggest that this patient had periodic rises in third ventricular pressure resulting in episodic diencephalic dysfunction and EH.