Mystery case: idiopathic bilateral stenosis of the foramina of Monro.

A 42-year-old man presented with chronic, continuous, bifrontal pressure headaches, slightly worse in the morning, forgetfulness, and confusion. There was no history of prior CNS hemorrhage or infection. The neurologic examination was unremarkable. No papilledema was present. Neuroimaging demonstrated symmetric enlargement of the lateral ventricles, a slit-like third ventricle, and downwards transtentorial herniation (figure 1). No mass lesion or abnormal enhancement was seen. A diagnosis of idiopathic bilateral stenosis of the foramina of Monro was considered. The patient underwent endoscopic Figure 1 MRI of the brain