Cavum Septum Pellucidum Causing Obstructive Hydrocephalus in a Toddler.

Cavum septi pellucidi (CSP) are benign developmental cystic midline cavities that are located between the lateral ventricles through the foramina of Monro. CSP are usually asymptomatic and have no cerebrospinal fluid (CSF) flow. Although their incidence is increased in association with head trauma, as well as psychiatric and behavioural disorders, this increase seldom causes disease. Herein, we discuss the case of a toddler who presented with episodic headaches for 6 weeks with associated vomiting triggered by strenuous activity. His neurological examination was normal. His MRI brain scan revealed large cavum septum pellucidum with obstructive hydrocephalus. He underwent endoscopic fenestration of the cyst with resolution of both hydrocephalus and the symptoms. Although CSP are generally asymptomatic, in rare situations, as in our illustrative case, they may cause obstructive hydrocephalus that requires urgent attention. CSF flow studies are helpful in confirming the diagnosis.