From Balloon to Brain Ballooning: A Case of Obstructive Hydrocephalus in a Child.

Background: Intraventricular simple cysts, often termed intraventricular arachnoid cysts, are rare benign intracranial lesions in children and are usually asymptomatic. When they become symptomatic, the presentation is typically related to obstructive hydrocephalus or seizures. Clear clinical triggers for abrupt decompensation are not well defined. Observations: A previously healthy 6.9-year-old boy presented in stupor with acute obstructive hydrocephalus. The only notable antecedent event was repetitive, forceful balloon inflation the night before, followed by early-morning headache and vomiting. Examination showed papilledema, nuchal rigidity, and positive Kernig and Brudzinski signs without focal deficits. CT revealed triventricular hydrocephalus with a normal fourth ventricle. Cerebrospinal fluid (CSF) and blood studies were unrevealing for infection. Worsening hydrocephalus prompted emergent frontal ventriculostomy. MRI confirmed supratentorial obstructive hydrocephalus with trans-ependymal CSF seepage. Endoscopic third ventriculostomy through the ventriculostomy tract exposed a thin, transparent, vascularized cyst bridging the right lateral ventricle and third ventricle near the foramen of Monro. Endoscopic cauterization and fenestration of the cyst wall restored CSF flow, and the child recovered fully without deficit. Lessons: This case suggests that repetitive, forceful Valsalva-like maneuvers during excessive balloon inflation can acutely raise intracranial pressure and precipitate decompensation in children harboring an unrecognized intraventricular arachnoid cyst, resulting in acute obstructive hydrocephalus.