Imaging of a fourth ventricle arachnoid cyst in a child

Abstract

A little girl aged 2.5 years presented with left-sided facial weakness of acute onset and approximately 9 months duration (according to the mother). There was no history of a previous viral illness, ear discharge or trauma. The child’s behaviour was reported as normal and there was no impairment in developmental and motor skills. Her delivery had been normal and her birth weight was 2.1 kg. Neurological examination confirmed a left 7th cranial nerve lower motor nerve palsy, with no associated 6th nerve involvement or bulbar palsy. Fundoscopy was normal and there were no signs of raised intracranial pressure, nor were cerebellar signs elicited. Power and deep tendon reflexes in the limbs were normal. CT demonstrated a cystic mass of the fourth ventricle, and MRI was requested for further evaluation. MRI of the brain was performed before and after gadolinium DTPA contrast injection, in the sagittal