"Growing" cerebellum in an infant after shunt insertion.

INTRODUCTION: Supratentorial cortical mantle growth after shunt surgery in infants with posthemorrhagic hydrocephalus is common. However, cerebellar growth and Chiari are rare. PATIENT DESCRIPTION: We describe a term newborn with an intraventricular hemorrhage and posthemorrhagic hydrocephalus who underwent endoscopic third ventriculostomy followed by shunt placement at age 4 months. RESULTS: After shunt placement, her head circumference growth rate rapidly decreased from the ninety-seventh percentile to the third percentile. Six months after a shunt placement, cerebellar disproportional growth was noticed. Five years after surgery, her cerebellar volume had increased by 300% whereas the cerebral hemispheres volume by 150%, and Chiari 1 appeared. She manifested early hemiparetic cerebral palsy, but, did not develop clinical evidence of increased intracranial pressure or brainstem abnormalities. CONCLUSION: This term newborn exhibited apparent cerebellar "growth" and posterior fossa crowding after shunt surgery for posthemorrhagic hydrocephalus. Our patient's findings may have resulted from shunt-related alterations in pressure dynamics, leading to decreased head growth rate with a relatively smaller posterior fossa, in face of a normal brain growth. The timing of intraventricular hemorrhage at term, beyond the vulnerable period of cerebellar development, may have been a contributing factor to the craniocerebellar disproportion and posterior fossa crowding cerebellar development may have been relatively spared and was a contributing factor to the craniocerebellar disproportion and posterior fossa crowding.