Tiny Brain, Huge Ventricles: A Surprising Case Behind Leg Weakness

A 44-year-old man in France presented with two weeks of left‑leg weakness. Neuroimaging showed an abnormally small brain (about half the average size) with massive fluid buildup and extremely dilated ventricles pushing brain tissue against the skull, a state likely causing his weakness. He had a history of an infancy shunt that was removed at 14. Doctors drained the excess fluid and inserted a new intracranial shunt, with his neurological exams improving over weeks. Neuropsych tests placed his IQ at about 75 and remained unchanged. The Lancet case report uses this vignette to reflect on human brain growth and its drivers, illustrating how a very small brain can be linked to significant clinical changes when ventricles are enlarged.