Summary
Chronic subdural haematoma is a well-known and relatively frequent entity in the elderly. It is originated by a slight trauma which provokes subdural veins to rupture after suffering stretching due to cortical atrophy.

We report the case of a 11 year old patient with a previous known arachnoid cyst who was diagnosed as chronic subdural haematoma without association to cranial trauma and with slight neurological impairment. He responded successfully to pharmacological therapy. The following clinical case permits review pathophysiology of chronic subdural haematoma and considers subarachnoid cyst as a risk factor.