Contralateral acute subdural hematoma occurring after removal of calcified chronic subdural hematoma

Supratentorial craniotomy for a nontraumatic lesion complicated by an acute subdural hematoma on the opposite side is rare. A 47-year-old woman presented with progressive headache and dizziness with no significant past history. Neuroimaging studies revealed a very large calcified chronic subdural hematoma over the entire right hemisphere with prominent mass effect. Despite a near total excision of the hematoma including the inner membranes by a large craniotomy with meticulous dissection, the brain parenchyma remained depressed. The dead space was therefore filled with saline and the operation was completed as usual. Repeat computed tomography scan for signs of left tentorial herniation demonstrated an acute contralateral subdural hematoma with severe shift of midline structures. We propose a prevention strategy for this event, which has not been previously described. We also discuss possible mechanisms involved in this unexpected complication.