Dear Sir, Approximately two-thirds of patients with traumatic brain injury (TBI) undergoing emergency cranial surgery have an acute subdural haematoma (ASDH) evacuated [2]. These haematomas are frequently associated with underlying cerebral parenchymal injury, which further exacerbates brain swelling [5]. Therefore, even though craniotomy and evacuation comprise the established primary treatment for ASDH, leaving the bone flap out (ie decompressive craniectomy) is an option either because the brain is swollen beyond the confines of the cranium or because the patient is thought to be at high risk for worsening brain swelling during the ensuing days.