An open head injury (also called a penetrating head injury) is one in which the scalp and skull are breached and brain tissue is exposed or penetrated, typically by a foreign object such as a fragment of bone, a projectile or a sharp implement. It is classified as a form of traumatic brain injury (TBI). The injury causes focal damage along the path of penetration, and the risk of infection, including meningitis and cerebral abscess, is significant because the protective barrier between the brain and the external environment has been compromised.
Open head injury is a relatively uncommon cause of acquired brain injury in the cardiac arrest population. The brain injury that follows cardiac arrest is hypoxic-ischaemic brain injury (HIBI), caused by a global interruption of oxygen-rich blood supply rather than by physical trauma. HIBI tends to produce a different pattern of injury from penetrating head trauma: rather than focal damage at a specific location, it affects vulnerable brain regions diffusely, including the hippocampus, cortical watershed zones and basal ganglia.
The distinction matters clinically because the management, prognosis and rehabilitation of TBI and HIBI differ in important ways. Penetrating head injuries may require neurosurgical intervention to remove bone fragments, debride damaged tissue and reduce infection risk. HIBI is managed medically, with targeted temperature management and supportive care in the intensive care unit. Both, however, share common rehabilitation needs including physiotherapy, neuropsychology, speech therapy and occupational therapy.
Cardiac arrest can occasionally follow a traumatic event such as a road collision or fall that has itself caused a head injury, producing a mixed picture of both TBI and HIBI. In these cases, neurosurgical and cardiology teams work together. For further information on brain injury specifically after cardiac arrest, see the Acquired Brain Injury entry.
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