25th June 2023

Head Injury

Assessment of head injury

Overview

Head injury is the commonest cause of death and disability in people aged 1-40 years old in the UK. Each year, over 1 million people present to emergency departments in England and Wales with a recent head injury. The spectrum of complications secondary to head injury ranges from concussion and headache, through to significant intracerebral haemorrhage and death. Certain populations, such as the elderly or those taking anticoagulant medications, are particularly at risk.

Glasgow Coma Scale

The Glasgow coma scale (GCS) is a key part in head injury assessment. Low GCS at the time of injury and on initial assessment are concerning features for significant injury. In addition, monitoring consciousness level in head injury is important to identify patients at risk of deterioration. The combined scores of eye, verbal and motor responses are used to assess the consciousness level, with a minimum score of 3 and a maximum score of 15.

Investigations

Plain (non-contrast) CT scanning is a key investigation in patients presenting with a head injury. CT has a number of advantages, including being quick and easy to perform, widespread availability, and high sensitivity for picking up intracerebral bleeding.

Intracerebral haemorrhage is one of the most significant complications of head injury. Prompt assessment and investigation are required to identify those with intracerebral bleeding in order to facilitate neuromonitoring, reversal of anticoagulation and surgical treatment where required.

NICE have specific criteria to identify which patients require CT imaging:

For adults who have sustained a head injury and have any of the following risk factors, perform a CT head scan within 1 hour of the risk factor being identified:

• GCS less than 13 on initial assessment in the emergency department
• GCS less than 15 at 2 hours after the injury on assessment in the emergency department
• Suspected open or depressed skull fracture
• Any sign of basal skull fracture (haemotympanum, “panda” eyes, CSF fluid leakage from the ear or nose, Battle’s sign)
• Post-traumatic seizure
• Focal neurological deficit
• More than one episode of vomiting

For adults who have sustained a head injury with no other indications for a CT head scan and who are having anticoagulant treatment, perform a CT head scan within 8 hours of the injury.

Intracranial haemorrhages

Intracranial haemorrhage is roughly subdivided into intra-axial and extra-axial haemorrhage. Intra-axial haemorrhage involves bleeding within the brain itself, typically seen as intraparenchymal or intraventricular haemorrhage in the context of stroke. Extra-axial haemorrhage occurs within the skull but outside of the brain tissue and includes subdural, extradural, and subarachnoid haemorrhage. These are more relevant in the context of head injury.

Extra-axial haemorrhages

Extradural haemorrhage

Caused by laceration of arteries or veins running along the inner aspect of the skull, often accompanied by associated skull fracture. The middle meningeal artery is typically implicated. Characterised clinically by a lucid interval where the patient is asymptomatic and not critically ill. However, once the haematoma reaches a large enough size, it can lead to significant mass effect with midline shift and trans-tentorial herniation and rapid progression to coma and death. These patients typically require close neuro-monitoring and emergency haematoma evacuation in the setting of neurological deterioration.

CT findings: Hyperdense collection in extradural space, extent is limited by suture lines. Forms a crescenteric or lens appearance.

Extradural haemorrhage with associated skull fracture.

Image Source: Wikimedia Commons (2018). EpiduralHematoma, Licensed under a creative commons licence. Available for free at: https://commons.wikimedia.org/wiki/File:EpiduralHematoma.jpg (Accessed on: 11 January 2023).

Subdural haemorrhage

Subdural haemorrhage occurs due to damage to the bridging veins that cross the subdural space and leads to blood collecting between the dura mater and arachnoid mater of the meninges. Signs and symptoms of subdural haemorrhages typically develop more slowly than extradural haemorrhage. Typically, patients with acute subdural haemorrhage will present with headache, confusion, loss of consciousness and focal neurological deficits in the context of a recent head injury. However, chronic subdural haemorrhage may present with behavioural change, disorientation, focal neurological deficit, or amnesia weeks after a traumatic injury, or without a history of witnessed head injury.

Patients with atrophic brain volume, such as the elderly, or with a history of alcohol excess are particularly vulnerable to subdural haemorrhage.

CT findings:

Acute subdural: Hyperdense crescent crescent-shaped homogeneously hyperdense extra-axial collection that spreads diffusely over the affected hemisphere. May see associated midline shift secondary to mass effect.

Chronic subdural: Similar in appearance to acute subdural haematoma, however, over time the collection becomes hypodense with respect to the cerebral cortex and may become isodense with the CSF.

Acute subdural haematoma with midline shift.

Image Source: Wikimedia Commons (2012). Subduralandherniation, Licensed under a creative commons licence. Available for free at: https://commons.wikimedia.org/wiki/File:Subduralandherniation.PNG (Accessed on: 11 January 2023).

Subarachnoid haemorrhage

Subarachnoid haemorrhage (SAH) occurs when there is an arterial or venous injury to the vessels coursing through the subarachnoid space overlying the brain parenchyma.

CT findings: Abnormal hyperdensity in the subarachnoid space.

Subarachnoid haemorrhage with extension of blood into the sulci.

Image Source: Wikimedia Commons (2010). SubarachnoidP, Licensed under a creative commons licence. Available for free at: https://en.wikipedia.org/wiki/File:SubarachnoidP.png (Accessed on: 11 January 2023).

Reversal of anticoagulation

Patients taking long term antiplatelet and anticoagulant medication (such as warfarin or direct oral anticoagulants (DOACs)) are at particular risk of intracranial haemorrhage following head injury. In managing these patients, it is important to consider the possibility of anticoagulant reversal. Some anticoagulants, such as warfarin, have specific antidotes that can be used to reverse their anticoagulant effect. Many patients presenting with life threatening intracranial haemorrhage whilst taking anticoagulants will warrant discussion with haematology to help guide anticoagulant reversal. The indication for antiplatelet and anticoagulant agents will influence ‘risk versus benefit’ decisions surrounding stopping these medications.

Warfarin reversal guidelines

UK guidelines from the British National Formulary and British Society of Haematology advise the following regarding warfarin management in the context of bleeding or raised INR.

• Major bleeding: Stop warfarin, give vitamin K IV; give prothrombin complex (PCC) (factors II, VII, IX, and X); if dried prothrombin complex is unavailable, fresh frozen plasma can be given but is less effective
• INR >8.0, minor bleeding: Stop warfarin; give vitamin K IV; repeat dose of vitamin K if INR still too high after 24 hours; restart warfarin when INR <5.0
• INR >8.0, no bleeding: Stop warfarin; give vitamin K by mouth using the intravenous preparation orally, repeat dose of vitamin K if INR still too high after 24 hours; restart warfarin when INR <5.0
• INR 5.0–8.0, minor bleeding: Stop warfarin, give Vitamin K, and restart warfarin when INR <5.0
• INR 5.0–8.0, no bleeding: Withhold 1 or 2 doses of warfarin and reduce subsequent maintenance dose

Reversal of DOACs

Reversal agents are available for dabigatran etexilate, apixaban and rivaroxaban.

• Idarucizumab is licensed for the rapid reversal of dabigatran in life-threatening or uncontrolled bleeding
• Andexanet alfa is licensed for the reversal of apixaban or rivaroxaban in life-threatening or uncontrolled bleeding