25th June 2023

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).