Primary Brain Injury

Primary Brain Injury is a result of direct mechanical forces exerted at the time of injury, and cannot be augmented by medical care. [32] [33]

This results in two types of injures - focal and diffuse brain injuries. [32]

FOCAL

Intracerebral Haemorrhage - following damage to the brain parenchyma, there may be bleeds within the brain itself. [32] [33]

Extradural Haematoma - Bleeding between the Dura Mater and periosteum of the skull. A common cause is disruption of the middle meningeal artery following a fracture to the ptyerion. [32] [33]

Subdural Haematoma - Bleeding between the Dura Mater and the Arachnoid Mater. Typically due to damage to dial artery or cortical veins. [32] [33]

Subarachnoid Bleed - Rapidly develops, normally due to arterial injury. May be associated with hydrocephalus due to disrupted cerebrospinal fluid flow. [32] [33]

Cerebral Contusion - Localised inflamed neural tissue with associated blood from local broken vessels. [32] [33]

Disruption of neural tissue - Gross cranial injury or penetrating injuries may directly disrupt the neural tissue. [32] [33]

DIFFUSE

Diffuse Axonal Injury (DAI) occurs throughout the brain following blunt injury. DAI is caused by shearing of the neuronal axons during acceleration / deceleration of cerebral tissue. [33] [34] Damage to neuronal axons can vary from complete disconnection to mild malfunction, leading to various symptoms. [33]

DAI can be broadly categorised as:

Grade 1 - Mild: Microscope changes to white matter - Brief loss of consciousness [33] [35]

Grade 2 - Moderate: Gross focal lesions in corpus callosum - Variable recovery, coma (unclear duration) [33] [35]

Grade 3 - Severe: As Grade 2, with additional lesions seen in the brainstem - Instant coma and posturing with incomplete recovery. [33] [35]

FRACTURES

Some texts include fractures as a part of focal brain injuries.

Can be classified as depressed or non-depressed, and open or closed. [32] [33]

Any bone of the skull can be affected. [32]

The pterion is the weakest point of the skull, and is especially vulnerable to fractures. [32] [33]

Basilar Skull Fracture - A fracture to any of the bones that make up the cranial base. May be associated with cerebrospinal fluid leakage due to tearing of the meninges. Patients may present with delayed periorbital / retroauricular echymossis. [32]

Fractures may result in cranial nerve damage, which are more common with basilar skull fractures. [32]

Any skull fracture is a cause for concern, and these patients must be assumed to have a severe head injury. [32] [33]