Pathology of head injury

Question 1

Commonest causes of head injuries in the UK?

Answer 1

Road traffic accidents
alcohol-related incidents
assaults

Question 2

What can be caused primarily by a head injury? (1)

Answer 2

Focal and/or diffuse brain trauma

Question 3

What things can occur as a result of a head injury? (secondary insult) (4)

Answer 3

Hypotension – low arterial BP
Hypoxia – O2 not reaching the brain due to continued low BP or increased ICP from brain tissue swelling.
Infection - Skull fractures can occasionally tear the membrane that surrounds the brain. If this happens, bacteria can enter the wound and cause an infection.
Haematoma – bleeding in/around brain

Question 4

What is used to assess a person’s conscious level?

Answer 4

Glasgow Coma Scale

Question 5

As the GCS is scored out of 15. What are the scores correlating with mild, moderate and severe head injury?

Answer 5

13-15 = mild injury
9-12 = moderate injury
3-8 = severe injury

Question 6

Significant consequences of a head injury (7)

Answer 6

Permanent physical disability

Post traumatic epilepsy - acquired epilepsy that results from brain damage

Intracranial infection

Psychiatric illness

Chronic subdural haemorrhage

‘Punch-drunk’ dementia or Chronic traumatic encephalopathy - repeated concussions or other traumatic blows to the head leading to memory problems, increased confusion etc

Fatal outcome (uncommon)

Question 7

what is a depressed skull fracture?

Answer 7

A focal impact which may push fragments inwards to damage the meninges, blood vessels and the brain

Risk of meningitis and post-traumatic epilepsy.

Not typical of a fall from standing onto a flat surface, e.g. pavement - fractures tend to be linear in this scenario

Question 8

Linear skull fracture

Answer 8

commonly temporo-parietal from blow or fall onto side or top of the head and may continue onto the skull base; “hinge” fracture

Question 9

Ring skull fracture

Answer 9

Fracture line encircling the foramen magnum caused by a fall from height, usually landing on the feet, but sometimes the head, leading to the skull base and cervical spine being forced together

Question 10

“Contre-coup” fracture

Answer 10

fracturing of the orbital plates (anterior fossa) caused by a fall onto the back of the head - fracture forms opposite side of cranium

caused by a moving head striking a fixed object or - contusions are found diametrically opposite the site of head impact, e.g. a fall onto the back of the head would result in contusions on the frontal and temporal poles and on the undersurface of the frontal lobes

Question 11

What is an intracranial haemorrhage

Answer 11

Accumulation of blood within the rigid skull causes an increase in intracranial pressure (ICP) and results in compression of the brain - this compression causes symptoms, including reduction in conscious level.

As ICP increases, without intervention, ultimately death will occur by compression of the brainstem due to herniation of the cerebellar tonsils into the Foramen Magnum

Question 12

What is an extradural haemorrhage

Answer 12

Bleeding occurring between the dura and the skull; accumulating blood strips the dura off the inner surface of the skull

Vast majority arise from damage to an artery in association with a skull fracture (80-90%)

Classically caused by bleeding from the middle meningeal artery

Question 13

What is a subdural haemorrhage

Answer 13

Bleeding occurring beneath the dura (and above the arachnoid)

Usually caused by bleeding from bridging veins which pass from the surface of the brain to drain into the large venous channels within the dura

Any motion which causes rotational or “shearing” forces can cause the veins to be stretched and torn due to the relative movement between the brain and the dura

Can get chronic subdural haemorrhage, particularly in elderly, and may be a cause of chronic confusion (and may be mistaken for dementia)

Question 14

What is a subarachnoid haemorrhage?

Answer 14

bleeding beneath the arachnoid membrane (and above the brain)

most common cause of SAH is actually natural disease - rupture of a cerebral artery (“berry”) aneurysm

frequently seen in association with cerebral contusions (bruising to the brain)

Collapse is usually rapid and death can occur very quickly due to the irritant effects of blood in the subarachnoid space

Question 15

Cerebral oedema

Answer 15

Common and rapid result of brain injury, especially in children (“malignant cerebral oedema”)

Can develop in minutes and lead to massive brain swelling with raised intracranial pressure and “coning” (brain compresses the brainstem and spinal cord)

Question 16

Cerebral contusion and laceration

Answer 16

Direct mechanical damage to the brain substance

May occur anywhere on the brain

Question 17

How is Diffuse Traumatic Axonal injury diagnosed

Answer 17

This diagnosis can only be made by microscopy of the brain tissue using special staining techniques

Usual scenarios associated with traumatic Diffuse Axonal Injury are vehicular collisions and falls from a height; serious rotational forces applied to the brain tissue causing shearing of axons. Can also be from child abuse - shaking baby syndrome. It occurs in about 50% of all cases of severe head trauma and may be the primary damage that occurs in concussion.

Clinically, victims are comatose when tDAI is fully developed - with over 90% of patients with severe DAI never regaining consciousness.

Concussion: may well be the clinical manifestation of lesser degrees of axonal injury - may have retrograde amnesia.