Head Injury Flashcards
What are the two stages of insult?
Primary and secondary
Describe the primary insult
Focal and/or diffuse brain trauma
Describe the secondary insult
- Hypotension
- Hypoxia
- Infection
- Haematoma
What is used to assess conscious level?
Glasgow Coma Scale
Describe the outcome of Glasgow coma scale
Correlates with severity of head injury:
• 13-15 - mild injury
• 9-12 - moderate injury
• 3-8 - severe injury
Name seven complications of head injury?
- Permanent physical disability – paralysis, loss of motor function or speech
- Post traumatic epilepsy
- Intracranial infection
- Psychiatric illness – depression, PTSD
- Chronic subdural haemorrhage
- ‘Punch-drunk’ dementia
- Fatal outcome (uncommon)
What are some reasons a person might fall?
- Accidental (falls, RTAs)
- Homicide - consequence of being struck by a weapon
- Natural disease can cause collapse with resulting head injury which can prove misleading on initial investigation
What are the five layers of the scalp
Skin, Connective tissue, Aponeurotic fascia, Loose connective tissue, Pericranium
What does the skull consist of?
Compact bone separated by spongy bone
Describe the meninges
- Dura mater (dense, tough, fibrous, adherent to inner surface of the skull)
- Arachnoid mater (delicate, transparent, envelopes the brain)
- Pia mater (delicate, applied to the brain surface)
Describe scalp injuries
- Laceration clean cut and bleed profusely
- Blunt force trauma may no be visible on the scalp
- Hair can obscure injuries
- May only have bruising/bleeding in the deeper layers of the scalp or between the scalp and skull
What are the two element to the skull?
- Skull vault (upper part) - frontal bone, squamous temporal bone and occipital, separated by sutures
- Skull base which can be divided into the anterior, middle and posterior cranial fossa
What are five different types of skull fractures?
- Linear
- Depressed
- Comminuted (mosaic
- Ring fracture
- Contre-coup
Describe linear skull fractures
Commonly temporo-parietal from blow or fall onto side or top of the head and may continue onto the skull base; “hinge” fracture as it will split along a suture i.e. sagittal and then the two sutures coming off of it
Describe focal skull fractures
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
Describe committed (mosaic) fractures
Fragmented skull
Describe ring fractures
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
Describe contre-coup fractures
Fracturing of the orbital plates (anterior fossa) caused by a fall onto the back of the head
How are intracranial haemorrhages named?
By their position in the skull i.e extradural, subdural and subarachnoid haemorrhage
What is an intracranial haemorrhage?
Accumulation of blood within the rigid skull which 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, death will occur by compression of the brainstem due to herniation of the cerebellar tonsils into the foramen magnum
What is an extra dural haemorrhage?
Bleeding occurring between the dura and the skull; accumulating blood strips the dura from the inner surface of the skull
Most due to damage to an artery is association with skull fracture
What artery classically causes an extra dural haemorrhage?
Middle meningeal artery where is crosses the inner aspect of the squamous temporal bone due to fracture of that bone with secondary damage to the artery in the vicinity of the fracture
Describe the outcomes of an extradural haemorrhage
Causes raised intracranial pressure with developing neurological symptoms; the time period for the development of symptoms is variable
“Lucid interval” can occur - victim of injury initially seems to be okay, without neurological symptoms, but can deteriorate catastrophically later
What is a subdural haemorrhage?
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
What is the pathway behind formation of a subdural haematoma?
Any motion which causes rotational or “shearing” forces can cause the veins to be stretch and torn due to the relative movement between the brain and the dura - frequently occurs with skull fracture.
Chronic subdural haemorrhage can occur, usually in elderly, and may be a cause of chronic confusion (may be mistaken with dementia)
Why are individual with atrophic (small) brains at an increased risk of a subdural haematoma?
The smaller brain has greater capacity for movement and the veins may be already stretched to some degree
What is a subarachnoid haemorrhage?
Bleeding beneath the arachnoid membrane
What is the most common cause of a subarachnoid haemorrhage?
Natural disease; rupture of a cerebral artery (‘berry’) aneurysm - main risk factor is hypertension
Name a specific type of subarachnoid haemorrhage
Traumatic basal SAH
What is traumatic basal SAH?
Result of a forceful impact to the upper part of the side of the neck causing abrupt rotational movement of the head leading to rupture of the vertebra-basilar circulation and SAH on the base of the brain
Collapse is usually rapid and death can occur very quickly due to the irritant effects of blood in the subarachnoid space.
What are two potential consequences of intrinsic brain injury?
- Cerebral oedema
* Cerebral contusion and laceration
Describe cerebral oedema
Can develop in minutes and lead to massive brain swelling with raised intracranial pressure and “coning” (herniation)
Describe cerebral contusion and laceration
Direct mechanical damage to the brain substance which can occur anywhere on the brain
Two types: coup and contre-coup
Describe the two types of cerebral contusion and laceration injuries
- Coup - occurs directly under site of impact
- Contrecoup - caused by a moving head striking a fixed object or unyielding surface - contusions are found diametrically opposite the site of head impact
What is an axon?
Elongated processes of nerve cells which permit transmission of signals between different parts of the brain and between the brain and body
