HEAD AND SPINAL INJURY Flashcards
Epidemiology of head injuries?
Commonest cause of death and disability in people aged 1-40
1.4 million ED attendances a year. >70% male. And 33-50% are children
Incidence of death from head injury is 0.2% and the majority of fatal outcomes are in the moderate or severe GCS head injry group - only accounts for only 5% (95% of people with head injury present with a normal or minimally impaired GCS)
What is primary brain injry?
The insult or damage done to the brain at the time of the injury
E.g. cerebral lacerations, cerebral contusions, skulls fractures, diffuse axonal injury
These are things that can only be cured by accident prevention strategies
What is secondary brain injury?
The damage to the brain that results from complications after the initial primary brain injury
E.g. hypoxia, reduced cerebral blood flow, raised ICP, metabolic abnormalities, infection etc
Classification of head injury based on GCS?
Mild GCS13-15
Moderate GCS 9-12
Severe GCS 8 or less
The is the Monro-Kellie doctrine?
the sum of volumes of brain, CSF, and intracranial blood is constant
What is the normal ICP?
10mmHg
How dou you calculate the cerebral perfusion pressure?
Mean arterial pressure - ICP
(This is used as an indicator of the cerebral blood flow)
Outline the head injury physiology?
When there is a mass in the brain the body responds by removing some venous blood and some CSF from the brain. The body can compensate with a normal ICP for a while.
Eventually you get to a poin where it is not possible to remove any more venous blood or CSF form the brain and this is known as the point of decompensation. This is when herniation of the brain
How is a head injury different to a traumatic brain injury?
Head Injury = a patient who has sustained any form of trauma to the head, regardless of whether they have any symptoms of neurological damage
Traumatic Brain Injury = evidence of damage to the brain as a result from trauma to the head, represented with a reduced Glasgow Coma Scale or presence of a focal neurological deficit
Features of transtentorial herniation?
Compression of 3rd nerve -> ipsilateral pupillary dilatation -> loss of eye movement
Compression of ipsilateral corticospinal tracts in brainstem -> contralateral hemiparesis
Features of foramen magnum/tonsillar herniation?
Decreased level of consciousness
Decorticate posturing
Irregular respirations
Loss of brainstem reflexes
Bilateral fixed and dilated pupils
Cushing triad: hypertension, bradycardia and abnormal breathing
Signs of basal skull fractures?
Panda eyes
Battles sign
Haemotympanum
CSF rhinorrhoea or otorrhoea
LMN facial nerve palsy
Features of depressed or open skull vault fractures?
Visible fracture to skull vault
Palpable depression or an irregularity in the skulls
What artery is typically involved in extradural haematoma?
Middle meningeal artery
What is the classic presentation of extradural haematomas?
Pt with head trauma who initially loss consciousness followed by an lucid interval before they lose consciousness again
What causes subdural haematomas?
Tearing of bridging veins between brain and dura
More common in elderly and alcoholics as bridging veins are stretched
Why is the prognosis of subdural haematomas worse than extradural haematomas?
More damage to underlying brain tissue
Often affect elderly and alcoholics - often have other health problems
How are intracerebral haematomas described?
Coup
Contra-coup
What is a coup injury?
Injury to the brain region directly related to the site of external injury
What is a contre-coup injury?
When the region affected is on the opposite side to the site of external injury due to the movement of the brain within the skull vault
What mechanism causes diffuse axonal injury?
Rapid acceleration and deceleration forces which cause shearing of the neurones
How do diffuse axonal injuries ted to present?
LOC at time of injury with prolonged coma
Decorticate and decerebrate posturing
Autonomic dysfunction
Hypertension
Hyperpyrexia
Why might a CT scan appear normal in a diffuse axonal injry?
As the damage is microscopic
How should pts with head injuries be managed?
A-E approach
If GCS 8 or less -> involve anaesthetist early for appropriate airway management - intubate, avoid hypoxia and aim for normal PaCO2
Avoid hypotension and hypoglycaemia
Treat seizures
Treat raised ICP
Wound management
Manage pain
Give pt written head injury advice