Traumatic Brain Injury Flashcards
what are the different types of brain injury?
non-missile (car crash or fall= rapid acceleration or deceleration of the head) vs missile (gun-shot), focal (small area) vs diffuse (larger area- axonal, oedema), primary (at the time of the injury) vs secondary (things that happen hour or day after the injury and what we are trying to minimise with our treatment), progressive neurological deterioration (normally due to repetitive brain injuries eg in boxing)
what does ischaemia in the brain cause?
brain swelling which causes a rise in ICP which causes reduced CPP (MAP-ICP) and the reduced CPP can result in ischaemic damage and further swelling, ischaemic damage to the brain is not uniform as some areas are more susceptible (wedge infarcts)
what is brain herniation caused by?
differential pressures in intracranial compartments may result in herniation of brain
what is coning?
transtentorial herniation caudally - transformanial herniation of the brainstem and cerebellar tonsils through the foramen magnum which causes ischaemia and loss of brainstem function and death
what are the biochemical changes in a brain injury?
a head injury triggers a cascade of biochemical changes- some have a protective effect and some contribute to cell injury
what happens to amino acids in brain injury?
widespread neuronal depolarisation causing massive release of excitatory amino aids including glutamate which contribute to release of free radicals
what happens to glutamate in brain injury?
widely distributed in the brain and acts of many receptors, over stimulation causes a massive calcium influx into neurones
what happens to calcium in brain injury?
calcium influx have a neurotoxic effect and activate phospholipidases which break down cell membranes causing cerebral oedema
what happens to nitrous oxide in a brain injury?
in the 1st hours after a head injury nitrous oxide is produces by neurones and endothelial cells which has vasodilator and neurotoxic effects
what is a scalp injury?
can indicate a potential underlying skull/parenchymal injury and may indicate type of object which caused injury
what does a scalp laceration cause?
extensive haemorrhage and route for infection
what does a skull fracture cause?
not always significant clinically but indicate reasonable force and increased risk of intracranial haemorrhage, can cause depressed fracture= significant force over a small area and can require elevation, diastolic fracture= follow suture lines and is more common in children, compound fracture= fracture and overlying skin break causing risk of infection
what does bruising of the head cause?
periorbital= orbital roof fractures, mastoid bruising= battle sign- blood tracking from a fracture of the petrous temporal bone
what are brain contusions?
tears of pill membrane are often associated with underlying contusions (bruising to cortex and white matter), contusions can be coup and contra-coup due to continues movement of the brain with the cranial cavity- particularly following rapid deceleration
what is an extradural haematoma?
typically egg/lens shaped haematomas that accumulate over a few hours and is caused by the dura being stripped from the skull
why and who does an extradural haematoma occur in?
results from direct impact and is uncommon at the extremes of age- 10% of HI patients, often associated with fractures of the squamous temporal bone and tear in the underlying MMA, accommodated quite well and then ICP rises too high for accommodation
what is a subdural haematoma?
caused from shearing/tearing of the riding veins in the outermost meningeal layer- between dura and arachnoid mater and on a CT scan will appear as a cresent shape as they are not limited by cranial sutures and may cause a degree of midline shift away from the haematoma
who does a subdural normally present in?
more common in the elderly and alcoholics as they have more atrophy in their brains making vessels more likely to rupture
who does a subdural normally present in?
more common in the elderly and alcoholics as they have more atrophy in their brains so more space for brain to move within the skull cavity making vessels more likely to rupture
what is a subarachnoid haemorrhage?
bleeding in the subarachnoid space where the CSF is located and is usually the result of a ruptured cerebral aneurysm
how does a SAH present?
thunderclap headache- sudden onset occipital headache that occurs during strenuous activity (described like being hit really hard in the back of the head), neck stiffness, photophobia, neurological symptoms
what are the risk factors for SAH?
hypertension, smoking, alcohol,
what are the risk factors for SAH?
hypertension, smoking, alcohol, black patients, female, age 45-70, cocaine
what investigations are usually done for suspected SAH?
immediate CT head is first line (may be normal), bloods will show hyper attenuation in the subarachnoid space
what investigations would then be done if CT normal?
lumbar puncture to collect sample of CSF for signs of SAH= red cell count will be raised and xanthochromia which is yellow colour to CSF caused by bilirubin
how is a SAH managed?
managed by specialist neurosurgical unit, surgical intervention may be used to treat aneurysms= coiling (endovascular) or clipping (surgical), nimodipine= CCBs to prevent vasospasm which is a common complication, anti-epileptic medications to treat seizures
what is a diffuse axonal injury?
widespread axonal damage within the brain which results from many possible insults= trauma/sheering (rapid acceleration/deceleration), hypoxia, ischaemia, hypoglycemia, common following RTAs or falling from height or assault and typically unconsciousness
what is axonal damage?
swollen transected fibres throughout white matter eg corpus callosum etc
