Head Injury Flashcards
Name the three categories trauma to the head may cause.
Skull fracture
Parenchymal brain injury
Traumatic vascular injury
List examples of parenchymal brain injury.
Concussion
Direct parenchymal injury: contusion, laceration
Diffuse axonal injury
List some examples of traumatic vascular injury.
Epidural (extradural haemorrhage)
Subdural haemorrhage
Subarachnoid, intraparenchymal (or intraventricular) haemorrhage
What is the presentation of concussion.
Immediate, but transient loss of consciousness with a short interval of amnesia
Some px may not lose consciousness, but appear dazed or confused
What chnages happen to the brain in concussion?
Caused by sudden deceleration of the head after blunt impact
No macroscopic or histological changes
Can be followed by brain compression by a developing haematoma = px put under observation
What is a contusion?
Bruise to the surface of the brain following a blunt impact to the head
Causes displacement and compression of brain tissue against the inner skull
Where do contusions occur?
In regions where cortical gyri impact rough or irregular bone surfaces
What other issues do contusions cause?
Petechial haemorrhage, oedema, tissue destruction
What are same side contusions called?
coup injury
A stationary blow to the head is more likely to produce a coup at the site of the blow
What are opposite side contusions called?
Contrecoup injury
A fall backward usually causes this on the inferior frontal lobes
What is the gross (macroscopic) morphology of a contusion?
Haemorrhage on brain surface or extending into underlying brain for a variable distance
Older lesions = depressed, yellow-brown plaques (plaque jaune)
What are the microscopic findings of a contusion?
Early: Haemorrhage, oedema, acute inflammation, extensive tissue loss in severe cases
Older lesions: gliosis (analogous to fibrosis in other tissues), macrophages containing hemosiderin (yellow, haemoglobin derived pigment)
*** if extensive tissue loss had occurred = cavity will result after resorption of necrotic material surrounded by gliosis
When does laceration of the brain occur?
With penetrating trauma (bullets or bone fragments from skull fracture) with tearing/disruption of brain tissue
What is diffuse axonal injury?
Damage to deep white matter structures of the brain (composed predominantly of myelinated axons)
What explains immediate and prolonged coma following severe head injury?
Extensive axonal damage (diffuse axonal injury) q
What are the macroscopic changes of diffuse axonal injury?
Edema
Petechial or splinter hemorrhages are present in the white matter = ruptured capillaries and small vessels
Axonal damage cannot be seen macroscopically
What is the microscopic damage of diffuse axonal injury?
Axonal swellings = retraction balls
These represent cellular proteins (organelles) that accumulate at the proximal stump of the severed axon
Axons distal to the injury degenerate
What does damage to a meningeal artery cause?
Epidural bleeding
What does rupture to a cerebral artery (aneurysm) cause?
Subdural haemorrhage
What does damage to a bridging vein cause?
Subdural bleeding
What does damage to a bridging vein cause?
Subdural bleeding
What usually causes an epidural haematoma?
Tearing of a middle meningeal artery following a fracture of the temporal bone
Why does the epidural haematoma rapidly expand?
The haemorrhage under arterial pressure dissects the dura from the skull
Where does the haemorrhage of an epidural haematoma stop?
Stops at suture lines where dura/periosteum is adherent to skull bones
How are epidural haematomas treated?
Evacuated acutely
What does the CT scan of an epidural haematoma look like?
Biconvex (lens-shaped) mass
Midline shift and ipsilateral (same side) ventricular compression
Acute haemorrhage will appear hyperdense (bright white) - globin molecule is dense and absorbs X-ray beams
As it becomes older & the globin molecule breaks down, it will lose its hyperdense appearance
Why are the bridging veins vulnerable to rupture?
Brain is slightly mobile, but the dural sinuses are fixed
Therefore traumatic displacement of the brain may rupture these veins
Who is at greater risk of injury to bridging veins and why?
Elderly patients with cerebral atrophy - atrophy puts greater traction on the veins & so milder trauma may cause tearing of the veins
Why may a subdural haematoma accumulate more slowly?
Bleeding is venous rather than arterial
What are the symptoms of a subdural haematoma?
Symptoms vary depending on the extent of damage of the vessels
Slow oozing with vague neurological symptoms e.g. headache, confusion
Greater vascular injury = acute symptoms
What does the CT scan of a subdural haematoma look like?
Sickle or crescent shaped, usually over the cerebral convexity
Bleeding can cross suture lines
Midline shift and ipsilateral ventricular compression
Describe the macroscopic appearance of subdural haematoma.
Mass of freshly clotted blood on the surface of the brain = variable flattening of the brain
Over time the blood clot organizes with lysis of the red cells and ingrowth of fibrous tissue from the dura
Eventually forms a dense connective tissue membrane adherent to the dura
What does the intercranial space contain?
Blood, brain, CSF
What is the normal ICP?
10-15mmHg
Why does head trauma (haemorrhage/oedema) cause the ICP to rise?
Skull is not distensible
What other pressures are affected when ICP rises?
Cerebral perfusion pressure (CPP)
CPP = MAP - ICP
An increase in ICP will cause a decrease in CPP which if severe enough could lead to ischaemic injury
What does increased ICP cause the brain to do?
Displacement of the brain/herniation of the brain because of the rigid dural folds (falx and tentorium)
List the different types of herniation.
Subfalcine herniation
Transtentorial herniation
Tonsillar herniation
What is a subfalcine herniation?
Displacement of the cingulate gyrus under the falx cerebri
What happens as a result of a subfalcine herniation?
No specific clinical signs
Can result in occlusion of one or both of the anterior cerebral arteries leading to ischaemia in the territory of these vessels
What causes a transtentorial herniation?
Herniation of the uncus of the medial temporal lobe downward through the tentorial notch
Results in pressure on and displacement of the rostral midbrain
What is the most common herniation?
Transtentorial herniation
Name the symptoms of a transtentorial herniation.
- compression of the third cranial nerve
- compression or one or both cerebral peduncles against tissue or the tentorial edge
- haemorrhage into the midbrain or upper pons related to arterial stretching = Duret haemorrhages
Name the three classical signs of a transtentorial herniation
1 - ipsilateral, dilated, unresponsive pupil “blown pupil”
2 - contralateral hemiparesis
3 - decreased level of consciousness or coma
What is Kernohan’s phenomenon?
Midbrain may be pushed to the opposite side of the tentorial notch, compressing the opposite cerebral peduncle leading to ipsilateral hemiparesis (weakness on the same side of the compression)
What is tonsillar/coning herniation?
Herniation of the inferior-medial aspects of the cerebellum down through the foramen magnum
What are the clinical signs of tonsillar herniation?
Causes compression of the medulla which can disrupt cardiac and respiratory centres = cardiac/respiratory arrest and death
Describe the time course of diffuse axonal injury?
Immediate coma because of immediate widespread transection of axons
What is the timecourse of epidural hematoma?
Arterial bleeding!!
Progressively symptomatic over a period of hours
Describe the timecourse of a subdural hematoma.
Venous bleeding!!
Over a period of days, but can be acute as well
What symptoms usually present in a head injury case?
Increase in intracranial pressure (as a result from the expanding hematoma)
- headache
- confusion
- nausea
- vomiting
- papilledema (swelling of optic disc, head of optic nerve)
- signs and symptoms of brain herniation if present
List longterm consequences of brain injury following trauma.
Post traumatic epilepsy
Post traumatic hydrocephalus
Chronic Traumatic Encephalopathy (CTE) - dementia following repeated head trauma
Psychiatric disorders
