Head Trauma Flashcards
Describe the different types of haemorrhage that can occur in head trauma
Extradural - torn meningeal arteries rupture between endosteal dural layer and calvarium
Subdural - usually after a blow that causes the brain to move within the skull: veins rupture within subdural space
Subarachnoid - blood collects beneath arachnoid layer of meninges (if blood gets into CSF or aneurysm rupture)
Intracerebral - rupture of a vessel within the brain
What are the characteristic features of raised intracranial pressure?
Follows pathway of localising signs, decreasing levels of consciousness, coma then death
What are the current diagnostic and management approaches for head trauma?
ATLS guidelines - assess whether damage is focal/diffuse
Is there a skull fracture?
Aim to prevent secondary brain damage by reduced cerebral perfusion (prevent hypoxia and hypotension)
Monitor ICP -> treat when rises above 25mmHg but maintain CPP
CT/MRI scans and GCS
What are the 3 key areas of the brain mainly affected by raised ICP?
Cingulate gyrus - herniates under the falx cerebri (falcine herniation)
The Uncus - herniates over the tentorium cerebelli (damages midbrain)
The Cerebellar Tonsils - herniates through foramen magnum to give tonsillar herniation
Outline ATLS
Advanced Trauma Life Support
Acute control of airway, breathing, circulation
Prevent hypoxia and hypotension
GCS/Neuro exam
Why are patients with head trauma kept normovolaemic?
Prevent hypotension -> reduced cerebral perfusion
Prevent hypertension -> SIRS/MOF
What is decompressive craniotomy surgery? When might it be used?
To open up part of the skull to allow the brain to swell outside and therefore relieve pressure - often used as a last resort and often in intracerebral haemorrhages
Shape-wise how can you tell the difference between an extradural and subdural haematoma?
Extradural are lemon shaped
Subdural are banana shaped - more crescent long and thin
What’s the normal ICP? At above what pressure is it usually treated?
0-10 mmHg
Treated above 20 mmHg (or 25)
What’s the equation for cerebral perfusion pressure?
CPP = MAP - ICP
usually 50-70 mmHg
In neurocritical care patients, why should free water not be administered?
Will decrease plasma osmolality and therefore increase water content of the brain tissue (as BBB is semi permeable membrane) further increasing ICP
Why are elevated blood sugar levels associated with worsening of ischaemic injury?
Ischaemic brain metabolises glucose into lactic acid, lowering tissue pH and exacerbating injury
What are the 5 glasgow outcome scores?
1 Dead
2 Vegetative state (sleep/wake cycle but not sentient)
3 Severely disabled (conscious but dependent)
4 Moderately disabled (independent but disabled)
5 Good recovery
What are some mental sequelae that can occur following head trauma? Why are these problematic?
Personality disorders Memory disorders Reduced reasoning power Apathy, lack of drive Temper tantrums Family disruption
= patients lack motivation and capacity to cope with therapeutic programmes without constant prompting
Which cranial nerve is most commonly damaged in head trauma and what are its symptoms?
What other brain damage might persist?
CN VIII
Vertigo, Nausea, Nystagmus
Hemispheric sequelae, cranial nerve palsies, anosmia
What’s the monro-kellie hypothesis?
The skull is a constant fixed volume, within it lie the brain, CSF and blood
Vtotal = Vbrain + VCSF + Vblood + Vmass
Brain uses that equation to maintain itself over a broad range of pressures, but once exhausted it rapidly and exponentially increases leading to rapid deterioration and death if not treated quickly
What’s the initial mechanism of the brain to cope with increased pressure?
CSF shunted into cisterns surrounding base of brain and spinal cord - particularly lumbar cistern and cisterna magna
What are the signs of raised ICP and why?
Papilloedema (optic disc appears to be bulging due to increased CSF surrounding optic nerve)
Fixed dilated pupil due to loss of parasympathetic supply to that eye because CN III can become compressed at the tentorial notch
What are the 4 main types of brain herniation?
Subfalcine herniation: below falx cerebri
Uncal herniation: uncus pushes into tentorial notch of tentorium cerebelli (trapping CN III)
Tonsillar herniation: cerebellar tonsils through foramen magnum
Coning: forced movement of brainstem through foramen magnum
Why is coning a medical emergency?
Forces brainstem through foramen magnum = cardiovascular, respiratory and conscious centres are at risk
What’s a transcalvarial herniation and how may it be used beneficially?
Extrusion of brain tissue through vault in the skull
Used in neurosurgery to reduce raised ICP and impact of swelling
What’s a Chiari malformation?
Congenital disorder where cerebellar tonsils project into foramen magnum
What’s Kernohan’s notch?
Fold in the cerebral peduncle of the midbrain, that forms as a result of tissue moving from one side of the skull to the other, causing the tissue to fold on itself
Seen on contralateral side to lesion
What type of blood collects between which two structures in an extradural haemorrhage?
Meningeal arteries rupture so arterial blood collects between dural endosteal layer and the calvarium
What type of blood is a subdural haemorrhage?
Vein
Where does blood collect and what type of blood in a subarachnoid haemorrhage?
Arterial blood - usually from mico aneurysm rupture
Collects in CSF beneath arachnoid layer of meninges
What type of damage causes DAI?
Twisting/rotational force applied to axons eg car crash - small lesions usually at border of grey and white matter
Why should free water/dextrose solutions NOT be administered to critical care head injury patients?
Decrease plasma osmolarity and therefore increase water content on the brain
Elevated blood sugar levels can worsen injury as ischaemic brain metabolises glucose to lactic acid = lowers pH and exacerbates injury
