PBL - Expanding Mass Lesion Flashcards
How do you test the olfactory nerve function?
Ask subject to sniff substances through each nostril in turn and name the substance
- e.g. Non irritants such as vanilla, toothpaste and coffee
What can cause olfactory nerve dysfunction?
Neurological lesion
- commonly trauma
- fracture passing through ethmoid bone
How do you test the optic nerve function?
Test for visual acuity, check visual fields and inspect optic disks
Inspect size and shape of pupils
- compare both sides
- test reactions to light
How do you test the trochlear, occulomotor and abducens nerve function?
Subjects head is held still by an examiner
Subject is asked to follow the examiner’s finger with eyes
- horizontal plane - medial and lateral rectus
- vertical plane (outwards) - superior and inferior rectus muscles
- vertical plane (inwards) - superior and inferior oblique
What problems would you also look for when testing the trochlear, occulomotor and abducens nerve function?
Squint Ptosis Nystagmus Derivation of eye Diploplia
How do you test the trigeminal nerve function?
Cutaneous sensation in appropriate areas of the face
Ask to clench jaw muscles (clenching teeth)
- palate the masseter and temporalis muscles
Jaw jerk reflex
Ask subject to keep mouth open against resistance
- pterygoids
How do you test the facial nerve function?
Puff out cheeks against resistance - buccinator
Keep eyes closed against resistance
Raise eyebrows
How do you test the vestibulocochealr nerve function? - hearing aspect
Rinne’s tests - press tuning fork against mastoid and then held next to pinna - sound should be heard longer through the air conduction
Weber’s test - press tuning fork against middle of the forehead
What are the different results you can get in a Weber’s test - and what do they mean.
Equal sound in both ears - normal hearing
Sound louder in right - left sensorineural problem
Sound louder in left - right sensorineural problem
How do you test the vagus and glossopharyngeal nerve function?
Subject has no huskiness, days phonic, dysphasia and palate moves symmetrically when subject says AHHHHHHHHHHHHH
How do you test the accessory nerve function?
Subject should be able to lift shoulders against resistance
- testing trapezium muscle
How do you test the hypoglossal nerve function?
Subject can hold tongue out of their mouth out of their mouth - equally on both sides
What are the main causes of head injury?
Motor and bicycle crashes Pedestrian impacts Sports Falls Assaults
What kind of problems can a head injury cause?
Skull fractures
Brain injury
Vascular damage
What other problems are heavily associated with a skull fractures?
Underlying sub/epidural heamorrhage
Entrance of bacteria (meningitis) or air (pneumocephalus)
CSF leaking
Cranial nerve damage
Which cranial nerve are most likely to be damaged in a skull fracture?
Olfactory, optic, oculomotor, trochlear, trigeminal, facial and auditory
What is the difference between a primary and secondary head injury? - list types of each
Primary - caused by the impact
- diffuse atonal injury
- focal lesions like lacerations, contusions and heamorrhage
Secondary - an injury resulting from a process started by impact
- concussion
- infection
- hypoxia brain injury
What is a cerebral contusion?
Focal brain damage resulting from contact between bony protuberances of the skull base
What are the characteristic distributions for cerebral contusions?
Orbital surface of the frontal lobes Frontal poles Around the lateral sulcus Temporal poles Under surfaces of the temporal lobes
What is a traumatic atonal injury?
Widespread axonal injury - as a result of shear and tensile forces acting on the brain when the head is accelerated or decelerated suddenly
What happens to the brain 5 weeks after getting a diffuse axonal injury?
Degeneration of the long tracts and white matter of the cerebral hemisphere
Describe the spectrum of traumatic axon injury.
Graded I-III with the most severe occurring without a lucid interval
Which compartments can a heamatoma arise in?
Epidural space
Subdural space
Subarachnoid space
Intracerebral heamatoma
Which artery tear is most common in causing an epidural heamatoma?
Middle meningeal - crosses the pterion of the skull
Why are epidural haemorrhages more common in young people?
Because the dura mater is less firmly attached to the skull - so is more easily separated from the inner surface, allowing expansion of the heamatoma
Does someone with an epidural heamatoma have a lucid period?
After the initial unconsciousness from the injury, they have a lucid period in which consciousness is regained.
What happens after the lucid interval in an epidural heamatoma?
Rapidly developing unconsciousness and focal symptoms related to the area of brain involved
What are the symptoms of an epidural heamatoma?
Ipsilateral symptoms - pupil dilation - eyes point down and out Contralateral symptoms - hemiparesis (from uncal herniation) - loss of visual field
What is the pathophysiology of a subdural heamatoma?
A tear in the small bridge veins that connect veins on the surface of the cortex to the venous sinuses
- readily snapped in head injury when brain moves suddenly in relation to the cranium
What is the largest danger with a subdural (venous) heamatoma?
Venous blood collects more slowly - and may not be recognised and the patient is sent home
Name the time frames of acute, subacute and chronic subdural heamatomas.
Acute - symptoms witching 24 hours
Subacute - symptoms seen from 2-10 days after injury
Chronic -symptoms seen several weeks after injury
What’s the main clinical difference between a subdural and an epidural heamatoma.
No lucid interval
Which factors often lead to a high mortality rate for a heamatoma?
Increased ICP Loss of consciousness Delay in surgical removal Oedema Ischaemia
Why are subdural heamatomas more common in old people?
The brains in older people begin to atrophy causing the brain to shrink away from the dura and stretch the fragile bridge veins
What causes the subdural heamatoma to become capsulated?
Fibroblastic activity
What is vasogenic cerebral oedema?
Defective blood brain barrier around contusions or heamatomas allows extravasion of water, sodium and protein molecules to enter the brain
What is congestive heamatoma?
Diffuse swelling of one or both hemispheres
What causes ischaemic brain damage?
Raised ICP
Hypoxaemia
Reduced cerebral perfusion pressure
- these all cause lack of oxygen and nutrients
- ischaemic cascade is initiated and leads to further neuronal damage
What is the difference between a missile and non-missile head injury?
Missile - open skull fracture
Non-missile - base of skull fracture
Which neurons are more susceptible to the effects of the ischaemic cascade?
Mechanically injured neurons
What are the main mechanisms involved in neuronal damage and cell death (ischaemic cascade)?
Raised intracellular calcium Increased neurotoxic (glutamate) release Increased free radical production Receptor dysfunction Inflammation
What are the three types of response that are assessed in the Glasgow coma scale?
Best motor response
Best verbal response
Eye opening
What are the max and min scores on the GCS?
15
3
What are the two compartments of state of awareness of self and the environment.
Arousal and wakefulness
- concurrent functioning of both hemispheres and intact reticular activating system in the brainstem
Content and cognition
- determined by function cerebral cortex
What three things determine intracranial pressure?
Pressure-volume relationships with brain tissues, CSF and blood in intracranial cavity
Monro-Kellie hypothesis, relates to reciprocal changes among the intracranial volumes
Compliance of the brain
What are the percentages of brain tissue, blood and CSF within the skull?
Brain - 80%
CSF- 10%
Blood - 10%
Which compartment is the most easily displaced in the skull?
CSF - can be displaced form the ventricles and cerebral subarachnoid space into the spinal subarachnoid space
- can also undergo increased absorption or decreased production
How is blood volume from the skull displaced?
Most of the blood in the skull is in venous sinuses - these are easily compressible, forcing blood out of the cranial cavity
Define compliance
Ease at which as substance can be compressed or deformed
- so a measure of the brain’s ability to maintain ICP during changes in intracranial volume
What is the compliance formula?
Compliance = change in volume/change in pressure
What mechanisms maintain cerebral perfusion pressure?
Auto regulation
Chemoregulation
What happens if auto regulation is damaged (e.g. After a head injury)?
Cerebral blood becomes pressure passive
- drop is CPP
- cerebral blood flow is reduced, causing ischaemia
How is CPP related to ICP?
CPP=MAP-ICP
- as ICP rises, the CPP will continually drop until it reaches a critical level
- blood flow ceases when ICP reaches MAP
What is the minimum CPP required for adequate cerebral function?
70mmHg
What are the clinical effects of raised ICP?
Headache - worse in morning or when stopping and bending
Vomiting - occurs with acute rise in ICP
Papilloedema- swelling of the optic disk and retina that can cause a disk heamorrhage
Which three ways can a brain herniate?
Under falx cerebri
Through tentorial notch
Incisura of tentorium cerebelli
All brain herniations fit into one of two categories, what are they?
Supratentorial
Infratentorial
What are the two main types of supratentorial herniation?
Cingulate
Transtentorial
Describe a cingulate herniation.
Displacement of the cingulate gurus and hemisphere beneath sharp edges of the flax cerebri to opposite side of the brain
What does a cingulate herniation commonly compress?
Branches of the anterior cerebral artery
- causes oedema and ischaemia, further increasing ICP
What are the two syndromes associated with a transtenorial herniation?
Central
Uncal
What happens during a central transtenorial herniation?
Downward displacement of the cerebral hemispheres, basal ganglia, diencephalon and midbrain through tentorial incisors
What clinical signs does a central transtenorial herniation cause?
Bilateral small, reactive pupils
Drowsiness
What pathology is happening during an uncal herniation syndrome?
The medial aspect of the temporal lobe is pushed through the incisura of the tentorium
Which cranial nerve is commonly affected in uncal herniation syndrome?
Oculomotor - causes ipsilateral pupillary constriction
What other structures are compressed during an uncal herniation?
Posterior cerebral artery
The contralateral cerebral peduncle
Increased pressure in which compartment causes an infratentorial herniation?
The infratentorial compartment
What problems does an upward herniation from the infratentorial compartment cause?
Blocks the aqueduct of Sylvius
- causes hydrocephalus and coma
What problems does a downward herniation from the infratentorial compartment cause?
Displacement of the midbrain through the tentorial notch
or
the cerebellar tonsils through the foramen magnum
Out of supratentorial and infratentorial herniation - which is more serious?
Infratentorial
- involves lower brainstem centres that control cardiopulmonary functions
How does the brain normally compensate for a drop in BP, to keep CPP up?
Cerebrovascular autoregulation causes cerebral vasodilation
Name two causes of hypoxic brain damage.
Extracranial blood loss
Uncontrolled seizures
- source of secondary insults due to increased metabolic rate and respiratory impairment
Name the four main stages of acute management of head injury
Assessment
Resuscitation
Investigation
Referral
What is the investigation most used when checking head injuries.
CT scan
What is the aim of the initial head injury assessment?
Prevent secondary trauma
Identify patients who require specialist neurosurgical care
When should surgery be used to manage a haematoma?
Mass lesions with a greater than 5mm midline shift
Intraparenchymal contusions with raised ICP
What is the management plan for those with a small haematoma?
if the patient is alert and neurologically intact - they can be managed conservatively
What can be used during surgery to reduce intracranial hypertension?
Mannitol
Mild hyperventilation
Describe the non-surgical management of rising ICP.
No obstruction to venous drainage Adequate systolic BP Compliance with artificial ventilation Ventricular drainage Mannitol Hyperventilation
List the medical treatments for head injuries
Mannitol
Furosemide - used with mannitol
Anticonvulsants - reduces severity of post-traumatic seizures (occur in 15% of patients)
Antibiotics - for bacterial meningitis
Barbituates - CNS depressors help reduce ICP
Can adult neurons regenerate?
Yes - but CNS neurons have a limited capacity compared to PNS neurons
Why is neuron regeneration poor?
Lack of factors which facilitate growth
Presence of factors which actively inhibit growth
Why is neuronal regeneration worse in the CNS neurons?
Because oligodendrocytes synthesis glycoproteins which inhibit axon outgrowth
Describe certain nerve grafts attempted in people with damaged nerves
Peripheral nerve grafts to promote growth to central axons
Transplantation of embryonic neurons into the adult brain can promote recovery of function
If neurons don’t regenerate easily - how does almost complete recovery occur in most brain injury patients?
Neuronal plasticity
- recovery of tissue that has only been partially damaged
- adaptation of uninjured tissue to undertake some of the function of the damaged tissue
List the main causes of morbidity after brain injury, one the person has been treated.
Incomplete recovery - cognitive impairment, hemiparesis Post-traumatic epilepsy Post-traumatic syndrome Benign paraoxysmal position vertigo Chronic subdural haematoma Hydrocephalus Chronic traumatic encephalopathy
Describe post-traumatic syndrome.
Describes vague complications of headache, dizziness and malaise
Depression is prominent
Prolonged symptoms
What is punch drunk syndrome?
Consists of cognitive impairment
Pyramidal and extrapyramidal signs
Little and often head injuries can eventually lead to one giant fuck up
What are the signs and symptoms of concussion?
Headache Dizziness Memory disturbances Balance problems Loss of consciousness Seizure Irritable Performance
Where is an intra-cerebral haemorrhage most likely to be found?
Frontal and temporal lobes
What kind of haemorrhage is associated with cerebral contusions?
Sub-arachnoid haemorrhage
How does diffuse axonal injury damage axons?
Sudden, shear, twisting force of the brain compared to the skull causes the axons to turn from being rubbery, to being brittle and then snapping
Describe the pathophysiology of diffuse axonal injury.
Initial glutamate bombardment of the axon
- excitatory neurotransmitters are released that excite the brain (reason for seizure)
- calcium enters
- neuronal death
- axonal degeneration (stretch)
Describe diffuse vascular injury
Multiple small haemorrhages
Cerebral hemispheres, brain stem
Death within minutes due to massive amount of force required to tear vessels in the first place
What is second impact syndrome?
Common in adolescents and young people
Even a mild injury (first or second) causes uncontrollable brain swelling
What is the pathology of punch drunk syndrome?
Loss of pigment in Substantia Nigra
Neurofibrillary tangles
Amyloid plaques
Cavum septum split
