PBL 4- An expanding mass lesion Flashcards
what are the types of traumatic brain injury and explain them
Primary brain injury- the result of the initial trauma on neural tissue. They are often described as focal or diffuse injuries
Secondary brain injury- refers to the development of further neurological damage subsequent to the primary injury, and this may progress over days or weeks
what does secondary injury result in
Occurs hours or days following primary injury: ischaemia increased ICP hypoxia cerebral swelling infection
Describe focal primary injuries
Results from direct mechanical forces (such as occur when the head strikes a windshield in a vehicle accident)
Localised to the site of impact on the skull.
Extent of damage is variable
Neurological symptoms that arise from this local injury is dependent on part of the brain that is damaged e.g. an injury over the motor cortex may result in contralateral weakness to the face and arm.
What are intracranial haemotamas and name the types
Three types of haematomas can occur after TBI known as epidural (extradural), subdural and intracerebral. Haematomas may expand slowly or rapidly, progressively compressing brain structures and increasing ICP.
what are the main causes of head/ traumatic brain injury
o Motor and bicycle crashes- most common (especially younger people) o Pedestrian impacts o Sports o Falls- more common in older people o Assaults
what do skull fractures provide entry of
skull fractures provide pathways for the entry of bacteria (meningitis) or air (pneumocephalus) to the CSF and for leakage of CSF out of the dura
A skull fracture can damage cranial nerves as they exit the cranial vault. what cranial nerves can be potentially damaged
o Olfactory o Optic o Oculomotor o Trochlear o Trigeminal (V1 and V2) o Facial o Vestibulocochlear
Describe focal primary injury (cerebral contusions)
Common sites for cerebral contusions
occur swhen the brain moves within the cranial cavity, causing parts of the brain to be crushed by violent contact with the skull or dural membranes. For the most part, these occur adjacent to the site of impact (coup lesions) and diagonally opposite (contrecoup lesions).
Common sites:
- underside of frontal lobes
- Frontal poles
- lateral sulcus
- Temporal poles
- Undersurface of temporal lobes
What is a concussion
temporary) disturbance in brain function as a result of trauma. Symptoms include headache, dizziness, memory disturbance , balance problems. Signs include loss of consciousness, seizure activity, irritability and poor performance.
what type of injuries are included in focal injuries
cerebral contusion
cerebral laceration
cerebral haemorrhage (epidural, subdural, intracerebral)
what are cerebral lacerations
brain injury in which the pia-arachnoid is torn
Describe diffuse primary injury
Occurs when movement of the brain within the cranial cavity causes widespread neuronal damage.
- Causes stretching and shearing of axonal white matter, which is called diffuse/traumatic axonal injury
- Coma is a consequence of axonal damage in the cerebral cortex.
What is an epidural haematoma and what signs can be seen in CT scan
- Bleeding develops in the epidural space between the dura mater and the cranium.
- The source of bleeding is mostly arterial -> fast bleeding
- Fracture of the temporal bone/ pterion commonly disrupts the middle meningeal artery, resulting in an acute epidural haemorrhage, thus it can expand rapidly and cause deterioration of neurological function
CT scan signs:
- lens shaped swelling (white = fresh blood)
- mid line shift
What results in an expanding epidural haematoma
Herniation- as haematoma grows in size, parts of brain moves as brain is not compressable.
e.g. Uncal herniation
what happens in uncal herniation and what is it a complication of
Complication of an expanding epidural haematoma
Uncal herniation- medial temporal lobe moves into the posterior cranial fossa across the tentorial opening.
- Uncus of temporal lobe squashed against midbrain
- -> Ipsilateral sign: compresses occulomotor nerve -> fixated dilated pupil
- -> Contralateral -> hemiparesis (weakness of one entire side of body)
What happens if an expanding epidural haematoma is not dealt with
increased ICP
tentorial herniation
brainstem affected- breathing affected
death due to cardio respiratory arrest
what is a subdural haematoma and what are the clinical signs seen on a CT scan
- Bleeding that forms in the space between dura and subarachnoid mater
- Usually a result of a tear in the small bridge veins that connect veins on the surface of the cortex to the dural sinuses
- venous bleeding –> slower bleeding
CT scan signs:
- No limitation on sutures -> blood spreads all the way around brain
- mid line shift
- crescent shaped bleeding
what is an intracerebral haematoma
- Bleeding directly to brain tissue
- can be single or multiple bleeds
- most common cause of stroke
- Frontal/Temporal intracerebral haematomas are the most common. Temporal ones are more serious as the brain can herniate laterally.
Explain the effects of local ischaemia and hypoxia on the injured brain
- Cerebral hypoperfusion and hypoxaemia result in lack of O2 and nutrients essential for cellular functioning and survival
- Results in failure of supply of energy sources
- ## Failure of energy supply to the brain causes death of neurones, with sparing of vessels and support cells.
what is excitotoxicity and list the steps
- important event in ischaemic damage
- activation of glutamate receptors
- increased glutamate (neurotoxin) release
- Activation of proteases and lipases that damage phospholipid membrane
- increased production of free radicals
- -> causes uncontrolled entry of Ca2+ ions into neurones, leading to cell death
what is used for clinical assessment of consciousness
Glasgow Coma scale
what is consciousness
Consciousness is a state of alertness and attentiveness to one’s environment and situation. A fully conscious individual is awake, alert, and oriented to time, person, place and current circumstances
describe the glasgow coma scale
- Maximum score: 15
- Minimum score: 3
Motor Response (graded 1 to 6):
- No response
- Extensor response
- Abnormal flexion
- Normal flexion
- Localising
- Obeys command
Verbal Response (graded 1 to 5):
- No response
- Incomprehensable sounds
- Inappropriate words
- Confused words
- Orientated
Eye-motor response (graded 1 to 4):
- No response
- To pain
- To speech
- Spontaneous
What is ICP (intracranial pressure)
ICP is the pressure exerted by the contents of the cranium (CSF, brain tissue, arterial + venous blood).
It ranges from 0-15 mmHg.
The skull is a rigid, closed system with a set volume and a finite ability to accommodate changes in volume before elevations in ICP occur.
Describe the monro-kellie hypothesis
Describes the compensatory responses to a change in volume if any of the 3 components of the cranium:
- CSF
- brain tissue
- arterial + venous blood
If there is a slight increase in one component, then the other 2 components have to decrease. The ability to accommodate changes in volume without significant increases in pressure is called compliance.
Intracranial compliance is however limited due to the rigidity of the skull.
How do blood vessels and CSF accommodate an increased ICP
- Cerebral blood vessels can reduce volume via vasoconstriction
- CSF can move easily to the spinal cord from the cranium
(In young children, head circumference will slightly increase)
What happens if ICP reaches above 15 mmHG
it is no longer compensable and this is called raised ICP
Raised ICP -> ischaemic damage
Describe the acute management of head injury
- Cardiopulmonary stabilisation is the first priority (Airway, Breathing, Circulation). Attention to the airway is vital, especially if there is potential damage to the respiratory centres in the medulla.
- Check Disability - neurological examination → use GCS - Radiological screening (CT, MRI) must be quickly carried to find surgically correctable lesions.
- Surgical intervention for depressed skull fractures, bleeding vessels and haematomas.
- Management of ICP - craniectomy, CSF drainage devices.
- Further therapy is individualised, seeking to maintain ICP, cerebral blood flow and cerebral oxygen utilisation within optimal ranges.
Why do CNS neurones have limited capacity for regeneration
CNS neurons have limited ability to regenerate in contrast to PNS neurones → due to lack of factors which facilitate growth in the CNS and the presence of factors which actively inhibit growth.
what is neural plasticity
Despite limited CNS regeneration, there is substantial recovery of function due to neural plasticity.
Describes the potential for brain to change its structure and function.
- involves the rewiring of existing neurones into new functional networks, but also the addition of new formed neurones.
- trains different brain areas to assume new functions
Give an example of neural plasticity
when a person has a stroke causing destruction of neurones in the motor cortex, it is possible to train nearby cortical neurones to assume some of the lost motor functions.
what are the long-term consequences of head injury
- Cognitive impairment
- Hemiparesis - weakness on entire left or right side of the body.
- Epilepsy - neurological disorder characterised by sudden, recurrent sensory disturbances, loss of consciousness and convulsions, associated with abnormal electrical activity of the brain.
- Post-Traumatic Syndrome - this describes the vague complaints of headache, dizziness and malaise that follow even minor head injuries.
- Chronic Subdural Haematoma
- Hydrocephalus
- Chronic Traumatic Encephalopathy
