PBL 4- An expanding mass lesion

Question 1

what are the types of traumatic brain injury and explain them

Answer 1

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

Question 2

what does secondary injury result in

Answer 2

Occurs hours or days following primary injury:
ischaemia
increased ICP
hypoxia 
cerebral swelling 
infection

Question 3

Describe focal primary injuries

Answer 3

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.

Question 4

What are intracranial haemotamas and name the types

Answer 4

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.

Question 5

what are the main causes of head/ traumatic brain injury

Answer 5

o Motor and bicycle crashes- most common (especially younger people)
o Pedestrian impacts
o Sports
o Falls- more common in older people
o Assaults

Question 6

what do skull fractures provide entry of

Answer 6

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

Question 7

A skull fracture can damage cranial nerves as they exit the cranial vault. what cranial nerves can be potentially damaged

Answer 7

o Olfactory
o Optic
o Oculomotor
o Trochlear
o Trigeminal (V1 and V2)
o Facial
o Vestibulocochlear

Question 8

Describe focal primary injury (cerebral contusions)

Common sites for cerebral contusions

Answer 8

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

Question 9

What is a concussion

Answer 9

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.

Question 10

what type of injuries are included in focal injuries

Answer 10

cerebral contusion
cerebral laceration
cerebral haemorrhage (epidural, subdural, intracerebral)

Question 11

what are cerebral lacerations

Answer 11

brain injury in which the pia-arachnoid is torn

Question 12

Describe diffuse primary injury

Answer 12

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.

Question 13

What is an epidural haematoma and what signs can be seen in CT scan

Answer 13

• 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

Question 14

What results in an expanding epidural haematoma

Answer 14

Herniation- as haematoma grows in size, parts of brain moves as brain is not compressable.
e.g. Uncal herniation

Question 15

what happens in uncal herniation and what is it a complication of

Answer 15

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)

Question 16

What happens if an expanding epidural haematoma is not dealt with

Answer 16

increased ICP
tentorial herniation
brainstem affected- breathing affected
death due to cardio respiratory arrest

Question 17

what is a subdural haematoma and what are the clinical signs seen on a CT scan

Answer 17

• 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

Question 18

what is an intracerebral haematoma

Answer 18

• 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.

Question 19

Explain the effects of local ischaemia and hypoxia on the injured brain

Answer 19

• 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.

Question 20

what is excitotoxicity and list the steps

Answer 20

• 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

Question 21

what is used for clinical assessment of consciousness

Answer 21

Glasgow Coma scale

Question 22

what is consciousness

Answer 22

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

Question 23

describe the glasgow coma scale

Answer 23

• Maximum score: 15
• Minimum score: 3

Motor Response (graded 1 to 6):

1. No response
2. Extensor response
3. Abnormal flexion
4. Normal flexion
5. Localising
6. Obeys command

Verbal Response (graded 1 to 5):

1. No response
2. Incomprehensable sounds
3. Inappropriate words
4. Confused words
5. Orientated

Eye-motor response (graded 1 to 4):

1. No response
2. To pain
3. To speech
4. Spontaneous

Question 24

What is ICP (intracranial pressure)

Answer 24

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.

Question 25

Describe the monro-kellie hypothesis

Answer 25

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.

Question 26

How do blood vessels and CSF accommodate an increased ICP

Answer 26

• 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)

Question 27

What happens if ICP reaches above 15 mmHG

Answer 27

it is no longer compensable and this is called raised ICP

Raised ICP -> ischaemic damage

Question 28

Describe the acute management of head injury

Answer 28

• 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.

Question 29

Why do CNS neurones have limited capacity for regeneration

Answer 29

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.

Question 30

what is neural plasticity

Answer 30

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

Question 31

Give an example of neural plasticity

Answer 31

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.

Question 32

what are the long-term consequences of head injury

Answer 32

• 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