Chapter 6 - Head Trauma Flashcards
What % of prehospital trauma-related deaths involved head trauma?
90%
What is the primary goal of someone who has a TBI (traumatic brain injury)?
To prevent secondary brain injury from inadequate oxygenation and hypoperfusion.
The anterior fossa houses what?
The frontal lobes
The middle fossa houses what?
The temporal lobes.
The posterior fossa houses what?
The lower brainstem and cerebellum.
Name the 3 layers of the meninges. (outside to in)
- The dura mater - tough and fibrous. 2 sublayers - the Periosteal Layer and Meningeal Layer.The large venous sinuses are housed in between these sublayers.
- Arachnoid mater
- Pia Mater (covers the brain)
The superior sagittal sinus drains into the bilateral transverse and sigmoid sinuses.
When consulting a neurosurgeon about a patient with TBI what information needs to be relayed?
- Age of patient
- Mechanism and time of injury
- Respiratory and cardiovascular status (Blood pressure and oxygen sats)
- Results of the neurological examination, including GCS score (with particular emphasis on the motor response, pupil size and reaction to light.
- Focal neurological deficits
- Presence and type of associated injuries
- Results of diagnostic studies, particularly CT scan (if available)
- Treatment of hypotension or hypoxia
Meningeal arteries are located between what two surfaces?
Meningeal arteries lie between the dura and the internal surface of the skull (Epidural space)
Describe the the anatomy of a epidural hematoma.
Skull fractures can lacerate middle meningeal arteries (most commonly the middle meningeal artery). An epidural hematoma will form.
What two injuries can cause epidural hematomas?
- Skull fractures
- Injury to Dural sinuses (Sagital sinus etc.)
How do you manage an epidural hematoma?
URGENTLY!!! They need to be evacuated by a neurosurgeon ASAP.
How do subdural hematomas form?
Bridging veins that travel from the surface of the brain to the venous sinuses within the dura may tear. These then fill the subdural space (between the dura mater and the arachnoid mater).
The pia mater is firmly attached to the surface of the brain. CSF fills the space between the watertight arachnoid mater and the pia mater (Subarachnoid space).
Subarachnoid hemorrhages are frequently caused by ?
- Brain contusion
- Injury to the vessels at the base of the brain.
The brain consists of what 3 structures?
- Cerebrum - right and left hemispheres and seperated by the falx cerebri.
- Cerebellum - responsible for coordination and balance.
-
Brain stem -
- Midbrain
- Pons
- Medulla.
Which cerebral hemisphere contains the language centers in virtually all right handed people and 85% of left handed people?
The left hemisphere
What functions does the frontal lobe control?
Executive functions, emotions, motor function and, on the dominant side, expression of speech.
What functions does the parietal lobe control?
Sensory function and spatial orientation.
What function does the temporal lobe control?
Memory functions
What function does the occipital lobe control?
Vision.
The midbrain and upper pons contain the ? activating system which is responsible for ?
- Reticular
- the state of alertness
Where does the vital cardiorespiratory center preside?
In the medulla
Where is CSF produced and reabsorbed?
It is produced in the choroid plexus in the lateral ventricles and is reabsorbed in the dural venous sinuses through the arachnoid granulation tissue.
NOTe: Blood in the CSF can inhibit reabsorption and can cause increased ICP
Which cranial nerve runs along the edge of the tentorium and can be compressed against it during temporal lobe herniation?
Cranial Nerve III
What is the physiological mechanism to explain a blown pupil?
Parasympathetic fibers from the 3rd cranial nerve constrict the pupil. If these are compressed (e.g. herniation, hematoma) then they cannot act and you get unopposed sympathetic activity. i.e. pupillary dilation.
What’s going on here?
The tentorial notch is opening that allows passage of the brainstem through the tentorium. The Uncus (medial part of the temporal lobe) is herniating (uncal herniation) through the tentorial notch and compressing the corticospinal (pyramidal) tract in the midbrain, which crosses at the brainstem. Therefore you will get in a contralateral hemiparesis.
What is the classic sign of uncal herniation?
Ipsilateral pupillary dilatation associated with contralateral hemiparesis.
What 3 physiological conepts related to head trauma?
- Intracranial pressure - if elevated it can reduce cerebral perfusion and exacerbate ischaemia.
- The Monro-Kellie Doctrine
- Cerebral Blood Flow -cerebral blood flow can be reduced after comatose inducing TBI. This can lead to cerebral ischaemia.
What is the normal ICP at resting stage?
~10mmHg
What ICP is related to poor outcomes?
20mmHg
What is the Monro-Kellie Doctrine?
The total volume of the intracranial contents must remain constant because the cranium is a rigid, nonexpansile container.
Venous blood and cerebrospinal fluid may be compressed out of the container, providing a degree of pressure buffering.
Once, the limit of displacement of CSF and intravascular blood has been reached, ICP rapidly increases.
How is cerebral perfusion pressure (CPP) defined?
CPP = MAP - ICP
Mean arterial pressure
Incracrainal Pressure
What level of MAP (Mean arterial pressure) maintains a constant CBF? (a.k.a. Pressure autoregulation)
What will happen if the MAP is too low?
What will happen if the MAP is too high?
50 to 150mmHg
If the MAP is too low then ischaemia and infarction can occur.
If the MAP is too high, marked brain swelling will occur with elevated ICP.
What 4 factors can induce secondary brain injury?
- Hypotension - need to maintain MAP
- Hypoxia
- Hypercapnia
- Iatrogenic hypocapnia.
Does CPP always equate with or assure adequate CBF?
NO. Once ICP increases dramatically then blood flow to the brain can be compromised.
What are the classifications of head injury?
- Minor = GCS 13-15
- Moderate = GCS 9-12
- Severe = GCS 3-8
True or False, we use the worst motor response to calculate the GCS score, because this is the most reliable?
FALSE. We use the BEST motor response score.
Describe the Glasgow Coma Score?
Remember Equation E4V5M6
Eye opening =
- 4 to sponteously
- 3 to speech
- 2 to pain
- 1 none
Verbal response
- 5 Oriented
- 4 Confused Speech
- 3 Inappropriate words
- 2 Incomprehensible sounds
- 1 None
Motor response
- 6 Obeys commands
- 5 Localizes pain
- 4 Withdrawal to pain
- 3 Abnormal flexion (decorticate)
- 2 Abnormal extension (decerebrate)
- 1 None (flaccid)
Skull fractures are divided into what two regions?
1/ Vault
- Linear or stellate
- Depressed/Non-depressed
- Open/closed
2/Basilar
- With/without CSF leak
- With/without 7th Nerve Palsy.
What are the clinical signs of a basilar skull fracture?
- Periorbital ecchymosis (racoon eyes)
- Retroauricular ecchymosis (Battle’s sign)
- CSF leakage from nose or ear (Rhinorrhea/Otorrhoea)
- 7th and 8th nerve disfunction (Facial paralysis and hearing loss.