Head Trauma Flashcards
What is the primary goal of treatment for patients with suspected TBI?
Prevent secondary brain injury
-ensure adequate oxygenation and maintain BP enough to perfuse the brain
True or false: scalp lacerations can result in major blood loss, hemorrhagic shock, even death.
True!
What are the 3 layers of the meninges?
DAP
- Dura
- Arachnoid
- Pia
* *Dura and arachnoid are NOT firmly adhered to each other so bleeding can occur in this space = subdural hemorrhage
* *Arachnoid and pia are also not firmly adhered to each other so bleeding can also occur in this space = subarachnoid hemorrhage
* *Pia is firmly adhered to the surface of the brain
Where are meningeal arteries located?
Between the skull and the dura = this is the epidural space
What is the most commonly injured meningeal vessel?
-where is it located?
Middle meningeal artery - most common site of bleeding in an epidural hematoma
-located beneath the temporal bone: temporal bone fractures can cause laceration of the middle meningeal artery and lead to epidural hematoma
Where are epidural hematomas located?
Between the skull and the dura
Where are subdural hemorrhages located?
Between the dura and the arachnoid
What are two potential sources of bleeding in epidural hematomas?
- Meningeal arteries (most commonly middle meningeal artery)
- Dural sinuses (this is venous bleeding so expands more slowly and puts less pressure on the underlying brain)
What is the source of bleeding in a subdural hematoma?
Bridging veins that lie between the dura and the arachnoid mater
Where are subarachnoid hemorrhages located?
Between the arachnoid and pia mater
What are the 3 parts of the brain?
- Cerebrum: made up of right and left hemispheres, separated by the falx
- Cerebellum
- Brainstem
What are the responsibilities of each of the following areas of the brain:
- frontal lobe
- temporal lobe
- parietal lobe
- occipital lobe
- Frontal lobe: emotions, executive functions, motor function, speech
- Temporal lobe: memory functions
- Parietal lobe: spatial orientation and directs sensory function
- Occipital lobe: vision
What are the 3 components of the brainstem?
-function?
- Midbrain
- Medulla
- Pons
- **Midbrain and upper pons: reticular activating system responsible for state of alertness
- medulla: vital cardiorespiratory centers
What is the function of the cerebellum?
Coordination and balance
What is the pathophysiology of a “blown pupil”?
Oculomotor nerve (CN 3) runs along the edge of the tentorium: if it becomes compressed against the tentorium during temporal lobe herniation, PARASYMPATHETIC FIBERS that constrict the pupils lie on the surface of CN 3 also become compressed and can no longer constrict the pupil. Thus you have unopposed sympathetic innervation of the pupil and get pupil dilatation (“a blown pupil”)
- **in COMPRESSION of CN3, you get impaired pupillary constriction since the parasympathetic fibers are on the surface of the nerve
- **In ISCHEMIA of CN3, you get impaired extraocular movements since the inner fibers of CN 3 control extraocular movements and the blood supply affects the inner fibers first
What are the functions of CN 3?
- Pupillary constriction
- Extraocular movements - innervates superior rectus muscle, (looking up), inferiour rectus muscle, medial rectus muscle
- Eyelid opening (remember the 3 greek columns that hold up the eye)
What is the tentorium?
Tentorium is a tough meningeal partition that separates the brain into the supratentorial component and infratentorial component
-the midbrain passes through an opening called the tentorial notch
Which part of the brain usually herniates through the tentorial notch in head trauma?
-what are the 2 classic signs of uncal herniation?
The medial part of the temporal lobe (known as the uncus) is usually what herniates through the tentorial notch
- uncal herniation causes compression of the corticospinal tract in the midbrain so you can CONTRALATERAL HEMIPARESIS
- you also get compression of the CN 3 in the midbrain so you get IPSILATERAL PUPILLARY DILATATION
- also get compression of the reticular system resulting in decreased GCS
- **Two classic signs of uncal herniation:
1. Ipsilateral pupillary dilatation
2. Contralateral hemiparesis
What is the most common cause of uncal herniation?
Lesion of the middle meningeal artery secondary to temporal bone fracture causing a temporal epidural hematoma
-uncus compresses the upper brainstem = decreased GCS (from compression of the reticular system in the midbrain), ipsilateral pupillary dilatation (from compression of the CN 3 in the midbrain), and contralateral hemiparesis (from compression of the motor tract at the midbrain)
What is the Monro-Kellie doctrine?
The total volume of intracranial contents MUST remain constant since the cranium is a rigid container incapable of expanding
- when the normal intracranial volume is exceeded, ICP rises
- Venous blood and CSF can be compressed out of the container providing a degree of pressure buffering
- Thus, very early after injury, a mass such as a blood clot can enlarge while the ICP remains relatively the same since the body is compensating by pushing out venous blood and CSF from the intracranial compartment
- However, once the limit of displacement occurs, ICP rapidly increases and can cause brainstem herniation or uncal herniation and result in reduction or cessation of cerebral blood flow
What are the intracranial contents?
- Brain
- Venous blood
- Arterial blood
- CSF
- **Once you add a mass such as blood/tumor, you have to get rid of something to maintain normal ICP: usually this is venous blood and CSF that the body tries to dump out of the intracranial contents
- as the mass gets bigger, the brain runs out of venous blood/CSF to dump out and then you get increased ICP
What is the equation for cerebral perfusion pressure?
CPP = MAP - ICP
***normal CPP may help improve cerebral blood flow (CBF) but CPP does NOT equate with or ensure adequate CBF.
What does CO2 do to your brain? What does it do to your lungs?
- CO2 in the brain causes vasodilation = increased blood flow
- CO2 in the lungs causes vasoconstriction = decreased blood flow (you want to shunt your blood AWAY from areas with high CO2 and towards areas that are actually being ventilated)
What are the goals in maintaining cerebral perfusion and limiting secondary brain injury in a head injury patient?
Maintain a normal MAP and reduce your ICP!
- Ensure adequate oxygenation
- Ensure normal CO2 (avoid hypercapnea, hypocapnea)
- Ensure normothermia
- Treat seizures as this increases brain oxygenation consumption
- Avoid hypotension - ensure adequate perfusion to maintain a normal MAP
- Try to evacuate any blood that could be increasing your ICP
What are the 2 broad categories of skull fractures?
- Vault: this is the top of the skull - linear vs stellate, depressed vs non depressed
- Basilar - with or without CSF leak
What are the two broad categories of intracranial lesions?
A. Focal:
- Epidural hematoma
- Subdural hematoma
- Intracerebral hemorrhage
B. Diffuse:
- Axonal injury
- Contusions
- Concussion
- Hypoxic/ischemic injury: usually occurs from prolonged shock or apneas leading to hypoxia
How do you classify mild vs. moderate vs. severe head injury using GCS?
Mild: GCS 13-15
Moderate: GCS 9-12
Severe: GCS 8 and below
What are the clinical features of a basilar skull fracture? (6)
- Battle’s sign
- Raccoon eyes
- CSF otorrhea
- CSF rhinorrhea
- CN 7 palsy (facial paralysis)
- CN 8 palsy (hearing loss)
What is the usual appearance of an epidural hematoma on a CT head?
Lenticular/lens shape = the blood pushes the adherent dura away from the inner skull
- most often located in the temporal or temporoparietal regions and are often a result of a middle meningeal artery tear
- can also result from major venous sinus disruption or bleeding from a skull fracture
What is the usual appearance of a subdural hematoma on a CT head?
Usually follow the contour of the brain
What causes a subdural hematoma (ie. what vessels are the cause of bleeding?)
Bridging veins that lie between the dura and the arachnoid mater
True or false: Damage underlying an acute subdural hematoma is typically much more severe than that associated with epidural hematomas due to the presence of concomitant parenchymal injury.
True
What is the target PaCO2 to maintain in traumatic brain injury?
PaCO2 35-40
What is the Canadian CT head rule?
Helps you determine which patients with mild TBI (GCS 13-15) requires CT head scanning:
High risk for neurosurgical intervention:
1. GCS < 15 at 2 hours after injury
2. Suspected open or depressed skull fracture
3. Basilar skull fracture
4. Vomiting > 2 episodes
5. Age > 65 yo
6. Anticoagulant use
Moderate risk for brain injury on CT:
- LOC > 5 minutes
- Amnesia before impact > 30 minutes
- Dangerous mechanism (pedestrian struck by motor vehicle, occupant ejected from motor vehicle, fall from height > 3 feet or more than 5 stairs)
True or false: you should reserve hyperventilation for patients with severe brain injury who have acute neurologic deterioration or signs of herniation
Yes! Do not hyperventilate until you see these signs
- can hyperventilate down to 25 mm Hg but no lower than this
- better to aim for normal PaCO2 = 35-40
If you have a multi-trauma patient with a traumatic head injury and hypotension: what is your first management priority?
- what if the patient is normotensive?
- what if the patient’s BP transiently improves but is slowly decreasing again?
FIND OUT THE CAUSE OF THE HYPOTENSION!!!
- Hypotension of course worsens traumatic head injury and once you find the source of bleeding, you need to manage this BEFORE you take the patient to the CT scanner for CT head
- example: if the patient has an intraabdominal bleed as cause of the hypotension, they need to go to OR for laparotomy immediately!!! Obtain CT head AFTER the laparotomy
- if there is clinical evidence of an intracranial mass, diagnostic burr holes or craniotomy can be undertaken in the OR while the laparotomy is being performed
- if the patient is normotensive and is found to have possible intracranial bleed, then take them to CT head
- if the patient is borderline (initially BP improves with resuscitation but then decreases again), then make every effort to get a head CT before taking the patient to the OR for a laparotomy but this should be coordinated between the trauma surgeon and neurosurgeon.
True or false: You can never assume that hypotension is due to an intracranial bleed.
CORRECT! Since the intracranial vault is an enclosed space, you can’t lose enough blood in the skull to cause hypotension. If you have hypotension with a head injury, you need to search for a second source of bleeding OR look for spinal cord injury as cause of hypotension (loss of sympathetic tone)
-intracranial hemorrhage cannot cause hemorrhagic shock
What is your target SBP for patients with head injury?
For patients 50-69 years old: maintain SBP 100 mm Hg or more
For patients 15-49 years old: maintain SBP 110 mm Hg or more
What is your target CPP for a patient with brain injury?
-target ICP?
CPP should be equal to or greater than 60 mm Hg
-target ICP 5-15 mm Hg
If you had to choose a muscle relaxant for intubation in a patient with head injury, which one should you choose?
Succinylcholine - avoid long acting paralyzing agents since this can impact your neurological assessment and also mask seizures
- **Try to perform a GCS and pupillary exam BEFORE sedating or paralyzing the patient
- try to use the shortest acting agents available when you need paralysis or sedation
A shift of ___ mm or greater on a CT head usually indicates the need for surgery to evacuate the blood clot or contusion causing the shift
5 mm
Why is prolonged hyperventilation bad in a patient with traumatic brain injury?
-what is the lowest PaCO2 you should go to when actively hyperventilating a patient because of acute neurological deterioration or brain herniation?
Hyperventilation causes decreased PaCO2 which results in brain vasoconstriction = this causes cerebral ischemia in an already injured brain
- lowest PaCO2 should be 30 mm Hg - DO NOT LET IT FALL BELOW 25 mm Hg in any circumstance!!!
- use hyperventilation in moderation only and for as limited a period as possible
Why should mannitol be avoided in patients with traumatic brain injury and concurrent hypotension?
Mannitol is an osmotic diuretic and can worsen hypotension, thus lowering cerebral perfusion
What is the dose of mannitol for a patient who is acutely deteriorating from an intracranial bleed?
Remember that you should only use mannitol in euvolemic patients
-Dose: Mannitol 1 g rapidly over 5 minutes
What is the current recommendation for anti-epileptics in traumatic brain injury?
Anticonvulsants can inhibit brain recovery so use only when necessary
- Can use phenytoin or fosphenytoin in the acute phase
- can also use benzos
- if the patient is actively seizing, then of course use anti epileptics since seizures can cause secondary brain injury if prolonged (> 30 minutes)
- **Overall: prophylactic use of antiepileptic is NOT recommended for preventing late posttraumatic seizures (PTS)
- phenytoin is recommended to decrease the incidence of early PTS (within 7 days of injury) when the overall benefit is felt to outweigh the complications associated with such treatment
In patients who require evacuation of an intracranial bleed, what is the definitive lifesaving procedure to decompress the brain?
Bone flap craniotomy
NOT a simple burr hole
