Head Injury Flashcards
An increase in intracranial pressure can cause brain herniation. What is a brain herniation?
displacement of the brain tissue under the falx cerebri or through the tentorial notch of the tentorium cerebelli
Intracranial pressure is normally kept within what range?
0-15 mmHg
Describe the Monro-Kellie Hypothesis regarding intracranial pressure?
Volumes within each of the three intracranial compartments (blood, brain tissue and CSF) can vary slightly without causing marked changes in intracranial pressure as small increases in the volume of one component are compensated for a by a decrease in volume in one or both of the other two components.
What is the cerebral perfusion pressure?
The difference between the mean atrial blood pressure and the intracranial pressure which gives the pressure which is perfusing the brain
Within what range does the cerebral perfusion pressure normally lie?
70-100mmHg
What is the difference between hypoxia and ischaemia?
Hypoxia is a deprivation of oxygen with maintained blood flow
ischaemia is a deprivation of oxygen (and glucose) with impaired blood flow and also insufficient removal of metabolic wastes
Hypoxia is fairly well tolerated by the brain especially in cases of chronic hypoxia. T/F?
True
Cerebral ischaemia can be focal as occurs in conditions such as…?
Stroke
Cerebral ischaemia can be global as occurs in conditions such as…?
Cardiac arrest
What is the term for the areas of the brain which sit between the overlapping territories supplies by different cerebral arteries which are extremely vulnerable to focal ischaemia?
Watershed areas
The metabolic depletion of energy associated with ischaemia can result in inappropriate release of excitatory amino acid neurotransmitters. What are the consequences of this?
In prolonged ischaemia, depletion of ATP leads to release of glutamate which initiates cell damage by allowing excessive influx of calcium ions which causes the release of intracellular enzymes that cause protein breakdown, free radical formation, lipid per oxidation, mitochondrial injury, nuclear breakdown and cell death
What type of oedema occurs in conditions which impair the function of the blood-brain barrier and allow transfer fo water and proteins from the vascular to interstitial space?
Vasogenic oedema
White matter is more affected by vasogenic oedema than grey mater. t/f?
True
What are the possible consequences of vasogenic oedema in the brain?
Displacement of a cerebral hemisphere, disturbances in consciousness, severe inter cranial hypertension
Ishcaemia of the brain is associated with what type of oedema?
Cytotoxic
What is meant by a primary brain injury?
The immediate response to the initial injury
Give an example of a focal lesion which may occur as a primary brain injury?
Contusion and haemorrhage
Give and example of a diffuse lesion which may occur as a primary brain injury?
concussion
diffuse axonal injuries
What is meant by secondary brain injury?
This involves complicated processes resulting from the initial injury which include brain swelling and infection
What is the most common cause of secondary brain injury?
Ischaemia
Contusions in the brain can cause secondary mass effects from oedema. What effects might these be?
Increased ICP and possible herniation syndromes
In an epidural haematoma, radii expansion of the haematoma compresses the brain. Why does this occur?
Because bleeding is arterial in origin
An epidural haemotoma develops between the inner side of the skull and the dura. How do these injuries usually occur?
Fracture of the skull
Acute subdural haematomas have a high mortality rate. T/F?
True
Chronic subdural haematomas develops weeks after the injury, so much later that the person may not remember having the injury. T/F?
True
What vessels are usually torn in a subdural haematoma?
The small bridging veins which connect veins on the surface of the cortex to dural sinuses.
In which lobes of the brain are traumatic intracereberal haematomas most common?
Frontal and temporal lobes
What is a cerebral concussion?
A transient neurogenic dysfunction caused by mechanical force to the brain
Recovery from concussion usually takes place within 24 hours but mild symptoms may persist for months. What symptoms are these?
Headache
irritability
insomnia
poor concentration and memory
What is diffuse axonal injury caused by?
Shearing of fragile axons by acceleration-deceleration forces at the time of trauma
Acute management of a head injury should involve resuscitation and ABCDEs. What are the ABCDEs?
A - check airway, clear debris, insert oropharyngeal airway of endotracheal tube if necessary
B-breathing - give oxygen if necessary
C - circulation - check pulse and bp
D - disability - assess general and neurological status
E - environment - hypothermia
G - glucose check for hypoglycaemia
What symptoms would you want to ask for when trying to get a detailed description of a head injury?
Loss of consciousness amnesia / lucid period seizures confusion deterioration of mental status vomiting headache
Describe the Glasgow coma scale?
Score out of 15, used to assess level of consciousness in patients
3 components: best eye responses (possible four points), best verbal response (possible 5 points), best motor response (possible 6 points)
What imaging modality is the first of choice for investigation of a patient with acute head injury?
CT
What are the long-term consequences of traumatic brain injury?
seizures, ocular and visual motor distrubances, cognitive deficits, post-concussive syndrome, depression, aggression, suicide, unemployment, social isolation, psychosis, premature death, progressive dementia, Parkinsonism, diabetes insidious, endocrine dysfunction, hypopituitarism, growth hormone insufficiency
Why do adult CNS neurons have a limited ability to regenerate in contrast to PNS neurons?
Lack of factors which facilitate growth in the CNS and presence of factors which actively inhibit growth
Despite limited CNS regeneration, there is substantial recovery of function following injury due to…?
Neural plasticity
What is neural plasticity?
The rewiring of existing neurons into new functional network and the addition of new formed neurons used to train differentiations brain areas to assume new functions.
CNS regeneration is limited, in part due to a lack of growth factors. For example there is a lack of expression of…?
Laminins
What cells in the CNS produce factors which inhibit demyelination and axon repair?
Glial cells - in particular oligodendrocytes
Why does slower degeneration of the distal segment of a CNS neurone compared to that of the PNS lead to poorer regeneration?
This contributes to the inhibitory environment because inhibitory myelin and axonal debris are not cleared away as quickly and this contributes the the formation of the glial scar which new axons cannot grow across.
What are the five layers of the scalp in order from most superficial to most deep?
Skin Connective tissue Aponeurosis Loose connective tissue Periosteum
From which layer of the scalp is tissue taken off from in scalping injuries?
Loose areolar connective tissue
What type of collagen makes up the loose areolar connective tissue of the scalp?
1 + 2
If the aponeurosis of the scalp is breached (particularly in the coronal plane) then the wound will gape. Why is this?
The action of the occipitofrontalis muscle
Infection can pass from the surface into the cranium. t/f?
true
What is the name of the thin part of the skull where the parietal, frontal and temporal bones meet?
Pterion
Intracranial haematomas and damage to the cranial nerves are particularly at risk of occurring with a head injury to what region?
The back of the head
What are the signs of an increasing ICP?
Decreasing GCS
Diminished pupil response to light
materialising signs e.g. weakness on one side
Why is there a diminished pupil response to light with raised ICP?
Raised ICP can cause brain herniation which often compresses the oculomotor nerve
Which branch of the middle meningeal artery lies closely underneath the pterion?
Anterior middle meningeal artery
What are the two layers of the dura mater?
Periosteal and inner meningeal layer
What is the name of the arachnoid mater projections which pass through the dura mater to drain CSF and blood into the venous sinuses?
Arachnoid granulation
CSF is removed from the subarachnoid space through the arachnoid granulations which project into which sinus?
Superior sagittal sinus
What is the characteristic shape of an epidural haematoma as seen on a CT scan?
Lens shaped
What type of brain haematoma is usually from arterial blood?
Epidural haematoma
Subdural haematomas in the brain are usually from arterial blood. T/F?
False - usually form venous blood
What are the clinical signs of a lesion of CN III?
Ptosis, abducted and depressed eye with dilated pupil
What are the clinical signs of a lesion of CN IV?
Eye position appears normal but is rotated outward and there is a compensatory head tilt to the opposite side
What are the clinical signs of a lesion of CN VI?
Adducted eye possibly with compensatory head tilt to the affected side
The supraorbital, infraorbital and mental nerves all exit through their foramen in the skull. From which branches of the trigeminal nerve do these nerves arise?
Supraorbital nerve from ophthalmic nerve
Infraorbital nerve from maxillary nerve
Mental nerve from mandibular nerve
Which nerves branch from the ophthalmic division of CN V?
Supraorbital nerve
Supratrochlear nerve
Lacrimal nerve
External nasal nerve
Which nerves branch from the maxillary division of CN V?
Infraorbital nerve
Zygomaticotemporal nerve
Zygomaticofacial nerve
Which nerves branch from the mandibular division of CN V?
Mental nerve
Buccal nerve
Auricotemporal nerve
In which part of the temporal bone does the vestibular apparatus reside?
Petrous part
Which part of the vestibular apparatus detectes angular acceleration?
Semi circular canals
Which part of the vestibular apparatus detected linear acceleration?
Utricle and saccule (otolith organs)
Nystagmus can arise as a result of the disturbance of which reflex?
Vestibulo-ocular reflex
How do the semicircular canals sense angular acceleration?
due to inertia, endolymph lags behind in the semi circular canals during head movement which causes deflection of the cilia leading to receptor transduction
Through which nerve does afferent information travel in the vestibuloocular reflex?
CN VIII
What tissues are the effector output of the vestibuloocular reflex?
Extrinsic eye muscles
Which is the purpose of the vestibuloocular reflex?
Stabilises images on the retina during head movements
How can the vestibuloocular reflex be tested?
Barany chair test
Caloric testing
Describe caloric testing of the vestibulooccular reflex?
Involves injecting water into the external auditory meatus leading to head transfer which sets up convection currents in the horizontal semi circular canal. fluid movement in the canal stimulates hair cells which activates the vestibulocular reflex and generated dizziness as a symptom and horizontal nystagmus
Removal of ear wax by syringing may elicit which reflex?
Vestibule-Ocular reflex
After how long following a traumatic axonal injury will wallerian degeneration occur?
5 weeks
How will a patient present with an epidural haematoma?
History of head injury
Brief period of unconsciousness followed by lucid period in which consciousness sin regained then a rapid progression to unconsciousness
What type of herniation will occur due to an epidural haematoma?
Tentorial herniation
What are the two types of supratentorial herniations?
Cingulate or transtentorial
What structures are commonly affected by uncle brain herniation?
CN III and posterior cerebral artery
What diuretic is commonly used to reduce ICP?
Mannitol
Other than use of mannitol, how can ICP be decreased?
Hyperventilation
Barbiturates
In the CNS, which cells synthesise glycoproteins which inhibit CNS regeneration?
Oligodendrocytes
