Head Injury Flashcards by Lauren Horsburgh

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

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Intracranial pressure is normally kept within what range?

0-15 mmHg

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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.

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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

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Within what range does the cerebral perfusion pressure normally lie?

70-100mmHg

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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

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Hypoxia is fairly well tolerated by the brain especially in cases of chronic hypoxia. T/F?

True

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Cerebral ischaemia can be focal as occurs in conditions such as…?

Stroke

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Cerebral ischaemia can be global as occurs in conditions such as…?

Cardiac arrest

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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

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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

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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

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White matter is more affected by vasogenic oedema than grey mater. t/f?

True

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What are the possible consequences of vasogenic oedema in the brain?

Displacement of a cerebral hemisphere, disturbances in consciousness, severe inter cranial hypertension

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Ishcaemia of the brain is associated with what type of oedema?

Cytotoxic

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What is meant by a primary brain injury?

The immediate response to the initial injury

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Give an example of a focal lesion which may occur as a primary brain injury?

Contusion and haemorrhage

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Give and example of a diffuse lesion which may occur as a primary brain injury?

concussion

diffuse axonal injuries

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What is meant by secondary brain injury?

This involves complicated processes resulting from the initial injury which include brain swelling and infection

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What is the most common cause of secondary brain injury?

Ischaemia

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Contusions in the brain can cause secondary mass effects from oedema. What effects might these be?

Increased ICP and possible herniation syndromes

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In an epidural haematoma, radii expansion of the haematoma compresses the brain. Why does this occur?

Because bleeding is arterial in origin

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An epidural haemotoma develops between the inner side of the skull and the dura. How do these injuries usually occur?

Fracture of the skull

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Acute subdural haematomas have a high mortality rate. T/F?

True

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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?

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