CT Head Flashcards by Lynaya schorschinski

What are the Indications for CT head scan?

Gcs 13 or less
vomiting
post traumatic seizures
suspected depressed/open fracture
Use or anti-coagulants

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What is hydrocephalus?

-dilation of the cerebral ventricular system.

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What does hydrocephalus look like on images?

dilated ventricle (x sign)
surrounding oedema
small sulci

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What causes hydrocephalus?

overproduction of CSF
failure of reabsorption of CSF
Obstruction of the flow of CSF

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Where is CSF produced, where does it travel and what does it do?

produced in cells in choroid plexus
moved from ventricles to subarachnoid space
bathed the brain and spinal cord

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What is CSF absorbed?

-CSF is absorbed by arachnoid granules in the walls of venous sinuses.

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What causes the failure of reabsorption of CSF?

choroid plexus tumour pressing on aqueduct of Sylvius
midbrain tumour pressing on aqueduct if sylvius
haemorrhage

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What is cerebral oedema?

Abnormal shifts of water between compartments of the brain.

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What are the two types of cerebral oedema?

vasogenic

- cytotoxic

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What is vasogenic oedema?

disruption of blood brain barrier.
usually around abscesses and tumours.
affects mainly the grey matter.
finger-like projections appearance on image.
can differentiate between white and grey matter.

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What is cytotoxic oedema?

when extra cellular water moves into the cells causing them to swell.
affects mainly the white matter.

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What is a cerebral infarct?

-an acute area of neurological deficit.

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What are the causes of cerebral infarct?

cerebral haemorrhage.
cerebral thrombus.
cerebral embolus.
subarachnoid haemorrhage.

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What is the predisposing factor of middle cerebral artery infarct?

-atherosclerosis

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What produced the grey scale in CT?

-voxels.

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Explain grey scale in CT

air is hypodense
CSF is hypodense
fresh blood is hyperdense
old blood is hypodense
bone is white/grey
metal is white/hyperdense
soft tissue is grey

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What happens when an infarct ages?

-gets more hypodense than the parenchyma it’s within.

What are the appearances of an acute infarct?

hyperdense area

- may have oedema surrounding it

What is an epidural haematoma?

-bleed between the dura mater and in table of the skull.

What causes an epidural haematoma?

head injury
skull fracture
laceration of meningeal vessels and dura sinus

What are the appearances of an epidural haematoma?

lens shapes
pushes on parenchyma of brain
does not cross sutures
can cross midline

What is a subdural haematoma?

-bleed between the dura and arachnoid mater.

What causes a subdural haematoma?

head injury

- laceration of the bridging vessels

What are the appearances of a subdural haematoma?

-noon/cresenteric shape

What do patients present with with a an epidural haematoma?

Period of relative lucency followed by declined consciousness

What type of contrast is air and when can it be used?

- negative contrast | - used in CT colonography

What is an oral contrast?

- iodine based preparations - given to patient 1 hour and 24 hours prior to examination to opacity the distal and proximal aspects of the gastrointestinal tract.

What is an IV contrast?

- usually iodine based contrast - can be given to vascular tree in phases - arterial= 20 seconds - venous= 70 seconds

What side affects do given contrast have?

- warmth feelings - metallic taste in mouth - feeling of urination

What is a contrast media?

- solution given to enhance tissues within the body. - has high molecular weight - high attenuation value of the organ it opacifies - can cause reactions

What is a glioma?

- most common primary tumour of the brain | - usually occupies the cerebral hemispheres and thalamus in adults and the posterior fossa in children.

What is a glioblastoma multiforme?

- high-grade glioma. - affects the temporal and frontal lobes of the brain. - causes seizures and raised intracranial pressure.

What is a cerebral haemorrhage?

-direct bleeding into the brain parenchyma

What causes a cerebral haemorrhage?

- hypertension | - head injury

What units is CT measured in?

-hounsfield units

What are the key midline structures?

- septum pellucidum - third ventricle - fall cerebri - pineal gland

What is a gyri and sulci?

- gyri is a fold of the brain surface | - sulci is a furrow between the gyri which contains CSF fluid

What are the three types of skull fractures?

- linear - depressed - basilar

What is a linear fracture?

- most common - break to bone but no displacement - involves entire thickness of the skull - tend to occur due to low-energy transfer from blunt trauma over a wide surface of the head - often no intervention is needed unless they involve vascular channel, venous sinus grove or a suture

What is a depressed fracture?

- clinically significant and require elevation - may be closed or open - require surgery - on plain film appear as prominent sclerotic margins along fracture site

What is a basilar fracture?

- most serious - linear break in the bone in base of skull - occur mostly in temporal/occipital condylar region - dural tear sign - fluid level in sphenoid sinus - raccoons eyes - CSF discharge from ears on nose - bruising behind ears