CT Head Flashcards
What are the Indications for CT head scan?
- Gcs 13 or less
- vomiting
- post traumatic seizures
- suspected depressed/open fracture
- Use or anti-coagulants
What is hydrocephalus?
-dilation of the cerebral ventricular system.
What does hydrocephalus look like on images?
- dilated ventricle (x sign)
- surrounding oedema
- small sulci
What causes hydrocephalus?
- overproduction of CSF
- failure of reabsorption of CSF
- Obstruction of the flow of CSF
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
What is CSF absorbed?
-CSF is absorbed by arachnoid granules in the walls of venous sinuses.
What causes the failure of reabsorption of CSF?
- choroid plexus tumour pressing on aqueduct of Sylvius
- midbrain tumour pressing on aqueduct if sylvius
- haemorrhage
What is cerebral oedema?
Abnormal shifts of water between compartments of the brain.
What are the two types of cerebral oedema?
- vasogenic
- cytotoxic
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.
What is cytotoxic oedema?
- when extra cellular water moves into the cells causing them to swell.
- affects mainly the white matter.
What is a cerebral infarct?
-an acute area of neurological deficit.
What are the causes of cerebral infarct?
- cerebral haemorrhage.
- cerebral thrombus.
- cerebral embolus.
- subarachnoid haemorrhage.
What is the predisposing factor of middle cerebral artery infarct?
-atherosclerosis
What produced the grey scale in CT?
-voxels.
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
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
