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CT brain

interpreting the CT brain

general concepts

  • is there any cerebral oedema, if so, what type and where?
  • is there evidence of a bleed, if so, what type of bleed, how old and where?
    • acute bleeds and clots are hyperdense
    • subacute bleed 2wks old is isodense with grey matter
    • chronic bleeds > 3-4wks old become “cystic” and appear hypodense like CSF
  • is there mass effect?:
    • midline shift
    • assess fourth ventricle and foramen magnum including effacement of CSF around the midbrain
    • herniation
  • is there any hydrocephalus - check the size of the anterior horns
  • in sudden unconsciousness with an apparently normal CT brain, look for a dense basilar artery tip to indicate a basilar artery thrombus which may warrant urgent life saving clot retrieval or catheter-directed thrombolysis
  • use a systematic approach
    • start at the vertex - assess grey-white matter differentiation, dura sinus, midline shift, look for subdurals, etc

current acute stroke protocols

  • non-contrast CT brain
    • looking for a bleed
  • CT carotid and Circle of Willis Angiogram
    • looking for occlusion, collaterals, ease of access for possible clot retrieval within 6hrs of symptom onset
    • eg. ICA embolus categorised as either:
      • ICA-T = fork shaped embolus extending up two branches of bifurcation
      • ICA-L = linear shaped embolus extending up one of the two branches of bifurcation
      • M1 = more distal embolus past the bifurcation
  • CT Perfusion scan
    • assess degree of potentially salvageable ischaemic penumbra (some patients may still have this up to 14hrs post onset whereas others may have none by 8 hours)

2 main types of cerebral oedema on CT scans

  • cytotoxic
    • BBB is intact and the pathophysiology is cellular swelling
    • CT features are loss of grey-white matter differentiation as BOTH become hypodense
    • due to either:
      • cerebral infarct
      • HSV encephalitis
      • hypoxic brain injury
  • vasogenic
    • BBB is lost, oedema is extracellular
    • CT features are heightened grey-white matter differentiation as only the white matter becomes hypodense
    • due to either:
      • tumour
      • metastasis
      • abscess
    • these cases usually warrant a contrast CT scan as likely to have an enhancing lesion

cerebral infarct territories

  • anterior cerebral artery (ACA) - fronto-medial
    • rare (2% of ischaemic strokes);
  • middle cerebral artery (MCA) - lateral involving Sylvian fissures
  • medial lenticulostriate arteries - fronto-medial aspects of basal ganglia
    • arise from the A1 segment of anterior cerebral artery (ACA), and supply the globus pallidus and medial portion of the putamen
  • anterior choroidal arteries - central and lateral aspects of basal ganglia
    • rare and usually incomplete; characterised by the triad of hemiplegia, hemianaesthesia and contralateral hemianopia
  • lateral lenticulostriate arteries - posterior aspects of basal ganglia
    • arise from the proximal middle cerebral artery (MCA) and supply the lateral portion of the putamen and external capsule as well as the upper internal capsule.
  • posterior cerebral artery (PCA) - occipital lobe
  • superior cerebellar artery (SCA) - cerebellum
  • posterior inferior cerebellar artery (PICA)
  • anterior inferior cerebellar artery (AICA)
    • rare; presents with vertigo, ataxia, peripheral facial palsy and/or hypoacusis

intracranial bleeds

  • extra-axial
    • extradural
    • subdural
    • subarachnoid
    • intraventricular
  • intra-axial
    • “primary”
      • hypertension
      • amyloid angiopathy
    • “secondary”
      • vascular malformation
      • tumour
      • haemorrhagic transformation of infarct
      • venous thrombosis
      • traumatic intraparenchymal
    • tip: if there is more oedema than haemorrhage, then think of an underlying tumour or infarct as a cause of the bleed
ctbrain.txt · Last modified: 2018/08/13 11:57 (external edit)