approach to CT head: BRAIN

CT HEAD

First, before ordering a CT brain ask yourself why. Will alter your management, and what you will do if it’s normal? What’s your differential, what’s your pre-test likelihood, and how will the the likelihood ratios of the CT alter this? Plain CT has a poor sensitivity for some conditions, and a zero sensitivity for others. Consider the differential for headache, which includes conditions outside the brain for which CT is useless, and inside the brain that non-contrast CT can miss; before ordering the CT you should ask yourself if you’ve considered causes outside the brain, or if there are conditions inside the brain that require additional tests if the CT is normal:

C: CARDIOVASCULAR

  • Outflow dissection: cervical artery dissection: need CTA of head/neck

D: NEUROLOGIC

  • Neuron seize: need EEG
  • Encephalitis/meningitis: need LP
  • Unregulated pressure: need LP
  • RBC: CT only good sensitivity for acute bleeds; can miss acute stroke, dural venous sinus thrombosis (need MRV), SAH (might need LP), or subacute subdural
  • Onco: CT can miss small tumous, or might need contrast to differentiate from ischemic changes
  • LOGIC: CT brain does not look at spinal or peripheral nervous conditions

E: ENDO

  • electrolyte: blood test
  • pheo: blood test

F: PELVIC

  • Pregnancy: PET

J: rheum, ophtho

  • temporal arteritis
  • otitis
  • acute glaucoma

 

Secondly, if you’ve ordered a Ct you need a rapid and systemic approach to reading it. Think BRAIN

Brain

  • black: CSF sulci increase (atrophy), decrease (edema, mass, hydro); air from open/basal skull fracture
  • white: blood peripheral (SDH, EDH, traumatic SAH), central (hemorrhagic CVA, SAH), posterior (DSVT); chronic calcification
  • isodense from subacute subdural
  • grey differentiation: increase from tumour (mass effect) or old stroke (volume loss); decrease from acute stroke

Rock (bone)

  • skull fractures
  • sinusitis
  • retro-orbital injury

Around brainstem

  • compression from mass effect
  • blood from SAH

Interventricular space

  • lateral ventricle: decrease +/- shift from tumour/bleed; increase size from hydro (decrease sulci) or encephalomalacia (preserve sulci)
  • third ventricle: dilated (becomes round) from hydro, disappear from edema
  • fourth ventricle: compress from ICP, dilated from communicating hydro, normal along with dilated 3rd ventricle from obstructive hydro

Not visible

  • CTA for dissection
  • contrast CT for small masses
  • LP for infection, intracranial hypertension, or to compete SAH workup
  • MRV for DSVT
  • intra-ocular pressure for glaucoma
  • ESR/biopsy for temporal arteritis

 

Third, you should ideally get a final report from the radiologist (or neuroradiologist) to confirm your read.

 

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