Head Scratcher of a Head CT?

Posted on by Wuya Lumeh

Hey there guys and gals and welcome back to my channel!

If you’re like me and TERRIBLE at reading your own imaging studies, settle in for a quick 20 minute run down for all those CT heads everybody be ordering without a second though. But before we get into it, don’t forget to like and subscribe. And give this TR pearl a thumbs up!

A few preliminaries:

Uno: You gotta get your basic windows down. There are three you gotta keep on deck – bone, brain, & blood. Basically, it makes the thing you’re looking for ~glow~ brighter. This is good for us EM folk/non-neurosurgeons/non-radiologists/noobs.

Dos: Scrolling. Axial is super standard — but never forget about a good coronal and sagittal view. We got them fancy helical scanners that can produce reconstruction in 3D if we reeeaaaallllyyy wanted to. Stop limiting yourself to one view PEOPLE. Live your best life and choose coronal for a change. That being said, do you — find what works best for the clinical question you are asking.

First things first…you gotta have a systematic approach. Same with EKGs, CXR, & POCUS — if do it the same every time, it becomes second nature. For head CTs — all you gotta do is remember that BLOOD CAN BE VERY BAD!

  1. B(lood). the good news is there is only so many places blood can collect in the head. the bad news is that too much blood means bad news bears for your patient. So don’t miss it – use that blood window. New blood is hyperdense/bright white (as it coagulates). Overtime blood then becomes isodense/kinda invisible-esque (1 week) and then hypodense/dark (2 weeks).
    • Epidural – lens shaped, does not cross suture lines, HPI with classic “lucid interval” prior to compensation
    • Subdural – crescent shaped, crosses suture lines, think extremes of age (pediatrics, geriatrics)
    • Subarachnoid – classic blood in the quadrigeminal cistern; majority d/t aneurysm rupture (up to 75%)
    • Intraparenchymal – can be 2/2 uncontrolled hypertension (typically in deep structures such as basal ganglia), traumatic, hemorrhagic stroke (or conversion from ischemic to hemorrhagic)
    • Intraventricular – blood in the ventricles, duh! can be traumatic or result from ventricular rupture of IPH or SAH
  2. C(an) – Cisterns. There are two key questions you answer by taking a gander at the 4 major cisterns (quadrigeminal, sylvian, supracellar, and cirummesencephalic — say that 3 times fast!) in the brain. Is there blood? and Is there increased pressure?
    • Is there blood? Like we discussed above, blood can look different at different phases of injury. So this may be a hard one to appreciate but new blood isn’t so hard — it’ll be white. Older blood may look like effacement if its isodense and lead you down the path of increased ICP — so be careful.  Or it may look dark like your normal cistern — I mean thats what MRIs are for…I think. It gets pretty tricky.
    • Is there increased pressure? If you’re worried about ICP, cisterns can help you out because they show ~the squish~  pretty well. You’re looking for effacement here or simply put, the edges of your gray matter to touch.
  3. B(e) – Brain. Lets talk parenchyma, using the brain window. There are 4 aspects to look at here.
    • Symmetry: does the unaffected side look the same as the affected side? #twinning
      • make sure the sulci and gyri are looking identical on both sides
      • check for effacement, girl. JUST DO IT.
    • Grey-White matter differentiation: this may be the first sign of ischemia. I’ll be the first one to admit that the old B side cave monitor prrroooobbably isn’t the best for this but that shouldn’t stop you from looking.
    • Shift
      • check that faulx cerebri (ya know, that thin membranous thing that sections off the two cerebral hemispheres?). There should be a nice sized ventricle on either side and it should be…STRAIGHT. DOWN. THE. MIDDLE.
    • Hyper/Hypodensities
      • things that are bright (other than fresh heme): bone/calcifications, IV contrast
      • things that are dark: ischemic/injured brain, fat, water/fluid, air
  4. V(ery) – Ventricles. Recall from Neuroanatomy that there are 4 ventricles in the brain: lateral ventricles (2) given way to the 3rd ventricle which dumps into the 4th ventricle via the aqueduct.
    • there can be blood here. the choroid plexus (that thing that makes CSF) lives in the ventricles and can sometimes become calcified — and, shocker! be bright white on scan. Be careful not to mistake this for bleeding — clinical context is key!
    • The ventricles are a space where you are encouraged to look for the squish, as these major structures are subject to pressure — they are compliant and will move/change. Are the ventricles big? small? non-existent? Are they shifted? Questions to ponder…
  5. B(ad) – Bone. You guessed it, you’re gonna use the bone window for this one.
    • Same rules as plain film here, follow the cortical lines and you can do no wrong
    • Given that the calvarium is a giant fused bone, you would think fractures would be very obvious. They are for the most part. But don’t get fooled because hairline fractures can give you the slip if you’re not careful.

And that is that on that! ’till next time, babes!

thanks to Omar for the inspo!

Resources

  • https://www.downeastem.org/downeastem/2016/11/19/how-to-read-a-head-ct-andrew-perron-md
  • https://radiopaedia.org/articles/ct-head-an-approach?lang=us
  • http://epmonthly.com/article/reading-head-ct-pressure/