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You are here: Home / 07. Imaging / Head Computed Tomography (CT)

Head Computed Tomography (CT)

July 14, 2011 by CrashMaster

Head CTs

Article

 

Mnemonic:  Blood Can Be Very Bad (1)

B

lood:

 

EDH (Lens Shaped) SDH (Sickle Shaped, Consider subdural window) Intraparenchymal Blood (Especially in the Basal Ganglia) Intraventricular Blood (Look for hydrocephalus) SAH (Blood in Cisterns and Fissures)

C

isterns:

 

Look for effacement and blood Circummesencephalic (Ring around the midbrain) Suprasellar (Star shaped at Circle of Willis) Quadrigeminal (W shaped) Sylvian (Between temporal and frontal lobes)

B

rain:

 

Symmetry Gray/White Matter differentiation (Insular Ribbon) Shift Hyper/Hypodensities Pneumocephalus

V

entricles:

 

Effacement Shift Hydrocephalus (Examine sulci to differentiate between hydro and atrophy) Blood

B

one:

 

Skull fractures, especially basilar (Consider bone windows) Sinuses and Air cells (Look for Air/Fluid levels)

1.  Perron, AD, et al:  A Multicenter Study to Improve Emergency Medicine Residents’ Recognition of Intracranial Emergencies on Computed Tomography.  Ann Emerg Med 1998;32:5, 554-562.

2.  Ouellette, H, et al:  Clinical Radiology made ridiculously simple.  Medmaster.  Miami, Florida:  2000.

 

 

 

 

 

a) Subfalcial (cingulate) herniation ; b) uncal herniation ; c) downward (central, transtentorial) herniation ; d) external herniation ; e) tonsillar herniation. Types a, b, & e are usually caused by focal, ipsilateral space occupying lesions, ie., tumor or axial or extra-axial hemorrhage

 

 

 

 

mediastinal windows (level 39, width 500)

lung windows (level 2775, width 850)

Head Level 40 Width 90

 

 

CSF made first in ventricles then flows through aqueduct of sylvius then through foramen lushkun then into the cisterns surrounding the outside of the brain

cisterns are the first thing to squish with edema and elevated ICP

 

three key cuts pons/suprasellar/midbrain

 

base of skull:

sphenoids up front they look like McDonald’s arches which culminate in anterior clinoids in suprasellar cistern

 

petrosal bones behind suprasellar a transverse crack can jeopardize 7th or 8th cranial nerve. CSF leak also problematic if dural tear

 

sphenoid sinus just in fron of suprasellar on base of skull cut

 

beam hardening artifact in cerebellum do to surrounding bone

 

can see blood in temporal tips

 

Mastoid Air cells towards back

 

ethmoid sinus on one cut up

 

see 4th ventricle and cistern forward of it, this is the circummesencephalic because it is around the midbrain=signet ring

 

4th ventricle is darth vaders helmut

 

Suprasellar cistern is the 2nd key cut

 

the star mans arms reach for the sylvian cisterns

legs dangle down over the midbrain

 

can see clinoids sticking up into starman

 

 

high midbrain

quadrigeminal cistern: w shaped right behind quadrigeminal plate where optic nerve runs

first cistern to get compressed

cerebellar folds also disappear c inreased icp

 

location of venous blood

rostral cerebellar vermis just behind quad cistern, they become prominent in etoh folks

sylvian fissures separate frontal and temporal lobes

 

 

TEMPORAL TIPS BLOW UP FIRST IN HYDROCEPHALUS, on same cut as suprasellar

 

Sulcal pattern disappears with tight brain

Circummesencephalic disappears

 

tentorium blood layers out in SAH

 

falx is what you look at for shift

 

subdurals can layer out over tentorium

falx subdurals can be confused c calcified falx

 

intraparenchymal bleeds can rupture into the ventricles, then they get hydrocephalus

calcified pineal gland at same level as occipital horns

day 3 is the worst day for bleeds blossoming

 

grey/white differentiation is early stroke, grey (which looks white on ct) takes on water and starts to look grey (which is how white matter looks)

 

acute hydrocephalus can gives trans-ependymal flow (exudes into brain tissue) dark around lateral ventricles, periventricular white matter disease can look similar

 

 

look at petrous bone for basilar skull fxs

 

no gross blood, cisterns are black and open, brain is symmetric with normal density, the skull and sinuses are normal, there is no evidence of hydrocephalus, no emergent dx noted on CT scan

 

1 in 5 get acute hydrocephalus from SAH

 

Suprasellar cistern is effaced then ipsilateral cerbellopontine angle is enlarged till progressive obliteration of suprasellar cistern and basilar cisterns

 

 

Look for it in the midbrain at the level of the star

Describe it as open (all three limbs open), partially closed (one or two limbs obliterated), or completely closed

 

Measure for midline shift at the foramen of monro.

Midline shift= (A/2)-B

measure B to the septum pellucidum

 

 

interpeduncular fossa

most dependent portion of SAH space when the pt is supine Rad 1986;158:699

 

 

 

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