10-15 Neuroimaging Flashcards
Systematic Approach to Head CT Interpretation
- Know normal - identify the normal structures in each slice, considering age of pt and symmetry of image
- Determine whether lesion is in the brain (intraaxial) or outside (extraaxial)?
- Does lesion take up space (e.g. mass, edema, hematoma) or is there loss of tissue volume (e.g. encephalomalacia, atrophy)?
- Is there edema? If so, is it cytotoxic and vasogenic?
Age differences in brain CT appearance?
babies - more shallow sulci/fatter gyri, larger ventricles, less mature
older folks - smaller size is normal, deep sulci
What are three different CT windows?
Bone, Stroke, Soft Tissue
Intraaxial vs. Extraaxial masses
Intraaxial - push gyri out making sulci more shallow (see less CSF between cortex & skull)
extraaxial - see increased CSF space, displaced veins that are more medial then they ought be
Lesions that take up space vs. lesions causing loss of tissue volume
lesions that take up space - shrunken ventricles, midline shifted, sulci crowded
loss of tissue volume - ventricles larger, no midline ∆, sulci wider
cytotoxic vs. vasogenic edema
- -appearance
- -etiology
- -pathophys
cytotoxic edema
- -appearance: loss of grey/white difference
- -etiology: Stroke, stroke, stroke (encephalitis, tumor can mimic)
- -pathophys: Cortical cell death —> cortex less dense
vasogenic edema
- -appearance: accentuated grey/white difference
- -etiology: Tumor, inflamm disease, HTN
- -pathophys: Leaky capillaries —> edema spreads in WM
imaging test of choice in suspected acute stroke? why?
non-contrast CT of the head
- -stroke is a CLINICAL DIAGNOSIS
- -CT is fast & will r/o hemorrhage or stroke mimic that would contraindicate tPA
What will you see in a stroke window, non-contrast CT of the head in a stroke patient? What causes these findings?
- -hopefully nothing, no CT ∆s in first 6-24 hrs s/p CVA
- -Afterwards, 4 SIGNS SEEN:
1. Dense middle cerebral artery = clot
2. Loss of gray-white differentiation*
3. Loss of insular ribbon*
4. Effacement of sulci and loss of basal ganglia* - Signs of cytotoxic edema! The hallmark of stroke!
Gold Standard to ID dead brain s/p CVA (after emergency is over and pt is stable)
–specificity? false positives?
diffusion-weighted MRI
- -positive w/in minutes and stays + for 2 wks s/p
- -Fairly specific for stroke; False (+) with brain abscess, hemorrhage, MS
Head trauma: Who should get imaged?
FYI only–NEW ORLEANS HEAD CT RULES:
1.LOC or post-traumatic amnesia if one or more (+):
HA, vomiting, age >60, drug/Etoh, short-term mem def, physical evidence of trauma above clavicle, sz, GCS65, physical evidence of basilar skull fracture, GCS3 feet or 5 stairs)
–100% sensitive at IDing pts in whom CT abnormalities are present (but only 10-25% specific, still lots getting scanned that didn’t need it)
Head trauma: What are the common intracranial injuries identified in trauma patients?
1 Epidural Hematoma 2 Subdural Hematoma 3 Traumatic Subarachnoid Hemorrhage 4 Brain Contusion 5 Diffuse Axonal Injury
Where is the epidural space?
space is between the dura*/periosteum (which are fused) and naked bone
*Reflections of dura form venous sinuses, for this reason, epidural hematomas generally don’t cross sutures
subdural space + review of arachnoid anatomy
Potential space between arachnoid and dura
The arachnoid matter : Oppose to the dura, Tightly bound at venous sinuses due to arachnoid granulations, and has cobweb-like projections connecting it to the pia mater
subarachnoid space + review of pia anatomy
space between pia and dura that CONTAINS THE CSF
recall that pia mater is closely applied to cortex and follows all contours of the brain
Facts about epidural hematoma (EDH)
EDHs:
- bi-CONVEX/lens-shaped
- ARTERIAL bleed that STRIPS THE DURA off of the skull bone
- doesn’t cross suture lines
- 90% w/ skull fx —> MIDDLE MENINGEAL ARTERY
- usu on COUP side
- generally better prognosis
- neurosurg emerg —> burr hole that shit
