Term
| what kind of radiation is CT? |
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Definition
| ionizing radiation: photon beam -> object -> detectors -> computer |
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Term
| how does density appear on CT? |
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Definition
| the more dense, the whiter (dense structures absorb photons = shadow). density is measured in houndsfield units (water: 0, calcium: ~1000, air: -1000). *fat is dark on CT. |
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Term
| how many planes are in CT? |
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Definition
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Term
| what is visible on CT (what is it used for)? (*know this*) |
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Definition
| calcification/metals (foreign bodies), blood (acute: white), fractures, CVA screening, and neoplasms (limited - MRI is better) |
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Term
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Definition
| accentuating different tissues on CT |
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Term
| what are the most common intra-axial gliomas? |
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Definition
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Term
| what are the most common extra-axial gliomas? |
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Definition
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Term
| when is dermoid/epidermoid CA seen? |
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Definition
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Term
| what is associated w/hypothalamic hamartomas? |
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Definition
| gelastic seizures (uncontrollable sudden outbursts of laughter) |
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Term
| what are the most common brain CAs in children? |
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Definition
| PNET (primitive neuro ectodermal tumors/medulloblastomas), pontine gliomas, pilocytic astrocytomas, hemangioblastomas - usually *infratentorial/posterior fossa. |
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Term
| *what kind of hemorrhage is associated w/a skull fracture? |
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Definition
| epidural (usually associated w/middle meningeal artery) |
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Term
| what does it mean if the brain is slightly hypodense? |
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Definition
| normal age related changes in a ~70 y/o, chronic alcoholic or hypertensive renal pt. |
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Term
| *what is the dense MCA sign? |
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Definition
| a sign that acute MCA ischemia due to an acute occlusion has occurred |
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Term
| how might there be sparing of the basal ganglia w/a L MCA stroke? (*possible exam question*) |
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Definition
| the thrombus must be distal to where the lateral or medial lenticulostriates come off the MCA. |
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Term
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Definition
| MRI works due to magnetization of protons in the body (hydrogen). protons are hit w/an RF pulse which knocks the spin off axis and a tiny microphone is placed near the body part of interest and it listens for the protons to realign themselves. each tissue has a specific time it takes to reach neutral again. |
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Term
| what are T1 and T2 MRI images? |
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Definition
| T1: water is dark (fat is bright). T2: water is white (H2O). |
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Term
| can the age of blood be determined via MRI? |
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Definition
| yes due to the appearance of hemoglobin breakdown products in T1/T2 |
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Term
| what is visible on MRI (what is it used for)? (*know this*) |
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Definition
| CVA (diffusion weighted imaging), neoplasms (skull base, brainstem), vascular imaging, blood (presence and age), demyelinating disease (MS, lyme), white matter disease (PML [AIDS], ALD), and congenital malformations. multiplanar capabilities make MRI superior to CT for characterizing pathology in almost all respects. |
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Term
| how big is a pituitary macroadenoma? |
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Definition
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Term
| what is a ring abscess seen on T@ considered? |
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Definition
| abscess or hemorrhagic metastasis until proven otherwise (not a primary neoplasm because there is too much edema). if the mass is touching the edema: intra-axial mass. |
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Term
| what sequence which can be done to determine if acute? |
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Definition
| diffusion weighted imaging |
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Term
| what is mild on the glasgow coma scale (GCS)? (*know this*) |
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Definition
| 13-15: mild lethargy, disoriented |
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Term
| what is moderate on the glasgow coma scale (GCS)? (*know this*) |
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Definition
| 9-12: sleepy/obtunded, able to follow commands w/arousal, confused |
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Term
| what is severe on the glasgow coma scale (GCS)? (*know this*) |
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Definition
| 3-8: typically comatose, cannot follow commands, may be decorticate or decerebrate |
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Term
| what are important characteristics of head injury? |
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Definition
| penetrating vs blunt. closed vs open. focal vs diffuse (focal: dysfunction specific to the injured area, diffuse: global dysfunction such as loss of consciousness/cognitive + memory problems). hemorrhagic vs non-hemorrhagic. |
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Term
| what are examples of primary vs secondary head injuries? |
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Definition
| primary: knife going through skull severs axons. secondary: mass effect from epidural hematoma = uncal herniation. |
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Term
| what does cerebral perfusion = ? |
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Definition
| MAP-ICP. thus cerebral perfusion is decreased by hypotension or ICP. |
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Term
| what characterizes excitotoxicity in head trauma? |
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Definition
| injury/ischemia release glutamate, aspartate and K+. intraneuronal Ca+ increases. this results in spreading depolarization, hypermetabolism and more ischemia. |
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Term
| what is therapy for head trauma? |
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Definition
| optimize perfusion, decrease metabolism (hypothermia), Ca++ channel blockers (keeps intraneuronal Ca++ decreased = stops spread of depolarization cascade) |
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Term
| what is management for head trauma? |
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Definition
| immediate sx for evacuation of hematoma (if necessary), monitor ICP w/implanted pressure gauge, medically manage cerebral edema to maintain cerebral perfusion pressure > 70 mmHg, and perform serial head CT scans as **~20% of cerebral contusions may enlarge to a surgical hematoma**. |
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Term
| what are the types of head injury? |
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Definition
| concussion, skull fracture, cerebral contusion, extra-axial hematoma (subdural [veins]/epidural [arteries]), diffuse axonal injury, and GSW |
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Term
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Definition
| a *brief loss of consciousness w/normal head CT and neuro exam, though pt may be lethargic and confused. observation particularly in athletes is important (if another injury: death is possible). |
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Term
| what characterizes skull fractures? |
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Definition
| ID any associated brain injury. determine if linear/non-depressed (if so, observe), open/compound (irrigate, close, antibx), depressed (surgical repair: dural tear/brain lac?), and basilar skull fracture (involve orbital roof, temporal bone? - battle's sign, raccoon eyes, CSF leaks) |
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Term
| what characterizes a cerebral contusion? |
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Definition
| focal tissue injury: deficit corresponds to area compromised. typically occurs in a coup/contrecoup pattern. blood +/- edema. on CT: rounded density +/- hypodense rim (marshmallow melting in hot chocolate). on MRI: mixed signal (all different blood ages) mass usually w/T2-hyperintense, T1 hypointense adjacent brain. **~20% expand to the point of requiring sx. ICU and f/u CT in 24 hrs**. |
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Term
| what is multi-compartment blood considered until proven otherwise? |
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Definition
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Term
| what is always the position for coupe/contrecoup injury? |
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Definition
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Term
| what is perfusion imaging? |
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Definition
| contrast is injected into the pt at a rate similar to the CTA (angiogram) and images are taken of the brain while the contrast is coming in. this allows drs to learn about the aggressiveness of tumors, predict strokes and enlarging areas of trauma based on cerebral perfusion (through measuring how much blood gets to a certain area in a certain given time). |
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Term
| what characterizes epidural tumors? (*know this*) |
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Definition
| arterial, rapid accumulation, lens-shaped, *do not cross suture lines (bound by suture lines) |
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Term
| what characterizes subdural tumors? (*know this*) |
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Definition
| venous, slow accumulation, c-shaped, and cross suture lines (dura has attachments at suture lines) |
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Term
| what characterizes diffuse axonal injury (DAI)? (*know this*) |
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Definition
| aka shear injury. this is due to high acceleration/deceleration w/shock waves and tissue distortion. microscopic tears of nerve fibers. petechial hemorrhages in white matter tracts. CT: tiny rounded hyperdensities (may be elusive). MRI: tiny rounded ***hypodensities (T2) - susceptibility/blooming artifact [iron = signal void] (MRI = study of choice for DAI***) |
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Term
| where are DAI's often seen? |
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Definition
| brain stem, corpus callosum grey-white matter junction |
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Term
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Definition
| combination skull fractures, DAI, intracerebral heme, SDH, EDH. direct tissue and major vessel injury. |
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Term
| where is gyriform blood on imaging? |
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Definition
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Term
| what is the most common reason imaging is ordered for the head? |
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Definition
| r/o vascular disease: altered mental status, hypertensive stroke or hemorrhage |
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Term
| what are the vascular diseases? |
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Definition
| ischemic cerebrovascular disease. hemorrhagic conditions. vasculitides (necrotizing/granulomatous, collagen vascular, drug-related, infectious), and vascular malformations. |
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Term
| what are the goals of imaging for ischemic cerebrovascular disease? |
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Definition
| make the definitive dx and assess for salvageable brain (perfusion imaging). assess for a non-ischemic cause such as tumor, intraparenchymal heme, and SAH. exclude any hemorrhagic component. |
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Term
| what is the most efficient assessment of acute CVA (ischemic cerebrovascular disease) w/in the first 24 hr? |
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Definition
| non-enhanced CT scan. relatively easy access. however - this is usually inconclusive for the first 6 hours. ultimately, MRI is better for acute CVA. if a CT is clear, tPA can be administered. |
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Term
| what characterizes MRI in evaluation of a CVA (ischemic cerebrovascular disease)? |
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Definition
| MRI is more sensitive and specific than CT, esp in the hyperacute stage (0-6 hrs). MRA can be performed simultaneously. limited accessibility. |
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Term
| what is diffusion weighted imaging (DWI)? ADC? |
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Definition
| DWI allows imaging of acute strokes. ADC (apparent diffusion co-efficient) maps then help determine if the bright T2 area is ischemic or not. ischemic areas will be bright on DWI and dark on ADC. |
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Term
| what characterizes carotid US in working up ischemic cerebrovascular disease? |
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Definition
| doppler measurements are 60% sensitive and 80% specific for stenosis greater than 70%. CTA/MRA are better. |
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Term
| what characterizes MRA (magnetic resonance angiography)? |
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Definition
| no contrast needed, can be obtained at the time of MRI, needs little time to process, artifacts, intubated pt, non invasive. also MRA really only measures flow (not looking at vessel per se) |
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Term
| what characterizes CTA (CT angiography)? |
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Definition
| requires iodinated contrast, rapid acquisition, less artifacts, post-processing time consuming, this dr's preference. CT looks at flow and the actual vessel structure. |
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Term
| what is the benefit of catheter angiography in working up ischemic cerebrovascular disease? |
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Definition
| the brain vasculature can be captured in different phases |
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Term
| what characterizes hemorrhagic conditions in the brain? (*possible exam question*) |
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Definition
| post-traumatic. spontaneous SAH. spontaneous intra-axial hemorrhage (anticoagulated/coagulopathy, **amyloid angiopathy [dementia]**, vascular malformation, metastases, hemorrhagic infarction, and HTN [basal ganglia, thalamus, and brainstem]) |
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Term
| if you suspect SAH ("worst h/a i've ever had") and CT is negative, what is the next step |
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Definition
| spinal tap, if positive then cerebral angiogram |
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Term
| what is the most common etiology for SAH? |
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Definition
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Term
| what characterizes aneurysmal SAH's? |
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Definition
| 10-15% die before getting to the hospital. 25% re-rupture w/in 14 days. vasospasm risk for 3-14 days. pts placed in neuro ICU. |
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Term
| what are risk factors for aneurysmal SAH? |
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Definition
| fam hx. female. HTN/ischemic heart disease/autosomal dominant polycystic kidney disease/hypercholesterolemia. smoking/heavy drinking. OCPs. |
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Term
| what are the 3 aneurysm shapes? |
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Definition
| 1) saccular containing a defined neck at the aneurysm/vessel interface. 2) fusiform dilation of the vessel w/o distinct neck. 3) ***dissecting pseudoaneurysm w/plane of dissection deep to the internal elastic lamina <- high association w/stroke and rupture*** |
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Term
| where is the most common aneurysm location? |
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Definition
| anterior circulation where the posterior communicating artery comes off |
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Term
| what are treatments for aneurysm? |
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Definition
| medical: induced hypotension. surgical: parent vessel ligation or aneurysm neck clipping. endovascular: parent vessel occlusion and aneurysm lumen coiling (better if neck is smaller than width of aneurysm, final angiogram should show no contrast in the aneurysm - recurrence is possible). |
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Term
| what can cause a spontaneous hematoma? (*possible exam question*) |
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Definition
| cerebral amyloid angiopathy - deposition of amyloid in the media and adventitia. this affects the superficial layers of the cerebral cortex and leptomeninges (spares deep gray nuclei). usually lobar, affecting frontal and parietal. risk factor - aging. |
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Term
| what should you think w/a 90 y/o presenting in the ER w/a lobar hemorrhage? (*possible exam question*) |
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Definition
| hemorrhagic stroke or cerebral amyloid angiopathy |
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Term
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Definition
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|
Term
| what is sensitive and specific for CVA? |
|
Definition
|
|
Term
| are both CTA and MRA good for determining vascular integrity non-invasively? |
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Definition
| yes - though catheter angiography is the gold standard |
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Term
| is it possible to have primary angiitis of the central nervous system? |
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Definition
| yes, but secondary vasculitis of the CNS is more common. |
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Term
| what might cause secondary angiitis of the central nervous system |
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Definition
| systemic illnesses including generalized autoimmune diseases such as SLE, sjogren, wegeners, PAN, GCA, and others (RA). also: cocaine, amphetamines, and some OTC cold meds. |
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Term
| can CT be used to image vasculitis? |
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Definition
| not really unless there is a hemorrhage |
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Term
| how can MRI/MRA be used to image vasculitis? |
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Definition
| this can show stenosis/dilatation/stenosis/dilatation pattern |
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Term
| what is the gold standard in imaging vasculitis? |
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Definition
| angiography - same as MRA but w/better resolution. may still be negative. |
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Term
| what is moyamoya disease? |
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Definition
| a pattern/disease where slow occlusion and high-grade stenoses of distal internal carotid arteries and their first order branches. on imaging: will see occlusion of the distal parts of the intracranial internal carotids and the collaterals that formed as a result of the occlusion. |
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Term
| what is the moyamoya appearance? |
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Definition
| sickle cell disease. atheromatous disease. XRT. neurofibromatosis. **kids: stroke/TIA-like symptoms (often present w/seizure). adults: SAH most common presentation. |
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Term
| what are some vascular malformations? |
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Definition
| capillary telangiectasias. cavernous angiomas/hemangiomas. venous angiomas/DVAs. true arteriovenous malformations. |
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Term
| what is an AVM (*test question*)? |
|
Definition
| a tuft of abnormal vessels w/an early draining vein where there are no intervening capillary beds. (congenital) |
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Term
|
Definition
| endovascular sx, sx, and radiation therapy. |
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|
Term
| where does the thalamus get its blood supply? (*know this*) |
|
Definition
| posterior circulation -> thalamo-perforators that come off the tip of the basilar artery and posterior cerebral artery |
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Term
|
Definition
|
|
Term
| how would a pt w/a pituitary macroadenoma present? |
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Definition
| bitemporal hemianopsia (micro: galactorrhea - prolactinoma) |
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