URR other cerebral abnormalities Flashcards
vertebral artery stenosis
-difficult to diagnose with US due to portions of the a are located within the trans proceses of the vertebrae
-normal flow is low resistive
-most common location of stenosis is at the vertebral origin
-can lead to steal phenomenon
diagnostic criteria for vertebral artery stenosis/occlusion
-abnormal PSV > 100 cm/sec in most stenosis
-ratio of pre and post stenotic velocities >2
-abnorm pulsatility (biphasic or triphasic)
-occlusion or stenosis or prox subclavian artery
-most common on left side
-dist subclavian artery fed by reversed flow through ipsilateral vert artery
-retrograde vert flow on affected side
-if suspected, bilat brachial pressures should be obtained, decreased or greater than 20 mmHg will be seen on affected side
-symptoms include limb paralysis, vertigo, ataxia, and syncope
subclavian steal
subclavian steal happens more often on what side?
left
proactive maneuvers can be done to make partial or complete steal
-if bidirectional or biphasic in vert , exercising the arm or applying a blood pressure cuff can be used to convert the flow to complete steal
-if suspected subclavian a should be evaled, mono flow detected on affected side
-ask patient to perform 40 flexion/ extensions of arm on affected side then re-eval the vert flow
-inflate above syustolic pressure on ipsilat arm and maintain for 1-2 mins, replace cuff and asess flow in abnormal vert a, if steal present, the flow should change from biphasic to complete reversal
early systolic deceleration in vert a
-stenosis of subclav a can cause changes in vert a flow
-systolic deceleration is a sign of a significant stenosis in ipsilat side
-systolic flow starts with sharp peak followed by a sharp decrease in flow to baseline
-then resumes, increase to decrease through diastole
-this is caused by stenosis in subclav a and less commonly the prox vert A
-waveform is considered a sign of “pre steal”
-provacative maneuvers can be done to make partial or complete steal
-inflammation of A wall
-causes difffuse or focal thickening of muscle layer
-may cause increased vasc in wall of inflamed segment
-increased velocities with decrease lumen size
arteritis
buerger, takayasu, polyarteritits, temporal (giant cell)
types of ateritits
the superficial temporal A courses anterior to the ear and can be palpated just above what?
the zygomatic arch
-inflammation of the superficial temp A leading to flow reduction to frontal and parietal branches
-stiffness in neck, jaw, claudication, headaches, and sudden uni blindness
-biopsy necessary for diagnosis
temporal arteritis (GIANT CELL)
what does temporal arteritis look like?
-images have thickened walls
-halo sign = ring of thickened vessel wall surrounding vessel
-normal flow patterns mimic ECA
-diffuse vessel wall thickening and distal ischemia cause increase velocity and decreased flow resistance
-areas of greater wall thickening can cause focal stenosis with increased resistance prox to stenosis and decrease resistance distal to stenosis
aneurysms area rarely seen where?
cervical carotid branches
if an aneurysm is found in intracranial vessels, it is what kind?
berry
-blood escapes into surrounding tissues and becomes encapsulated
-risk of hemorrhage/death, trauma, infection, or true aneurysm
pseudoaneurysm
what is an AVM?
congenital connection between arterioles and venules (lack of capillary bed); usually has multiple connections and surrounding venous collaterals and dilated veins
severe form of intracranial AVM in fetuses?
vein of galen aneurysm
what is an AV fistula?
direct connection between aterial and venous systems caused by tauma or vascular procedure, usually single connection and no surrounding collaterals
-causes increased volume of flow in venous system with pulsatility and turbulence
-reduces resistance in arterial inflow and increased diastolic flow
-large or chronic arteriovenous connections can lead to heart failure
-acute tear in vessel intima
-creates false lumen
-associated with marfan syndrome and ehler danlos syndrome
dissection
if ICA affected by dissection, usually affects which part?
first 2-4 cm
CCA dissection can by continuation into where?
aortic arch
dissection is more common in ICA or ECA?
ECA
-collagen growth in medial layer
-most common in renal A
-usually occurs mid-distal ICA (atherosclerosis more common in prox)
-causing flow limited lesions
fibromuscular dysplasia
what does fibromuscular dysplasia look like?
-string of pearl appearance
-abnorm growth of medial layer
-doesnt shadow
-causes stenosis/occlusion
carotid body (sinus):
-located at CCA bif, near angle of jaw
-above this numerous baroreceptors are located to monitor BP
