Cerebrovascular Disease Flashcards
Contraindications to TPA in ischemic stroke
Multiple randomized controlled trials have supported the safety and efficacy of intravenous alteplase (0.9 mg/kg; maximum dose of 90 mg) for confirmed ischemic strokes of less than 3 hours duration.
Contraindications
- Age older than 80 years and a history of diabetes are contraindications for patients with a history of ischemic stroke of 3 to 4.5 hours duration
- Concurrent intravenous abciximab administration
- blood pressure of 185/110 mm Hg or higher
- intracranial hemorrhage on CTA
- a history of stroke, severe head trauma, or intracerebral or intraspinal surgery within 3 months
- gastrointestinal bleeding within 21 days
- concurrent usage of low-molecular weight heparin/thrombin or factor Xa inhibitors
Indications for treating carotid dissection
Indications for surgical or endovascular repair of traumatic carotid dissection
- is fluctuating or deteriorating neurologic symptoms despite optimal medical management
- a contraindication for antithrombotic therapy
- or symptomatic/expanding carotid aneurysm
Carotid Body tumors: % sporadic vs hereditary
Carotid body tumors (CBT) are sporadic in 75% of cases; however, 25% are associated with familial history and/or underlying germline mutations.
When to get genetic testing for carotid body tumors
Genetic testing is recommended in all patients with multi-focal tumors, CBT associated with paraganglioma, CBT associated with pheochromocytoma and or a positive family history.
Carotid Body Tumors are associated with what gene?
The succinate dehydrogenase complex subunit D (SDHD) gene is the most common gene associated with familial paraganglioma. This autosomal dominant, highly penetrant mutation involves the genes encoding 3 subunits of the mitochondrial complex II (succinate dehydrogenase), a component of the Kreb cycle metabolic pathway. These hypoxia-related pathways can be activated by chronic hypoxia (e.g., living at high altitude), leading to increased neural crest call proliferation with decreased apoptosis. Patients with familial CBT tend to be younger (mean age 35 years), have bilateral involvement, and may have associated pheochromocytoma and/or other paraganglioma
Management of acute stent thrmbosis during transfemoral or TCAR procedure
Acute thrombosis of the ICA during carotid stenting is a devastating complication with insufficient data to provide level 1 recommendations. The most recent consensus documents and observational data suggest that the most appropriate first step in this patient who is acutely neurologically decompensated is to attempt to disaggregate the platelet plug and thrombus with administration of intra-arterial abciximab and thrombolytic therapy directly into the ipsilateral carotid artery. Endovascular salvage attempts may ensue, including suction thrombectomy, repeat stenting, and balloon angioplasty. While conversion to CEA may ultimately be required, immediate conversion may also be too time-consuming and physiologically stressful for the patient.
What is cerebral hyperperfusion and how is ot managed?
Cerebral hyperperfusion is an uncommon but potentially life-threatening complication following carotid revascularization, particularly in patients undergoing revascularization (carotid stenting) opposite of severe stenosis or contralateral occlusion.
Characterized by severe hypertension and unilateral migraine-like headache, if left untreated symptoms can progress to seizures and intracerebral hemorrhage, which is associated with mortality rates as high as 75% to 100%. There is no role for heparin in cerebral hyperperfusion syndrome, given the risk of intracerebral hemorrhage. As this clinical scenario is associated with cerebral edema and likely results from dysfunction of the cerebral autoregulation, the primary goal is to strictly control the blood pressure in the postoperative period, using vasodilators such as sodium nitroprusside, nicardipine, nitroglycerin, and others. Most clinicians attempt to maintain the blood pressure to within 20 mm Hg of the preoperative level.
What is the ischemic penumbra?
The ischemic penumbra is the zone of viable, but injured, tissue surrounding an infarct
Segments of the vertebral artery
The vertebral artery is typically divided into 4 segments:
V1 (preforaminal): origin to the transverse foramen of C6;
V2 (foraminal): from the transverse foramen of C6 to the transverse foramen of C2/
V3 (atlantic, extradural or extraspinal): from C2 to the dura/
V4 (intradural or intracranial): from the dura to their confluence to form the basilar artery.
Signs of posterior circulation stroke
Posterior circulation strokes may present with symptoms such as balance disturbances, vertigo, nausea/vomiting, blurred vision or diplopia/oculomotor dysfunction, facial numbness, altered consciousness, or dysarthria. Lymphocele may occur due
Shamblin Classification
The anatomic extent of the carotid body tumor described is consistent with a Shamblin III. The Shamblin classification of carotid body tumors describes the extent of the tumor and correlates with the difficulty of surgical resection and the probability of arterial reconstruction and cranial nerve injury. Class I tumors are localized and are generally resected with a very low probability of carotid artery reconstruction or nerve injury. Class II tumors are adherent to or partially circumscribe the carotid artery. Class III tumors encase the common, external, or internal carotid artery. Resections of large Class II tumors and Class III tumors have a higher probability of necessitating carotid resection and reconstruction and are associated with a higher probability of cranial nerve injury. Preoperative embolization of large Class II and Class III tumors should be considered, but is not mandatory. Proponents of preoperative embolization of carotid body tumors cite a lower blood loss after embolization. The idea that embolization may reduce the risk of cranial nerve injury has not be supported in multiple studies. If preoperative embolization is performed, surgical resection should ensure within 24-36 hours after embolization to minimize the peri-tumor inflammation that ensues after embolization.
What normal flow abnormality can be found in the carotid bulb?
Why?
Flow reversal
Related to diameter and angle of branch vessels
Which vessel has highest diastolic component on doppler? Highest pulsatility during systole and diastole and why?
ICA
ECA, due to reflect waves from branches
What are normal blood flow velocities in the ICA in >60yo? How does it changes in younger patients?
60-90cm/sec
higher likely due to increased CO
How much does blood flow change between mid CCA and CCA near bifurcation? Where should peak CCA systolic velocity be measured?
It increases by 10-20cm/sec
2-4cm below the bulb
What are normal flow velocities in the ECA?
80-115 cm/sec
What are normal peak systolic velocities in the ICA?
usually <100 cm/sec
What things can cause elevated flow velocities? (4)
Stenosis
kinking, coiling
elevated CO
technical error (transducer error)
What features distinguish ICA from ECA? (6)
ICA usually bigger
ICA branches rare
ICA proceeds deep and post towards mastoid (ECA anteriorly)
ICA low resistance
ECA, oscillations with temporal tap
ICA less color variation from diastole to systole (ECA flickers)
What is normal intima-media thickness formula?
(0.009 x age in years) + 0.116
What is usually considered abnormal intima-media thickness?
>0.9mm
What is the international classification for carotid plaque?
type I uniformly sonolucent (>90%)
type 2 predominantly sonolucent (>50%)
type 3 predominantly echogenic (>50%)
type 4 uniformly echogenic
type 5 unclassified (poor visualization)
What method of measuring stenosis did ECST use?
(residual lumen d - original lumen d)/ original lumen d *100%
What method of measuring stenosis did ACAS/NASCET use?
(residual lumen d - lumen d normal distal)/lumen d normal distal * 100%
What parameters can characterize ICA stenosis? (3)
peak systolic velocity
VICA/VCCA
end-diastolic velocity
What can cause unexpected readings of the PSV?
low CO
hypertension
tandem lesions
contra occlusion
tortuous vessel
What can alter readings of VICA/VCCA?
external or bulb disease
At what degree of stenosis do Doppler values begin to become abnormal?
50%
What is the Washington criteria?
normal ICA PSV 125 EDV 125 EDV >140
For the SRU consensus, what cutoff values are use for PSV and ratio in carotid stenosis?
50-69% PSV 125-230, EDV 40-100, ratio 2-4
>70% to near occlusion PSV >230, EDV >100, ratio >4
near occlusion high/low/undectec
What is the incidence of stroke for an occluded ICA compared to gen pop?
same
What is the incidence of stroke for a nearly occluded ICA?
11%/year
What are features of near occlusion on US?
distal ICA small beyond stenosis
ICA smaller then ECA
What is the issue with NASCET measurement of ICA stenosis?
because the distal ICA gets smaller in near occlusion the nascet method no longer applies.
What are features of carotid occlusion on doppler?
hypoechoic/anechoic region that occupies entire lumen
no spectral, color or power dopple in lumen
occluded vessel may not be identifiable
externalization of the CCA
What is CCA externalization?
when the CCA flow pattern resembles ECA when the ICA is occluded. may not occur if ECA is serving as a large collateral.
What features on doppler indicate siphon or distal ICA occlusion?
absent diastolic flow in ICA
What scenarios can eliminate diastolic flow in the ICA
distal lesion, increase ICP, ICA dissection
How should ICA with string sign be managed?
string signs are associated with diffuse stenosis and there may not be a lesion to endarterectomize. Ligation may be the best management if causing stroke/TIA.
What are issues with measuring CCA stenosis?
PSV is variable along the CCA
How to measure CCA stenosis?
doubling of PSV to indicat4ee moderate stenosis
quad for severe >70%
How to measure origin CCA stenosis?
difficult as not visualized
ipsi/contra ratio normal 0.7-1.3
parvus tardus waveform
turbulent flow
Stenosis of the innominate artery can cause symptoms related distributions?
anterior circulation (stroke/TIA)
posterior circulation (cerebellar, brainstem strokes, dizziness)
cerebral circulation
arm ischemia
What % of arch dissection include carotid arteries?
3-7%
What % of carotid dissection resolve spontaneously? suffer disabling neuro? fatal?
70%
25%
5%
What features does carotid dissection have on US?
long tapering stenosis
visible flap
occluded artery with no calcified lesion
duplication of the carotid color flow
What features do you need to report on when assessing a carotid dissection with US?
extent
patency
stenosis
flow direction in false lumen
What features are important to assess when examining a pseudoaneurysm with US
size and location
to and fro in the neck (confirm its a pseudoaneurysm)
length and d of neck
proportion of flow/thrombosis in pseudoaneurysm
What is the most common site for AV fistula?
femoral
What are clinical findings of AVF in carotid?
neck trauma
ecchymosis
palpable hematoma
palpable or audible thrill
dilated, hyperdynamic draining vein
What can be the consequence of large AVF?
high output cardiac failure
What are US features of AVF carotid?
turbulent, pulsatile flow in jugular vein
high velocity jet between the two structures
What size and location of carotid body tumor?
1-1.5cm in adventitia at carotid bifurcation
What are US features of carotid body tumors?
highly vascular
at bifurcation
can encase ECO or ICA
