Cerebrovascular Evaluation

1
Cerebrovascular Evaluation

• The Role of Ultrasound in the Management of
  Cerebrovascular Disease

2
Stroke

• gt700,000 strokes per year in the US
• The leading cause of permanent disability
• Annual cost to patients, hospitals society is
  51 billion dollars
• Ultrasound provides a fast, portable,
  noninvasive, repeatable inexpensive diagnostic
  technique
• Ultrasound directly impacts the clinical
  decision-making

3
Stroke

• Ultrasound directly impacts the clinical
  decision-making in the following situations
• The early detection, quantification
  characterization of extracranial atherosclerosis
  occlusive disease
• The consequences of proximal arterial occlusive
  disease on the distal cerebral vasculature
• The detection of microemboli associated with
  cardiac aortic pathology carotid artery
  surgical manipulation
• Selection of children with sickle cell disease
  for blood transfusion as an effective tool in
  primary stroke prevention
• The natural history response to treatment of
  acute arterial occlusion that causes hyperacute
  stroke
• The time, course reversibility of cerebral
  vasospasm after subarachnoid hemorrhage

4
Definitions

• Transient Ischemic Attack (TIA)
• A neurologic deficit which resolves within 24
  hours
• Most resolve within a few minutes
• Resolving Ischemic Neurologic Deficit (RIND)
• A neurologic deficit which lasts gt24 hours but
  does eventually resolve
• Cerebrovascular Accident (CVA) stroke
• Permanent neurologic deficit

5
TIA

• Medical emergency
• 10 of patients with TIA will have a stroke
  within three months
• 50 of strokes will occur within 2 days after
  the initial symptoms
• Clinical history, knowledge of neurologic
  symptoms timely evaluation are essential in the
  work-up of these patients

6
Stroke Risk Factors

• Hypertension
• Hyperlipidemia
• Cholesterol
• Triglycerides
• Tobacco abuse
• Diabetes Mellitus

7
Elective Cerebrovascular Testing

• Carotid arteries supply the anterior circulation
• Territories supplied by the
• Middle cerebral artery
• Anterior cerebral artery
• Symptoms associated with the anterior circulation
• Unilateral weakness
• Arm or leg
• Dysphasia or Aphasia
• Difficulty with speaking (expressive aphasia)
• Inability to speak
• Hemianopsia
• Partial loss of a visual field
• Amaurosis fugax
• Transient monocular blindness
• Behavioral disturbances

8
Elective Cerebrovascular Testing

• Vertebral-Basilar arteries supply the posterior
  circulation
• Brainstem
• Cerebellum
• Midbrain
• Visual cortex
• Symptoms associated with the posterior
  circulation
• Bilateral weakness
• Dysarthria - slurred speech
• Dizziness
• Ataxia - disturbance of movement coordination
• Loss of consciousness - syncope, near syncope
• Drop attacks - sudden falling to the ground,
  usually without loss of consciousness
• Cortical blindness
• Diplopia - double vision
• Paresthesia - abnormal sensation, e.g. tingling
  numbness, without objective cause

9
Other Terms

• Paresis
• Partial or incomplete paralysis
• - plegia
• Suffix meaning paralysis or stroke
• Paraplegia
• Hemiplegia

10
Mechanisms of Stroke

• Large vessel athero-thrombotic stroke
• Cardiogenic embolic stroke
• Primarily patients with atrial fibrillation
• Lacunar stroke
• Occlusive lesions develop in the small
  perforating vessels of the brain
• Other
• Dissection
• Coagulopathy
• Paradoxical embolism
• Cryptogenic (indeterminate)

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Nonatherosclerotic

• Nonatherosclerotic causes
• Cardiogenic embolic
• Paradoxical embolism, e.g. due to patent foramen
  ovale
• Dissection
• Coagulopathy
• Fibromuscular Dysplasia (FMD)
• Trauma
• Carotid body tumor
• Aneurysm
• Radionecrosis

12
Indications for First-Ever Assessment

• Symptoms of stroke or TIA attributable to carotid
  artery distribution
• Carotid bruit asymptomatic
• Suspicion of carotid stenosis from other imaging
  tests, i.e. MRA, CTA
• Preoperative screening for carotid stenosis
• Assessment of a high cardiovascular risk patient

13
Re-evaluation Indications

• Follow-up to known disease (surveillance)
• Q 6 12 months
• Follow-up to treatment (surveillance)
• After 6 weeks - 3 months then Q 6 12 months
• Recurring symptoms following treatment

14
Carotid Trials

• NASCET North American Symptomatic Carotid
  Endarterectomy Trial
• ACAS Asymptomatic Carotid Atherosclerosis Study
• ECST European Carotid Surgery Trial

15
Carotid Trials

• Established guidelines for type of intervention
  based on the level of ICA stenosis
• Types of intervention
• Surgical
• Endarterectomy
• Endoluminal
• Balloon angioplasty wall stent placement
• Medical
• Antiplatelet
• Aspirin
• Plavix

16
Treatment How When

• Symptomatic patients
• Carotid Endarterectomy (CEA) beneficial when
  the ICA stenosis is gt70 diameter reduction
• CEA potentially better than medical treatment
  when the ICA stenosis is 50-69 diameter
  reduction
• Medical treatment (antiplatelet) when the ICA
  stenosis is lt50 diameter reduction

17
Treatment How When

• Asymptomatic patients
• Patients with gt60 stenosis
• 2 per year have a stroke
• CEA reduces this to 1 incidence
• Risks may outweigh the benefits
• CEA if life expectancy is gt5 years
• CEA in select patients found to have the
  following
• high risk unstable appearing plaques on B-mode
  imaging
• Frequent distal embolization or impaired
  vasomotor reactivity on transcranial Doppler
  (TCD)

18
Carotid Endarterectomy Trials

• NASCET
• North American Symptomatic Carotid Endarterectomy
  Trials
• Established there is significant benefit of CEA
  medical treatment for symptomatic patients with
  70-99 ICA stenosis
• ACAS
• Asymptomatic Carotid Atherosclerosis Study
• Established there is little surgical benefit to
  CEA in asymptomatic, good-risk patients with
  asymptomatic ICA stenosis of 60-99
• ECST
• European Carotid Surgery Trial
• Established that CEA reduced the risk of stroke
  in patients with 70-99 ICA stenosis
• However, a 70 ICA stenosis by the ECST method is
  equal to an approximate 50 ICA stenosis by the
  NASCET method

19
Stenosis Determination Methods

• (N) method utilized during the NASCET ACAS
• Compares the ICA residual lumen at the point of
  greatest stenosis to a distal ICA normal segment,
  beyond the carotid bulb
• Most widely used
• (E) method utilized during the ECST
• Compares the measured residual lumen to an
  assumed normal ICA bulb dimension

20
NASCET - ACAS MethodNorth American (N) Method
Stenosis
Residual Lumen (N) Normalized distal ICA
diameter (D)
100 x
1 -
21
Percent Stenosis - Bulb MethodEuropean (E) Method
TL
RL
True lumen is the estimated size of bulb at
the point of maximum narrowing
22
NASCET/ACAS vs. ECST Methods
23
Consensus Panel 2002
Primary Parameters
Additional Parameters
Degree of stenosis ()
ICA PSV (cm/s)
Plaque Estimate ()
ICA/CCA PSV Ratio
ICA EDV (cm/s)
Normal
lt125
None
lt2.0
lt40
lt50
lt125
lt50
lt2.0
lt40
50 69
125 230
gt50
2.0 4.0
40 100
70, but lt near total occlusion
gt230
gt50
gt4.0
gt100
Near occlusion
High, low or undetectable
Visible
Variable
Variable
Total occlusion
Undetectable
Visible, no detectable lumen
N/A
N/A
Plaque estimates (diameter reduction) with gray
scale and color Doppler US
24
Ultrasound Plaque Characterization

• US can be used to characterize plaque formation,
  assessing its relative risk for causing stroke
• Evaluate for
• Location
• Composition
• Echo characteristics
• Surface characteristics

25
Carotid Plaque High Risk

• Majority of patients have mild to moderate
  plaquing
• B-mode characteristics of high risk plaque
• Hypoechoic plaque
• Uniformly or predominantly echolucent plaques,
  types 1 2 respectively
• Heterogeneous plaque

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Calcified PlaqueAcoustical Shadow
Where do I sample?
27
Ulcerative Plaque
28
Extracranial Duplex Scan Other Roles

• Assessment for carotid lesions other than
  atherosclerosis
• Dissection
• FMD
• Radionecrosis
• Vertebral artery evaluation
• Stenosis or occlusion
• Direction of flow, i.e. subclavian steal
• Dissection

29
Radiologic Methods

• Catheter angiography
• Invasive, utilizes ionizing radiation contrast
  material, water soluble iodine, which is injected
  through the catheter
• Benefits
• Very detailed representation of blood vessels
• Possible to assess blood vessels at several body
  sites
• Catheter makes it possible to diagnose treat in
  single session
• Risks
• Reaction to contrast
• Access vessel blockage due to clot formation on
  the catheter
• Contrast material can damage the kidneys, esp.
  diabetics and renal patients
• Vessel rupture leading to hemorrhage
• Disruption of plaque in the access vessel leading
  to embolization
• Access vessel dissection
• Pseudoaneurysm

30
Radiologic Methods

• Computed Tomography Angiography (CTA)
• Utilizes ionizing radiation contrast material,
  water soluble iodine, which is injected into a
  small peripheral vein
• Benefits
• Noninvasive, except for peripheral IV
• No risk of damaging an artery
• Detailed images of blood vessels in key areas of
  the body
• More detail than MRA
• Less time consuming, considered safer is
  possibly more cost effective than catheter
  angiography
• Risks/Limitations
• Allergic reaction to the dye
• Should be avoided in diabetics renal patients
  as the dye may further impair kidney function
• Leakage of the dye under the skin can cause
  damage
• Avoided in first three months of pregnancy

31
Radiologic Methods

• Magnetic Resonance Angiography (MRA)
• Utilizes radiofrequency waves in a strong
  magnetic field causing the release of
  electromagnetic energy, contrast material
  (gadolinium) may or may not be administered
• Benefits
• No ionizing radiation
• Less time cost than catheter angiography
• No risk of damaging an artery
• High quality images of blood vessels even without
  contrast
• Risks/Limitations
• Not as detailed as catheter angiography or CTA
• Metal implants can make good image acquisition
  difficult or impossible
• Cannot be utilized in patients with pacemakers
• Avoided in the first three months of pregnancy