A 57-year-old left-handed man smoker with hypertension and coronary artery disease presented to the clinic with complaints of left arm pain. He worked predominantly at a desk job but did multiple tasks around the house that required vigorous use of the upper extremity and hand. He stated that when he used his left hand for even short periods of time, he developed cramping and fatigue in his hand and forearm. If he performed a significant amount of work with his left arm he became dizzy and light-headed. He denied any focal neurologic deficits or loss of consciousness.

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  Symptoms associated with vertebrobasilar ischemia are^1,2

  
  
  
  
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    Disequilibrium

    
    
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    Vertigo

    
    
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    Diplopia

    
    
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    Cortical blindness

    
    
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    Alternating paresthesia

    
    
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    Tinnitus

    
    
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    Dysphasia

    
    
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    Dysarthria

    
    
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    Drop attacks

    
    
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    Ataxia

    
    
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    Perioral numbness

  
  
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  The vertebrobasilar system is frequently not symptomatic because it has built-in redundancy via the basilar artery.

  
  
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  Collaterals from the external carotid artery, the thyrocervical trunk, and multiple small branches of the cervical vertebral artery also supply the vertebrobasilar system.

  
  
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  In patients with subclavian steal the most frequent symptoms are

  
  
  
  
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    Arm pain with exercise

    
    
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    Dizziness or vertigo

    
    
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    Diplopia, bilateral visual blurring

  
  
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  Motor or sensory symptoms are typically only present with concurrent carotid artery disease.

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  Vertebrobasilar “spells” that occur in association with subclavian steal syndrome represent a common example of hemodynamically based transient cerebral ischemia. In the presence of subclavian occlusion proximal to the vertebral takeoff (Figure 15-1), exercise of the affected arm may cause flow resistance to drop in the arm because of exercise-induced vasodilatation. This drop in resistance may result in retrograde flow down the ipsilateral vertebral artery with subsequent steal from the vertebrobasilar distribution and posterior circulation symptoms (diplopia, bilateral visual loss, drop attacks, etc).

  
  
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  These symptoms subside when the arm is rested.³ With more severe subclavian disease, steal physiology and symptoms can occur in the absence of ipsilateral arm exercise.

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  The syndrome exists when a patient has compromised upper extremity blood flow as a result of high-grade stenosis or occlusion in the corresponding subclavian artery proximal to a patent vertebral artery.

  
  
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  Subclavian steal symptoms occur if vertebrobasilar territory symptoms (eg, syncope or presyncope) develop because of steal of blood from the posterior cerebral circulation down the vertebral artery to supply the arm.

  
  
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  Disease of the brachiocephalic (innominate) trunk on the right can cause a similar phenomenon secondary to altered vertebral or carotid flow, or both.

  
  
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  Revascularization of the upper extremity should eliminate the steal. In addition, the presence of anatomic reversed flow in the vertebral artery on angiography or duplex ultrasound imaging at rest or during stress is sometimes referred to as subclavian steal (Figure 15-2).

  
  
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  There is no evidence that the presence of subclavian steal with or without symptoms is an indicator of a high risk for stroke.^2,4 Again, it may be reasonable to initially consider carotid intervention in patients with global symptoms and severe carotid bifurcation disease.