Subclavian steal

In severe occlusive disease of the subclavian artery (SCA) blood supply of the arm is mainly provided by reversed flow through the vertebral artery (VA) arising behind the obstruction. The so-called subclavian-steal syndrome consists of ischemic symptoms in the arm, especially after exercise, such as pain or numbness or coolness (Reivich et al. 1961). Consequently a diminished or delayed pulse in the radial artery or decreased blood pressure on the side of SCA stenosis can be palpated. Rarely neurological symptoms such as spells of dizziness may be brought about by exercise ofthe arm. Even more rare are ischemic brainstem strokes in subclavian-steal syndrome (Bornstein and Norris 1986). 

Bornstein NM, Norris JW (1986) Subclavian steal a harmless haemodynamic phenomenon Lancet 2 303-305 Bousser MG, Chiras J, Bories J et al (1985) Cerebral venous thrombosis-a review of 38 cases. Stroke 16 199-213 Brandt T, Dieterich M (1993) Skew deviation with ocular torsion a vestibular brainstem sign of topographic diagnostic value. Ann Neurol 33 528-534... 

Subclavian steal is caused by retrograde flow in the vertebral artery. It is a common angiographic or ultrasound finding when there is stenosis or occlusion of the subclavian artery proximal to the vertebral artery origin, particularly on the left, or of the innominate artery. When the ipsilateral arm is exercised, the increased blood flow to meet the metabolic demand may be enough to steal more blood down the vertebral artery, away from the brainstem into the axillary artery. If there is poor collateral blood flow to the brainstem, then symptoms may occur, but this is very rare. The subclavian disease is almost always severe enough to be detectable by unequal radial pulses and blood pressures, and often there is a supraclavicular bruit (Cho et al. 2007). 

Cheshire WP, Santos CC, Massey EW et al. (1996). Spinal cord infarction aetiology and outcome. Neurology 47 321-330 Cho HJ, Song SK, Lee DW et al. (2007). Carotid-subclavian steal phenomenon. Neurology 68 702... 

Although asymptomatic subclavian steal is quite common (reversed vertebral artery flow detected by ultrasound or vertebral angiography), symptomatic subclavian steal is rare. 

Bornstein NM, Norris JW (1986). Subclavian steal a harmless haemodynamic phenomenon Lancet ii 303-305... 

Spiral (helical) CT. Radiology 189 647-656 Hennerici M, Klemm C, Rautenberg W (1988). The subclavian steal phenomenon a common... 

In the neck, time of flight techniques are preferred over phase contrast techniques due to the longer scan times of phase contrast techniques needed to provide the same coverage and spatial resolution. 2D TOF MRA provides superior flow-related enhancement and allows coverage of the entire neck. Compared to 2D TOF MRA, 3D TOF MRA provides superior spatial resolution and is less susceptible to phase dispersion artifacts, but is more susceptible to saturation effects and cannot cover a large area. 3D TOF flight techniqnes are, therefore, used to delineate the carotid bifurcation only. 2D PC techniques are used to evaluate flow direction in the vertebral arteries when subclavian steal is... 

Fig. 6.15 Slow flow or subclavian steal syndrome. 2D TOF MRA source image (a) and MIP image of the TOF MRA (b) show absent flow and possible occlusion of the left vertebral artery (arrows in b). ceMRA (c), however, shows flow in this...

D Phase contrast (2D PC MRA) Can show direction and magnitude of flow No artifact from T1 hypeiintense lesions Can show very slowly moving blood. Can be obtained after contrast Can be repeated if suboptimal Low spatial resolution More susceptible to turbulent dephasing than TOF MRA Can have abasing artifact 2D PC of neck is longer than 2D TOF of neck Can determine collateral flow around COW Can detect subclavian steal and abnormal flow direction in neck Can detect slow flow if near-occlusion is suspected... 

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