persistent sciatic artery

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A persistent sciatic artery is a rare vascular anomaly where there is the persistence of the embryological axial limb artery, representing a continuation of the internal iliac artery into the thigh through the greater sciatic foramen below the piriformis muscle and down the thigh alongside the sciatic nerve. In normal embryologic development of the lower limb, the axial artery normally regresses after week 12.

The sciatic artery may be the dominant artery supplying the lower limb in which case the superficial femoral artery and/or profunda femoris artery may be correspondingly small. The majority (~80%) are complete (continuing as the popliteal artery) but some are incomplete where the vessel is interrupted somewhere along its course but remains connected to the popliteal fossa through collaterals vessels .

Epidemiology

Its incidence is only 0.05% of the population and may be bilateral in up to 20% of cases . It is more common in the right lower limb and there is no sex predominance .

Clinical presentation

Most patients are asymptomatic until mid-adult years (mean age of presentation is 44 years ) ​therefore most cases are found incidentally. There are a range of clinical presentations:

  • vascular symptoms and signs
    • buttock pain
    • lower limb pain
    • claudication
    • poor capillary refill in the toes
    • cool lower limbs
    • black toes
  • neurologic symptoms and signs
    • lower motor nerve weakness
    • sensory deficits
    • pain in the sciatic nerve distribution
  • Cowie's sign: described as a diminished or absent femoral pulse in combination with a palpable popliteal pulse
    • considered to be pathognomonic for a persistent sciatic artery
    • present in only a minority of cases

Associations

Several other congenital malformations have been found to be associated with persistent sciatic artery :

Related pathology

A superficial course through the buttock renders the persistent sciatic artery susceptible to repetitive trauma from sitting and hip flexion-extension. This, coupled with congenital arterial wall hypoplasia, can result in early atherosclerosis and aneurysm formation. One systematic review found aneurysm of the persistent sciatic artery occurs in 48% of cases . An aneurysm, in turn, can compress the adjacent sciatic nerve. As with any aneurysm, it can also rupture .

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