Angioplasty of a Persistent sciatic artery : case report

Persistent sciatic artery (PSA) is a rare congenital vascular anomaly, and its prevalence corresponds to 0.010.05% of the population. It was described by Green in 1832 and first confirmed − using arteriography − by Cowie in 19601,2. This anomalous artery, an atypical extension of the internal iliac artery, provides the major supply of blood to the lower limbs in 63% of the PSA cases. In such cases, it is the most important artery in the lower limbs, and the superficial femoral artery is hypoplastic or absent3. PSA has a predisposition to form aneurysms, found in 42% of the cases; about 50% of which have a complicated progression. They are bilateral in 12-32% of the cases4,5. This anomaly also predisposes to early atheromatous degeneration, distal thromboembolism and arterial occlusion6. Percutaneous transluminal balloon angioplasty is a well established technique for treating significant stenosis and short occlusions. This study describes a case of PSA with atheromatosis and ischemic complications of the left lower limb that was successfully treated using an endovascular technique. Abstract


Case report
An 81-year-old woman presented with a history of rest pain in the left lower limb and trophic ulcers in the first and third toes (Figure 1).The patient, who had a history of hypertension, had no pulses in the left lower limb and no posterior tibial pulse in the right lower limb.The patient was examined by a vascular surgeon, who requested aortography and pelvic and lower limb arteriography.Results revealed that aorta and right iliac system were normal.However, an anomalous artery in the left was shown, which originated in the internal iliac artery and extended inferiorly towards the limb (Figure 2).The superficial femoral artery was hypoplastic (Figure 3).This anomalous artery had several wall abnormalities and was occluded distally at a point close to the transition to the popliteal artery (Figure 4).The anterior and posterior tibial arteries were occluded distally; the fibular artery was pervious, but had moderate stenosis in its proximal third (Figure 5).
The hypothesis was raised from persistent sciatic artery with atheromatous degeneration and an occluded segment.Endovascular treatment was suggested for obstructive lesion.Using a contralateral approach and a 45-cm-long 6F introducer sheath, a 0.018 guidewire was advanced through the obstruction.Angioplasty was performed using a 5 x 20 mm balloon (Figure 6).The fibular artery was also submitted to angioplasty using a 3 x 120 mm balloon (Figure 7).Follow-up arteriogram showed that the artery was pervious and contrast medium flow rate was good (Figure 8).
Dual antiplatelet therapy was initiated with 100 mg/day of acetyl salicylic acid and clopidogrel at 300 mg loading dose and 75 mg/day thereafter.Immediately after surgery, the patient reported pain relief.She is currently being followed-up in our outpatient service.At 90 days after the endovascular procedure, trophic lesions did not progressed and the patient has no pain.

Discussion
PSA is a vascular anomaly whose origin is well known.Embryos reach 9 mm at about the 6th week.In this phase, the sciatic artery, or axial artery, arises from the dorsal root of the umbilical artery and becomes the major source of blood to the primitive foot.When the embryo is 10 mm long, the femoral system starts to develop as a continuation of the external iliac artery, which expands and branches out to irrigate the thigh.When the embryo reaches 14 mm, at about 8 weeks, the lower limb has a dual blood supply system, the sciatic and the femoral ones.At about 12 weeks, the sciatic artery involutes, and the superficial femoral artery develops.In adults, remnants of the sciatic artery participate in the formation of gluteal arteries, popliteal artery, and the origin of anterior tibial and fibular arteries, and contribute to the terminal anastomosis of the foot 1,2,7 .

PSA has two different presentations:
-complete (63-79% of the cases), in which this artery is the major blood supply to the lower limb, and the superficial femoral system is hypoplastic, but rarely absent.This is the presentation found in the case reported here 4 .-incomplete (about 20% of the cases), in which PSA is hypoplastic and communicates via several branches with the femoral system, which, in this case, has no abnormalities 8 .
There is no difference in incidence between sexes, and bilateral incidence is about 12%.The anomalous artery follows the trajectory of the sciatic nerve to the distal thigh.There are associations with other malformations, such as neurofibromatosis, bone hypertrophy, single kidney and other arterial and venous anomalies 2 .PSA is usually symptomatic and associated with aneurysm formation, which is seen in 25-58% of the cases.This high incidence of aneurysms is assigned to repeated micro traumas in the gluteal area and to hypoplasia of elastin fibers in the arterial wall 9,10 .Another possible symptom is acute or chronic ischemia due to accelerated atherosclerotic disease and consequent thromboembolism 11 .
The diagnosis may be suspected if a patient presents with reduced or absent femoral pulse but palpable popliteal and distal pulses associated or not with a pulsatile gluteal mass 12 .The differential diagnosis should include lumbosciatalgia, arteriovenous fistula, gluteal abscess and, principally, gluteal artery aneurysm 2 .
Digital subtraction arteriography is the standard criterion for the diagnosis of PSA.The iliac arteries, femoral system and distal arteries should also be examined to plan treatment accurately.Other studies, such as computerized tomography (CT) angiography, MR angiography and Doppler ultrasound may also be useful.There is no consensus in the literature about the best therapy for this entity, and treatments should be selected for each specific case.Some reports describe the use of several grafts, synthetic prosthesis and autologous veins, and results have been good [12][13][14] .There are also a few reports of successful endovascular treatment using thrombolysis, embolization, covered stents and angioplasty 10,13,15 .
In the case described here, the occluded segment and the distal vascularization suggested the use of balloon angioplasty and, according to the results of angiographic follow-up that showed the artery was pervious and there was a good contrast medium flow rate, we decided not to use stents.Distal angioplasty of the fibular artery was necessary to improve distal circulation and to ensure better chances of success.The immediate improvement of pain symptoms, reported by the patient immediately after operation and three months later, confirmed the success of the treatment used.

Conclusion
PSA is a rare vascular anomaly and should be included in the differential diagnosis of lower limb vascular diseases.Arteriography, the standard criterion for the diagnosis of this condition, is a useful aid in its treatment planning.Several treatment options are available and should be chosen individually for each specific case.The endovascular approach combined with angioplasty is a possible alternative for the treatment of this condition.

Figure 1 -
Figure 1 -Image shows trophic ulcers in foot.

Figure 7 -
Figure 7 -Angioplasty of fibular artery using 3 x 120 mm balloon.Figure 8 -Control arteriogram confirms good results of treatment.

Figure 8 -
Figure 7 -Angioplasty of fibular artery using 3 x 120 mm balloon.Figure 8 -Control arteriogram confirms good results of treatment.