Cath Lab Digest

Abstract

Persistent sciatic artery (PSA) is a rare congenital vascular anomaly that occurs when the sciatic artery fails to regress during fetal development. This failure to regress is often associated with superficial femoral artery (SFA) hypoplasia and the PSA then becomes the dominant arterial inflow to the lower limb. PSA is prone to several complications due to its anatomical course that exposes it to repeated trauma, with the most common complication being aneurysm formation. Here we describe the case of a 64-year-old female patient who presented with acute right lower limb ischemia due to embolization from a partially thrombosed PSA aneurysm.

VASCULAR DISEASE MANAGEMENT 2010;7:E82–E85

Key words: aneurysm ligation, lower-limb ischemia, superficial femoral artery hypoplasia, vascular anomaly

Introduction

The sciatic artery is a continuation of the internal iliac artery and in early embryological development it serves as the principal blood supply to the developing lower limb. As development progresses the femoral arterial system becomes the major arterial inflow to the lower limb and the sciatic artery atrophies. Persistence of the sciatic artery (PSA) was first described by Green in the Lancet in 1832,¹ and the first account of a PSA aneurysm rupturing and resulting in death was by Fagge in 1864.² PSA is extremely rare and has a reported incidence of just 0.05% by angiographic studies.³ A recent review by Van Hoft et al⁴ found there were 122 published cases of PSA from 1964 through 2007. We found another 12 cases reported in the literature since 2007 for a total of 136 cases published since 1964. Ikezawa et al⁵ found in their review of the literature that PSA had no gender predilection, a mean age of presentation of 54 years, and it occurred bilaterally 22% of the time. PSA is prone to atherosclerotic changes and is associated with aneurysmal change in 46% of all cases.⁴ The most frequent symptoms associated with a PSA aneurysm are a painful pulsatile buttock mass, sciatic neuropathy caused by sciatic nerve compression and lower limb ischemia caused by thrombosis or distal embolization. Here we describe a case of PSA aneurysm presenting with lower limb ischemia treated surgically with aneurysm ligation and femoral-popliteal bypass.

Case Report

A 64-year-old African-American female presented to the emergency department with severe right leg pain that had started 3 months prior and had been progressively worsening. The patient described the pain as starting in the right buttock and traveling down the back of the leg. Pertinent medical history included hypertension, obesity and Type II diabetes. Physical examination revealed normal femoral and popliteal pulses bilaterally, normal dorsalis pedis and posterior tibial pulses on the left and a cool right lower extremity with severely diminished dorsalis pedis and posterior tibial Doppler signals. In addition, the 1st and 5th digits appeared grossly necrotic, so the patient was admitted and sent to the angiography suite for an abdominal aortogram with distal runoff. The aortogram (Figure 1) was remarkable for a prominent right internal iliac artery with a fusiform aneurysmal dilatation approximately double the size of the more proximal artery. This large artery was determined to be a PSA due to its origin from the internal iliac, its lateral course along the sciatic notch, sluggish flow compared to a normal superficial femoral artery (SFA), and finally, for its torturous and dilated course through the lateral thigh with final runoff into the popliteal artery. The right illiofemoral arterial system appeared hypoplastic, and the right SFA tapered to an end high in the thigh with no connection to the popliteal artery (Figure 2). There was severe tibial disease with proximal occlusion of all three vessels without distal reconstitution (Figure 2).

The above findings established the diagnosis of a “complete” type of PSA. The patient’s symptoms were thought to be due to expansion and embolism to the tibial vessels from the right sciatic artery aneurysm. Therefore, thrombectomy was first attempted in the tibial vessels, however, because of the chronicity of the thrombosis, it was unsuccessful. For similar reasons, we believed that thrombolysis would not have been effective; therefore, the patient was taken to the operating room for ligation of the PSA aneurysm and revascularization. The PSA was ligated at its junction with the above-knee popliteal artery using a medial popliteal approach. Femoral-popliteal bypass utilizing a 6 mm polytetraflouroethylene (PTFE) prosthesis was then performed to restore distal flow to the lower limb. The patient tolerated the procedure well, but her pulses remained barely detectable by Doppler in the dorsalis pedis and posterior tibial arteries postoperatively. Unfortunately, the patient later required a right below-knee amputation (BKA) due to the foot having been ischemic for so long prior to presentation. At follow-up 1 year later, the patient is ambulating well with a prosthesis and reported no complaints or symptoms of claudication. She will be followed up periodically with computed tomographic (CT) angiography and duplex ultrasound. If there is evidence of PSA aneurysm enlargement, or if the patient develops symptoms consistent with compression of the surrounding neurovascular structures, endovascular treatment via coil embolization/occlusion or surgical ligation of the aneurysm will be considered.