Thenar/hypothenar arterial aneurysms are rare, and the management of these uncommon lesions is not well defined in the literature. While surgical repair has typically been the mainstay of treatment, there are isolated cases reported in which endovascular management was performed [1,2]. Here, we detail two such cases successfully managed with endovascular coil embolization, followed by a brief literature review. Based on our limited experience, we propose a management algorithm for thenar/hypothenar aneurysms.

Institutional Review Board approval was waived due to the retrospective nature of this case report.

1) Case 1

A 54-year-old right-handed male, a tailor by profession, presented with pain and a gradually increasing pulsatile swelling in the hypothenar aspect of his right hand for 2 months (Fig. 1A). This was associated with occasional mild digital pain, finger claudication, cold sensitivity, and phasic blanching for 4 days, suggestive of impending acute digital ischemia. Imaging revealed a large aneurysm arising from the superficial palmar arch of the ulnar artery in the hypothenar aspect. Therefore, a diagnosis of hypothenar hammer syndrome was made. Angiography (Fig. 1B) performed via the ipsilateral brachial artery using a 5Fr vascular access sheath confirmed the aneurysm arising from the superficial palmar arch. Manual compression of the ulnar artery during angiography (Fig. 1C) was performed to confirm arch patency.

Figure 1. (A) Physical examination of the hand showed a swelling on the hypothenar eminence of the hand. (B) Digital Subtraction Angiography confirmed the aneurysm (white arrow) arising from the superficial palmar arch of the ulnar artery. (C) Manual compression of the ulnar artery during angiography confirmed arch patency. There was filling of the palmar arch (white arrow) via the radial artery. (D) Angiogram from the ulnar artery confirmed the aneurysm. (E) Selective cannulation of the aneurysm was performed. (F) Coil embolization was performed using detachable 4×80 mm coils (Interlock; Boston Scientific). (G) Final angiogram showed exclusion of the aneurysm and retrograde filling of the fourth and fifth digits (thin white arrows) from the radial artery via the patent palmar arch (white arrow).

Considering the patent arch and the retrograde filling of the digits from the radial artery during manual compression of the ulnar artery, we opted for endovascular treatment. Following selective cannulation of the ulnar artery (Fig. 1D, E), coil embolization was performed using detachable coils (Interlock-18 Fibered IDC Occlusion System 4×80 mm; Boston Scientific) (Fig. 1F). The final angiogram (Fig. 1G) demonstrated an occluded superficial palmar branch of the ulnar artery, exclusion of the aneurysm, and retrograde filling of the fourth and fifth digits from the radial artery via the patent palmar arch. A total of 5,000 IU of intravenous heparin was administered during the procedure, and access site closure was achieved with manual compression.

The patient underwent follow-up assessments at 1, 3, and 6 months, and yearly thereafter. Mild discomfort and pain during daily activities were encountered during the first month, likely attributable to the presence of the coils and thrombus. However, this did not significantly impact the patient’s quality of life, and the symptoms gradually resolved completely after the first month. No ischemic side effects or short- or long-term complications were observed. At the 2-year follow-up, no new complaints were reported, and there was no need for any repeat intervention.

2) Case 2

One week after a blunt injury caused by a fall on an outstretched hand, a 40-year-old male, a known case of hemophilia type B, presented with a painful, tender swelling on the thenar aspect of his left hand. No signs of digital ischemia were observed. Ultrasound and computed tomography (CT) angiography revealed the presence of a traumatic arterial pseudoaneurysm likely arising from the princeps pollicis artery, the first digital arterial branch of the radial artery (Fig. 2A, B). Manual compression failed to obliterate the pseudoaneurysm. Considering the high possibility of thrombin injection causing non-target digital ischemia, thrombin injection was not attempted.

Figure 2. (A) Computed tomography angiography coronal reformatted image showed a pseudoaneurysm (white arrow) arising from the first digital artery or the princeps pollicis artery. (B) Volume-rendered image confirmed the pseudoaneurysm (white arrow) arising from a small offshoot branch (*) of the princeps pollicis artery. (C) Digital Subtraction Angiography confirmed the pseudoaneurysm (white arrow) and the presence of a stump for coil embolization. (D) Selective cannulation using a microcatheter was performed. (E) Coil embolization was performed using 2×20 mm pushable microcoils (MicroNester; Cook). (F) Post-embolization images showed exclusion of the aneurysm with patent main princeps pollicis artery (white arrow) and antegrade supply to the thumb. (G) Patent main artery and thrombosed aneurysm confirmed on Doppler ultrasound.

Due to the elevated risk of bleeding associated with open surgical repair in the history of hemophilia, endovascular treatment was deemed appropriate. A preprocedural hematological consultation and workup were conducted at the hospital hemophilia treatment center. The coagulation parameters of the patient were as follows: a normal bleeding time of 4 minutes (range 3-6), a normal prothrombin time of 11.2 seconds (range 10-14), a normal international normalized ratio of 0.96, and an increased activated partial thromboplastin time of 42 seconds (range 15-30). Preprocedural laboratory workup included testing for factor VIII (FVIII) and factor IX (FIX) inhibitors. Medications causing platelet dysfunction and acquired thrombocytopenia were discontinued. After assessing the bleeding and thrombotic risks, a hemostasis plan was devised in consultation with a hematologist, adhering to the guidelines of the World Federation and National Hemophilia Foundation’s Medical and Scientific Advisory Council. Factor IX Clotting Factor Concentrate (CFC) was administered. Preoperative peak factor IX activity was targeted between 60% and 80%, with postoperative targets set at 40%-60% on day 3, 30%-50% between days 4 and 6, and 20%-40% at 1-2 weeks. A preoperative bolus of CFC was administered 30 min prior to the procedure.

Digital subtraction angiography (DSA) was performed via ipsilateral brachial access, confirming the aneurysm’s origin from a branch of the princeps pollicis artery (Fig. 2C). Since the pseudoaneurysm arose from a small offshoot branch of the digital artery with a good stump, endovascular management was deemed feasible. Selective cannulation of the feeding artery was achieved (Fig. 2D) using a 2.4Fr microcatheter (Terumo). Coil embolization was performed (Fig. 2E) using 2×20 mm pushable microcoils (MicroNester). Post-embolization angiography displayed exclusion of the aneurysm with a patent main princeps pollicis artery and antegrade supply to the thumb (Fig. 2F). The sheath was then removed, followed by manual compression. A Factor IX CFC bolus was kept on standby in case of atypical or unexpected bleeding at the puncture site. Post-procedure factor supplementation continued for 7 days, as per the standard protocol, to mitigate the risk of delayed bleeding. Follow-up Doppler ultrasonography confirmed the patent main artery and thrombosed aneurysm (Fig. 2G).

Thenar/hypothenar arterial aneurysms are rare. These aneurysms can be true aneurysms secondary to vasculitis or connective tissue disorders, or pseudoaneurysms secondary to repetitive trauma (case 1) or underlying coagulopathy (case 2). Pseudoaneurysms are much more common than true aneurysms [3]. Management of these uncommon lesions is not well-defined in the literature. Although initially asymptomatic, they may become complicated by rupture, intraaneurysmal thrombus formation, and distal emboli, leading to digital ischemia and tissue loss. Therefore, these cases require further treatment [4].

Traditionally, surgery has been the mainstay of treatment for distal radial, ulnar, and digital aneurysms, involving resection with or without microvascular reconstruction [1,2,5]. Surgical options depend on the presence of adequate perfusion to the hand and fingers after excluding the aneurysm. Simple resection is a viable surgical option if the hand and fingers are adequately perfused; however, if the perfusion is inadequate, arterial reconstruction using a microsurgical technique becomes mandatory [6].

Endovascular treatment options for distal radial, ulnar, and digital aneurysms include stent graft placement and coil embolization. Few isolated case reports on endovascular treatment of forearm and thenar/hypothenar aneurysms have been described [7-9]. The advantages of stent graft placement include maintaining patency of the main parent vessel. In addition, stent grafts may also be used, particularly for aneurysms with larger necks. However, this is possible only if the artery has a straight course; also, it may be technically challenging, with a risk of stent thrombosis. Regarding coil embolization, various case reports have been presented in diverse clinical situations [7,10-12]. Complete coil embolization of aneurysms, with the sacrifice of distal radial or ulnar arteries, has been reported when the remaining single vessel runoff and the palmar arch to the fingers are patent [10,11]. Additionally, coil embolization has been successfully employed for thenar/hypothenar aneurysms in cases with a patent palmar arch [7,12]. Meanwhile, although coil embolization is technically easier, it would invariably entail sacrificing the parent vessel, and is only feasible when the palmar arch is patent. If the aneurysm arises from a small offshoot branch, coil embolization emerges as the optimal choice, provided that distal digital vascularity is maintained.

Based on our limited experience, we propose the following suggestions for the management of distal thenar/hypothenar aneurysms:

(1) These aneurysms should be treated to prevent rupture, thrombosis, distal embolization, and tissue ischemia.

(2) Once diagnosed using Duplex ultrasonography, CT angiography may be considered to confirm the diagnosis and explore potential endovascular options. Cross-sectional reformatted images may provide information on the size, neck, and anatomical variations.

(3) Traditionally, surgical excision with or without reconstruction have been the mainstay of treatment. With the latest advances in endovascular techniques, including microcatheters with smaller internal diameters and detachable microcoils, endovascular treatment can be considered.

(4) DSA should be performed prior to endovascular intervention. It serves various purposes. First, an intact palmar arch should be documented, with retrograde flow in the artery of concern. An occlusion test during the DSA should be performed to confirm the presence of an intact palmar arch. This will serve as a safety net if the concerned artery is compromised inadvertently. Second, the exact origin of the aneurysm can be established, whether from the main radial or ulnar artery, or a small digital branch. If the origin is a small digital branch, compromise of the branch may be considered if the supply to that digit remains intact. In cases of unfavorable anatomy or if the palmar arch is not intact, open surgical repair should be considered.

(5) An ipsilateral brachial approach is recommended for shorter manipulation courses compared to the femoral or contralateral approach. Variant anatomy, such as a high brachial bifurcation and accessory interosseous arteries, should be identified prior to vascular access. Ipsilateral brachial arterial access using a micropuncture set and ultrasound guidance was employed in both cases and access site closure was achieved by manual compression for 20 min.

(6) Stent grafts can be considered for more proximal ulnar and radial artery aneurysms in the forearm, where the anatomic course is straight. For thenar/hypothenar and digital aneurysms, coils are the main embolization materials of choice. We do not advocate the use of liquid/particle embolization because of the high risk of non-target and distal digital embolization in the small arteries of the hands and digits.

(7) Further studies and reports comparing the technical challenges of endovascular versus open surgical treatment for thenar, hypothenar, and digital artery aneurysms are necessary.

None.

The authors have nothing to disclose.

Concept and design: KMA, BAP, AVK. Analysis and interpretation: KMA, BAP. Data collection: KMA. Writing the article: KMA. Critical revision of the article: BAP, AVK. Final approval of the article: all authors. Statistical analysis: none. Obtained funding: none. Overall responsibility: KMA.