Drizenko et al. proposed that variations of the radial artery suggest hemodynamic insufficiency of the axial vascular network, allowing persistence of certain portions of the superficial system of the upper limb [10
]. The most frequently encountered distal anatomic variation of the radial artery is a sizable palmar branch – but more slender than the radial artery itself – located in a more superficial plane than the tendon of the flexor carpi radialis muscle and situated on its radial side before turning to the dorsum of the hand at the distal extremity of the radius [11
]. Unusual findings suggested by pulse or Doppler vascular signals being in wrong place indicate a developmental variation of the forearm arterial anatomy. In our case Doppler ultrasound detected a fusiform aneurysm of the superficial branch of the radial artery. In an extensive series of dissected specimens of 750 upper extremities, McCormack et al. reported an incidence of 6 radial artery duplications [1
]. These brachial and antebrachial arterial variations are probably caused by an abnormal embryologic development of the vascular plexus of the limb buds [12
]. Their incidence has been reported at between 1% - 15%, depending on their location in the upper or lower forearm respectively.
Most aneurysms in the forearm are found in the distal ulnar artery, called ulnar hammer syndrome [8
]. The incidence of radial artery aneurysms is rare and often combined with traumatic events, especially after access of the radial artery in anesthesia for blood pressure monitoring [9
]. There is paucity in the literature for true aneurysm case reports [13
]. Traumatic pseudoaneurysms are histologically described as hyperplasia of the intima due to transsection of the entire vascular wall. In our case, the aneurysm was found to be a pseudoaneurysm of the accessory radial artery with intimal wall hyperplasia.
Walton and Choudhary described a similar case of an idiopathic radial artery aneurysm in the anatomical “snuffbox”, draining into the second digital artery [14
]. It was also described as a pulsatile mass, confirmed to be an aneurysm by MRI of 1.5 cm diameter. In contrary to our case this aneurysm originated from the radial artery itself and was a shortcut to the second digital artery. This aneurysm was not resected, so no histological comparison can be made. Our patient turned out to have a pseudoaneurysm of an accessory radial artery. We performed Doppler Ultrasound examination of the extremity and serial arteriograms preoperatively, instead of MRI investigation.
Current standard in diagnosis is arteriography, which may help to evaluate for other aneurysm and weather a reconstruction will need to be done. In addition high resolution sonography and MRI are described for diagnostic imaging studies [15
]. However MRI imaging is costly and sonography can only be used as diagnostic imaging study, whereas an arteriogram offers evaluation and treatment in one step. In our case we chose an arteriogram to evaluate the lesion, which is in concordance with the current imaging standard.
The current standard of care of a radial artery aneurysm is ligation of the radial artery proximal to the aneurysm, provided that the Allen’s test showed perfusion of the deep palmar arch via the ulnar artery. In our case, the patient presented with an aneurysm of a high bifurcation of the palmar branch of the radial artery, where the aneurysm occurred after a fall. The superficial and deep arches were formed regularly by the radial and ulnar artery respectively. Both arches were complete and dominance of the deep palmar branch allowed complete resection without reconstruction. Only few cases are described where embolization or even an angioplasty was performed in radial artery aneurysms [17
Imaging studies to evaluate the lesion comprise of angiography, sonography or event MRI. The treatment most commonly performed is ligation of the artery, with or without vascular reconstruction. The exact criteria for reconstruction are not defined and good clinical assessment is necessary in the immediate post ligation time [9
Radial accessory arteries and radial artery aneurysms are rare. Accessory radial arteries and varying bifurcations are due to abnormal embryologic development of the vascular pattern of the forearm [19
]. Pseudoaneurysms are most due to traumatic events. The clinician has to keep a high suspicion to look for further existing illnesses. The location of the accessory radial artery in the anatomical snuffbox may have been prone to trauma and the formation of a pseudoaneurysm.