Ulnar Artery Thrombosis and Nerve Entrapment at Guyon's Canal: Our Diagnostic and Therapeutic Algorithm

Discussion

Analyzing our experience and according to the literature, although rare, vascular compromise can be a cause of hand pain (11). Physical examination usually enables differentiation between vascular causes and isolated ulnar nerve compression; the diagnosis can be confirmed with US, MR, multidetector computed tomography (CT), conventional angiography, CT angiography, or MR angiography (12-15). The selection of the imaging modality to be used for further work-up for peripheral neuropathies depends on the anatomic location of the abnormality, the clinician's preference, local availability, and the individual experience of the radiologist with each modality. However, angiography is the gold standard of diagnosis for well-evaluated blood flow (11) and it is required in order to determine the most appropriate treatment (16). However, several authors, such as Blum et al. and Andreisek et al., suggest that MR imaging may provide useful information with regard to the exact anatomic location of the lesion or may aid in narrowing the differential diagnosis, and in patients with peripheral neuropathy, MR imaging may establish the origins of the condition and provide information crucial for management or surgical planning (2, 3).

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Figure 4.

Diagnosis and treatment (main steps in bold).

Special care had to be taken for a correct diagnosis, performing angio-MR that showed clearly ulnar artery thrombosis and incomplete palmar arches (Figure 2). Nevertheless, we believe that in the presence of pain and digital ischemia along the hypothenar eminence and the little and ring fingers, Allen's test showing arterial insufficiency (with eventually US imaging demonstration) and MR imaging can be sufficient. These techniques confirmed the presence of HHS and Guyon's canal syndrome. Therefore, and in agreement with previous authors, we suggest that MR imaging is the modality of choice for evaluating the ulnar nerve and causal factor of compression. T1-weighted sequences are best suited for identifying the ulnar nerve within Guyon's canal: the bifurcation of the ulnar nerve and the course of both branches are well depicted, all the loose bodies with adherence to synovium and synovial cysts are detected, as well as osteoarthritis, synovitis, bone and muscle anomalies, accessory muscle and fibrous bands can be seen at MR imaging (2, 3, 17). On T1-weighted images (Figure 3), effectively, the ulnar nerve appears as a round structure with altered size and signal intensity, edema and fatty atrophy of the ulnar intrinsic muscles indicative of ulnar muscle denervation, and the presence of mass lesion is excluded. Furthermore, MR imaging is an excellent method for demonstrating nerve compression by detecting abnormalities in the hand. The MR imaging and the clinical features allow a diagnosis to be made. US confirms lesions of the ulnar artery that may include wall thickening, stenosis, aneurysm, occlusion, and corkscrew configuration. In addition, although angiography is very efficient for the diagnosis of HHS, we understand that is not the modality of choice because physical examination and MR are sufficient. In fact, Allen's test is specific for arterial insufficiency and MR evaluates well the condition of the ulnar nerve and surrounding structures, demonstrating pathologic compression of the ulnar nerve within Guyon's canal with edema and atrophy of the ulnar intrinsic muscles of the left hand. Therefore, the diagnosis can be made easily and early for the surgeon to develop a therapeutic plan.

According to the literature, treatment of Guyon's canal syndrome begins with rest and splinting of the wrist. If compression is present, surgical decompression may be performed (2). Treatment of HHS consists of rest from the offending activity and therapy with vasodilators. Asymptomatic ulnar artery occlusions do not need surgical intervention (2, 11, 18). Therapeutic approach of this syndrome is strictly correlated to its symptoms starting from a simple oral anti-platelet aggregation therapy to a surgical excision of the affected vessel and its bypass reconstruction (11, 19). Klitscher et al. assert that the thrombotic form is mainly treated conservatively (20). But we believe that only surgical decompression of the ulnar nerve and resection of the ulnar involved arterial segment and anastomosis with autologous vein graft are effective. Moreover, we suggest that surgical decompression must be considered to avoid irreversible nerve alterations such as axonocachexia (21). Similarly, the thrombotic form must be resected to avoid occlusions of digital branches presumed to be secondary to thromboembolism (22).

In conclusion, we report the diagnosis and treatment of HHS in which the ulnar arterial thrombosis induced severe chronic inflammation in Guyon's canal and ulnar nerve compression (Guyon's canal syndrome); and we discuss the management of the two syndromes associated. In the presence of upper limb digital ischemia and pain, history should be carefully obtained and investigations should be conducted before irreversible consequences take place: amputation of ulcerated necrotic finger tips may be required in advanced cases. Correct management suggested is Allen's test and MR with US images for diagnosis, and operative treatment with nerve decompression and vein interposition graft after resection of the arterial thrombotic segment (Figure 4). In our experience, within this framework, patients recover swiftly and effectively.