Sonographic Evaluation of Trigger Finger at the Wrist and Carpal Tunnel Syndrome Resulting From a Deep Soft Tissue Leiomyoma

Trigger finger at the wrist is a unique condition in which finger motion results in triggering at the wrist. Suematsu et al1 classified this condition into 3 types: type A is caused by a tumor on the flexor tendon or flexor tendon sheath; type B is from an anomalous muscle belly; and type C is from a combination of a tumor and an anomalous muscle belly. The etiology is typically identified with imaging and confirmed on surgical exploration. We present a case of a deep soft tissue leiyomyoma triggering at the distal margin of the flexor retinaculum, causing both triggering of the fingers at the wrist and carpal tunnel syndrome. A 30-year-old right-hand–dominant woman presented with a 3-month history of atraumatic right volar wrist pain, “clicking” at the wrist with finger flexion, intermittent shooting pain and numbness into her fingers, and mild grip weakness. She otherwise denied persistent sensory loss or paresthesias. Physical examination of the right wrist and hand were only remarkable for a palpable click over the volar wrist with active finger flexion and extension and a positive Tinel sign. There were no palpable masses. Her range of motion, strength, and sensation were normal. Radiographs of the right wrist did not reveal any abnormalities. Sonography of the right wrist revealed a well-defined, noncompressible, heterogeneous, relatively hypoechoic mass measuring 18 mm in diameter (long axis) at the level of the carpal tunnel and in the vicinity of the second and third flexor tendons (Figure 1, A and B). The mass did not show any increased signal on power Doppler imaging. On dynamic evaluation, flexion and extension of the fingers caused the mass to abruptly translate in and out of the carpal tunnel (Videos 1 and 2). The median nerve measured at the pisiform was mildly enlarged, with a crosssectional area of 12 mm2. A cross-sectional area of greater than 10.5 to 11 mm2 at the level of the pisiform bone has been considered indicative of carpal tunnel syndrome.2,3 Magnetic resonance imaging (MRI) of the right wrist with contrast was obtained for further characterization and surgical planning. It revealed a 13 × 6 × 16-mm hyperintense T1 and mildly hyperintense T2 lesion with diffuse enhancement just distal to the carpal tunnel (Figure 1C). The lesion appeared to be localized between the flexor tendons and base of the third metacarpal. The patient was subsequently scheduled for an open excision of the soft tissue mass and carpal tunnel release. Surgical exploration through a longitudinal incision over the volar aspect of the wrist with complete release of the transverse carpal ligament revealed a 2 × 1-cm wellencapsulated, gray-white soft tissue mass that was adherent to the finger flexors (Figure 1D). Substantial inflammation of the tenosynovium was also noted within the carpal tunnel, prompting tenosynovectomy of the finger flexors. The mass was sharply excised without difficulty and sent for pathologic analysis. Histologic examination of the mass revealed spindle cells, and immunohistochemical analysis yielded positive results for α-smooth muscle actin and showed absence of nuclear β-catenin and S100 protein. These findings were most consistent with a leiomyoma. The patient followed up 12 days postoperatively and reported complete resolution of clicking, pain, and finger paresthesias. There have been 2 prior case reports that presented leiomyomas at the wrist, one resulting in triggering of the middle finger at the wrist4 and the other resulting in carpal tunnel syndrome.5 Our case is unique in that this individual had both triggering of the finger at the wrist and carpal tunnel syndrome. Furthermore, we were able to correlate sonographic characteristics with MRI and surgical pathologic findings. Sonographic characterization of soft tissue masses typically includes assessment of the size, depth, margins, echogenicity, consistency, vascularity, and relationship with surrounding structures. These features help differentiate between simple cystic, complex cystic, and solid lesions. Characteristic features of cystic lesions include sharp margins, internal hypoechogenicity or anecho genicity with a homogeneous echo texture, the presence of posterior acoustic enhancement, and the absence of intralesional vascularity.6 However, it is not uncommon for solid lesions to be mistaken as cystic. Lee et al6 reviewed 23 soft tissue masses incorrectly interpreted by sonography to be cystic lesions. It was noted that small masses (1–2 cm in diameter) tended to appear avascular on color Doppler imaging and were more likely to be mistaken as cystic. Additionally, although not uniformly observed, avascularity appeared to be evident on giant cell tumors of the tendon sheath, schwannomas, fibromas of the tendon sheath, gran-