Synovial Angioma of the FDP Flexor Sheath: A Rare Cause of Carpal Tunnel Syndrome
A 34 year old right hand-dominant male, who works as a chef, presented with a 4 month history of left wrist mass. It had increased rapidly in size during the final month. The patient also began to experience numbness of his left thumb, index and middle fingers. He was normally well and not on regular medications. There was no family history of note.\nAn ultrasound was initially performed which showed a large, complex cystic structure within the carpal tunnel. A subsequent MRI revealed a heterogeneous, well defined mass with fluid and solid components. The mass was located middle and ring fingers. It appeared to arise from the tendon sheath of the middle and ring finger flexors, but was not between the superficial and deep flexor tendon sheaths of the invading the tendons. It extended distally to the carpal tunnel, with overall dimensions of 19 x 24 x 38 mm. It showed peripheral enhancement and areas of necrosis, and there was no flow void (Fig. ). The median nerve had a normal appearance. In light of the clinical history and radiological features, a malignant lesion such a synovial sarcoma, was considered the likely provisional diagnosis.\nThe patient was referred to our unit for urgent review. On examination he had a mobile and palpable mass which moved from the mid palm to the volar wrist region with flexion and extension of his wrist. The mass was not adherent to overlying skin. He had full power in his left hand and there was no thenar muscle wasting. He had decreased sensation in his thumb, index and middle finger, and Tinel’s test was negative.\nHe underwent surgical exploration and removal of tumour within one week of the consultation. An extended carpal tunnel incision was made (Fig. ), from the mid palm to the volar wrist. After the TCL was divided, a large tan coloured soft-tissue tumor was visible on the ulnar aspect of the median nerve. It appeared to arise from the deep flexor tendon sheath of the ring finger, extending distally to the lumbrical muscle of the 4th ray, and it infiltrated these structures only minimally. A persistent median artery was observed overlying the median nerve, which did not appear to be involved by the tumour. The tumour was resected with macroscopic margins. Post-operative recovery was uneventful and the patient reported immediate relief of compressive median nerve symptoms.\nHistological analysis was consistent with a synovial haemangioma, comprising of numerous thin-walled blood vessels with a central cystic cavity filled with blood and fibrin (Fig. ). There was no evidence of malignancy.\nA three month follow-up confirmed complete resolution of his neurosensory symptoms and showed a well healing scar.