Carpal Tunnel Syndrome: Diagnostic Application of MRI and Sonography

ABSTRACT

OBJECTIVE: The diagnosis of carpal tunnel syndrome(CTS) can usually be made on the basis of clinical criteria and nerve conduction velocity. Until now, radiological examinations cannot give great influences on diagnosis and treatment of CTS. Recently, technology of MRI and sonography was advanced significantly as widely applicable they were used widely in the neurosurgical field. We investigated the usefulness of high resolution MRI and sonography for the diagnosis of CTS. METHODS: MRI of 30 wrists in 16 patients who had been clinically diagnosed as CTS was performed using axial T1-weighted and short tau inversion recovery sequences. The study of sonography consisted of 17 wrists in 10 patients and control group of 14 wrists in 7 people who were asymptomatic. We investigated the increased median nerve signal, swelling and flattening of the median nerve, bowing of the flexor retinaculum, and the change of median nerve configuration during wrist flexion and extension. RESULTS: Increased signal of the median nerve was seen in 14 patients(88%), proximal swelling and distal flattening of the median nerve in 13(81%), and bowing of the flexor retinaculum in 13(81%) by MRI. Increased signal of the thenar muscles was found in 13 wrists, which was more frequent than gross thenar muscle atrophy(9 wrists). MRI revealed causative pathologies in 5 patients, which were tumor (1), radius fracture (1), and tenosynovitis (3). The sonography revealed more increased flattening ratio(3.4+/-0.7) and increased cross area(16.5+/-7.7cm2) of the median nerve than control group(2.4+/-0.5 in flattening ratio and 7.2+/-1.4cm2 in cross area). There was no configuration change during wrist flexion and extension. But, no movement of the median nerve, suggesting adhesion, was revealed during wrist flexion and extension in one wrist. CONCLUSION: Although most cases of carpal tunnel syndrome are clinically straightforward, those with confusing clinical pictures may benefit from imaging studies. Imaging criteria for the diagnosis of carpal tunnel syndrome can apply to both sonography and MRI.