Dynamic MR imaging of carpal tunnel syndrome.

OBJECTIVE: To evaluate the diagnostic value of the MR imaging syndrome before and after performance of provocative exercises in patients with dynamic carpal tunnel syndrome.

DESIGN: Fat-suppressed proton-density and T2-weighted spin-echo images of the wrist were obtained prior to and after provocative, standardized exercises. Images were interpreted in masked fashion with regard to six MR criteria of carpal tunnel syndrome: (a) bowing of the transverse ligament, (b) and (c) deformation of the median nerve at the pisiform and hamate levels respectively, (d) signal abnormality of the median nerve, (e) presence of fluid in the wrist joints and/or carpal tunnel, and (f) presence of synovial swelling.

PATIENTS: Twenty-one wrists in 20 patients with subjective complaints of carpal tunnel syndrome and equivocal or negative clinical findings and negative electrodiagnostic examinations were included (age range 21-61 years, mean 37 years, 2 men and 18 women). The diagnosis of dynamic carpal tunnel syndrome was made and confirmed by surgery in 18 of the 21 symptomatic wrists. The control group consisted of 15 asymptomatic wrists in volunteers (age range 22-60 years, mean 35 years, 8 men and 7 women).

RESULTS AND CONCLUSIONS: Sensitivities and specificities of the six MR criteria were 90.5-100%, and 6.7-86.7%, respectively, both before and after exercise. Likelihood ratios proved statistically significant differences between the symptomatic and asymptomatic wrists (P < 0.0001-0.0002) for the prevalence of all MR criteria with the exception of fluid within the carpal joints and/or carpal tunnel. Changes of the MR appearance after exercise had a low sensitivity (4.8-71.4%) but high specificity (86.7-100%) for dynamic carpal tunnel syndrome. In conclusion, MR imaging contributes to the diagnosis of carpal tunnel syndrome when clinical signs are confusing and electrodiagnostic studies are negative. Dynamic examinations improve specificity of MR imaging for such diagnosis.