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Magnetic resonance imaging as a first-choice imaging modality in carpal tunnel syndrome: new evidence.

BACKGROUND
Carpal tunnel syndrome (CTS) is the most common type of peripheral nerve compression. Magnetic resonance imaging (MRI) is becoming more popular in practice in the evaluation of CTS.


PURPOSE
To evaluate the diagnostic value of MRI in CTS.


MATERIAL AND METHODS
A cross-sectional study of 39 wrists was conducted. Clinical and nerve conduction study findings were evaluated and graded according to the Boston Carpal Tunnel Questionnaire (BCTQ) and the American Association of Neuromuscular and Electrodiagnostic Medicine. MRI was performed using a 1.5-T scanner. MRI parameters included cross-sectional area (CSA) of the median nerve and the ratio change in CSA at four levels: distal radioulnar joint (DRUJ-CSA); pisiform (p-CSA); middle of the carpal tunnel (i-CSA); and hook of hamate. The ratio change in CSA was expressed as p-CSA/DRUJ-CSA and ΔCSA (difference between iCSA and DRUJ-CSA), the flattening ratio of the median nerve, the thickness of the flexor retinaculum, flexor retinaculum bowing ratio, signal intensity ratio of the median, nerve and hypothenar muscle signal intensity.


RESULTS
With a cutoff point of 10.9 mm2 of the p-CSA, MRI had a sensitivity and specificity of 97.4% and 80% for diagnosis of CTS, respectively. There was a significant association between the clinical and electrophysiological stage with MRI findings (P < 0.001). There was a positive correlation between the BCTQ score and MRI parameters (0.5 < r < 0.7, P < 0.01).


CONCLUSION
MRI has good diagnostic value in evaluating CTS. We recommend using p-CSA ≥10.9 mm2 and ΔCSA ≥2.3 mm2 as MRI diagnostic criteria of CTS.