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Erschienen in:
01.08.2015 | Ultrasound
Sonographic cross-sectional area measurement in carpal tunnel syndrome patients: can delta and ratio calculations predict severity compared to nerve conduction studies?
Erschienen in: European Radiology | Ausgabe 8/2015
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Objective
To evaluate the accuracy of two different sonographic median nerve measurement calculations in predicting carpal tunnel syndrome (CTS) severity in a study population with clinically and electrophysiologically confirmed CTS.
Methods
643 wrists of 427 patients (325 females and 102 males, age range: 17–90 years, mean ± SD: 57.9 ± 14.7) were included with CTS diagnosis based on clinical and nerve conduction studies (NCS). Cross-sectional area (CSA) measurement of the median nerve was performed at the carpal tunnel level (CSAc) and at the pronator quadratus muscle level (CSAp). Two parameters were calculated: delta (∆-CSA), which is the difference between proximal and distal measurements, and ratio (R-CSA), calculated by dividing distal over proximal measurements.
Results
Patients were classified into mild, moderate and severe CTS based upon NCS. The mean ∆-CSA (4.2 ± 2.6, 6.95 ± 2.2 and 10.7 ± 4.9 mm2) and mean R-CSA (1.5 ± 0.4, 1.95 ± 0.4 and 2.4 ± 0.7) values were significantly different between all groups (p < 0.001). Optimal cut-off values for ∆-CSA and R-CSA were 6 mm2 and 1.7, respectively, to distinguish mild from moderate disease, and 9 mm2 and 2.2, respectively, to distinguish moderate from severe disease.
Conclusion
Threshold values for the calculated sonographic parameters ∆-CSA and R-CSA are useful in predicting CTS severity compared to NCS.
Key Points
• Two proposed parameters were calculated (∆-CSA, R-CSA) and compared to NCS.
• A defined sonoanatomical proximal landmark was used for the calculation.
• Both parameters showed ability to detect CTS severity comparable to NCS.
• Cut-off values could be determined for both parameters.