Focused high-resolution sonography of the suprascapular nerve: A simple surrogate marker for neuralgic amyotrophy?

OBJECTIVES

To define the diagnostic value of high-resolution ultrasound (HRUS) of the suprascapular nerve (SSN) in the diagnosis of neuralgic amyotrophy (NA).

METHODS

The cross-section areas (CSA) of the SSN at the C5 root (CSA1) and the omohyoid muscle in the midclavicular line (CSA2) were assessed bilaterally in 15 healthy volunteers and 14 patients with clinically and electrophysiologically verified NA. Receiver-operator-characteristics (ROC) curves were generated and cut-off values, sensitivity, specificity, positive (PPV) and negative predictive values (NPV), likelihood (LR) and odds ratios (OR) were calculated.

RESULTS

Patients with NA had significantly higher CSA2-values than controls (6.36±2.75vs. 2.79±0.83mm2, p<0.0001) and significantly higher ratios of SSN CSA2-values of the affected vs. contralateral side (224.6±78.5% vs. 127.7±51.1%, p<0.0001). The ratios of SSN CSA2-values vs. CSA1-values (146.7±74.5% vs. 99.9±28.3%, p=0.008) and CSA1-values were also significantly higher (4.70±2.00vs. 2.90±0.90mm2, p=0.0028) than in controls. Beyond a CSA2 cut-off value of 4.2mm2, the ROC-AUC was 0.939 [0.861-1.00] when compared against healthy volunteers and 0.971 [0.901-1.00] when compared to patients with degenerative shoulder pain. Sensitivity was 85.7% [57.2-98.2%], specificity 96.7% [82.8-99.9%], PPV 92.3% [64.0-99.8%], NPV 93.5% [78.6-99.2%], OR 174.0 [14.4-2106.0] and LR 25.7 (95% confidence intervals in brackets).

CONCLUSION

SSN swelling in the lateral cervical region could be a supportive finding to identify NA patients.

SIGNIFICANCE: This method allows for the rapid sonographic identification of NA.