Objective: To examine diagnostic accuracy of semiquantitative and qualitative magnetic resonance neurography criteria in common peroneal nerve (CPN) neuropathy.
Materials and Methods: Institutional review board approval was obtained with a waiver of informed consent for this Health Insurance Portability and Accountability Act-compliant retrospective study. A review of 28 knees in 28 subjects (12 males and 16 females; age range, 13–84 years; mean [SD] age, 42  years) who had undergone magnetic resonance neurography of the knee was performed. Thirteen patients who had a final diagnosis of CPN were classified as cases, and 15 patients who lacked a final diagnosis of CPN neuropathy were classified as controls. Morphological characteristics of the CPN, including nerve T2 signal intensity, nerve size, nerve course, fascicles morphology, regional muscle edema, and fatty infiltration, and an overall assessment of the CPN as being normal or abnormal were evaluated by 2 independent radiologists blinded to the clinical history. Overall sensitivity, specificity, and accuracy compared against our reference standards were expressed as percentages. Interobserver agreements were assessed using linear weighted κ statistics.
Results: Common peroneal nerve T2 signal abnormality had the highest sensitivity (77%) in identifying CPN neuropathy. Except for T2 signal abnormality, overall specificity for the nerve morphological parameters and muscle denervation change assessed was fairly high, ranging from 94% to 100%. The consensus accuracy ranged from 68% to 79% for the morphological characteristics assessed. The interobserver reproducibility was very good (k = 0.90 to 0.91) for assessment of regional muscle denervation changes and moderate (k = 0.46 to 0.59) for morphological CPN characteristics.
Conclusion: Magnetic resonance neurography is a useful modality in supplementing the diagnosis of CPN. Using predefined classification criteria helps standardize the morphological criteria of CPN neuropathy diagnosis.