Novel MRI signs for differentiating neurogenic and non-neurogenic peripheral nerve Tumors: Insights from Contrast-Enhanced magnetic resonance neurography

Abstract

Objects: To investigate the specific manifestations of neurogenic and non-neurogenic tumors involving peripheral nerves on contrast-enhanced magnetic resonance neurography (CE-MRN) and explore the potential of CE-MRN in aiding differential diagnosis.

Materials and methods: Twenty-nine patients with neurogenic tumors and 23 with non-neurogenic tumors involving peripheral nerves were enrolled in this study. Both routine MRI and CE-MRN scanning were performed on all subjects. The location, pattern of involvement, classical MRI signs, and novel CE-MRN signs of nerve involvement were evaluated and compared between the two groups. The novel CE-MRN signs included "Enhanced target sign", "Nerve effacing sign", "Nerve wrapping sign", "Nerve compressing sign", "Nerve tail sign", and morphological changes of nerves. Diagnostic confidence in identifying nerve involvement and lesion conspicuity were assessed and compared between routine MRI and CE-MRN.

Results: The majority of neurogenic tumors were schwannoma (79.3 %) and involved a single nerve (75.9 %), whereas the majority of non-neurogenic tumors were malignant tumors (78.3 %) and involved multiple nerves (78.3 %) (P < 0.001). In terms of classical MRI signs, neurogenic tumors exhibited a significantly higher incidence of the "Tail sign" (75.9 % vs 13 %), "Dumbbell sign" (31 % vs 4.3 %), "Target sign" (51.7 % vs 8.7 %), and "Split fat sign" (55.2 % vs 4.3 %), while showing a lower incidence of the "Effacement of fat plane" (3.4 % vs 60.9 %) compared to non-neurogenic tumors (all p < 0.05). Regarding novel CE-MRN signs, neurogenic tumors demonstrated a significantly higher incidence of the "Enhanced target sign" (65.6 % vs 13 %) and the "Nerve tail sign" (100 % vs 13 %), while exhibiting a lower incidence of the "Nerve effacing sign" (0 % vs 52.2 %) and the "Nerve wrapping sign" (0 % vs 17.4 %) compared to non-neurogenic tumors (all p < 0.05). CE-MRN yielded significantly higher diagnostic confidence scores (2.87 ± 0.35 vs 1.75 ± 0.84), but lower lesion conspicuity scores (2.35 ± 0.71 vs 2.92 ± 0.27) compared to routine MRI (all P < 0.001).

Conclusion: CE-MRN is a valuable imaging modality for the identification of tumor-related peripheral nerve involvement, as it offers supplementary indicators and enhances diagnostic confidence.

Keywords: Contrast-enhanced magnetic resonance neurography; Magnetic resonance imaging; Peripheral nerve; Tumor.