Objective: Detection and pattern analysis of fascicular nerve hyperintensities in the T2-weighted image are the backbone of magnetic resonance neurography (MRN) as they may represent lesions of various etiologies. The aim of this study was to assess the prevalence of fascicular nerve hyperintensities in healthy individuals with regard to a potential association with age or cerebral white matter lesions.

Methods: Sixty volunteers without peripheral nerve diseases between the age of 20 and 80 underwent MRN (high-resolution T2-weighted) of upper (median, ulnar, radial) and lower (sciatic, tibial) extremity nerves and a fluid-attenuated inversion recovery (FLAIR) sequence of the brain. Presence of peripheral nerve hyperintensities and degree of cerebral white matter lesions were independently rated by two blinded readers and related to each other and to age. T test with Welch's correction was used for group comparisons. Spearman's correlation coefficients were reported for correlation analyses.

Results: MR neurography revealed fascicular hyperintensities in 10 of 60 subjects (16.7%). Most frequently, they occurred in the sciatic nerve (8/60 subjects, 13.3%), less frequently in the tibial nerve at the lower leg and the median, ulnar, and radial nerves at the upper arm (1.7-5.0%). Mean age of subjects with nerve hyperintensities was higher than that of those without (60.6 years vs. 48.0 years, p = 0.038). There was only a weak correlation of nerve lesions with age and with cerebral white matter lesions, respectively.

Conclusion: Fascicular nerve hyperintensities may occur in healthy individuals and should therefore always be regarded in conjunction with the clinical context.

Key points: • MR neurography may reveal fascicular hyperintensities in peripheral nerves of healthy individuals. Fascicular hyperintensities occur predominantly in the sciatic nerve and older individuals. • Therefore, fascicular hyperintensities should only be interpreted as clearly pathologic in conjunction with the clinical context.