Magnetic Resonance Imaging appearance of regenerative peripheral nerve interface

Purpose

To describe the MRI appearance of regenerative peripheral nerve interface (RPNI) and the potential association between the MRI appearance and RPNI revision.

Material and methods

A retrospective assessment was undertaken of the MRI appearance of RPNIs performed at our institution between 1/1/2010 and 7/29/2023 with clinical correlation.

Results

Fourteen patients (8 men and 6 women, age range 31–80 years, median age 51 years) with technically adequate MRI of RPNIs were included in this study including 5 patients with below knee amputation with 5 tibial and 4 common peroneal nerves RPNI, 8 patients with above knee amputations (AKA) with sciatic RPNIs, and 1 patient following forequarter amputation with a brachial plexus RPNI. Two patients underwent revision RPNI surgery thrice (AKA-sciatic nerve) for a total of 6 RPNI revisions. On T1 weighted sequences, all RPNIs were isointense to the muscle and blended with the surrounding scar and muscle tissues whereas on T2 weighted sequences, all RPNIs were hyperintense in signal compared to the muscle. All but 1 RPNI underwent post contrast enhancement in variable patterns. No statistically significant difference in MRI appearance was found between RPNIs with or without a following RPNI revision surgery.

Conclusion

RPNI on MRI typically have a bright and intermediate signal on T2 and T1 weighted sequences, respectively, and typically undergo postcontrast enhancement in variable patterns without a statistically significant difference between the cases with and without follow-up RPNI revision. However, enhancement of RPNI should not be misconstrued as pathological.