MRI appearance of regenerative peripheral nerve interface

Abstract

PurposeTo describe the MRI appearance of Regenerative peripheral nerve interface (RPNI) and the potential association between the MR appearance and RPNI revision. Material and methodsA retrospective assessment was undertaken of the MR appearance of RPNIs performed at our institution between 1/1/2010- 7/29/2023 with clinical correlation. Results14 patients (8 males, 6 females, 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 (BKA) with 5 tibial and 4 CPN RPNI, 8 patients with above knee amputations (AKA) with sciatic RPNIs and one patient following forequarter amputation with a brachial plexus RPNI. Two patients had undergone revision RPNI surgery x3 (AKA-sciatic nerve) for a total of 6 RPNI revisions. On T1 weighted sequences, all RPNIs were isointense to muscle and blended with the surrounding scar and muscle tissues while on T2 weighted sequences, all RPNIs were hyperintense in signal compared to muscle. All but one RPNI underwent post contrast enhancement in variable patterns. No statistically significant difference in MR appearance was found between RPNIs with or without a following RPNI revision surgery. ConclusionRPNI on MRI typically have a bright and intermediate signal on T2 and T1 weighted sequences accordingly, and typically undergo postcontrast enhancement in variable patterns without a statistically significant difference between cases with and without a following RPNI revision. Enhancement of RPNI should not be misconstrued as pathological.