Magnetic Resonance Neurography Findings in Clinically Suspected Posterior Interosseous Neuropathy

Lateral elbow pain affects 1% to 3% of the general population. Neuropathy involving the posterior interosseous nerve (PIN) is a potential cause of lateral elbow pain but shares overlapping symptoms with other pathologies, particularly lateral epicondylitis, which may be difficult to distinguish based solely on patient history, physical examination, or electrodiagnostic testing (EDX). Conventional magnetic resonance imaging may reveal denervation edema or atrophy in PIN-innervated muscles, but abnormal signal intensity within the nerve may not be apparent.

By incorporating magnetic resonance neurography (MRN) as a diagnostic tool, physicians may be able to identify peripheral nerve pathologies and differentiate PIN neuropathy from other conditions.

Cross-sectional study; Level of evidence, 3.

The authors conducted an institutional review board-approved retrospective study to evaluate MRN findings of patients with clinically suspected PIN neuropathy. Patients were initially identified via a radiology report database. Patients with previous elbow surgery or trauma and those with EDX-confirmed Parsonage-Turner syndrome were excluded. The cohort was age-matched and compared with a control group of patients with clinically suspected cubital tunnel syndrome. Two radiologists, blinded to patient symptoms, graded the MRN examinations focusing on peripheral nerves, muscles, and extensor tendon pathology. Independent-samples t tests and chi-square tests were used to compare means and proportions, respectively, between the 2 cohorts.

The final cohort consisted of 47 patients with suspected PIN neuropathy and 47 control patients. No significant demographic differences were found between the groups. Statistically significant findings in the study cohort compared with the control group included abnormal T2-weighted hyperintensity of the PIN-innervated extensor muscles (P = .0052), and the PIN (P = .0002), as well as enlargement of both the PIN (P < .0001), and the radial nerve proper (P = .0410).

This study found that MRN can identify imaging characteristics indicative of PIN involvement compared with the control group. Future studies should focus on determining the prognostic value of these MRN findings for nonsurgical versus surgical intervention.