Ultrasonographic Findings in Isolated Neuritis of the Posterior Interosseous Nerve

Isolated palsy of the posterior interosseous nerve (PIN) can occur without nerve compression and is often referred to as isolated neuritis or neuralgic amyotrophy because of its characteristic elbow pain at the onset, lasting days to weeks with subsequent weakness. The diagnosis is based on the clinical course because, to our knowledge, there have been no objective tests, in particular imaging features, that can be used to differentiate this from other disorders. In this report, we describe the ultrasonographic findings of a case of isolated PIN palsy and compare the findings with those in unaffected individuals. In addition, the images were correlated with surgical findings.