Non-Traumatic “Isolated” Posterior Interosseous Nerve Palsy: Reinterpretation of Electrodiagnostic Studies and MRIs

Publication date: Available online 27 November 2016
Source:Journal of Plastic, Reconstructive & Aesthetic Surgery
Author(s): Andrés A. Maldonado, Kimberly K. Amrami, Michelle L. Mauermann, Robert J. Spinner
IntroductionDifferent hypotheses have been proposed for the pathophysiology of posterior interosseous nerve (PIN) palsy: compression, nerve inflammation or fascicular constriction. We hypothesized that critical reinterpretation of electrodiagnostic studies (EDX) and MRIs of patients with a diagnosis of PIN palsy could provide insight into the pathophysiology and treatment.Materials and MethodsA retrospective review was performed of all patients with a diagnosis of non-traumatic PIN palsy and an upper extremity EDX and MRI. The original EDX studies and MRIs were re-interpreted by a neuromuscular neurologist and musculoskeletal radiologist respectively, both blinded to our hypothesis.ResultsFifteen patients met the inclusion criteria as having an "isolated" PIN palsy. Four cases (27%) had a defined mass compressing the PIN. The other 11 cases (73%) presented with at least one finding incompatible with the compression hypothesis: physical examination revealed weakness in muscles not innervated by the PIN in 4 cases (36%); EDX abnormalities not related to the PIN were found in 4 cases (36%); and reinterpretation of the MRIs showed muscle atrophy or nerve enlargement beyond the territory of the PIN in 9 cases (82%), without any evidence of compression of the PIN in the proximal forearm.ConclusionThe eleven patients in our series with presumed isolated, idiopathic PIN palsy had evidence of a more diffuse nerve - muscle involvement pattern, without any radiologic signs of nerve compression of the PIN itself. These data would favor an inflammatory pathophysiology, when a structural lesion compressing the nerve is ruled out with imaging.



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