Ultrasound combined with electrodiagnosis improves lesion localization and outcome in posterior interosseous neuropathy.

Introduction: Posterior interosseous nerve (PIN) syndrome is a rare compression neuropathy. Electrodiagnostic studies (EDx) combined with neuromuscular ultrasound (US) enable precise lesion localization and may improve patient outcome.

Methods: In 4 patients with finger extension weakness, US was used to accurately localize concentric electromyographic (EMG) needle placement in PIN muscles and to visualize the lesion site.

Results: EMG with US guidance showed decreased recruitment with abnormal configuration in PIN muscles. Active denervation was not always observed. US scanning demonstrated larger PIN diameter in the affected arm. All patients had surgical intervention to confirm EDx and US findings and had improved outcome on follow-up.

Conclusion: These cases demonstrate the benefits of augmenting EDx with US by guiding accurate electrode localization and providing diagnostic information about lesion location.