Ultrasonography of Peripheral Nerves

Pathology of peripheral nerves can occur secondary to a variety of etiologies, including mechanical entrapment, compression by external factors, trauma, infectious and inflammatory causes, neoplasm, or as a complication of surgery. Clinical evaluation often begins with a detailed history and focused physical exam and may include electrodiagnostic studies or advanced imaging. With recent innovations in MRI techniques, high-resolution MRI of peripheral nerves is possible and is often referred to as “MR neurography.” MR imaging can demonstrate both primary signs of nerve injury and secondary signs such as muscle denervation. Ultrasound can be used as a complementary or alternative imaging modality for diagnostic evaluation of peripheral nerves. Advantages of ultrasound include dynamic assessment of peripheral nerves, easy evaluation of the contralateral side for comparison, and utility in patients who cannot tolerate MRI or in cases where MRI is limited by metallic hardware. Ultrasound can also be used to guide diagnostic and therapeutic perineural injections with anesthetic and/or corticosteroids. This chapter reviews ultrasound findings of peripheral nerve pathology.