Objective: To compare accuracy of ultrasound and MRI for detecting focal peripheral nerve pathology, excluding idiopathic carpal or cubital tunnel syndromes.Methods: We performed a retrospective review of patients referred for neuromuscular ultrasound to identify patients who had ultrasound and MRI of the same limb for suspected brachial plexopathy or mononeuropathies, excluding carpal/cubital tunnel syndromes. Ultrasound and MRI results were compared to diagnoses determined by surgical or, if not performed, clinical/electrodiagnostic evaluation.
Results:We identified 53 patients who had both ultrasound and MRI of whom 46 (87%) had nerve pathology diagnosed by surgical (n 5 39) or clinical/electrodiagnostic (n 5 14) evaluation. Ultrasound detected the diagnosed nerve pathology (true positive) more often than MRI (43/46 vs 31/46, p , 0.001). Nerve pathology was correctly excluded (true negative) with equal frequency by MRI and ultrasound (both 6/7). In 25% (13/53), ultrasound was accurate (true positive or true negative) when MRI was not. These pathologies were typically (10/13) long (.2 cm) and only occasionally (2/13) outside the MRI field of view. MRI missed multifocal pathology identified with ultrasound in 6 of 7 patients, often (5/7) because pathology was outside the MRI field of view.Conclusions: Imaging frequently detects peripheral nerve pathology and contributes to the differential diagnosis in patients with mononeuropathies and brachial plexopathies. Ultrasound is more sensitive than MRI (93% vs 67%), has equivalent specificity (86%), and better identifies multifocal lesions than MRI. In sonographically accessible regions ultrasound is the preferred initial imaging modality for anatomic evaluation of suspected peripheral nervous system lesions. Neurology â 2013;80: [1634][1635][1636][1637][1638][1639][1640] Nerve imaging augments patient management by providing information regarding lesion morphology, anatomic location, relationship of lesions to surrounding soft tissue, and evaluation of areas difficult to evaluate by electrodiagnostic testing. Imaging can also identify peripheral nerve lesions that are not apparent on electrodiagnostic testing. Types of peripheral nerve abnormalities suited to visualization by imaging include changes in nerve caliber, continuity, and echogenicity or magnetic resonance signal characteristics.1-3 Imaging can identify peripheral nerve tumors, traumatic neuromas, lacerations, entrapments with nerve damage, inflammation, demyelinating features, and infections. [4][5][6][7][8][9][10][11][12][13][14][15] Ultrasound and MRI are the most commonly used methods for visualizing peripheral nerves. Ultrasonography of nerve lesions impacts management beyond the electrodiagnostic findings in as many as 43% of patients 16 and, by identifying nerve continuity, can change surgical decisions after traumatic neuropathies.17 MRI visualizes nerves, characterizes soft tissue structures when evaluating atypical sites of compression, identifies features of malignancy in peripheral ner...