US imaging of the musculocutaneous nerve

Abstract

US is promising for evaluating traumatic injuries of the MCN. By providing unique information on the entire course of the nerve, US can be used as a valuable complement of clinical and electrophysiologic findings.

High-resolution 3-Tesla magnetic resonance neurography of musculocutaneous neuropathy

“…1,[5][6][7]9,11 Most injuries to the musculocutaneous nerve involve the brachial plexus concomitantly, as was seen in our patients. 9 Rarely, patients present with isolated traumatic injury to the musculocutaneous nerve. 11 The clinical presentations of patients with musculocutaneous nerve injuries depend on the site of the lesion.…”

“…5 High-resolution MRN and ultrasound imaging are play an important role in the diagnostic algorithm of peripheral neuropathies because they allow direct visualization of normal and abnormal nerves as well as the perineural compressive lesions. 1,3,9,12 Acute muscle denervation presents as uniform T2 hyperintensity on MRN within the first 24 to 48 hours, whereas these changes may not be depicted on EMG for 2 to 3 weeks. 5 Depiction of musculocutaneous nerve continuity is important because an earlier surgical intervention is associated with better prognosis.…”

“…The normal nerve is sub 5-mm in diameter, T1 and T2 isointense, and barely apparent on MRN as it courses through the various musculofascial planes of the upper arm. 9 An abnormal nerve is, however, easily apparent as an enlarged and T2 hyperintense structure along the expected course of the musculocutaneous nerve. It can be differentiated from the adjacent vessels due to its nonbranching configuration and lack of tortuosity.…”

“…Previous published reports have discussed the ultrasound and MRI findings that are consistent with musculocutaneous neuropathy but none have successfully delineated the entire course of the abnormal musculocutaneous nerve and associated brachial plexopathy. 5,9 The higher resolution and higher contrast of 3T MRN compared with those at 1.5T allows improved visualization of the specific segmental brachial plexus as well as associated peripheral nerve abnormalities. 10 The high resolution MRN protocol used at our institute has been highlighted in Table I (A and B).…”

“…In patients with more distal injuries, pain and paraesthesia may be present along the lateral aspect of the forearm in the lateral antebrachial cutaneous nerve distribution. 5,9 The physical examination usually reveals flaccidity of the biceps and an absent biceps reflex. 7 However, the clinical presentation may vary due to aberrant branching patterns of the musculocutaneous nerve and anastomoses between musculocutaneous and median nerves.…”