Magnetic resonance neurography for the evaluation of peripheral nerve, brachial plexus, and nerve root disorders

Clinical article

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Object

Treatment of spinal and peripheral nerve lesions relies on localization of the pathology by the use of neurological examination, spinal MR imaging and electromyography (EMG)/nerve conduction studies (NCSs). Magnetic resonance neurography (MRN) is a novel imaging technique recently developed for direct imaging of spinal and peripheral nerves. In this study, the authors analyzed the role of MRN in the evaluation of spinal and peripheral nerve lesions.

Methods

Imaging studies, medical records, and EMG/NCS results were analyzed retrospectively in a consecutive series of 191 patients who underwent MRN for spinal and peripheral nerve disorders at the University of California, San Francisco between March 1999 and February 2005. Ninety-one (47.6%) of these patients also underwent EMG/NCS studies.

Results

In those who underwent both MRN and EMG/NCS, MRN provided the same or additional diagnostic information 32 and 45% of patients, respectively. Magnetic resonance neurograms were obtained at a median of 12 months after the onset of symptoms. The utility of MRN correlated with the interval between the onset of symptoms to MRN. Twelve patients underwent repeated MRN for serial evaluation. The decrease in abnormal signal detected on subsequent MRN correlated with time from onset of symptoms and the time interval between MRN, but not with resolution of symptoms. Twenty-one patients underwent MRN postoperatively to assess persistent, recurrent, or new symptoms; of these 3 (14.3%) required a subsequent surgery.

Conclusions

Magnetic resonance neurography is a valuable adjunct to conventional MR imaging and EMG/NCS in the evaluation and localization of nerve root, brachial plexus, and peripheral nerve lesions. The authors found that MRN is indicated in patients: 1) in whom EMG and traditional MR imaging are inconclusive; 2) who present with brachial plexopathy who have previously received radiation therapy to the brachial plexus region; 3) who present with brachial plexopathy and have systemic tumors; and 4) in patients under consideration for surgery for peripheral nerve lesions or after trauma. Magnetic resonance neurography is limited by the size of the nerve trunk imaged and the timing of the study.

Abbreviations used in this paper: DESS = double echo steady state; EMG = electromyography; MRN = MR neurography; NCS = nerve conduction studies; STIR = short tau inversion recovery.

Article Information

Address correspondence to: Rose Du, M.D., Ph.D., Department of Neurological Surgery, Brigham and Women's Hospital, 75 Francis Street Boston, Massachussets 02115. email: rdu@partners.org.

Please include this information when citing this paper: published online August 7, 2009; DOI: 10.3171/2009.7.JNS09414.

© AANS, except where prohibited by US copyright law.

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Figures

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    Axial (A) and coronal (B) 3D DESS images obtained in a 34-year-old man with ulnar neuropathy. The patient presented with right hand pain and numbness in the ulnar distribution after an elbow joint arthroscopy; EMG/NCS showed right ulnar nerve injury, and MRN of the arm showed a diffusely abnormal ulnar nerve extending from 7 cm cephalad to 11 cm caudal to the medial condyle. The nerve was intact but enlarged, and had abnormal increased T2 signal. The patient subsequently underwent ulnar nerve transposition with improvement in his symptoms. Arrows indicate the ulnar nerve.

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    Images obtained in a 74-year-old man with radiculopathy who presented with right arm pain, numbness in the thumb and index finger, deltoid, biceps, and triceps weakness 5 months after cervical laminectomy and foraminotomies at C4–7. Electromyography demonstrated C-5, C-6, and C-7 myotomal injuries with evidence of subacute denervation changes and chronic partial denervation with reinnervation. Axial CTs of the cervical spine revealed severe neuroforaminal narrowing at bilateral C4–5 (A), right C5–6 (B), and right C6–7 (C). Abnormal increased T2 signal was shown on MRN, and mild enlargement of the right C-6 root was seen on coronal (D) and axial (E) STIR images (arrows). The patient underwent reexploration surgery for right C4–5 and C5–6 foraminotomies with initial improvement in his symptoms followed by subsequent recurrence of symptoms. Repeated MRN performed 6 months after the second surgery showed a decrease in abnormal signal in the right C-6 root (coronal STIR image, F). However, there was a new finding of abnormal signal within the cord involving the dorsal gray matter on the right adjacent to the nerve root (axial STIR image, G) consistent with intramedullary edema or gliosis.

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    Coronal, Gd-enhanced T1-weighted MR (A) and coronal STIR (B) images obtained in a 42-year-old woman with radiation plexopathy and a history of right apical hemangiosarcoma after resection and radiation therapy 6 years previously. She presented with tingling in the right shoulder and arm. Electromyography/NCS showed a mixed demyelinative and axonopathic process involving the entire brachial plexus, and MRN showed a resection cavity/operative site adjacent to enlarged right C-5, C-6, and C-7 roots and upper and middle trunks, with increased STIR signal and no significant contrast enhancement, suggestive of radiation change. The patient's clinical symptoms and radiographic findings have remained stable at follow-up.

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    Preoperative (A) and postoperative (B) coronal STIR MRN images obtained in a 53-year-old man with thoracic outlet syndrome who presented with right arm pain, paresthesias in the fourth and fifth digits, and weakness in the triceps and brachioradialis that was aggravated by lowering of his shoulders. Cervical MR images failed to demonstrate abnormalities. Repeated EMG/NCS studies demonstrated decreased amplitude in ulnar sensory nerve action potentials with normal latency and no conduction block, and MR images of the upper arm and an angiogram showed no vascular compression. The preoperative image shows the right C-7 root displaced superiorly around the right costocervical artery, and the right C-8 root displaced inferiorly by the subclavian artery. The patient underwent a right first rib resection with anterior and middle scalenotomy, and right brachial plexus neurolysis with improvement in his symptoms. The postoperative images shows C-7 and C-8 to be normally oriented and linear in their course with no abnormal signal.

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    Images obtained in a 62-year-old woman with a metastatic tumor to brachial plexus and a history of metastatic breast cancer. After a course of chemotherapy, the patient noted right index finger numbness that progressed to full arm numbness and paresis of the biceps brachii and wrist movement. Routine coronal (A) and axial (C) MR images failed to reveal abnormalities. Coronal (B) and axial (D) STIR images through the brachial plexus, however, showed abnormal increased T2 signal in the right C-6 and C-7 roots (arrows). The patient underwent exploration for biopsy which confirmed infiltrating ductal breast carcinoma within the epineurium and perineurium. Intraoperatively, the nerves looked grossly normal and selection of the biopsy site relied entirely on MRN images.

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    Coronal MRN images obtained in a 19-year-old man with traumatic avulsion and pseudomeningocele. This patient is a injured in a motorcycle accident 6 months previously, during which he sustained a left humerus fracture. He subsequently developed weakness of the left shoulder and upper arm. Left brachial plexopathy with severe loss of axons in the upper and middle trunks and milder injury to the lower trunk was revealed on EMG/NCS. Coronal MRN revealed pseudomeningoceles at C-5, C-6, and C-7 (A) and complete avulsion of the left C-7 root with retraction of the distal segment, confirming that irreversible injury had occurred (B).

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