Diagnostic accuracy of MRI in characterizing brachial plexus injuries

Abstract

Objective To analyze the diagnostic accuracy of MRI in determining brachial plexus preganglionic injury and the factors that affect the accuracy. Methods Twenty-seven patients who presented with brachial plexus root avulsion injuries underwent MRI scanning with multiple sequences before the operation.Images of MRI were reviewed for features that would lead to the diagnosis of a preganglionic injury. MRI diagnosis was then verified and compared with surgical findings and electrophysiological diagnosis. The accuracy rate for individual nerve root avulsion was calculated. Results There were direct signs and indirect signs of MRI features that indicated preganglionic injuries. The direct signs included disappearance or loss of continuity of the ventral and dorsal rootlets of the spinal nerve on coronal plane, axial plane or multiplanal reconstruction, and spinal cord shift (midline shift ＞ 1.5 mm). The indirect signs included traumatic pseudomeningocele, CSF collection in the vertebral canal, spinal cord deformation or shift, black line sign, and abnormal signals in the paraspinal muscles. Direct MRI signs of postganglionic injuries included thickening, rupture or distortion of the nerve root, with or without increase signal in T2 weighted images, and neuroma formation. Muscle denervation was also an indirect sign for postganglionic injury. The diagnostic accuracy by MRI of C5 to T1 avualsion was 59.3%,85.2%,100%,88.9% and 92.6% respectively. Conclusion The capability of MRl to evaluate lesions of each nerve root is different. A diagnosis should be made combining MRI, electrophysiological and clinical findings. Key words: Brachial plexus; Injuries; MRI; Diagnosis