Diagnostic Function of 3-Tesla Magnetic Resonance Imaging for the Assessment of Brachial Plexus Injury

Traumatic injury to peripheral nerves

This article reviews the epidemiology, classification, localization, prognosis, and mechanisms of recovery of traumatic peripheral nerve injuries (PNIs). Electrodiagnostic (EDx) assessments are critical components of treating patients with PNIs. In particular, motor and sensory nerve conduction studies, needle electromyography, and other electrophysiological methods are useful for localizing peripheral nerve injuries, detecting and quantifying the degree of axon loss, and contributing toward treatment decisions as well as prognostication. It is critical that EDx medical consultants are aware of the timing of these changes as well as limitations in interpretations. Mechanisms of recovery may include recovery from conduction block, muscle fiber hypertrophy, distal axonal sprouting, and axon regrowth from the site of injury. Motor recovery generally reaches a plateau at 18 to 24 months postinjury. When patients have complete or severe nerve injuries they should be referred to surgical colleagues early after injury, as outcomes are best when nerve transfers are performed within the first 3 to 6 months after onset.

Axial T2-DRIVE MRI myelography is highly accurate in diagnosing preganglionic traumatic brachial plexus injuries: why pseudomeningoceles should not be used as a primary diagnostic sign

AIM

To evaluate the accuracy of brachial plexus magnetic resonance imaging (MRI) utilising the three-dimensional (3D)-T2-turbo spin echo (TSE) with 90° flip-back pulse ("DRIVE") myelography in detecting nerve root avulsions in patients with traumatic brachial plexus injuries.

MATERIALS AND METHODS

A prospective study of 24 patients planned for brachial plexus reconstructive surgery following trauma from April 2019 to October 2021. Preoperative 1.5 T MRI of the brachial plexus was performed utilising axial T2-DRIVE, looking for signs of avulsions (absent dural rootlets, pauci-rootlet appearance and thickened rootlets; the presence of pseudomeningoceles was noted only as an ancillary sign). Comparison against the reference standard of extra-dural brachial plexus exploration was performed. The sensitivity, specificity, positive predictive value (PPV), negative predictive value (NPV), and accuracy were calculated.

RESULTS

Eighteen patients had at least one root avulsion at surgery, five showed isolated post-ganglionic injuries, and one had normal brachial plexus exploration. Thirty-nine avulsed roots were found at surgery (out of 108 explored in 24 patients). Preoperative MRI identified the specific avulsed roots accurately in each patient. Two false-positive diagnoses of C5 and C6 avulsions were made in one patient. On MRI, absence of the rootlets was seen in 73.2% (n=30) of avulsions, pauci-rootlet appearance in 24.4% (n=10) and thickening of the rootlets in 2.4% (n=1). Pseudomeningoceles were found only in 68.3% (n=28) of avulsions. The overall sensitivity, specificity, PPV, NPV, and accuracy of MRI were 100%, 97.1%, 95.1%, 100% and 98.1%, respectively.

CONCLUSION

3D-T2-DRIVE is highly accurate in evaluating pre-ganglionic traumatic brachial plexus injuries. Pseudomeningoceles can be considered an ancillary feature of avulsion given the clarity of rootlet visualisation by this sequence.