Presentation
Blunt trauma from a car crash at around 45 km/h. The patient, who was wearing a seatbelt, had the airbag fail to deploy. The patient presented to the hospital 11 days prior to this MRI with decreased muscle strength in the rotator cuff and decreased range of motion in the glenohumeral joint.
Patient Data
Postganglionic traumatic plexopathy of the left brachial plexus with long segment elevated T2 signal and caliber change of the C5-C7 roots and a 25 x 23 x 17 mm nodular thickening along the course of proximal superior and middle trunks without significant enhancement indicating rupture. The inferior trunk appears to be preserved.
Edema of the rotator cuff muscles is in keeping with early denervation injury.
Case Discussion
The degree and location of traumatic injury are crucial factors in determining the treatment approach for brachial plexus injuries. Injuries are categorized based on their location into preganglionic or postganglionic types, relative to the dorsal root ganglion of the cervical nerve roots. Preganglionic injuries typically involve high-grade damage with complete avulsion of the nerve roots, which is an unfavorable type of injury for surgical repair of the injured nerve 1.
Postganglionic injuries are further classified into six categories based on anatomic and pathophysiological criteria (Seddon and Sunderland classifications) 2. There is considerable overlap between these categories in MR imaging, leading to a more practical classification of "low grade" (nonsurgical) versus "high grade" (surgical). High-grade injuries are characterized by disruption of the brachial plexus components and traumatic neuroma-in-continuity.
Nodular thickening along the course of a nerve following trauma may be attributed to various causes, including nerve transection with retraction, adjacent hematoma, neuroma in continuity, or nerve sheath tumors 1, 3. Although neuromas can appear similar on T1 and T2 sequences, as in this case, and demonstrate a wide range of enhancement, from subtle to intense, most exhibit avid enhancement 1, 3, 4. Importantly, traumatic neuromas typically take longer to develop, with animal models showing neuroma formation occurring between 60-90 days post-injury. Early imaging (e.g., day 11 post-trauma) would not have revealed a fully formed neuroma 5.
Notably, denervation edema in skeletal muscles does not reliably differentiate between high-grade and low-grade injuries 1.
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