Neonatal Brachial Plexus Palsies Workup

Updated: Sep 06, 2018
  • Author: Jennifer Semel-Concepcion, MD; Chief Editor: Elizabeth A Moberg-Wolff, MD  more...
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Workup

Laboratory Studies

Lab studies generally are not necessary for the diagnosis of brachial plexus palsy.

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Imaging Studies

Until the advent of MRI, computed tomography (CT) myelography was the standard method for evaluating the integrity of the brachial plexus, and it remains arguably the most sensitive radiographic study to detect nerve root injuries. A water-soluble dye is injected intrathecally, and CT scans of the area in question are obtained. The main drawbacks to the procedure are radiation exposure, the need for sedation, a significant false-positive rate, and the lack of information on the distal brachial plexus. Some medical centers have abandoned the use of CT myelography, because direct observation during surgical exploration does not always correlate with CT myelographic findings.

High-resolution MRI is the best imaging study available for evaluating neonatal brachial plexus palsy. MRI requires no radiation exposure, is noninvasive, and provides more detail than does CT myelography. This test is most useful preoperatively to show the extent of trauma, including pseudomeningocele, and the presence of roots in the neural foramen.

While of little use in providing information on the anatomy of the brachial plexus, plain radiographs can be helpful in diagnosing hemidiaphragm paralysis from phrenic nerve involvement and fractures of the clavicle or humerus. Axillary radiographs also should be performed in children who show progressive loss of external rotation, to rule out posterior shoulder dislocation.

A retrospective study by Somashekar et al indicated that ultrasonography can be used for preoperative assessment of the postganglionic brachial plexus in neonatal brachial plexus palsy. For example, ultrasonography had 84% sensitivity for upper trunk neuroma involvement and 84% for middle trunk neuroma involvement. Ultrasonographic examination also revealed the presence of shoulder muscle atrophy in 11 of 21 children evaluated, with the imaging findings leading to nerve transfer surgery in eight of the 11 patients. [15]

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Other Tests

Electrodiagnostic studies are used as an extension of the physical examination and can provide data on the severity and timing of the injury. The initial study usually is performed 2-3 weeks after injury, when signs of denervation are seen in children with moderate or severe injuries. Some authors feel that EMG provides useful information to track the reinnervation process and guide in surgical decision-making. Others feel that EMG does not provide prognostic information.

The examination typically includes study of latencies of musculocutaneous and axillary nerves in Erb's palsy. In complete injuries, motor and sensory nerve conduction studies (NCS) of median, ulnar, and, on occasion, radial nerves are performed. Sensory NCS are useful in discerning an avulsion injury; if the sensory nerve potential is intact in the context of a clinically insensate arm, an unfavorable prognosis is suggested. If respiratory distress was noted at birth, ipsilateral phrenic nerve conduction also is tested. Needle EMG is performed on muscles innervated by the affected nerve. In Erb's palsy, these muscles include the supraspinatus, deltoid, infraspinatus, triceps, and biceps; in cases of total brachial plexus palsy, the muscles tested include those above, as well as the dorsal interossei and opponens pollicis.

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