Histopathologic study of the neuroma-in-continuity in obstetric brachial plexus palsy

Operative treatment of traction lesions in obstetric brachial plexus palsy is still controversial. The authors analyzed the histopathology of neuroma-in-continuity of the upper trunk by study of the resected neuroma.

The neuroma-in-continuity of the upper trunk was studied histopathologically in 28 children with Erb palsy who had undergone resection of the neuroma and nerve reconstruction of the plexus at the age of 3 to 11 months. The authors recorded the distribution of myelinated motor nerve fibers and the proportions of collagen and regenerating nerve fibers traveling the neuroma, analyzed the relationship between the percentage of nerve fibers across the neuroma and findings of intraoperative neurophysiologic investigations and the patient's age at surgery, and compared the number of nerve fibers in C5 and C6 proximal to the neuroma with that in their normal counterparts.

In the central segment of the neuroma, the structure of the upper trunk was replaced by copious collagen and sporadic nerve fibers wrapped by an undeveloped myelin sheath, and the percentage of collagen was statistically greater than that of the normal upper trunk. The mean percentage of regenerating nerve fibers across the neuroma was 41.83 percent (95 percent confidence interval, 38.69 to 44.69 percent) and this was not statistically correlated with the outcome of intraoperative neurophysiologic investigations or the patient's age at surgery. The number of nerve fibers was statistically less in C5 and C6 proximal to the neuroma than in their normal counterparts.

The nerve structure of the neuroma-in-continuity is substantially damaged in obstetric brachial plexus palsy. Its resection followed by nerve reconstruction of the plexus is favored.