Clinical and ultrastructural study of painful neuroma.

A clinical and light and electron microscopic study of three cases of painful neuroma, surgically resected, was made. It was found (a) that painful neuromas contain large numbers of small diameter, unmyelinated fibers, in an apparently much larger proportion than myelinated fibers and (b) that a consistent, unrestrained growth of perineurial cells parallels the constant regeneration of axis cylinders. This results in the unabated formation of large numbers of "nerve minifascicles" growing in a chaotic fashion. Degeneration of axis cylinders and/or of myelin is minimal. It is suggested that the increased numbers of unmyelinated axis cylinders in traumatic neuromas could be related to the painful symptoms in some patients. It is further postulated that the unrestricted growth of perineurial cells is an attempt to contain the regeneration of axis cylinders and that the maintenance of perineurial integrity by fascicle ligation is important in the relief of painful human neuromas.