Internodal segments in human laryngeal nerves.

The laryngeal nerves of a recently deceased patient were examined in order to determine whether the prenatal elongation of the recurrent nerves (especially of the left) is accompanied by significant elongation of internodal segments among their myelinated fibres. No evidence was found to support this notion. In the nerve roots of the cauda equina, internodal elongation is known to accompany ascent of the spinal cord during fetal life. The difference in behaviour in the two cases seems to lie in the fact that the laryngeal nerves reach their final positions before myelination commences, whereas the spinal nerve roots elongate later, at a time when Schwann cell multiplication has largely ceased.