The number and size of axons central and peripheral to inferior alveolar nerve injuries in the cat.

We have observed the effect of three different lesions on the inferior alveolar nerve of the cat. If the nerve is transected and the cut ends reapposed there is no significant difference between the number of myelinated axons in the nerve proximal to the lesion and the number in contralateral control nerves at 9 or 15 weeks post-operatively. Counts distal to the lesion also do not differ significantly from control values although the size of the myelinated axons is reduced. If recovery is impeded, but not completely blocked, the number of proximal myelinated axons remains at control values but the number of non-myelinated axons is reduced by 74%. If recovery is completely blocked a neuroma forms in the proximal stump and is characterised by large numbers of small myelinated axons and a relative increase in the number of non-myelinated axons. The additional axons are presumably sprouts and recurrent loops. No effects on the contralateral inferior alveolar nerve were detected. The ability to accurately reappose the cut ends of the nerve within the bony canal counts for the high level of recovery. Changes in the nerve are clearly related to the nature and extent of the injury.