Cell counts in the trigeminal ganglion of the cat after inferior alveolar nerve injuries.

This investigation was designed to determine the change in cell numbers in the trigeminal ganglia following unilateral section of one of its peripheral branches. In 9 young adult cats, under general anesthesia, the inferior alveolar nerve was transected. In 3 of the animals the cut ends were reapposed and in the other 6 regeneration was blocked. After 15 weeks the trigeminal ganglia were removed, and the number of neurons present estimated by counting nucleoli in every third section. The counts were compared with those obtained from 3 unoperated control animals. The mean number of cells in the ganglia of control animals was 14,324 with no statistically significant difference between sides. There was no significant difference between counts from opposite sides of cats whose nerves were allowed to regenerate. In the animals in which regeneration was prevented the mean count on the operated side was 13,874 and on the unoperated 18,374. These differences were statistically significant and appeared to result from an increase in cell counts on the unoperated side rather than a reduction in the counts on the operated side. This may be explained by the presence of neurons with inconspicuous nucleoli in normal ganglia, which are stimulated to enlarge and become more prominent following peripheral nerve injury. This change could occur on both sides and would mask cell loss on the operated side and produce an apparent increase in the count on the unoperated side.