Pathway of the primary afferent nerve fibres serving proprioception in monkey extraocular muscles

Following intracranial section of either the oculomotor or ophthalmic nerve, Wallerian degeneration studies revealed 1.38-3.7% of nerve fibres in the nerves to the inferior and superior rectus muscles were of ophthalmic nerve origin; more than half of them were unmyelinated. The results of the two experiments were complementary. The proportion of fibres identified as sensory is substantially smaller than the 10%, estimated in other studies, required to serve muscle receptors. These results indicate, contrary to some reports, that a substantial majority of proprioceptive fibres are conducted from extraocular muscles to the brainstem in the motor nerves and that their somata are not housed in the trigeminal ganglion.