Innervation of the feline eyelids.

The innervation of the eyelids is incompletely understood. This is a particular problem for those who wish to develop animal models of eyelid dysfunction in humans. Blepharospasm, for example, is a disease of uncontrolled eyelid spasm that is difficult to manage clinically because the aetiology is not understood. The anatomical literature on eyelid innervation is sparse and even conflicting. We attempted to study eyelid innervation, both sensory and motor, with injection of horseradish peroxidase (HRP) into the superior eyelid, inferior eyelid, and bulbar conjunctiva. We used 13 anesthetized weanling cats. Shape and structure of the facial nucleus varied along its rostrocaudal extent, but there was a clear demarcation of lateral and medial division. HRP-filled facial nucleus cells were ipsilateral to the injection site, and label appeared throughout the rostrocaudal length. All injection sites, including bulbar conjunctiva, labelled facial nucleus neurons located with overlapping distribution, predominantly in the dorsal part of the lateral division. Likewise, heavy labelling occurred throughout the entire ipsilateral cranial cervical ganglion and the trigeminal ganglion in all kittens. Injection of upper or lower eyelids caused some labelling in the second through the fourth cervical spinal ganglia.