Spatial anatomy of facial nerve fibers--a preliminary report.

Horseradish peroxidase (HRP) was used to tag axons to the orbicularis oculi muscle in eight adult cats. Retrograde axonal transport in some animals resulted in fiber labelling such that the spatial anatomy of fibers was determined. In those few animals in which labelling occurred, a definite spatial orientation was retained in the extra-temporal nerve. Problems with the HRP technique are discussed in the paper, and the literature is reviewed with regard to spatial orientation of facial nerve axons. This technique, previously used to label neurons in the facial nucleus, appears to be of value in labelling of the peripheral fibers as well.