The intermediate root of the trigeminal nerve in the dog (Canis familaris).

Abstract

AbstractThe intermediate root of the trigeminal nerve in the dog has been investigated both macroscopically and microscopically. Sixty‐two trigeminal complexes (trigeminal ganglion, trigeminal roots and the portion of the pons to which the roots were attached) in the dog were dissected out and removed. Each of the complexes was fixed in 10% formalin, dehydrated and embedded in paraffin. The paraffin blocks were cut serially at 10 μ. Every other slide was either stained with Luxol Fast Blue or impregnated with Bodian's silver method. In all cases, between the motor and sensory roots an intermediate root composed of one distinct rootlet was identified. Most frequently the intermediate root was attached to the pons from 0.5 to 3.0 mm lateral to the motor root and rostral to the sensory root from 0.5 to 2.0 mm. From its pontine attachment the intermediate root extended anteromedially for a distance of from 2.0 to 5.0 mm before it became incorporated in the lateral aspect of the free motor root. Closer to the trigeminal ganglion the motor root and the intermediate root fused with the expanding sensory root. The fibers in the intermediate root ranged from 1.5 to 7.5 μ in diameter with the majority of fibers (60 to 70%) having a diameter of from 4.0 to 6.0 μ. Approximately 10% of the fibers were unmyelinated. The total number of fibers in the intermediate root varied from 170 to 416 with an average of 266 fibers. The morphological data obtained in an experimental animal such as presented in this paper may provide a basis for future experimental work on the clarification of the functional role of the trigeminal intermediate root.