Innervation pattern of the temporalis muscle.

The purpose of this article is to describe the neural anatomy of the temporalis muscle as dissected along the intramuscular temporal fascial plane. This sagittal plane is a natural cleavage plane of the muscle, which is explored along with its relationship to the deep temporal nerve. Eight temporalis muscle specimens were removed in their entirety from 8 preserved cadavers. The muscles were selected based on whether they were grossly intact prior to procurement for processing. The muscle specimens were then processed over a 3-month period using Sihler's staining technique. Muscle dissection was performed along the intramuscular fascial plane under an operating microscope, taking care to preserve the underlying nerve and arterial anatomy. Dissections demonstrated an anterior and posterior division of the deep temporal nerve running within the deep portion of the muscle below the intramuscular fascial plane. This fascial layer provided a natural dissection plane to expose and evaluate the underlying nerve and arterial anatomy. In all specimens the deep temporal artery originated with the anterior temporal nerve and then branched into an anterior and posterior division. The innervation density and nerve caliber of the anterior portion of the muscle was much greater than that of the posterior, correlating with a greater anterior muscle bulk. This may have implications in differences in fiber type and functional regionalization of the muscle. The results of this anatomic study support the finding of an anterior and posterior division of the deep temporal nerve within the deep portion of the temporalis muscle. In addition, differences in the innervation density and muscle bulk lend credence to the possibility of regional muscle specialization. The natural cleavage plane of the intramuscular temporal fascia may have clinical ramifications for temporalis myofascial flaps while preserving the underlying neural anatomy to allow for normal residual temporalis muscle function.