The Fascial Planes of the Temporal Region Related to the Frontal Branch of the Facial Nerve

Sir: We read with great interest two recent articles regarding the anatomical study of the course of the frontal branch of the facial nerve: (1) the article by Agarwal et al. entitled “The Course of the Frontal Branch of the Facial Nerve in Relation to Fascial Planes: An Anatomic Study” (Plast Reconstr Surg. 2010;125:532–537)1; and (2) the study by Trussler et al. entitled “The Frontal Branch of the Facial Nerve across the Zygomatic Arch: Anatomical Relevance of the High-SMAS Technique” (Plast Reconstr Surg. 2010;125:1221–1229).2 In the first article, Agarwal et al. describe the frontal branch of the facial nerve as it crosses the zygomatic arch within the innominate fascia, which is located deep to the superficial musculoaponeurotic system (SMAS) and superficial temporal fascia. They beautifully show the hemiface dissection in a layer-by-layer fashion and illustrate histologic evaluation of the relationship between the nerve and the fascial planes above and below the zygomatic arch. Their facial dissection demonstrates that the frontal branch travels within the innominate fascia as it crosses the zygomatic arch into the temporal region. In the second article, Trussler et al. defined the depth and fascial boundaries of the frontal branch of the facial nerve over the zygomatic arch using histologic evaluation. They demonstrated that the frontal branch coursed under a separate fascial plane, the parotid-temporal fascia, which is deep to the SMAS in its course to the zygomatic arch and remained within this deep fascia over the arch. They concluded that the frontal branch of the facial nerve was protected by a deep layer of fascia, termed the parotid-temporal fascia, which is separate from the SMAS as it travels over the zygomatic arch. We agree with the authors that the position of the frontal branches of the facial nerve were described in the literature on two-dimensional nerve trajectory, with conflicting descriptions of the fascial depth of the frontal nerve branches, such as in subcutaneous tissue,3 within the superficial temporal fascia,4 in the loose areolar layer5,6 and in close proximity to the zygomatic periosteum.7 The authors stated that the confusion stems in part from the dense adherence of fascial planes in preserved cadavers. Also, the inconsistency of nomenclature used to describe the different fascial layers makes it more difficult to understand the anatomy in this region. Generally, there are nine layers in the temporal region, including the skin, the subcutaneous tissue, the superficial temporal fascia, the loose areolar layer, the superficial layer of the deep temporal fascia, the superficial temporal fat pad, the deep layer of the deep temporal fascia, the deep temporal fat pad, and the temporalis muscle. The superficial temporal fascia (temporoparietal fascia) in the temporal region is the most superficial layer beneath the subcutaneous tissue. It is continuous with the galea superiorly, the frontalis muscle anteriorly, and the SMAS inferiorly. Deep to the superficial temporal fascia is a loose areolar fascial layer, which is called the innominate fascia by Agarwal et al. in the first article,1 the parotid-temporal fascia by Trussler et al. in the second article,2 and the intermediate temporal fascia by Wang et al. in a Chinese journal in 1992.8 Deep to the fascia is the deep temporal fascia that covers the temporalis muscle. Wang et al.8 stated that the intermediate temporal fascia was in loose continuity with the parotid masseteric fascia in the cheek. The frontotemporal branch of the facial nerve exited the parotid gland within the parotid-masseteric fascia and continued within the intermediate temporal fascia across the zygomatic arch. The result is the same with Agarwal et al. and Trussler et al., although the nomenclature is different. It is necessary to clarify the relationship of the fascial planes of the temporal region with consistent nomenclature, because the planes may be obliterated when previous surgical procedures have been performed in this region. We suggest that the fascia be named by its location as the intermediate temporal fascia, because it is located between the superficial and the deep temporal fascia. It is also uniform in the temporal region and easy to understand. Daping Yang, M.D. Department of Surgery Second Hospital of Harbin Medical University Harbin, Heilongjiang Province, China Jenny F. Yang, B.Sc. Steven F. Morris, M.D., M.Sc. Department of Anatomy and Neurobiology and Department of Surgery Dalhousie University Halifax, Nova Scotia, Canada

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