Periorbital and Temporal Anatomy, “Targeted Fat Grafting,” and How a Novel Circulatory System in Human Peripheral Nerves and Brain May Help Avoid Nerve Injury and Blindness During Routine Facial Augmentation

The paper “Anatomical Study of Temporal Fat Compartments and its Clinical Application for Temporal Fat Grafting”¹ in this issue is important to the aesthetic surgeon on a number of levels. The authors’ description of temporal anatomy can be translated directly to the surgical correction of temporal hollowing. In addition, their observations suggest ways to avoid some of the most disastrous complications of periorbital and temporal augmentation such as nerve injury and blindness. This work supports 2 of our clinical impressions: that safe and effective facial augmentation requires as much skill as surgery; and of all the specialties, it is the aesthetic surgeon who most requires an expert understanding of facial anatomy.

PERIORBITAL AND TEMPORAL ANATOMY

The authors first define the boundaries of the temporal fossa before illustrating the 10 layers as defined by the classic work by Davidge et al.² Their meticulous dissections identify the 2 known subcutaneous compartments of the temporal region: the lateral temporal-cheek and the lateral orbital. However, the authors’ diverge from past work as they describe the loose areolar layer beneath temporoparietal fascia (TPF) as a well-defined region. They further subdivide the areolar layer into superior and inferior compartments. This anatomy is beautifully presented in the authors’ Figure 4A, a cross-section of the temporal region viewed from lateral to medial. Cross-sectional dissections are the most difficult to perform without disturbing the septal boundaries between compartments. They are also the most valuable for precise facial augmentation because they enable the aesthetic surgeon to envision a 3-dimensional model. We congratulate the authors for this work.

Figure 4.

Lymphatic injections can travel to nerves. (A) We injected a lymphatic (black arrow) traveling to this nerve with molecular gold. (B) Imaging shows gold particles not only in perineurium (white arrow), but in endoneural channels as well (400x).

The authors’ findings agree with, and further expand, our current model of facial anatomy. Previous models suggested that adipose tissue exists as a confluent layer throughout the entire face. These models have been supplanted by our current understanding that adipose tissue is regionally compartmentalized. We find it helpful to simplify facial anatomy with a model that applies to all regions with minor variations specific to each region.

Superficial and deep fat occur over most regions of the trunk and thorax. In the face, the distribution of deep fat is more restricted due to the specific needs and functions of each region. The authors define the loose areolar layer as a deep fat compartment deep to superficial fascia (superficial temporal fascia or TPF), analogous to the finding of SOOF, buccal fat, and deep cheek fat deep to the superficial fascia (SMAS) elsewhere on the face. The inferior temporal septum subdivides the loose areolar fat into upper and lower compartments. This novel finding is repeated in other deep fat compartments, including the SOOF (upper/lower) and deep cheek fat (medial/lateral), and shows how basic structural designs are iterated in different anatomical regions. The inferior temporal septum is formed by a fusion between superficial and deep temporal fascia. SMAS fusion zones determine the deep fat compartments. The ITS is analogous to the orbicularis oculi retaining ligament (SMAS-periosteum) and to the lateral border of the buccal space (SMAS-masseteric fascia).

We would offer one caveat when analyzing temporal hollowing: the appearance of temporal hollowing may occur due to age-related descent of the temporal lobe of the buccal fat pad. The authors noted adipose tissue directly above the temporalis fascia.

This is the temporal lobe of the buccal fat.³ If one critically analyzes an aging face with prominent jowls, one sees loss of projection in the submalar region. The buccal space expands with age due to stress imparted by muscles of mastication.⁴ Buccal fat prolapses inferiorly, often to the inferior border of the mandible. This is part of a cascade. As buccal fat in the cheek descends, it pulls with it the temporal lobe leading to marked temporal hollowing. The diagnosis is confirmed by using the tilt test.

“TARGETED FAT GRAFTING”

The authors summarize their approach to temporal augmentation with the statement “targeted fat grafting in an anatomically correct site via an anatomically appropriate incision.”¹ They access all 4 compartments at the intersection of the temporal and anterior hairline, shown in the authors’ Figure 9A. The description of loose areolar tissue as deep fat having 2 separate compartments provides the information needed for precise augmentation. It is noteworthy that the authors’ technique results in movement of the cannula parallel to the inferior temporal septum. Motion parallel to the inferior temporal septum, a SMAS fusion zone, helps avoid damaging structures that transit from superficial to deep along these membranes including blood vessels, nerves, and lymphatics.^4,5

“Targeted” or site-specific facial augmentation is superior to technique-based approaches. It is also always safer. We have heard the statement made that cannula position directly on periosteum with the bevel down (a technique-based approach) ensures safety in complication-prone regions. We could not disagree with this more.

HOW A NOVEL CIRCULATORY SYSTEM IN HUMAN PERIPHERAL NERVES AND BRAIN MAY HELP AVOID NERVE INJURY AND BLINDNESS DURING ROUTINE FACIAL AUGMENTATION

An expert understanding of the basic structural designs of anatomy is an absolute requirement to avoid nerve injury and blindness during routine facial augmentation. The authors suggest the anterior (medial) 1/2 of the deep temporal fat is a “danger zone.”

We suggest an even broader admonition: injection into a temporal or periorbital lymphatic can travel to the optic nerve or brain. Only 4 pieces of information are required to explain.

An Extravascular Circulatory System Exists Throughout the Human Nervous System

Heldermon et al used the term “extravascular neurocirculation” to describe this system. The entire meningeal surface of dura and the covering of nerves (epineurium) are networks of interconnected, avascular neurochannels (Figure 1).

Figure 1.

(A) The entire meningeal surface of human dura is an interlaced network of neurochannels (black arrow). (B) The histology of dura shows vessels (V) with intervening channels (C). This circulatory system has molecular and structural characteristics similar to xylem/pholem (ie, vessels and tracheids) (100×). (C) Nerves are invested by a prolific network of neurochannels (black arrow). (D) Neurochannels exist in all layers including the perineurium seen here (white arrows) (1200×3D volume view).

The Primary Drainage of the Neurocirculation is From the Temporal Fossa

Cerebrospinal fluid in the human brain ultimately drains to a plexus in the temporal fossa, before these vessels exit the skull and travel along the posterior internal jugular vein to the thoracic duct (Figure 2). We recently “rediscovered” this anatomy, only to find that Paul Mascagni identified and illustrated this over 200 years ago.⁶

Figure 2.

Cerebrospinal fluid ultimately drains to a plexus of vessels in the temporal fossa (black arrows). We have cannulated the falx in the dissection. This is a flow system from sagittal sinus to thoracic duct.

CSF Drains Secondarily From Neurochannels Directly to Facial Lymphatics

Brierly and Fields described this communication in 1948.⁷ One can see direct neurochannel-to-lymphatic bypasses in the periorbital region, at points of fixation between galea and periosteum, and in the anterior temporal fossa (Figure 3).

Figure 3.

Secondary drainage of CSF occurs from neurochannels through bony foramina directly to lymphatics. (A) Neurochannels exist the skull at the occipital protuberance (black arrow). (B) We injected these channels with fluorescent dye. (C) Dura is turned down. (D) The dura, as well as the arachnoid, fluoresces. This is iatrogenic retrograde flow from lymphatic vessels to brain.

Intralymphatic Injections Can Travel to Nerve and Brain

Intranasal injections can travel to the brain via the olfactory nerve.^7,8 Direct lymphatic injection can travel retrograde into neurochannels in the perineurium and endoneurium of nerves (Figure 4).

Multiple foramina are present in the orbit and temporal fossa. Neurochannels drain from the optic nerve and dura through these foramina to subcutaneous lymphatic vessels. Creases are determined by lymphatic vessels. Whenever a crease in injected, especially with a small-caliber needle pointed towards the orbit, one risks retrograde injection to the optic nerve. When direct injection against temporal bone, especially medially where multiple bony foramina exists, one risks retrograde intracranial injection.

The authors’ work, and even our team’s work over the past 4 years on the neurocirculation, emphasizes the point that the basic structural designs of facial anatomy are usually fairly simple. Complexity exists at the molecular level. Consider the basic design of adipose tissue. Deep fat is partitioned by SMAS fusion zones; SMAS fusion zones traffic neurovascular/lymphatic structures; superficial fat is partitioned by the SMAS-dermal insertion of these membranes. Understanding the temporal fossa simply requires inserting landmarks. Basic structural designs are repeated throughout biology. When our group failed, after 285 anatomic dissections and countless immunohistochemistry studies, to prove that neurochannels are lymphatics, we looked elsewhere in biology. Only then did we recognize similarities between neurochannels (glucose transport system) and the sucrose transport system of plants.

This is a brief discussion of some of the points raised by this paper.¹ The authors further define the anatomy of the temporal fossa. Their superb dissections enable the reader to envision a 3D structure in agreement with our current model of facial anatomy. It is critical to understand that the temporal fossa is the terminal site of CSF drainage to avoid disastrous complications during routine facial augmentation. The authors are to be congratulated for their work that again shows why it is the aesthetic surgeon, of all subspecialties, who most requires and benefits from an expert knowledge of facial anatomy.

Disclosures

The authors declared no potential conflicts of interest with respect to the research, authorship, and publication of this article.

Funding

This work was supported by The University of Florida Gatorade Trust and imaging for this study was supported by NIH grant IS10OD020026.