Facial surgery: Anatomy demands constant attention

La Jolla, Calif. - To paraphrase English surgeon and anatomist Sir Ashley Paston Cooper, the best surgeon is the one who makes the fewest mistakes.

For dermatologic surgeons, minimizing mistakes means always being aware of underlying facial anatomy, says Hugh T. Greenway, M.D., chairman, Division of Procedural Dermatology, Scripps Clinic, La Jolla, Calif.

"The rest of our surgical colleagues in most specialties tend to identify things before operating. That's probably something we as dermatologic surgeons need to pick up, rather than perhaps identifying structures after the fact," Dr. Greenway explains.

To that end, he says, the facial region contains "a tremendous amount of material, located both superficially and deep. When you look at anatomy, it's important to group things in terms of muscle groups or locations, such as the scalp, as well as nerve, sensory and motor vessels, and specialized structures such as the parotid and parotid gland."

Periorbital area

In the facial area, superficial muscles surrounding the orbit and mouth merit special consideration, Dr. Greenway says.For example, he advises proceeding especially cautiously with surgical procedures in the vicinity of the levator palpebrae superioris, which raises the eyelid.

"When dermatologists first start," Dr. Greenway says, "they either totally avoid the periorbital area or blindly wander in. Just remember that there is an underlying functional eye there."

The tarsus is extremely heat-sensitive, for example, "so if you're doing any type of electrocautery, remember you can destroy the tarsus."A surgical wound closed with electrocautery may look great, he says, "but two days, later it could all fall apart because of the amount of heat you've used."

Mouth area

When it comes to learning the muscles in the mouth area, Dr. Greenway says, "It's important to be a grouper when you first start.#&34

The group of muscles that elevates the lip includes the zygomaticus major and minor and others, while other muscle groups worth noting here include the depressors of the lip, he says. Additional muscles in this area include the risorius or "smile muscle," which lacks a bony attachment, and the orbicularis oris.More complex still is the facial neural network and blood supply, Dr. Greenway says. The facial artery, for example, originates below the face and branches into the superior labial, inferior labial, lateral nasal and angular arteries. The superficial temporal artery comes up anterior to the ear.

"You can palpate both this vessel and the facial artery either in front of the ear or down at the jawline," says Dr. Greenway.

Sensory innervation

Nerves responsible for sensory innervation of the face include the trigeminal nerve, with its maxillary branch (which includes the infraorbital, zygomaticofacial and zygomaticotemporal nerves) and mandibular branch (which includes the mental nerve). Despite the complexity of the facial neural network, Dr. Greenway says that when performing nerve blocks in the face, "You don't necessarily have to hit the nerve. You just want to bathe it in the local anesthesia area and then give the anesthetic time to work."

Motor innervation

More important is motor innervation of the face, he says. Motor innervation of the face comes from the facial nerve, which includes temporal, zygomatic, buccal, mandibular, cervical and posterior auricular branches.

Dr. Greenway says the area on the side of the face anterior to the ear contains a reverse C- shaped region that carries the greatest risk.

"The parotid gland covers the facial nerve. The problem is, there are no true definitions of the anterior border of the parotid gland.

"If we draw a line from the outer canthus straight down, anything midline to that probably is already divided, with the exception of the marginal mandibular," he says.

Scalp

The scalp contains five varied skin layers, represented in the SCALP mnemonic often taught in medical schools: the Skin (epidermis/dermis), subCutaneous tissues (vessels, nerves, hair bulbs, fibrous bands), the Aponeurosis, Loose connective tissue and the Periostium.

Anatomic considerations in these areas include respecting the scalp's nerve and vascular supply, Dr. Greenway says. In particular, he says, the scalp's preponderance of blood vessels explains why this area bleeds profusely."When we cut the scalp, it's actually the connective tissue retinaculum that pulls those vessels apart, which is why in our training we spend so much time in an emergency room sewing up the scalp as opposed to other anatomic areas," he says.

As for sensory innervation of the scalp, in the anterior area, "It's the supraorbital and supratrochlear that we use in our nerve blocks. Also, knowing where those nerves are can help us in terms of our surgical technique both intraoperatively and preoperatively,&34 he says.

Neck

Structures at risk during superficial neck surgery include several nerves, blood vessels and glands."The neck is probably an area where we run the risk of getting into a little more trouble, probably because we aren't quite as familiar with it," Dr. Greenway says.

Superficially, its borders include the mandible, clavian and trapezium.

"The nerves are probably the most important area for dermatologic surgeons to pay attention to," he explains.

Because all facial structures fall as people age, Dr. Greenway says that surgeons must remember "those nerves that typically are located in the facial area (such as the marginal mandibular) may partially be down in the neck now."

Additionally, he says, the marginal branch of the facial nerve and the accessory nerve are the most important facial nerves for surgeons to be aware of; severing either will cause long-standing or permanent deformity.

Also in the neck area, Dr. Greenway says, "Solid masses may well be metastatic tumor from the nose, mouth, larynx or pharynx. Tumors within the parotid may appear extremely superficial, and any attempt to remove them may damage the facial nerve."

Overall, he says, "Superficial head and neck anatomy is very complicated, so breaking it into groups helps to keep it simple." DT

Disclosure: Dr. Greenway reports no relevant financial interests.