Cosmetic Incidence of Cervical Branch Injury with “Marginal Mandibular Nerve Pseudo-Paralysis” in Patients Undergoing Face L

Home , Deep cervical fascia, Mandibular nerve, Mentalis, Nerve, Platysma muscle

Cosmetic

Incidence of Cervical Branch Injury with “Marginal Mandibular Nerve Pseudo-Paralysis” in Patients Undergoing Face Lift

Stephen P. Daane, M.D., and John Q. Owsley, M.D. San Francisco, Calif.

The anatomy of the cervical and marginal mandibular corner of the mouth. Transient lip depressor branches of the facial nerve is reviewed. In the senior au- dysfunction had been a common observation thor’s practice, “pseudoparalysis of the marginal mandibular nerve” due to cervical branch injury occurred in 34 of 2002 in patients undergoing neck dissection with 3 4 superficial musculoaponeurotic system–platysma face lifts platysma excision. In 1979, Ellenbogen de- (1.7 percent) and was associated with a full recovery in 100 scribed two cases of transient “pseudoparaly- percent of cases within a time period ranging from 3 weeks sis of the marginal mandibular nerve” due to to 6 months. Cervical branch injury can be distinguished cervical branch injury; they were distin- from marginal mandibular nerve injury by the fact that the patient will be able to evert the lower lip because of a func- guished from marginal mandibular nerve in- tioning mentalis muscle. (Plast. Reconstr. Surg. 111: 2414, jury by the fact that these patients could still 2003.) evert the lower lip because of a functioning mentalis muscle.

Concern exists regarding the potential for injury to a branch of the facial nerve during a ANATOMY OF THE MARGINAL MANDIBULAR AND face lift. Because of variable and overlapping CERVICAL BRANCHES nerve supply to the perioral musculature as The marginal mandibular nerve exits the well as the overlapping functions of several anterior-inferior portion of the parotid near muscles (particularly the lip depressors), it can the angle of the mandible and remains deep be difficult clinically to distinguish the exact to the investing cervical fascia. It courses for- cause of postsurgical lip dysfunction. With the ward deep to the anterior facial vein in con- classic subcutaneous facial dissection and su- tact with the superolateral surface of the sub- perficial musculoaponeurotic system (SMAS) mandibular gland as it curves down as much techniques, the frontal and marginal mandib- as 3 cm below the inferior border of the ular branches of the facial nerve are injured mandible.1,5 Near the mandibular mid-body, most often.1 the marginal mandibular nerve swings up- For most patients, loss of platysma motor ward and perforates the deep cervical fascia function due to cervical nerve injury in near the mandibular border to continue SMAS–platysma elevation is of relatively little within the fibroareolar tissue between the consequence. However, in the 2 percent of deep fascia and platysma. The nerve crosses patients noted by Rubin2 to exhibit a “full the anterior facial artery to innervate the denture smile,” the platysma co-functions deep surface of the depressor quadratus labii with depressor anguli oris to contribute sig- inferioris and mentalis muscles. It may anas- nificantly as a lip depressor. Injury to the tomose with cervical and buccal branches cervical branch in these patients results in that supply the depressor anguli oris and the loss of depressor function to the affected cephalic portion of the platysma.

In private practice and from the Department of Plastic Surgery, University of California, San Francisco. Received for publication May 6, 2002; revised August 23, 2002. DOI: 10.1097/01.PRS.0000061004.74788.33 2414 Vol. 111, No. 7 / MARGINAL MANDIBULAR NERVE PSEUDO-PARALYSIS 2415 slightly anterior to the angle of the mandible; then it immediately perforates the deep investing fascia and continues upward in the fibroareolar connective tissue that attaches to the platysma near its superolateral border. The platysma can be dissected from the deep fascia in this area with a combination of scis- sor spreading and blunt “peeling” of areolar tissue from the undersurface of the muscle with a peanut sponge. As the region of the branch (or branches) of the cervical nerve is approached, the areolar connection be- comes more dense and firm, usually prevent- ing blunt dissection from damaging the nerves (Fig. 2). When the senior author first began per- forming subplatysma–SMAS dissections in the 1970s, care was taken to limit any dissection in the lateral danger zone, and there were no cases of disturbances in mouth movement following surgery.8 In an effort to improve the mobility of the SMAS–platysma skin flap in an upward rotary fashion, more FIG. 1. Diagram of the dissection zones of the face and neck. The green zone delineates the area where sharp dissec- dissection was undertaken in the lateral dan- tion is safe without risk of injury to any branch of the facial ger zone area; consequently, temporary de- nerve. The yellow zone represents the area of cautious dissec- pressor muscle dysfunction occurred on a tion, where blunt sponge or gentle spreading dissection with number of occasions. The incidence of tem- scissors is appropriate. The red zone represents an area that is porary depressor muscle dysfunction due to protected with extreme caution using only the peanut sponge dissector. platysma paralysis was in the 3 percent range.9,10 Muscle dysfunction typically resolved within 6 weeks, but on rare occasions The vulnerable point for injury of the mar- it lasted for 5 to 6 months. In the majority of ginal mandibular nerve is after it exits the deep cases, the patient’s left side was affected, per- cervical fascia and courses up over the anterior haps because after right-sided facial closure, mandible in the region of the facial artery. dissection in the area of the left mandibular Nerve injury can occur during dissection in the superficial subcutaneous layer if the platysma is penetrated in the region of the anterior jowl with scissors or even with a liposuction cannu- la.1 Superficial dissection over the mid-anterior mandible should be performed with great care and preferably under direct vision. Injury can also occur during dissection beneath the platysma from below with scissors. The “danger zone” for the marginal mandibular nerve ex- tends from the angle of the mandible to its crossing by the anterior facial artery and reaches from the inferior border of the mandible to a parallel line 3 cm below (Fig. 1).6,7 Beyond the danger zone, scissors can be passed from the lateral neck to the submental area FIG. 2. The protective stalk of areolar tissue beneath the and spread without risk of injury to the mar- platysma muscle that contains the cervical branch of the facial nerve delimits the lateral margin of the “danger zone.” This ginal mandibular nerve. areolar bridge also protects the underlying marginal man- The cervical branch of the facial nerve dibular nerve, which passes anteriorly along the inferior mar- exits the inferior margin of the parotid gland gin of the mandible. 2416 PLASTIC AND RECONSTRUCTIVE SURGERY, June 2003

FIG. 3. Case 1. A 47-year-old patient with cervical branch injury: (left) asymmetrical, “full denture-type smile”;(center) intact, symmetrical mentalis protrusion of the lower lip; (right)a“zygomaticus-type smile” disguises the disability. angle and superior lateral neck where the cervical branch is at risk is more awkward for the right-handed surgeon. Starting in the mid-1980s, the senior author made a con- certed effort to protect the cervical branch; the current incidence of transient lip depressor dysfunction is approximately 1 percent.

CASE REPORTS In 2002 cases of SMAS–platysma face lift performed between 1977 and 2001, there were 34 cases of cervical branch injury (1.7 percent), all of which resolved (case 1, below). Only one patient with diminished depressor function of the lip had an associated mentalis weakness suggesting a marginal mandibular branch injury; the patient’s lip returned to normal in 2 months. Only one patient has persistent resid- ual disability in mouth movements (case 2, below). There were no instances of injury to the frontal, zygomatic, or buccal branches of the facial nerve.

Case 1 FIG. 4. Case 1. The patient had recovered her normal A 47-year-old woman was seen 10 days after her SMAS– smile. platysma face lift and coronal brow lift. Her “full denture-type smile” was asymmetrical on the left side (Fig. 3, left). Man- dibular branch function was demonstrated by intact mentalis Case 2 protrusion of the lower lip in a symmetrical fashion (Fig. 3, center). She adopted a “zygomaticus-type smile” during con- A 54-year-old woman was seen 2 years after her SMAS– valescence to disguise the disability (Fig. 3, right). After an- platysma face lift. She exhibited symmetrical eversion of other month, the patient had recovered her normal smile the lower lip with intact mentalis function (Fig. 5, left). She (Fig. 4). had left platysma function cephalic to the location of Vol. 111, No. 7 / MARGINAL MANDIBULAR NERVE PSEUDO-PARALYSIS 2417

FIG. 5. Case 2. A 54-year-old patient with marginal mandibular nerve injury: (left) symmetrical eversion of the lower lip with intact mentalis function; (center) intact mandibular and cervical branches as demonstrated by functioning mentalis and platysma muscles; (right) evident weakness of the depressor labii quadratus. platysma transection with a visible platysma depressor ef- After a face lift, if lip depressor dysfunction fect of the lateral oral commissure. The functioning men- is noticed that was not present on preopera- talis and platysma muscles suggested that both the mandibular and cervical branches were intact (Fig. 5, center). tive photographs, pseudoparalysis of the However, when the patient attempted to smile, there was marginal mandibular nerve due to cervical evident weakness of the depressor labii quadratus (Fig. 5, branch injury can be distinguished from true right). The exact location of the nerve lesion was not clear, marginal mandibular nerve injury by the fact but it was believed to be the peripheral branch of the that the patient will still exhibit lip eversion marginal mandibular nerve to the depressor labii quadratus with a distal intact branch to the mentalis. Most likely, with a functioning mentalis muscle. Cervical the injury occurred in the lower anterior buccal space near branch injury is associated with an excellent the anterior facial artery, above the mandibular border. prognosis, with complete recovery within 3 to 4 weeks on average. CONCLUSIONS Stephen Daane, M.D. 2186 Geary Blvd., No. 212 Because any motor function disturbance is San Francisco, Calif. 94115 very distressing to both the patient and the [email protected] surgeon, the senior author avoids aggressive sharp dissection in the lateral danger zone REFERENCES near the angle of the mandible in an effort to 1. Baker, D. C., and Conley, J. Avoiding facial nerve inju- prevent cervical branch injury. It is quite pos- ries in rhytidectomy: Anatomical variations and pit- sible to limit subplatysmal dissection to falls. Plast. Reconstr. Surg. 64: 781, 1979. “stretching” of the fibroareolar stalk contain- 2. Rubin, L. R. The anatomy of a smile: Its importance in ing the cervical motor nerve branches and still the treatment of facial paralysis. Plast. Reconstr. Surg. obtain a satisfactory upward rotation of the 53: 384, 1974. 3. Baker, D. C. Manhattan Eye, Ear and Throat Hospital, SMAS–platysma flap. Since refinement of this personal communication. New York: 1999. technique as described in the mid-1980s, it has 4. Ellenbogen, R. Pseudo-paralysis of the mandibular been safe and reliable, with an incidence of branch of the facial nerve after platysmal face-lift op- transient labial depressor dysfunction of 1 per- eration. Plast. Reconstr. Surg. 63: 364, 1979. cent and no marginal mandibular nerve inju- 5. Skandalakis, J. E., Gray, S. W., and Rowe, J. S., Jr. Sur- gical anatomy of the submandibular triangle. Am. ries. There has been no compromise of the Surg. 45: 590, 1979. effectiveness of the lift achieved with the 6. Owsley, J. Q. Face lift. In: Aesthetic Facial Surgery. Phila- SMAS–platysma rotation flap. delphia: Saunders, 1994. Pp. 29–115. 2418 PLASTIC AND RECONSTRUCTIVE SURGERY, June 2003

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