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In order to prepare recipient facial nerve branches for neurovascular muscle, transfer in the treatment of facial paralysis, endoscopic facial nerve dissection was employed. Under endoscopy recipient facial nerve branches innervating the zygomaticus major muscle were successfully dissected. A stab incision was sufficient for nerve suture with the donor nerve. This method is preferable for young or female patients in whom conventional cheek incisions should be avoided.
first reported the use of neurovascular free gracilis muscle transfer for treating long-standing facial paralysis, many reconstructive surgeons have preferentially used this method.
Cross-face nerve graft with free-muscle transfer for reanimation of the paralyzed face: a comparative study of the single-stage and two-stage procedures.
Compared to the two-stage method combined with cross-face nerve grafting, the one-stage method offers advantages including a shorter recovery period and no need for harvesting the sural nerve. However, the length of the muscle motor nerve is limited and not long enough to reach a contralateral pre-auricular incision. Thus, an incision on the intact cheek is required to expose recipient facial nerve branches and link them to the motor nerve of the transferred muscle. Although such cheek scarring is largely inconspicuous among elderly patients,
scarring on the non-paralyzed cheek can represent an annoyance, particularly for children and young women.
To avoid such morbidities during one-stage free muscle transfer, we developed an endoscopic technique for dissecting recipient facial nerve branches through small pre-auricular incisions. Using this endoscopic technique, facial nerve branches suitable as a recipient motor source are accurately dissected, and a small stab incision to the cheek is sufficient to allow the facial and grafted motor nerves to be sutured under microscopy. Even after developing this endoscopic dissection technique, we still appreciate conventional recipient facial nerve dissection through a small incision, about 2 cm long,
at the anterior region of the parotid gland as a first choice. However, we consider this novel technique an option worthy of consideration for young or female patients.
1. Operative technique
After creating a subcutaneous pocket for subsequent muscle transfer in the paralyzed cheek, two incisions of about 1 cm each in length are placed on the pre-auricular region of the non-paralyzed side (Fig. 1) . From each incision, the superficial musculoaponeurotic system (SMAS) plane is dissected blind, anterior to the intercross point of the inferior edge of the zygomatic arch and the anterior margin of the parotid gland. The two incisions are thus connected subcutaneously. After the right-handed surgeon introduces an endoscope (30° angle, 4 mm diameter, 17.5 cm long) through the left incision, dissection is continued using a microdissector inserted through the right incision. In cases where sufficient optic space cannot be attained, the pre-auricular skin is hooked and lifted, or adjunctive traction of the cheek skin is performed using 3–0 silk thread (Fig. 2) . Dissection proceeding anteriorly under video assistance enables visualization of several facial nerve branches at the anterior margin of the parotid gland. Among these branches, those innervating the zygomaticus major muscle can be found by dissecting the undersurface of this muscle (Fig. 3) .
Fig. 1Two incisions are placed on the pre-auricular region of the non-paralyzed side. From each incision, the SMAS plane is dissected blind as the dotted lines indicate.
Fig. 2After the right-handed surgeon introduces an endoscope through the left incision, dissection is continued using a microdissector inserted through the right incision. The pre-auricular skin is hooked, and adjunctive traction of the cheek skin is performed using 3–0 silk thread, since sufficient optic space cannot be attained.
Fig. 3Endoscopic dissection enables visualization of several facial nerve branches. Among these branches, those innervating the zygomaticus major muscle can be found by dissecting the undersurface of this muscle. M: zygomaticus major muscle, N: facial nerve branch.
After dissecting these branches proximally and distally as far as possible, a small stab incision is created on the non-paralyzed cheek to pull out the stump of these facial nerve branches. In order to pull out these branches sufficiently, the stab incision should be made parallel to the nerve about 2 cm proximal to the point at which the branches are severed. When the stab incision is created just above the nerve stumps, pulling out a sufficient length of nerve stump for subsequent microsurgical nerve suture to the muscle motor nerve stump is impossible. Vessel tape is inserted from this stab incision to bind around and retract the nerve from the incision. Recipient facial nerve branches are then severed as far distally as possible (Fig. 4) , followed by removing the vessel tape to bring the nerve stumps outside the stab incision (Fig. 5, Fig. 6) . After setting the harvested neurovascular muscle segment into the recipient cheek pocket, the muscle motor nerve is passed through the upper lip using a specially designed nerve passer, then pulled out from the same stab incision. The muscle motor nerve and selected recipient facial nerve branches are then joined epineurally under a microscope using 10–0 monofilament nylon sutures. Finally, the sutured nerves are reintroduced into the subcutaneous space, followed by confirmation of nerve suturing under endoscopy. Compression dressing on the non-paralyzed cheek is not required.
Fig. 4Recipient facial nerve branches are severed as far distally as possible. V: vessel tape, N: facial nerve branch.
Endoscopic facial nerve dissection was performed on 8 patients (7 females, 1 male) who underwent one-staged facial paralysis reconstruction using the latissimus dorsi muscle (Table I) . Patients ranged in age from 15- to 50-years-old (mean, 32.1-years-old) at time of surgery. Morbidities causing the facial paralysis are listed in Table I. Ancillary procedures accompanying muscle transfers comprised gold plate loading in the upper eyelid of patients 1 and 8, temporal muscle transfer to the eyelid of patients 2 and 5, and endoscopic eyebrow lift for patients 2, 5, and 8.
Table IPatient data
Patient
Age
Sex
Original disease
Paralyzed side
Time (min) for endoscopy
Initial contraction (pom)
Anicillary procedures
1
38
F
Parotid tumor
lt.
50
5
LL
2
38
F
Acoustic neurinoma
rt.
40
6
EEL, TT
3
25
F
Bell's palsy
rt.
30
5
4
15
F
Neck tumor
lt.
30
5
5
50
F
Acoustic neurinoma
lt.
30
6
EEL, TT
6
37
M
Bell's palsy
rt.
30
9
7
28
F
Acoustic neurinoma
rt.
30
7
8
26
F
Otitis media
rt.
30
4
EEL, LL
pom, postoperative months; EEL, endoscopic eye-brow lift; LL, lid load with a gold plate; TT, temporal muscle transfer to the eyelid.
Mean duration of endoscopic facial nerve dissection was 34 min, ranging from 30 to 50 min. Muscle contraction was confirmed in all patients between 4 and 9 months postoperatively, to ensure that the endoscopic procedure had not damaged recipient nerves. Cheek scars were imperceptible in all patients (Fig. 7) .
Fig. 7Pre-auricular and cheek scars were imperceptible.
Since the aim of microvascular free muscle transfer is the reconstruction of a synchronous natural smile, the facial nerve branches innervating the zygomatic and levator labii muscles on the contralateral side should be selected as recipient motor nerves. Suitable branches of the facial nerve can be identified through either a pre-auricular face-lift incision or a small incision placed on the intact cheek. According to Manktelow et al,
the pre-auricular approach is preferable because it allows more accurate identification of all nerve branches and their functions through the use of a nerve stimulator. In this method, since sufficient sural nerve can be harvested to cross the face and reach the contralateral pre-auricular region, nerve suture between the sural nerve and recipient facial nerve can be performed under microscopy from the pre-auricular incision. The pre-auricular incision method may be useful when the two-stage operation combining muscle transfer with cross-face nerve grafting is selected. However, when the one stage muscle transfer is employed, nerve suture from the pre-auricular incision is almost impossible even though the incision extends anteriorly over the mandibular angle. This is because the length of the motor nerve of donor muscles is not long enough to reach the contralateral pre-auricular region. For this reason, most authors who report one-stage free muscle transfer use an incision placed on the cheek for nerve juncture.
Cross-face nerve graft with free-muscle transfer for reanimation of the paralyzed face: a comparative study of the single-stage and two-stage procedures.
most female patients and children in his series preferred the two-stage procedure to avoid scarring of the cheek on the intact side. In order to address this problem, we attempted a technique using endoscopic facial nerve dissection enabling nerve suture through a stab incision on the cheek.
Compared to the pre-auricular or cheek incision methods, endoscopic facial nerve dissection cannot assure nerve selection using the nerve stimulator. However, control of the nerve stimulator requires experience, and contraction of the upper lip orbicularis oris can be misinterpreted as that of the levator and zygomaticus muscles.
Conversely, nerve branches selected as recipient for muscle transfer can be clearly identified under endoscopic magnification as innervating the zygomaticus major muscle.
Generally, the benefits of surgical endoscopy include enhanced visualization, fewer and smaller incisions, and reduced iatrogenic morbidity compared to conventional approaches. However, our endoscopic technique requires more skin incisions and the area of subcutaneous dissection needed for endoscopic visualization is larger than that of the cheek approach, although the method is still less invasive than the pre-auricular approach. This technique is, therefore, not indicated for senile patients in whom skin incisions on the cheek are always inconspicuous. An endoscopic approach is indicated for young female patients who prefer two pre-auricular skin incisions to a larger incision on the cheek, for cosmetic reasons.
The time required for endoscopic procedures is another problem for both physicians and patients. Even with technical improvements, endoscopic facial nerve dissection required at least 30 min. Conversely, conventional nerve dissection from a cheek incision requires 10–15 min on average. However, facial preparation, including endoscopic facial nerve dissection, can be performed while the neurovascular muscle flap is harvested. The time required for endoscopic procedure, therefore, does not represent a major problem.
References
Harii K
Ohmori K
Torii S
Free gracilis muscle transplantation, with microneurovascular anastomoses for the treatment of facial paralysis.
Cross-face nerve graft with free-muscle transfer for reanimation of the paralyzed face: a comparative study of the single-stage and two-stage procedures.
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