Anatomy

The frontal or temporal branch of the facial nerve innervates the upper division of the orbicualris oculi muscle, whose function is to close the upper eyelid and secondarily to depress the brow.4 This branch also innervates the frontalis muscle, the primary elevator of the forehead and brow, and the corrugator and depressor supercilli muscles, which act as medial brow depressors. The zygomatic and some branches of the buccal division of the nerve innervate the lower lid portion of the orbiculars oculi muscle, which acts as the protractor of the lower lids.4 Besides closing the eyelids and depressing the brows, specific potions of the orbicularis oculi are involved in the active process of tear drainage.5 With this in mind, the characteristic ophthalmic manifestations of facial nerve damage become obvious and include ( Fig. 21.1 ):

1. 
   

   Brow ptosis (from frontalis weakening)

   
   
2. 
   

   Upper lid retraction, lagophthalmos, and incomplete closure (from orbicularis weakness)

   
   
3. 
   

   Lower lid laxity, weakness, or frank ectropion (from orbicularis weakness)

   
   
4. 
   

   Epiphora from lower lid weakness, reduced tear pump, and punctual malposition if ectropion present

   
   
5. 
   

   Ocular exposure, corneal dryness, and corneal abrasion or ulcer (from poor corneal coverage)

Ophthalmic Evaluation

The range of ocular and periocular complications related to facial nerve dysfunction is varied and ranges from a mild inconvenience to potential threats to vision. For this reason, a thorough ophthalmic evaluation is needed in every case, and an individualized plan should be created to protect the eye, restore function, and re-create appearance.6 Ocular protection and restoration of function are necessary steps in the process, and doing so in the most aesthetically acceptable way is desired.

Visual acuity is assessed and if reduced the cause sought out. In these patients, vision is usually reduced related to ocular surface irregularities (corneal dryness, abrasion, or infection) or welling up of tears from poor drainage. An examination of the pupils, motility, visual fields, and fundus is performed. Obviously, special time and attention is given to the slit-lamp and external evaluations. There are a number or corneal protective mechanisms that are assessed. These include tear production, eyelid closure, corneal sensation, and the Bell phenomenon. Reflex tear production is controlled in part by a distal autonomic branch of the facial nerve (the greater superficial petrosal nerve).7 As such, tear production may decrease in facial paresis. As already mentioned, lid closure can be reduced if the orbicularis muscle is sufficiently damaged.

The cornea receives sensory innervations from the first division of cranial nerve V (ophthalmic nerve). If the pathology causing facial nerve disease also involves cranial nerve V, then corneal sensation may be affected. Corneal innervation is an integral part of maintaining epithelial integrity of the cornea. If sensation is reduced (neurotrophic cornea), corneal exposure is more difficult to treat. In addition, if sensation is reduced, the patient may not complain of pain, which is a primary warning sign to seek medical attention. Finally, the Bell phenomenon is a reflex supraduction of the globe (elevation) when the lids close ( Fig. 21.2 ). It protects the corneal surface when lid closure is reduced as the globe elevates under the upper lid. When reduced, the cornea is exposed during times of poor lid closure ( Fig. 21.3 ). When all these mechanisms are intact, the cornea can typically withstand some degree of dryness and exposure. In the setting of facial nerve weakness, if one or all of these mechanisms fails, the cornea can decompensate.

Conservative Therapy

The most important steps in managing the ocular issues in facial paresis are to restore corneal protection. In cases that are milder where the cornea is generally stable, several noninvasive steps can be taken. The patient can manually lower the upper eyelid various times throughout the day and even tape (or patch) it closed for periods if necessary. This reduces exposure and may improve symptoms. Ocular lubrication with various over-the-counter lubricants can be applied on a frequent basis. Lubricant ointments provide more protection of the cornea but blur vision. The author typically suggests such ointments at bedtime as vision is not an issue then, and they provide greater protection than tears for nocturnal lagophthalmos. At night, the lids can be taped closed, swimmer goggles can be used (acting as a humidifier), a humidifier can be placed in the bedroom, air conditioning can be turned off, and lubricants can be applied. If patients can be kept comfortable and out of harm′s way with any of these measures and they tolerate their implementation, then surgery can be avoided. If not, surgical intervention should be considered.

Surgery

Brow Lift

Lifting a paretic brow can be a challenging endeavor. If paresis is mild and the concerns are primarily aesthetic, an endoscopic procedure, temporal lift, or even transeyelid browpexy may suffice. In more significant brow paresis, frontalis weakness limits the final result. In these cases, especially in patients who are older with preexisting forehead rhytids,8 a direct brow lift is preferred. In the most severe cases, a perisoteal suspension is added for support. With meticulous three-layered closure, the scars heal well and are barely noticeable. The most difficult area to camouflage an incision is in the medial eyebrow where the thicker sebaceous skin tends to scar more significantly.

An ellipse is drawn above the brow in the area that is ptotic. After infiltration with anesthesia, an incision beveled in the direction of the brow hairs is made. The skin and subcutaneous tissue is excised, and hemostasis is assured. The wound is closed in layers. First deep tissue (muscle/subcutaneous fat) is secured with interrupted absorbable suture (5–0 Vicryl [Ethicon, Inc., Somerville, NJ] recommended). If periosteal fixation is performed, the deep sub-brow tissue at the inferior edge of the wound is engaged with a 4–0 Prolene suture (Ethicon, Inc.). This tissue is secured to the periosteum at the desired level by passing the suture through the deep brow tissue at the upper edge of the wound and tying the knot. This gives more brow support and creatures a more fixed brow position. Subcutaneous interrupted bites of the same 5–0 Vicryl suture are used to oppose the wound edges. The bites should be taken very close to the skin edge as to reduce tension on the wound. Finally, the skin is closed with a running 6–0 nylon suture. A running vertical mattress technique is preferred, but as long as the skin edges are intact and everted, any closure is appropriate ( Fig. 21.4 ).

A direct brow lift is a very effective technique in the appropriate patient. When periosteal fixation is employed, brow animation is reduced. However, the author typically uses this technique only in the most severe cases where the paretic brow has little or no animation to start with.

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