unilateral paralysis of facial mimetic muscles and loss of taste in the anterior two-thirds of the tongue. Hearing is The path of the facial nerve can be divided into three main segments: intracranial, intratemporal, and extratemporal. This is clinically relevant as knowledge of the anatomy can help identify the site of damage or compression of the nerve. There are no branches within the intracranial segment, so a lesion at this site would cause complete loss of facial nerve function with no sparing of individual branches. The intratemporal segment has three subdivisions: labyrinthine, tympanic, and mastoid (Fig. 47.1). Four nerve branches are given off within this region in the following order: the greater petrosal nerve (within the labyrinthine section), the nerve to stapedius, the sensory branch to the external auditory canal, and the branch to chorda tympani (within the mastoid section). The patient described has a lesion affecting the chorda tympani and the extratemporal nerve, with sparing of the greater petrosal nerve, the nerve to stapedius, and the nerve to external auditory meatus. Therefore, the lesion is located within the distal mastoid segment. A lesion within the parotid would spare all four of the intratemporal branches.1–4 Fig. 47.1 Anatomy and relations of the facial nerve. Geniculate ganglion Labyrinthine segment Tympanic segment Mastoid segment Stylomastoid foramen Submandibular gland Lacrimal gland Greater superficial petrosal nerve Becomes temoral, zygomatic, buccal, mandibular, and cervical branches
Hitselberger’s sign refers to hypesthesia of the external auditory canal, secondary to compression or damage to the sensory branch of the facial nerve within the mastoid segment of the intratemporal nerve pathway.1 Hitselberger and House1 described this in 1966 as an early diagnostic indicator of acoustic neuroma formation. Decreased taste sensation in the tongue would occur secondary to compression of the chorda tympani, which joins the lingual nerve to supply parasympathetic innervations to the submandibular and sublingual glands, as well as taste to the anterior two-thirds of the tongue. Pain during facial movement is more likely to be associated with trigeminal or dental pain rather than facial nerve compression. Sound dampening is controlled by the nerve to stapedius which originates in the mastoid segment. A dry, gritty eye may well be present in association with a facial nerve palsy as a result of the incomplete eye closure and loss of the corneal reflex but is not specific to Hitselberger’s sign.1,2
3. Gosain AK. Surgical anatomy of the facial nerve. Clin Plast Surg 1995;22(2):241–251
The mentalis, levator anguli oris, and buccinator muscles represent the deepest layer of facial musculature and receive their innervation on their superficial surfaces. All other muscles receive innervation on their deep surface. The facial musculature comprises 23 paired muscles and single orbicularis oris, grouped into four layers. Those described in option A (depressor anguli oris, zygomaticus major, and orbicularis oculi) represent layer one and are the most superficial. Those in option B (depressor labii inferioris, risorius, and platysma) include some of the muscles in layer two. Layer three contains only two muscles: orbicularis oris and levator labii superioris.1,2
There are a number of facial mimetic muscles involved in producing a smile, but the major muscle involved is the zygomaticus major. One particular study has shown that observers perceive a smile when the zygomaticus major functions to achieve 40% of its maximal movement.1 The zygomaticus minor also has an important contribution to a smile and these two muscles work together to elevate the corner of the mouth and the upper lips as they pass obliquely across the central face between the zygoma to the upper lip. The levator labii superioris alaeque nasi contributes to smile by elevating the medial nasolabial fold and nasal alae. The risorius aids the smile with lateral pull and is more pronounced is some individuals. The levator anguli oris pulls the angle of the mouth upward and medially. The levator labii superioris elevates the upper lip and midportion of the nasolabial fold.1,2
Some patients are concerned about appearing tired or grumpy because of glabellar frown lines. The muscles responsible for this action are the corrugator and procerus. The corrugator moves the eyebrow medially and downward and can be easily palpated in the medial brow area when patients are asked to frown. The procerus is a pyramidal muscle that passes between the nasal bone and the frontal bone in the midline between the medial brows, which it moves downward. Frown lines can be treated with botulinum toxin injections to the corrugator and procerus muscles. Starting doses are upward of 20 units for most patients, depending on brand. Botulinum toxin is also used to target the orbicularis oculi muscles laterally to reduce crow’s feet wrinkles. Frontalis is also treated with toxin to smooth out wrinkles, particularly in the midline, but care must be taken to avoid lateral and low injection as this can lead to unwanted brow ptosis. The nasalis either flares or dilates the nostrils. The risorius is a muscle that aids lateral pull of the smile. These two muscles would not typically be treated with neurotoxin.1–4
weakness of the lower lip. During a neck dissection (particularly level I clearance), the marginal mandibular nerve is at risk of damage because it frequently lies below the lower mandibular border deep to platysma. Damage to this nerve results in elevation of the lower lip on the affected side from paralysis of the depressor labii inferioris. Subsequent treatment can involve injection of botulinum toxin to the depressor labii inferioris on the unaffected side or surgical transfer of the anterior belly of digastric to the lower lip.1 Platysma receives innervation from the cervical branch of the facial nerve and may be denervated during neck dissection; however, this is not usually of any great clinical concern, so less emphasis is placed on this nerve branch’s preservation. Mentalis is also innervated by the marginal mandibular nerve, but dysfunction tends to be well masked. This muscle pulls the skin of the chin upward. Levator anguli oris pulls the mouth upward, not downward, and is innervated by the buccal branches. Orbicularis oris forms the oral opening and functions to close and compress lips in order to achieve an oral seal. It also receives innervation from the buccal branches.
This man is likely to have a malignancy within the parotid and this must be fully investigated. This clinical presentation can indicate a primary malignancy; however, given his previous partial pinnectomy (presumably for a squamous cell carcinoma of the ear), he is likely to have metastatic disease that has spread to the parotid. This is a common pathway for such disease. In general, presentation with a facial paralysis is a poor prognostic sign and treatment involves parotidectomy at a minimum, often combined with neck dissection, skin resection, and reconstruction. Postoperative radiotherapy may also be indicated. Primary facial reanimation surgery may be incorporated into the surgical plan with static or dynamic midface support, lower eyelid suspension, and brow lifting. Benign parotid tumors such as pleomorphic salivary adenomas typically present in younger patients without facial nerve involvement. Acoustic neuroma would most often present with unilateral hearing loss or tinnitus. Other symptoms typically include vertigo, headache, or ataxia, rather than a parotid swelling. Facial nerve symptoms are observed in a small number of patients at presentation. Cholesteatoma also tends to present with hearing problems as with acoustic neuroma, and facial paralysis is a less common presenting sign. Again parotid swelling would not be expected. Both of these conditions can result in facial nerve paralysis following surgery to remove the primary tumors, and plastic surgeons may only become involved at this stage.1,2
The most common cause of facial palsy is Bell’s palsy, representing around 85% of cases, and this is a diagnosis of exclusion. It is usually self-limiting and is treated with steroids with or without antiviral medications. The risk of Bell’s palsy is significantly increased during pregnancy. Given that this patient has negative findings clinically, on further investigation, Bell’s palsy would be the diagnosis given here. The proposed cause of Bell’s palsy is viral–vascular insult which causes swelling in the temporal segment and subsequent facial nerve impairment. Ramsay Hunt syndrome is an alternative diagnosis in this patient when otalgia or a facial rash is present. This is caused by varicella zoster virus and is treated accordingly with steroids and acyclovir. Möbius syndrome is a congenital condition associated with bilateral facial nerve absence. Acoustic neuromas present with unilateral hearing loss or vertigo and headaches. Facial myokymia involves continuous undulating, writhing contraction of facial muscles and may be caused by multiple sclerosis, polyradiculopathy, or peripheral nerve injury.1,2
Melkersson-Rosenthal syndrome involves recurrent facial paralysis that may alternate sides. The cause is unknown, and treatment is usually conservative. Nerve decompression should be considered in some cases. Bell’s palsy is a diagnosis of exclusion and could explain this presentation but would not include the other clinical findings.1,2 Essential blepharospasm involves an involuntary spastic eyelid closure rather than facial weakness. Meige’s syndrome involves blepharospasm, grimacing mouth movements, and tongue protrusion, again without facial nerve paralysis.3 The most common cause of bilateral facial paralysis is Lyme disease which is itself caused by the spirochete Borrelia burgdorferi.4
Congenital unilateral lower lip palsy (CULLP) affects the marginal mandibular branch on one side only with the remainder of the facial nerve branches intact. There is normal resting tone in the facial muscles and the condition results in an asymmetrical appearance of the lower lip, particularly noticeable when the child cries. Facial paralysis is only present in a small proportion of patients with hemifacial microsomia. Hemifacial spasm is usually seen in middle-aged and elderly adults and reports in children are rare. It is a disorder of the seventh cranial nerve, characterized by irregular, involuntary, and recurrent tonic and clonic contractions of the ipsilateral muscles of facial expression. The cause is usually vascular compression at the brainstem, but can be seen secondary to other tumors.1 Bell’s palsy is a diagnosis of exclusion and is observed in children as well as adults. Cholesteatoma is a localized expanding tumor of the middle ear with keratinizing squamous epithelium that can cause facial nerve palsy in both children and adults. It is not an infective process, but can be associated with or confused with chronic episodes of otitis media.1
Möbius syndrome is a congenital condition involving absence of the facial (CN VII) and abducens (CN VI) nerves. This results in facial paralysis, the inability to abduct the eye, and subsequent strabismus. Other cranial nerves may also be affected. Limb abnormalities such as club foot and micrognathia are quite often present. However, hyperacusis is not seen because the cell bodies of the nerve to stapedius are not located in the facial nerve nucleus; therefore, its function is preserved.1,2
The House-Brackmann scale categorizes facial nerve function into six grades (I to VI).1 Grade I is normal facial nerve function, and grade VI is a total paralysis. The remaining grades pass from mild to severe. Each grade is based on gross appearance and motion. Gross appearance assesses muscle power, asymmetry, and tone. Motion assesses forehead, eye, and mouth movement. This patient is classified as having moderate dysfunction according to this scale. House-Brackman Scale: • Grade I: Normal facial function • Grade II: Mild dysfunction Gross: Slight weakness on close inspection, normal at rest Motion: Forehead, slight to moderate; eye, complete closure with effort; mouth, slightly weak with • Grade III: Moderate dysfunction Gross: Obvious but not disfiguring, normal asymmetry and tone at rest Motion: Forehead, slight to moderate; eye, complete closure with effort; mouth, slightly weak with • Grade IV: Moderately severe Gross: Obvious weakness with disfiguring asymmetry at rest Motion: Forehead, none; eye, incomplete closure; mouth, asymmetrical with maximum effort • Grade V: Severe dysfunction Gross: Only barely perceptible motion, asymmetry at rest Motion: Forehead, none; eye, incomplete closure; mouth, slight movement • Grade VI: Total paralysis No movement Other grading systems include the Burres-Fisch and Sunnybrook systems. The latter has become a popular alternative as an objective measuring tool in facial paralysis patients. It has three components: resting symmetry, symmetry of voluntary movement, and synkinesis.2,3 Comparison is based on the normal side. Assessment of the symmetry of voluntary movement involves five areas: the forehead wrinkle (raising eyebrows), gentle eye closure, open-mouth smile, snarl, and lip pucker. Patients with normal resting symmetry and those with no synkinesis will have a score of zero on this subsection. The composite or final score is calculated by assessing the symmetry of voluntary movement and then subtracting resting symmetry and synkinesis scores. A patient with no evidence of facial palsy should have a score of 100.1–3
Patients with frontal branch weakness are at high risk of developing brow ptosis, which can be treated with a brow-lift procedure. This candidate is young and probably prefers to minimize visible scarring on the brow. For this reason, an endoscopic approach is probably most favored as the scars are small and well hidden, sensation is retained, alopecia risk is low, and recovery should be fairly quick. Alternative options include open coronal lift, direct mid or lower forehead lift (superciliary), and transpalpebral approaches. The transpalpebral approach can work well with scars hidden in the upper eyelid fold. The other options will leave visible scarring in the forehead. The method of fixation of the brow is probably as important as the approach and once adequate release of the brow soft tissues has been achieved, the brow can be sutured internally from orbicularis to frontalis periosteum or directly to bone with a variety of bone-anchored devices such as MitekTM or EndotineTM, or with screws or drill holes.1,2 Corneal neurotization can be helpful to protect the globe following facial nerve injury, but will not help brow ptosis. It involves coaptation of the supraorbital and supratrochlear nerves from the contralateral trigeminal to the cornea of the facial palsy eye in order to provide protective sensation on that side.3 Tarsorrhaphy is a surgical technique that joins part or all of the upper and lower eyelids to partially or completely close the eye. Temporary tarsorrhaphies are used for protection of the cornea during a short period of exposure or disease. Permanent tarsorraphies are used to protect the cornea from a long-term risk of damage such as where there is facial nerve paralysis, which is unlikely to recover. A permanent tarsorrhaphy usually only closes the lateral (outer) eyelids, so that the patient can still see through the central opening and the eye can still be examined. It tends to round the lateral canthal area and so is not aesthetically pleasing.
Patients with long-standing facial nerve paralysis are at risk of damage of their eyes from incomplete eye closure and loss of blink reflex. Insertion of a gold or platinum weight into the upper eyelid is a technique commonly used to assist with eye closure. The disadvantages are that closure can remain incomplete when a patient is supine, because gravity is not acting to close the eye, the weight may be palpable and visible, and the weight can displace over time. Some patients simply find them uncomfortable and prefer to have them removed after placement. Conservative management with lubrication of the cornea is important but it alone is not the ideal long-term plan. Chemodenervation with botulinum toxin of levator palpebrae superioris or Muller’s muscle is possible, but will risk unwanted or excessive ptosis and inability to open the eyelid adequately. Tarsorrhaphy should not be used as a primary treatment as it is cosmetically disfiguring and reduces the visual field. Upper eyelid blepharoplasty risks making the problem worse as it could leave the eye with insufficient eyelid skin to close (lagophthalmos). For this reason, very careful consideration must be given prior to proceeding with blepharoplasty in facial palsy patients.1–3
Lower eyelid laxity is a common problem in facial palsy patients because of atrophic changes in the orbicularis oculi. Various techniques can be used to tighten or shorten the lower eyelid to reduce ectropion and corneal exposure. Tightening of the canthal tendon with a lateral tarsal strip and canthopexy or canthoplasty can be helpful. In doing this procedure, it is important to ensure that the lateral canthal tendon is lifted deeply and posteriorly into the orbital socket so the eyelid is not pulled away from the globe. This is usually achieved by lifting a periosteal flap from the lateral orbital rim and following this medially into the orbit. The canthal tendon can then be secured to this periosteum for support with a permanent suture. The tarsal strip involves removing the epithelial surface of the canthal tendon (skin/mucosa) so the tendon end can be buried deeply in the orbit as described. A canthopexy involves tightening of the tendon without dividing it, whereas a canthoplasty involves formal division and repositioning of the canthal tendon. A lower eyelid blepharoplasty may include elements of canthal resuspension but this patient is unlikely to have an excess of lower eyelid skin/tissue, but rather flaccid tissue. Therefore, blepharoplasty is not indicated here. If the patient had a cicatricial ectropion with deficiency of the anterior lamella (skin and/or orbicularis muscle) then importation of additional skin such as a full-thickness graft or Tripier transposition flap would be indicated. However, this is not the primary problem in this case. A Frost stitch is part of the surgical procedure in some lower eyelid suspension approaches and it is a temporary suture which holds the eyelids closed. This alone will only help such a problem unless the paralysis is expected to be transient.1–3
The basic principles of facial reanimation surgery are to provide innervation to the mimetic muscles if they are viable, or to supplement them when absent with a muscle transfer. After a period of 3 years, the facial mimetic muscles atrophy and have no potential for useful function even if reinnervated. In this case, a new muscle must be imported to provide dynamic facial movement for “smile surgery.” Muscle transfers can be either regional or free tissue subtypes. Regional options include temporalis, masseter, or anterior belly of digastric. Free tissue transfers include gracilis (which is the most favored option), pectoralis minor, partial latissimus dorsi, or partial rectus abdominis. Nerve supply for the free muscle transfers may be provided by the contralateral facial nerve, the hypoglossal nerve, or the nerve to masseter. The gracilis is the preferred choice because the excursion suites the requirement to replicate that of zygomaticus major well, it allows a two-team approach, it has a reliable vascular and nerve pedicle, there is no donor site functional loss, harvest is straightforward, and the muscle can be safely thinned to decrease bulk. In general, free tissue transfers are felt to offer the best option for younger patients like in this case to achieve a spontaneous smile.1,2 Temporalis and masseter are both regional options that can work well but tend to be reserved for older individuals or those who do not want the associated risks of free tissue transfer. They are most often not able to produce a spontaneous smile. Digastric transfer is specific to lower lip dysfunction rather than overall dynamic smile surgery.3
In this scenario, direct nerve repair is the best option. It may be worthwhile considering the babysitter procedure as well if an extended denervation time is anticipated in complete transection cases (partial hypoglossal nerve to facial nerve branch). Nerve axons typically regenerate at 1 mm per day so the time to reinnervation depends on the distance of nerve regrowth required. An ipsilateral nerve graft is only indicated where there is nerve loss, that is, repair cannot be made directly or is under tension. A cross-face nerve graft is indicated when the proximal stump of the facial nerve is unavailable for grafting, but a distal stump is present. Neither muscle transfer or fascial slings are indicated in this setting.1,2
This patient should have both proximal and distal nerve stumps available for grafting and the motor end plates and facial mimetic muscles will be suitable for reinnervation given the immediate reconstruction planned. In this case, interpositional nerve grafting using either sural, great auricular, or antebrachial nerves is indicated. This is most likely to provide spontaneous facial movement in the longer term. Direct repair is clearly not an option given the nerve substance loss. A cross-face nerve graft would only be required if the facial nerve was resected more proximally, thereby leaving no suitable stump for coaptation. The hypoglossal nerve could be used in this setting to coapt directly to the proximal end of the facial nerve as it is easy to access, and provides excellent tone and normal appearance at rest. It also protects the eye and allows intentional facial movement although not spontaneous mimetic function. A major downside is the effect on the tongue which will be partly paralyzed and become atrophic. This can impact speech and swallowing. Furthermore, involuntary grimacing can occur with tongue movement. A compromise is to use a split hypoglossal nerve transfer.1–3
Loss of marginal mandibular nerve branch results in functional loss of the depressor anguli oris (DAO) muscle with the inability to pull the corner of the mouth downward. The anterior belly of the digastric muscle can be transferred and inserted into the lower lip, close to the insertion of DAO, just medial to the oral commissure. This provides restoration of lower lip depression. Alternatively, botulinum toxin can be used on the unaffected side to provide better lower lip symmetry, as an alternative to surgery. The other procedures listed target the midface and upper lip in order to reproduce a smile, but do not provide a suitable vector to restore marginal nerve function.1