Facial Nerve PDF

# The Management of the Paralysed Face ## Introduction - Facial nerve paralysis is a distressing and disfiguring condition. - It impacts facial symmetry and expression. - It impacts both at rest and during voluntary movement. - Patients with facial paralysis tend to avoid social interactions. - It...

# The Management of the Paralysed Face ## Introduction - Facial nerve paralysis is a distressing and disfiguring condition. - It impacts facial symmetry and expression. - It impacts both at rest and during voluntary movement. - Patients with facial paralysis tend to avoid social interactions. - It can severely compromise psychosocial development. - It can result in corneal exposure keratitis, epiphora, and difficulty with speech and alimentation. - It can lead to respiratory difficulties due to collapse of the internal nasal valve. - It can impair the specialized functions of taste, hearing, and lacrimal gland secretion. - Facial paralysis results in a combination of functional and aesthetic concerns with profound psychosocial difficulties. ## History of Surgery for Facial Palsy - Sir Charles Bell first identified the facial nerve as the motor supply to the muscles of facial expression in 1829. - Drobnick performed the first facial nerve repair by coaptation of the facial and spinal accessory nerves in 1879. - Bunnell attempted the first intratemporal repair of the facial nerve in 1927. - Thompson reported the first series of non-vascularized muscle transplants for facial paralysis using the palmaris longus and extensor digitorum brevis muscles in 1971. - Scaramella pioneered the use of cross-facial nerve grafting as a technique for the reinnervation of unilateral facial paralysis, heralding the modern era of reanimation surgery. - Harii et al. described the first successful use of vascularized free muscle transfer for facial reanimation, using the gracilis muscle to reproduce a smile in 1976. - Today, free tissue transfer remains the gold standard of facial reanimation surgery. - Terzis and Manktelow described the dual innervated pectoralis minor transfer making use of two separate cross-facial nerve grafts to improve independent motor control for eyelid closure and lip elevation in 1982. - Manktelow described the 'minitransfer' of a thinned segment of the gracilis as a means of reducing bulk in the cheek without compromising muscle power or excursion. ## Functions of the Facial Nerve - The frontalis, orbicularis oris and oculi, zygomaticus major, levator labii superioris and depressor labii inferioris are functionally the most important muscles innervated by the facial nerve. - Paralysis of the frontalis results in ptosis of the forehead and brow that worsens over time with gravity and the loss of skin elasticity associated with ageing. - Paralysis of the orbicularis oculi prevents normal eyelid closure and may compromise the ability to blink. - Globe exposure is further exacerbated by retraction of the upper eyelid due to the unopposed action of the levator palpebrae muscle. - Loss of tone in the lower lid due to paralysis of the orbicularis and the effects of gravity, results in ectropion and loss of contact between the globe and the canalicular system, precluding normal tear drainage. - Desiccation of the globe, exposure keratitis and epiphora, as well as an expressionless, staring eye, can result from a combination of lacrimal gland dysfunction and abnormal tear drainage. ## Facial Nerve Anatomy - The facial nerve is composed of approximately 10000 neurons, 70 per cent of which supply the muscles of facial expression. - The remaining 30 per cent of the facial nerve's neurons are composed of the 'nervus intermedius'. - The facial nerve's nerve nucleus receives bilateral cortical projections destined for the upper facial muscles, and unilateral projections innervating the lower facial muscles. - Clinically, an injury proximal to this level will spare function in the orbicularis oculi and frontalis muscles allowing for eyelid closure and forehead elevation. - The facial nerve nuclei receive afferent input from both the trigeminal nerve and acoustic nuclei, respectively forming a component of the corneal and stapedial reflexes. - Neurons exiting the facial nerve nucleus pass around the abducens nucleus as they emerge from the brainstem. - A lesion near the fourth ventricle may therefore involve both these nerves and the superior salivatory nucleus resulting in a dry eye, as well as cranial nerve (CN) VI and VII dysfunction. ## The Pathophysiology of Facial Palsy - Bell's palsy accounts for more than half of all cases of facial palsy. - The incidence is approximately 20 cases per 100 000 per annum and increasing with age. - There is an equal male to female ratio. - Less than 1 per cent of cases are bilateral. - The recurrence rate is about 10 per cent. - Diabetics and pregnant women are known to be at increased risk. ## History and Physical Examination - The patterns of signs and symptoms associated with facial paralysis often point to the likely site and aetiology of the lesion. - A thorough history and clinical examination must therefore be undertaken of each new patient. **The history should include:** - facial nerve pathology. - clinical course. - patient's specific concerns and expectations. - examination. - review of options and communication with the patient. **The physical examination:** - The speed of onset, duration and progression of the paralysis should be noted. It can suggest an aetiology. - Past medical history should include previous episodes of facial palsy, trauma or relevant surgery. - Concurrent medical conditions should be noted. - In infants, family history, gestational history, and drug consumption should be documented. - Patients should be encouraged to communicate their concerns and expectations. - Discomfort and oral competence should be assessed as part of the examination. ## Investigations for Facial Palsy ### Blood tests - Blood tests may be ordered according to the patient's general health. - They can be based on the history and the proposed operation. - They can determine the aetiology of facial palsy based on the history and physical examination. **Blood tests include:** - Fluorescence in situ hybridization for velocardiofacial syndrome. - Toxoplasmosis, rubella, cytomegalovirus and herpes simplex screening. - Chromosomal analysis to determine syndromic cases. ### Imaging studies - Computed tomography (CT) and magnetic resonance imaging (MRI) are useful in the diagnosis of injury to, or tumour around, the intratemporal or intracranial portions of the facial nerve. - They can show the path of the facial nerve. - They can show the extent of swelling or disruption. - They can determine the developmental aetiology of the facial nerve palsy. ### Electromyography - Electrophysiological testing can help to determine the site and extent of injury. - It can assess the potential for recovery. - It can determine the progression of nerve function. **Electrophysiological tests:** - Nerve excitability test (NET) is low-cost and practicable, but subjective. - Maximum stimulation test (MST) is a modified version of the NET. - Electroneuronography (ENOG) objectively measures neural degeneration following facial nerve stimulation. - Electromyography (EMG) can be used to assess the potential for muscle recovery. ## The Treatment of Facial Palsy - Following accurate diagnosis and thorough physical assessment, supplementary electrophysiological testing is required to estimate the probability for spontaneous recovery. - Conservative therapies or temporary surgical procedures should be used to protect the eye from exposure keratitis. **The treatment of facial paralysis can be either medical or surgical.** ### Medical therapy - Eye protection is the most urgent consideration. - Exposure keratitis is prevalent in facial nerve injuries involving the frontal and zygomatic branches lateral to the outer canthus. - Artificial tears should be used during the daytime and an ointment at night to protect the eye. - Drops containing hydroxypropyl cellulose, hydroxypropyl methylcellulose or polyvinyl alcohol are commonly used by day. - Thicker ointments containing petrolatum, mineral oil or lanolin are used at night. - The eye may be taped closed at night. - Medication can speed the resolution of facial paralysis. - Corticosteroids can be used for traumatic facial paralysis in newborns. ### Surgical therapy - Direct coaptation is the most ideal surgical approach. - Intraoperative nerve simulation should be used to locate the distal branches of the nerve. - Nerve repair should be tension free. - Interpositional nerve grafts are used when direct repair is not possible. - Muscle transfers can be used when nerve repair is either impossible or inappropriate. - Slings, brow lifts, and blepharoplasties are used to correct facial symmetry when there is no possibility of nerve repair or recovery. **The specific procedures available for facial reanimation will be considered by region:** ### The Brow - Brow ptosis can be compensated in the non-paralysed face by contraction of the frontalis muscle, but it can lead to obstruction of the visual axis, especially in older people with long-standing paralysis. **Corrective procedures:** - Suprabrow excision of redundant forehead skin is often sufficient. - Endoscopic brow lifts may be undertaken. ### The Upper and Lower Eyelids - Inability to close the eye fully and loss of the blink reflex due to orbicularis muscle paralysis renders the cornea prone to injury, which can be painful and cause blindness. - The ectropic lower eyelid exacerbates the problem by interfering with tear transport, resulting in epiphora. **Corrective procedures:** - Gold weights are placed on the upper eyelid, anterior to and secured to the tarsal plate. - Spring devices are used to aid in eye closure. - Permanent tarsorraphy may be required to aid eye closure. - Temporalis muscle transfer can be used to correct dynamic eyelid closure. ### The Smile - Reanimation of the smile is the most challenging aspect of facial paralysis surgery, especially in the elderly patient with poor health or unwilling to undergo more major surgery. **Corrective procedures for the smile:** - **Static procedures** utilize slings of plantaris, palmaris, second, or third toe extensor tendon, fascia lata or, less commonly, Gore-tex® or Endotine® rib-bon. - Thread lifting. - Facelift procedures can be combined with static slings. - **Dynamic reanimation** of the smile is appropriate for well-motivated patients with no contraindications to free muscle transfer. - **Muscle transposition** involves the use of local muscle. - **Free muscle transfer** is generally regarded as the most reliable method for dynamic reanimation. ### The Lower Lip - The lower lip is animated by the orbicularis, the depressors anguli oris and labii inferioris, mentalis and the platysma. - Marginal mandibular nerve palsy causes elevation of the ipsilateral lower lip and drooling. - Direct neurotization of the depressors can be attempted by cross-facial nerve grafting, but this is infrequently used. **Corrective procedures for the lower lip:** - Static slings between the lateral orbicularis oris muscle and the zygomatic arch can be used to improve resting posture. - Resection of the depressor anguli oris muscle on the normal side of the lip. - Botox can be used temporarily to address lip asymmetry. - Transfer of the anterior belly of the digastric or platysma. - Wedge excision of the flaccid lower lip may be required on occasion. ## Follow-up Care and Rehabilitation - Free muscle transfers must be closely monitored for flap viability. - Physical therapy, including biofeedback and facial expression exercises, should begin early to achieve optimal results. - Rehabilitation is relatively straightforward with a cross-facial nerve graft. - The rehabilitation is more demanding for the patient when the masseter nerve is used as a donor. - The therapist should evaluate donor site morbidity, including parasthesiae, tongue atrophy, and difficulty with mastication. - The patient must learn to control the smile by clenching of the teeth. ## Complications - Facial reanimation and static procedures are subject to the same general complications as any surgery. **Complications include:** - Infection. - Haematoma. - Delayed wound healing. - Flap failure. ## Outcome and Prognosis - More than 90 per cent of adults with Bell's palsy and children with facial nerve paralysis caused by blunt trauma will recover spontaneously. - In other cases, including congenital paralysis, the optimal outcome is rarely fully achieved without surgical intervention. **Factors which impact the outcome and prognosis for facial nerve palsy:** - Bilateral cases, which are most often congenital, are difficult to treat. - Women tend to do better than men. - Younger people tend to do better than older people. - Patients with developmental causes of facial nerve paralysis tend to do better than those with post-traumatic nerve palsies. ## Key Evidence - Single-stage facial reanimation procedures are becoming the gold standard and obviate some of the potential for complications and the delay in recovery associated with two-stage procedures. - Bilateral facial paralysis precludes the use of the contralateral facial nerve for reanimation procedures and necessitates a different approach. - In all cases of facial paralysis surgery, the need for multiple primary and revisional procedures can be anticipated to achieve optimal results. ## Key Learning Points - Facial paralysis is aesthetically deforming and functionally disabling. - The aetiology is varied but the treatment options for established paralysis are less so. - The objectives and commitment of the patient are as important as the experience and skill of the surgeon and multidisciplinary team. - Surgical treatment involves static and dynamic procedures, or a combination of both. - A sound and consistent approach is necessary for a good outcome. - Managing such patients is a long-term undertaking and careful follow up is essential. - The results can be highly rewarding for the patient and surgeon alike.