Surgical Reanimation Techniques for Facial Palsy/Paralysis

Clinical Significance and Psychosocial Impact

• Functions of the Facial Nerve: The facial nerve (CN VII) provides motor control of facial musculature, both conscious and subconscious. Its roles include:

  • Ocular protection.

  • Nasal airflow.

  • Oral continence.

  • Bilabial speech articulation.

  • The ability to smile, a defining human characteristic.

• Psychosocial Consequences: Facial palsy causes functional, aesthetic, and psychosocial insults. McGrouther ($1997$) described facial disfigurement as the “last bastion of discrimination,” leading to workplace and social bias.

• Psychological Effects: According to Newell ($1991$) and Ryzenman et al. ($2005$), individuals may suffer from social isolation, decreased self-esteem, negative self-image, and a high incidence of depression.

• Intervention Determinants: Psychological stress, rather than functional deficit alone, often predicts the need for surgical intervention (Van Swearingen et al. $1998$; Bradbury et al. $2006$). The degree of injury does not always correlate with the severity of psychosocial disturbance (Robinson $1997$).

Anatomy of the Facial Nerve (CN VII)

• Embryology: Derived from the second branchial arch.

• Intracranial Segment:

  • Origin: Pontine region of the brain stem.

  • Frontal Branch Input: Cell bodies for the frontal branch receive bilateral cortical input. Other facial nuclei received contralateral input.

  • Lesion Types:

    • Supranuclear (Upper Motor Neurone) Lesion: Results in contralateral facial paralysis with bilateral sparing of the frontalis muscle.

    • Lower Motor Neurone Lesion: Results in ipsilateral facial hemiplegia, including the frontalis muscle.

  • Exit: Enters the temporal bone at the internal auditory meatus with the vestibulocochlear nerve (CN VIII).

• Intratemporal Segment (Fallopian Canal):

  • Labyrinthine Segment: $3-5\,mm$ long; courses to the geniculate ganglion. It is the narrowest part ($1.42\,mm$ diameter); the nerve occupies $83\%$ of available space. Shearing often occurs at the junction with the tympanic segment. The greater petrosal nerve (parasympathetic to lacrimal/palatal glands) branches here.

  • Tympanic Segment: $8-11\,mm$ long; courses from the geniculate ganglion to the lateral semicircular canal.

  • Mastoid Segment: $9-12\,mm$ long; extends to the stylomastoid foramen. It gives off:

    • Tympanic nerve: Sensory to the external auditory canal. Injury causes Hitselberger’s sign (hypoaesthesia).

    • Nerve to stapedius: Dampens loud noise. Spared in Möbius syndrome.

    • Chorda tympani: Provides parasympathetic innervation to submandibular/sublingual glands and taste to the anterior two-thirds of the tongue.

• Extratemporal Segment:

  • Exits stylomastoid foramen; protected by the mastoid tip, tympanic ring, and mandibular ramus. In children under $2$ years, the nerve is more superficial and prone to injury.

  • Arborisation: Enters the parotid gland and divides at the pes anserinus into superior (temporozygomatic) and inferior (cervicofacial) divisions.

  • Terminal Branches:

    • Temporal (Frontal): Travels along Pitanguy’s line ($0.5\,cm$ below the tragus to $1.5\,cm$ above/lateral to the eyebrow). Supplies the frontalis.

    • Zygomatic: Supplies orbicularis oculi; critical for eye protection. Injury causes lagophthalmos (inability to close the eye), risk of exposure keratitis, and blindness.

    • Buccal: Located $1\,cm$ below the zygomatic arch. Supplies buccinator and upper lip. Zuker’s point (midpoint between helical root and oral commissure) helps locate branches to zygomaticus major. Interconnections exists in $70-90\%$ of cases.

    • Marginal Mandibular: Supplies depressor anguli oris. Runs deep to platysma and superficial to facial vessels. Only connected to other rami in $15\%$ of cases; injury usually causes clinical weakness.

    • Cervical: Supplies platysma from its deep surface.

Aetiology of Facial Paralysis

• Congenital Causes:

  • Obstetric Injury: Most common; often due to forceps delivery. Most recover within a month.

  • CULLP (Congenital Unilateral Lower Lip Palsy): Asymmetrical crying facies affects $1$ in $160$ live births. Linked to other anomalies in $10\%$ of cases, primarily cardiovascular ($44\%$).

  • Möbius Syndrome: Rare, unknown origin. Involves CN VII (always), CN VI ($75-100\%$), and CN XII. Associated with limb abnormalities ($25\%$), Poland’s syndrome ($15\%$), and Pierre-Robin sequence.

  • Goldenhar’s Syndrome: Includes hemifacial microsomia and vertebral anomalies.

• Acquired Causes:

  • Bell’s Palsy: Accounts for $66-85\%$ of cases. Incidence of $1$ in $5000$; lifetime risk of $1$ in $60$. Linked to latent herpes virus and nerve swelling in the fallopian canal. Management: Prednisolone ($30\,mg$ twice daily for $5$ days, then taper over $5$ days). Recovery: $85\%$ within $3$ weeks; $15\%$ at $3-6$ months.

  • Trauma: Second most common; includes temporal bone fractures (transverse fractures carry higher risk of paralysis) and penetrating wounds.

  • Tumours: Progressing weakness over months or abrupt onset without return of function at $6$ months suggests neoplasm (e.g., parotid gland malignancy, acoustic neuroma).

  • Infections: Ramsay-Hunt syndrome (Varicella zoster), Lyme disease (Borrelia bacteria resulting in bilateral palsy), and HIV-related conditions.

  • Melkersson-Rosenthal Syndrome: Triad of non-inflammatory facial oedema, lingua plicata (fissured tongue), and facial palsy.

Clinical Assessment

• Multidisciplinary Team: Otolaryngology, plastic surgery, neurosurgery, ophthalmology, psychology, and therapy (speech, occupational, physical).

• Top-Down Examination:

  • Upper Third: Assess forehead wrinkles and brow position. Measure lagophthalmos. Perform the "snap-test" for lower lid laxity. Check for Bell’s phenomenon (upward globe movement on closure attempt, present in $75\%$ of people).

  • Middle Third: Cottle’s manoeuvre for nasal valve collapse. Check nasolabial crease symmetry and oral commissure excursion. Use Zuker’s point for zygomaticus major function.

  • Lower Third: Assess depressor anguli oris and chin position. Platysma assessment involves asking the patient to pretend to shave.

• Grading Scales:

  • Sunnybrook Facial Grading System: Composite score for resting symmetry, movement, and synkinesis (longitudinal data).

  • FaCE Scale: $51$ items ($7$ VAS, $44$ Likert scale points) measuring perception of impairment.

  • House-Brackmann Score: Designed for monitoring, not for postoperative outcomes of reconstruction.

• Adjuncts: Electromyography (<$18$ months), medical photography/videography, and CN V/XI/XII assessment as potential donor nerves.

Management and Non-Surgical Treatment

• Primary Goal: Eye protection. Regular lubricating drops (day) and gel (night), taping, protective glasses, or humidification chambers.

• Botulinum Toxin: Used on the normal side to improve symmetry (e.g., weakening the contralateral frontalis or depressor anguli oris). Also treats platysmal bands and synkinesis.

• Therapies: Mime therapy, speech therapy, and cognitive behavioural therapy (CBT) for psychological support.

Static Surgical Procedures

• Indications: Elderly or unfit patients, established paralysis without viable muscle, or as a temporising measure.

• Eyelid/Brow Procedures:

  • Tarsorrhaphy: Narrowing the palpebral fissure. McLaughlin tarsorrhaphy is a lash-preserving procedure.

  • Gold Weights ($1-1.6\,g$): Sutured to the tarsal plate. insertion crease is $10\,mm$ from the lid margin. $10\%$ extrusion rate at $5$ years.

  • Müllerectomy: Advancing levator aponeurosis/Müller’s muscle. Ratio: $1\,mm$ resection for $0.32\,mm$ elevation.

  • Brow Lift: Endoscopic or open. Transpalpebral brow-pexy places the scar in the eyelid.

• Slings and Lifts:

  • Static Slings: Using Tensor fascia lata (TFL) ($5\,cm \times 25\,cm$) or palmaris longus to support the corner of the mouth or open the external nasal valve.

  • Facelift: Suborbicularis oculi fat lift suspends fat with zygomaticus/levator origins to deep temporal fascia.

Dynamic Surgical Reanimation Strategies

• Early Reconstruction (<$1$ year): Nerve-based repairs.

• Late Reconstruction (>$1$ year): Muscle-based reconstruction (segmental free muscle transplants).

• Nerve Repair Principles:

  • Tension-free coaptation: Minimal epineural sutures ($8-0$ gauge or finer). If the gap is >$2\,cm$, a nerve graft is required.

  • Regeneration Rate: Approximately $1\,mm$ per day after an initial $2-4$ week delay.

• Donor Nerves for Grafting:

  • Greater Auricular Nerve: In the same surgical field; sensory loss to the earlobe/mandible angle. Found at Erb’s point.

  • Sural Nerve: Distant donor site (allows two-team approach). Provides $30-35\,cm$ of length. Found posterior to the lateral malleolus.

• Cross-Facial Nerve Grafting (CFNG):

  • Harnesses the uninjured side. Two-stage approach typical.

  • Stage $1$: Sural nerve coapted to functional buccal branches. Stage $2$: ($9-12$ months later after positive Tinel’s sign) Graft coapted to paralysed stump or free muscle.

Nerve Transfers and Local Muscle Flaps

• Hypoglossal Nerve Transfer (CN XII to VII):

  • Classic: Entire CN XII divided and reflected to CN VII. Causes ipsilateral tongue hemiatrophy.

  • Split Technique: $30\%$ of CN XII diameter used to reduce synkinesis.

  • Jump Graft: $30\%$ incision into CN XII with a nerve graft to preserve tongue function.

• Nerve to Masseter (Preferred Option):

  • Branch of mandibular division (CN V3). Located $3\,cm$ anterior to tragus and $1\,cm$ below zygoma, approximately $1.5\,cm$ deep to SMAS.

• Temporalis Lengthening Myoplasty (Labbé):

  • Detaching temporalis insertion from the coronoid process of the mandible. The muscle is rotated and lengthened to reach the nasolabial fold.

  • Surgical Steps: Bicoronal/modified incision down to deep temporal fascia. Preservation of temporal fat pad. Coronoid process tip severed by saw. Tendinous fibres sutured into upper/lower lips and oral commissure. Soft diet required for $3$ weeks post-op.

Free Muscle Transfer for Reanimation

• Indications: Longstanding paralysis where native muscle is non-viable (irreparable atrophy after $12-24$ months).

• Gracilis Muscle (Most Common):

  • Reliable vascular and nerve patterns (long motor nerve). Segmental dissection reduces bulk. Inset into orbicularis oris and anchored to deep temporal fascia or zygoma.

• Pectoralis Minor: Flat muscle, transferable without excess bulk; anatomy of neurovascular pedicle can be variable.

• Other Options: Latissimus dorsi (often used for bilateral Möbius syndrome), serratus anterior, or extensor digitorum brevis (though results for EDB were disappointing).

• Success Factors: Results typically decrease with increasing patient age.