Facial Paralysis: Static and Dynamic Treatment

ANATOMIC ESSENTIALS

What are the four functional components of the facial nerve?

1. Somatic motor efferent—muscles of facial expression, auricular muscles, occipitalis, posterior belly digastric, stylohyoid and stapedius.

2. Special sensory afferent—(chorda tympani nerve running with lingual nerve) taste anterior 2/3 tongue, hard and soft palate.

3. General sensory somatic afferent—(posterior auricular nerve) sensation to skin of concha, small area behind ear, posterior ear canal. Arnold’s nerve (CN X)—major contributor to external ear canal sensation.

4. Visceral motor efferent—(greater petrosal nerve) autonomic parasympathetic to mucus glands nose, hard palate, soft palate and lacrimal gland (chorda tympani nerve) submandibular, sublingual, and minor salivary glands.

What landmarks are commonly utilized to identify the main trunk of the facial nerve?

The nerve lies approximately 1 cm deep to the tragal pointer and medial to the posterior belly of the digastric muscle.

What landmarks describe the course of the frontal branch of the facial nerve?

Pitanguy’s line: A line extending 0.5 cm below the tragus to 1.5 cm above the lateral brow with the nerve running on the undersurface of the temporoparietal fascia.

What structures can facilitate identification and protection of the marginal mandibular nerve branches?

The branches consistently lie on top of the facial artery and vein 1 to 3 cm below the mandibular border.

Which facial muscles are innervated on their superficial surface?

Most muscles of facial expression are innervated on their deep surface with the exception of the levator anguli oris, buccinator, and mentalis.

Why does the anterior belly of the digastric muscle remain functional with facial nerve injury?

The anterior belly is innervated by the mylohyoid branch of the inferior alveolar nerve (Trigeminal).

Hyperacusis suggests injury at what level of the facial nerve?

Injury of the facial nerve proximal to the branch of the stapedius muscle (middle ear) often produces increased perception of sound intensity.

FACIAL PARALYSIS ETIOLOGY

A patient presents with the onset of mild flu-like symptoms and pain behind the right ear followed hours later by a complete unilateral hemi-facial paralysis. After neurologic evaluation to rule out a cerebrovascular accident what medical treatment is frequently prescribed?

This is a classic presentation of Bell’s palsy that is believed to represent a herpes simplex virus (HSV) type 1 infection of the facial nerve. A course of oral steroids should be prescribed within 72 hours of the onset of the paralysis. Antiviral medications (i.e., Acyclovir) are also frequently utilized, however, their benefit is less clear. Facial paralysis and painful vesicles involving the ear are associated with varicella zoster infection (VZV) known as Ramsay Hunt syndrome. The treatment for both is the same, however, more limited recoveries are frequently encountered with Ramsay Hunt syndrome when compared to Bell’s palsy.

A patient is referred by their primary care physician for surgical correction of Bell’s palsy. The patient reports a slowly progressive, unilateral weakness of the midface and impaired ability to smile. What is the next step in this patient’s treatment?

Slow onset of facial weakness is highly suspicious for extratemporal causes of facial paralysis such as tumors of the parotid gland. A thorough head and neck examination followed by imaging (CT, MRI) should be undertaken prior to surgery.

A patient presents with unilateral facial paralysis and reports a “bull’s eye” rash, fatigue and fever after a hiking trip. What is the suspected diagnosis?

Lyme disease is a spirochete (Borrelia burgdorferi) infection disseminated by tick bites. The diagnosis is confirmed with serologic testing and optimal treatment with antibiotics (ceftriaxone, doxycycline, azithromycin).

Postoperative radiation therapy is planned following radical parotidectomy with segmental resection of the facial nerve. Should nerve graft reconstruction be delayed?

There is no functional advantage to delaying nerve graft reconstruction until radiation therapy is completed. In addition, more accurate identification of the transected nerve branches will be possible during the initial surgical procedure.

A child with bilateral facial paralysis presents for evaluation. What is the second most common cranial nerve effected by this syndrome?

Moebius syndrome is a rare disorder effecting 1 in 50,000 births. It has a genetic component, however, most cases are sporadic and multifactorial. The facial nerve is involved in all cases. The abducens nerve (CN VI) is the second most frequently involved cranial nerve (approximately 75%) producing a lateral gaze palsy. The hypoglossal nerve (CN XII) is affected in approximately 25% of cases and is associated with a hypoplastic tongue. Cranial nerves VIII, III, and IV are usually spared. Other associated anomalies include club foot (approximately 30%), hand and upper limb deformities, Poland’s anomaly (approximately 15%) and high-arched palate. Intelligence is usually normal, however, the autistic behavior spectrum is present in approximately 30% of cases.

What is the optimal time for exploration of the facial nerve following sharp laceration?

Exploration should take place within 72 hours. The transected distal nerve branches continue to conduct during this period allowing for more straightforward operative identification.

Do facial nerve lacerations immediately adjacent to the nasolabial fold require repair?

Reasonable recovery can be expected with cheek lacerations medial to the lateral canthus without direct nerve repair due to the extensive arborization of the buccal and zygomatic branches. However, all transected branches should be repaired if identified.

What clinical presentation of a temporal bone fracture favors operative intervention?

Immediate onset of facial paralysis often requires surgical exploration, while delayed paralysis is commonly managed with steroids and observation.

Which facial nerve branch is most frequently injured during rhytidectomy?

The buccal branches. The clinical sequelae of injury to the buccal branch is less than that seen with injury to the marginal and frontal branches. This is due to the extensive arborization of the marginal and frontal branches.