FACIAL PARALYSIS

Facial paralysis is a disfiguring disorder that has a great impact on the patient. Facial nerve paralysis may be congenital, neoplastic, or result from infection, trauma, toxic exposures, or iatrogenic causes. The most common cause of unilateral facial paralysis is Bell palsy, also known as idiopathic facial paralysis. Bell palsy is thought to account for approximately 60-75% of cases of acute unilateral facial paralysis.

Pathophysiology: The course of the facial nerve is tortuous, both centrally and peripherally

The facial nerve nucleus lies within the reticular formation of the pons, adjacent to the fourth ventricle. The facial nerve roots include fibers from the motor, solitary, and salivatory nuclei. The fibers of the facial nerve then course around the sixth cranial nerve nucleus and exit the pons at the cerebellopontine angle. The fibers go through the internal auditory canal along with the vestibular portion of the eighth cranial nerve. The narrowest portion of the internal auditory canal is the labyrinthine segment. This is the location that is thought to be the most common site of compression of the facial nerve in Bell palsy.

The facial nerve passes through the stylomastoid foramen in the skull and terminates into the zygomatic, buccal, mandibular, and cervical branches. These nerves serve the muscles of facial expression, which include frontalis, orbicularis oculi, orbicularis oris, buccinator, and platysma. Other muscles innervated by the facial nerve include stapedius, stylohyoid, posterior belly of the digastric, occipitalis, and anterior and posterior auricular muscles.

Bell palsy is thought to be caused by edema and ischemia resulting in compression of the facial nerve in its course through the bony canal. The cause of the edema and ischemia is still being debated. In the past, cold exposure (eg chilly wind, cold air conditioning, or driving with the car window down) were considered the only triggers to Bell palsy. However, most authors believe that the herpes simplex virus (HSV) is the most likely cause.

Frequency:

• Internationally: Most population studies generally show an annual incidence of 15-30 cases per 100,000 populations.

Mortality/Morbidity:

• The majority of patients who suffer from Bell palsy have neurapraxia or local nerve conduction block. These patients are likely to have a prompt and complete recovery of the nerve.
• Patients with axonotmesis, with disruption of the axons, have a fairly good recovery but it is usually not complete.
• The risk factors thought to be associated with a poor outcome in patients with Bell palsy include (1) age greater than 60 years, (2) complete paralysis, and (3) decreased taste or salivary flow on the side of paralysis (usually 10-25% compared to the patient's normal side). Other factors thought to be associated with poor outcome include pain in the posterior auricular area and decreased lacrimation.

• Patients generally have a good prognosis; approximately 80-90% of patients recover without noticeable disfigurement within 6 weeks to 3 months. Patients aged 60 years or older have an approximately 40% chance of complete recovery. Patients younger than 30 years have only a 10-15% chance of less than complete recovery. If no recovery occurs by 4 months, then the patient is more likely to have sequelae from the disease, which include synkinesis, crocodile tears, and rarely hemifacial spasm.
• Synkinesis is an abnormal contracture of the facial muscles while smiling or closing the eyes. It may be mild and result in slight movement of the chin when the patient blinks, eye closure with smiling, or contracture around the mouth while blinking. Crocodile tears are observed; patients shed tears while they eat.
• Facial spasm is a very rare complication of Bell palsy. It occurs as tonic contraction of one side of the face. Spasms are more likely to occur during times of stress or fatigue and may occur during sleep.
• Diabetic patients are 30% more likely than nondiabetic patients to have only partial recovery; recurrence of Bell palsy is also more common among diabetic patients.

• Bell palsy recurs in 10-15% of patients. It may recur on the ipsilateral or contralateral side of the initial palsy. Recurrence usually is associated with a family history of recurrent Bell palsy. Approximately 30% of patients with recurrent ipsilateral facial palsy were found to have tumors of the seventh nerve or parotid gland.

Sex:

• Bell palsy appears to affect the sexes equally. However, young women aged 10-19 years are more likely to be affected than men in the same age group.

• Pregnant women have a 3.3 times higher risk of being affected by Bell palsy than nonpregnant women (due to more chances of edema formation); Bell palsy occurs most frequently in the third trimester.

Age: The lowest incidence is found in persons younger than 10 years and the highest incidence in persons aged 60 years or older.

History: Bell palsy is a diagnosis of exclusion. The diagnosis must be made on the basis of a thorough history and physical examination and use of diagnostic testing when necessary.

• Symptoms of Bell palsy

• Acute onset of unilateral upper and lower facial paralysis (over a 48-h period)

• Posterior auricular pain

• Decreased tearing

• Taste disturbances

• The paralysis must include the forehead and lower aspect of the face. The patient may report inability to close the eye or to smile on the affected side. He or she also may report increased saliva on the side of the paralysis. If the paralysis involves only the lower portion of the face, a central cause should be suspected (ie, supranuclear). If the patient complains of contralateral weakness or diplopia in conjunction with the supranuclear facial palsy, a stroke or intracerebral lesion should be strongly suspected.

• Half of the patients affected with Bell palsy may complain of posterior auricular pain. Ask the patient if he or she has experienced trauma, which may account for the pain and facial paralysis.

• One sixth of patients experience decreased lacrimation.

• If a patient has gradual onset of facial paralysis, weakness of the contralateral side, or history of trauma or infection, other causes of facial paralysis must be strongly considered. Patients who have bilateral facial palsy must be evaluated for GBS, Lyme disease, and meningitis.

• Recurrent ipsilateral facial paralysis must raise the suspicion of a tumor of the seventh nerve or parotid gland. If the patient reports sudden onset of hearing loss and severe pain with the onset of facial paralysis, Ramsay Hunt syndrome must be considered.

Physical:

• Initial inspection of the patient demonstrates flattening of the forehead and nasolabial fold on the side affected with the palsy.

• When the patient is asked to raise the eyebrows, the side of the forehead with the palsy will remain flat.

• When the patient is asked to smile, the face becomes distorted and lateralizes to the side opposite the palsy.

• The patient is not able to close the eye completely on the affected side. On attempted eye closure, the eye rolls upward and inward on the affected side. This is known as Bell phenomenon and is considered a normal response to eye closure.

• A careful examination of the head, ears, eyes, nose, and throat (HEENT) must be carried out in all patients with facial paralysis.

• The external auditory canal must be inspected for vesicles, injection, infection, or trauma.

• The patient may have decreased sensation to pinprick in the posterior auricular area.

• Bell phenomenon is observed on attempted eye closure.

• With weakness/paralysis of the orbicularis oculi muscle (facial nerve innervation) and normal function of the levator muscle (oculomotor nerve innervation), eye closure may be partial or absent. The patient may have decreased tearing and susceptibility to corneal abrasion and dryness of the eye. The patient may appear to have loss of corneal reflex on the affected side; however, the contralateral eye blinks when testing the corneal reflex on the affected side.

• A careful oral examination must be performed.

• Taste and salivation are affected in many patients with Bell palsy.

• Taste may be assessed by holding the tongue with gauze and testing each side of the tongue independently with salt, sugar, and vinegar. The mouth must be washed after testing with different substances. The affected side has decreased taste as compared to the normal side.

• Careful neurologic examination is necessary in patients with facial paralysis. A neurologic abnormality warrants neurologic referral and further testing such as MRI of the brain, lumbar puncture, and electromyography (EMG) where appropriate.

Medical Care: In general, persons with true Bell palsy have an excellent prognosis. The goals of treatment are to improve function of the facial nerve and reduce neuronal damage. Many issues must be addressed in treating patients with Bell palsy. The most important consideration is the onset of symptoms. Treatment may be considered for patients who have the onset of paralysis within 1-7 days of the initial office visit. The American Academy of Neurology published a practice parameter in 2001 stating that steroids are probably effective and acyclovir (with prednisone) is possibly effective for treatment of Bell palsy.

The most widely accepted treatment for Bell palsy is corticosteroids. However, the use of steroids is still controversial because most patients recover without treatment.

• The recommended dose of prednisone is 1 mg/kg or 60 mg/d for 6 days, followed by a taper, for a total of 10 days.
• When using corticosteroids for the treatment of Bell palsy, caution should be used in patients with tuberculosis, peptic ulcer disease, diabetes mellitus, renal or hepatic dysfunction, or malignant hypertension.

• Since HSV is widely accepted as the likely etiologic agent of Bell palsy, trials using acyclovir have been conducted. The dose of acyclovir is 400 mg orally 5 times per day.

• Whether to use prednisone alone or combination therapy is left to the discretion of the physician. For patients who have a contraindication to steroid therapy, acyclovir may be given as solitary treatment.

• That eye care is imperative in Bell palsy is accepted universally. The patient's eye is at risk for drying, corneal abrasion, and corneal ulcers. Eye care includes artificial tears for use during the day as well as eyeglasses or shields. At night, eye lubricants may be used. If artificial tears are not effective during the daytime, then lubricants may be used; however, they may cause blurring of vision.

Surgical Care: Surgery for Bell palsy is controversial. In the past, surgical decompression of the facial nerve was considered for patients whose facial muscles demonstrated less than 90% of normal activity on electrophysiologic studies. Surgical decompression of the facial nerve involves a middle fossa craniotomy with an extradural approach. However, recent trials suggest this is not beneficial in patients with Bell palsy.

Complications:

• Approximately 30% of patients with Bell palsy experience sequelae of the paralysis, which include incomplete motor recovery, incomplete sensory regeneration, and parasympathetic impairment.

• Incomplete motor recovery may manifest as oral incompetence or epiphora.

• Incomplete sensory recovery may result in dysgeusia (impairment of taste) or ageusia (loss of taste).

Prognosis:

• The natural course of Bell palsy varies from early complete recovery to substantial nerve injury resulting in persistent paralysis.

• One third of patients regain complete recovery of facial motor function.

• The remainder of patients have permanent neurological and cosmetic abnormalities.

Patient Education:

• To prevent corneal abrasions, the patient should be educated concerning eye care.

• They also should be encouraged to do facial muscle exercises using passive range of motion as well as actively closing their eyes and smiling.