Case Study

 54 year old black male presented to clinic complaining of sudden onset of left sided facial weakness for the past three days. He denies any extremity weakness, numbness, facial or ear pain, fevers, rashes, recent viral illnesses, or head trauma. Past medical history is non-contributory and denies history of stroke, hypertension, diabetes, cancer, sarcoidosis, or previous facial weakness. He is not on any medications.

Physical exam:Vitals- T-98.1 BP- 160/100

HEENT-PERRLA, EOM I

Left facial weakness including forehead

Left eye will not close completely and rolls upward, outward with attempt

Ears- normal tympanic membranes; no canal erythema, exudate, or lesions

No mastoid or sinus tenderness, no parotid masses

Oral cavity/oropharynx: poor dentition, no erythema or lesions

Neck- Supple, no adenopathy

CV- RRR, no murmurs

Lungs- Clear

Neuro- Alert, oriented x 4, CN II-XII intact except left 7^th palsy,

motor 5/5, DTR’s 2+/= all extremities, sensory intact

Assessment/Plan: 1.) Bell’s Palsy -eye protection with lacrilube as needed, eye patch at night

                                -prednisone 1 mg/kg/d taper over 10 days

                               -follow-up appt. in one week

                           2.) Hypertension -start hydrochlorothiazide 25 mg po qD

Bell’s Palsy is an acute, idiopathic, unilateral facial nerve paralysis and is reserved as a diagnosis of exclusion. It was named after Sir Charles Bell, a British Neurologist, who first described a syndrome in 1829 of complete facial paralysis with intact facial sensation after transection of the facial nerve at the stylomastoid foramen.^,

Bell’s Palsy is the most common cause of unilateral facial weakness. Occurrence rate is 10-30 cases per 100,000 people in general population. All ages are affected but it occurs most commonly between the ages of 15-45. Both sexes are affected equally as well as the right and left sides of the face. There is a 7-10% incidence of ipsilateral or contralateral recurrence. Family history is positive in 8-10% of patients. It is usually described as an acute onset of facial weakness over the preceding hours or days and sometimes associated with postauricular pain or abnormal taste sensation. It is often preceded by a recent upper respiratory tract infection, viral syndrome, or a cold draft to the affected side of the face. Diabetics are 4.5 times more likely to develop Bell’s Palsy than the general population. 11% of Bell’s Palsy patients and 32% of recurrent Bell’s Palsy patients have diabetes. Pregnancy is also associated with Bell’s Palsy. Pregnant women are 3.3 times more likely to develop the disease and 8 times more likely than the general population during the third trimester. 70% of all patients fully recover within 6 weeks. The remaining 30% develop various degrees of axonal degeneration which leads to persistent weakness, synkinesis, or contracture.^,,

It is still unknown what causes Bell’s Palsy. There are several theories which have been proposed but not clearly proven. Hilger and Kettle in 1931 proposed that Bell’s Palsy is due to ischemic neuronitis secondary to arteriolar constriction that is caused by autonomic nervous system dysfunction. They felt the ischemia led to nerve swelling within the bony confines of the facial canal. Fisch believes that entrapment neuropathy is the cause of Bell’s Palsy and based his theory on anatomic studies of histopathology of specimens, the fallopian canal, and results of intraoperative evoked electroneuronography. The viral cause theory has been proposed because of circumstantial evidence that has linked several viruses to Bell’s Palsy patients, especially herpes simplex. Adour showed in one study that 93-100% of patients with Bell’s Palsy had serum antibodies to herpes simplex compared to 85% of the control patients without the disease. Histologically, the affected facial nerve has infiltration by small, round inflammatory cells, disruption and breakdown of myelin sheath, or edema of the nerve in absence of arterial or venous thrombosis. This appearance is similar nerves affected with herpes zoster. It is proposed that the cause of the facial paralysis is reactivation of latent herpes simplex infection which is consistent with the reactivation of herpes zoster seen in the Ramsey-Hunt Syndrome (also causes a facial nerve palsy).^,,

The facial nerve has approximately 10,000 fibers in which 70% are motor fibers that innervate facial muscles and 30% are somatic afferent, visceral afferent, or visceral efferent fibers. The somatic afferent fibers are responsible for touch and pain in the external auditory canal. The visceral afferent fibers are involved with taste from the anterior 2/3 of the tongue. The visceral efferent fibers supply preganglionic parasympathetic innervation to the pterygopalatine and submandibular autonomic ganglia which are responsible for lacrimation(tearing) and salivation, respectively.

The facial nerve separates from the vestibulocochlear nerve in the internal auditory canal. It travels through the fallopian(facial) canal which is the largest bony canal in the body and exits via the stylomastoid foramen. The fallopian canal is found within the temporal bone is divided into segments called the labyrinthine, tympanic, and mastoid segments. The facial nerve first travels through the labyrinthine segment laterally and this segment is found between the internal auditory canal and the geniculate ganglion. It is the narrowest portion of the canal and the site of 90% of facial nerve injuries caused by temporal bone fractures. The greater petrosal nerve branches in this segment from the geniculate ganglion to supply parasympathetic autonomic innervation to the pterygopalatine ganglion which is responsible for lacrimation. Lesions medial to the geniculate ganglion which would be proximal to the greater petrosal nerve would produce all deficits of the facial nerve including decreased tearing, stapedius muscle paralysis, impaired taste to the anterior 2/3 of tongue, decreased salivation, and paralysis of ipsilateral facial muscles. Lesions lateral to the geniculate ganglion would therefore show all lesions except lacrimation would normal since the greater petrosal nerve is not involved. The facial nerve then travels horizontally 10 to 12 mm in the tympanic segment which is found between the first and second genu. After the second genu, the nerve travels vertically in the mastoid segment 15 to 20 mm until it exits the stylomastoid foramen and into the face. The stapedius and chorda tympani nerves branch in this segment. A lesion above the stapedius branch would result in an absent stapedius reflex and a lesion proximal to the chorda tympani branch would impair taste to the anterior 2/3 of tongue and decrease salivation. After the facial nerve exits the stylomastoid foramen, it enters the parotid gland and divides into the temporal, zygomatic, buccal, marginal mandibular, and cervical branches to innervate the muscles of facial expression.

Site of lesion testing can be performed by evaluating lacrimation, stapedial reflex, and salivation. However, the inflammation and demyelination usually occurs horizontally and not perpendicular to the facial canal. Therefore, these tests are only partial indicators of severity and can only be used to supplement other diagnostic information.^,

Important information to obtain from patients presenting with facial weakness includes date of onset, duration of symptoms, and precipitating factors. Diagnostic testing and therapy often depends on how many days they have had weakness. The most common accompanying symptoms seen in an analysis of 1,000 Bell's palsy patients by Adour et al in 1978 were postauricular pain in 60%, dysguesia(altered taste) in 57%, hyperacusis (abnormal sensitivity to sound) in 30%, and altered lacrimation in 17%. History which may lead to another cause of facial paralysis includes head trauma, ear drainage, tick exposure, recent facial surgery, hearing loss, tinnitus, vertigo, or gradual onset of paralysis over several weeks.^,

A thorough head and neck exam is required to accurately assess a patient with facial paralysis. Cranial nerve testing, inspection of the skin and oral cavity, palpation of the parotid gland, and otologic exam should all be performed. It is imperative to evaluate the involved eye as it may develop corneal abrasions or ulcers. A facial nerve grading system was developed by House and Brackmann in 1985 to help standardize reporting of the degree of facial paralysis as shown in and is helpful for grading a patient's recovery. It ranges from a Grade I in patients with normal facial function in all areas to a Grade VI in patients with total paralysis.

Signs of facial nerve (CN VII) paralysis includes drooping of the corner of mouth, lack of creases and skin folds including the forehead, and inability to close the eye on the affected side. Patients can be asked to wrinkle their forehead, raise their eyebrows, show their teeth or gums, close their eyes tightly, or tense their neck muscles to better assess function of this nerve. Upon attempted closure of the eyelids, many patients have Bell's phenomenon which is upward and outward movement of the eye on the paralyzed side. Other findings of facial paralysis may include food collection between teeth and gums, saliva dribbling from the corner of the mouth, loss of taste in the anterior portion of tongue, and hyperacusis. Sensory function remains intact.

Patients with prolonged paralysis may develop synkinesis where movement of one muscle group involuntarily moves other muscles due to faulty regeneration of nerve fibers. Another example of faulty regeneration in facial paralysis patients are crocodile tears where excess tear formation occurs on the affected side during eating because fibers originally innervating the salivary glands crossed over to innervate the lacrimal gland. Since Bell's palsy is a diagnosis of exclusion, physical findings of other causes of facial paralysis should be ruled out and will be discussed in the next section.^,,

Although idiopathic (Bell's) palsy is the most common cause of facial paralysis, many other pathologic processes may explain the paralysis as shown in Table 1. A detailed history and physical can often lead you to the correct diagnosis.

Idiopathic: A recurrent facial nerve paralysis associated with a fissured tongue and edema of the face and lips suggests Melkersson-Rosenthal Syndrome which often runs in families. These patients usually recover and are treated symptomatically with antihistamines and steroids.

Infectious: Vesicles surrounding the external auditory meatus, on the auricle, or within the external auditory canal is suggestive of Ramsay Hunt Syndrome (herpes zoster oticus). A rising herpes zoster titer or virus found in the vesicle fluid is diagnostic. Treatment includes acyclovir but recovery of facial nerve function is often incomplete. A presence of cellulitis or granulation tissue in the external auditory canal, especially in diabetics, could be caused by malignant otitis externa which involves bacterial invasion of the stylomastoid foramen by Pseudomonas. Acute otitis media can cause paralysis by bacteria gaining access to the nerve sheath through a bony dehiscence of the facial canal. Chronic otitis media can cause compression or abscess formation around the tympanic segment of the nerve. These infections require prompt intravenous antibiotics and an urgent ENT evaluation to assess the need for surgery to help preserve function of the nerve. Lyme disease is associated with facial palsy in 4.5 to 11% of cases and is the most common neurologic manifestation of the disease. Although a history of a recent tick bite may help lead to this diagnosis, 75% of Lyme disease patients diagnosed by Lyme titers never recall a tick bite. These patients are treated with tetracycline for 10 to 14 days.

Neopastic: A parotid mass would suggest a malignant neoplasm as the etiology. Unilateral hearing loss, tinnitus, or vertigo may suggest vestibular schwannoma, glomus tumor, or facial nerve neuroma. The diagnosis of intracranial masses are made by CT or MRI.^,

Neurologic: Peripheral neurologic abnormalities may suggest Guillain-Barre, myasthenia gravis, or CNS neoplasms. Unilateral extremity muscle weakness or facial paralysis sparing the forehead distribution can lead you to diagnosing a cerebrovascular accident. A CN VI lesion with ipsilateral abducens nerve paralysis may be found in a brain stem lesion.^,,

Traumatic: Trauma is the second most common cause of facial nerve paralysis and is usually evident by the history and physical exam. Closed head injuries frequently cause temporal bone fractures within the petrous portion. 80% of temporal bone fractures involve the longitudinal axis of the temporal bone and they result in facial nerve paralysis 20% of the time. Transverse fractures occur when the temporal bone fracture crosses the axis of the petrous bone and they include facial paralysis 50% of the time.

Misc.: A variant of acute sarcoidosis, Heerfordt syndrome, causes parotid enlargement, facial palsy, and uveitis.

Audiogram is performed to screen for middle or inner ear pathology as a reason for the facial paralysis and often tests the stapedial reflex at the same time. In Bell's palsy, the audiogram should be normal.

MRI/CT should be considered in all patients with complete facial paralysis or if there is not recovery of nerve function within 6 months to rule out other causes of facial paralysis. An MRI is not needed to diagnose Bell's palsy, but it does show multiple sites of inflammatory lesions with gadolinium enhancement. A single enhanced segment would be more suggestive of cancer.

Stapedius reflex was showed by Adour and Hetzler to be an accurate prognostic indicator in 80% of patients. An intact stapedial reflex indicates there is incomplete paralysis which usually recovers completely within 3 to 6 weeks. An initially absent reflex which returns by the 2^nd or 3^rd week is associated with recovery of facial nerve function within 8 weeks with minimal impairment.

Schirmer's II test evaluates lacrimation by using filter strips placed in each eye and the length of moistness is measured after 5 minutes. A decrease of 25% on the affected side compared to the unaffected side is significant. A positive Schirmer's test is thought to predict accuracy of incomplete recovery with 90% accuracy.

Nerve excitability test (NET) determines the minimal current required for muscle contraction on both the affected and normal side. It is considered significant if the difference between the two sides is greater than 2 to 3 mAmps. This test is easily performed and has minimal discomfort to the patient.

Maximal nerve excitability test (MST) determines the maximal stimulus tolerated by the patient on the non-paralyzed side. The same intensity is applied to the affected side and is graded as normal, slightly decreased function, greatly decreased function, or absent. If the results are normal or slightly decreased, there is a 92% chance of complete recovery. If the results are greatly decreased or absent, there is an 86% chance of incomplete recovery. However, this test is not popular with patients since it is painful.

Electromyography (EMG) measures involuntary muscle contractility and is able to quantitate the degree of denervation. If none or just one muscle group had motor action potentials, then the prognosis for facial nerve recovery is poor. If there are 4 or 5 muscle groups with action potentials, then the prognosis is favorable for recovery. At 10 days after onset of paresis, this test has been shown to be 75% accurate in predicting poor outcome and 62% accurate in predicting a favorable outcome. The prognostic value of this test is limited because the denervation potentials do not appear until 10 to 21 days after onset of nerve degeneration and maximal nerve degeneration occurs within this time period.^,

Electroneurography (ENoG) assesses muscle compound action potentials (CAP) in the affected nerve and compares it to the normal side. There is a good correlation between ENoG results and the amount of damaged axons. Fisch showed that if there is <90% reduction of CAP amplitude reduction within 3 weeks of onset, there are satisfactory facial movements without any form of therapy. If there is a 95 to 100% amplitude reduction within 2 weeks of onset, then there is a 50% chance of having an unsatisfactory spontaneous recovery. If 10% of the CAPs remain conductive, a sufficient number of endoneural tubes remain intact and ensure proper regeneration of degenerated nerve fibers. It has been proposed that immediate surgical decompression is indicated if there is a >90% CAP reduction within 2 weeks of onset to prevent progression over the critical 95% limit.

Eye protection is important in the prevention of keratitis or corneal ulcers since the eyelid will not close with facial paralysis. The eye can be protected with artificial tear solutions to be used during the day and ophthalmic ointment at night. An eye patch may also be used at night but taping the eye closed is not recommended due to corneal injury if it is not done properly. Eyeglasses or sunglasses should be used during the day. An ophthalmology consult should be obtained if there is persistent eye pain or evidence of corneal abrasions or ulcers.

Corticosteroids are used for the assumption that the paralysis is caused by nerve edema within the bony confines of the fallopian canal. Prednisone 1 mg/kg in divided doses is used for 3 to 6 days and then is tapered over the next 10 to 14 days. Contraindications of steroid use include peptic ulcer disease, uncontrolled diabetes or hypertension, glaucoma, pregnancy, drug allergy, bone disease, and recent vaccination. Stankiewicz reviewed 92 articles on the benefit of steroids in facial paralysis and found only a few of these were properly controlled, randomized, prospective trials and they showed no benefit. Several less valid prospective or retrospective studies did show benefit of steroids. Although steroids may not prevent partial denervation or contracture, they may prevent total denervation or paralysis, relieve pain associated with the paralysis, help shorten the time needed for recovery, and prevent or lessen synkinesis or crocodile tearing.

Acyclovir has been used in combination with steroids for the assumption that herpes simplex virus may be the cause of the facial paralysis. Adour et al in 1996 designed a double-blind, randomized, control trial comparing final outcome of 99 Bell's palsy patients treated with acyclovir-prednisone or placebo-prednisone. They concluded that Bell's palsy patients treated with both acyclovir and prednisone within 3 days of onset had better recovery and less neural degeneration than patients treated with prednisone alone. Recommended dosing of acyclovir is 400 mg five times/day for 10 days.

Physiotherapy is electrical stimulation of paralyzed muscles in the hopes to improve function. However, this therapy is no longer recommended because some evidence has shown it to be detrimental by retarding ingrowth of neurofibrils to motor endplates.

Surgical Decompression is unroofing the facial canal including the labyrinthine segment in an effort to preserve the remaining axons in view of the entrapment syndrome theory. It is usually reserved for patients who show >90% axonal degeneration on ENoG within 2 weeks of onset. Surgical decompression remains controversial as the benefit has not been well proven. Risks of surgery include hearing loss, anesthetic complications, infection, dizziness, and possibility of no improvement after surgery.^,

Facial Reanimation Procedures can be performed in patients with residual paralysis or sequelae such as synkinesis or crocodile tears. Nerve crossover techniques can be performed during the first 18 months if the facial muscle and distal facial nerve branches are healthy. If paralysis has lasted >2 years, patients are more likely to benefit from static procedures such as transposition of the temporalis, masseter, or digastric muscle, which often provides adequate tone and facial symmetry at rest and some voluntary movement. Patients who develop corneal abrasions or keratitis despite protective measures may need surgical protection such as gold weight implantation in the upper eyelids to aid closure.

The management of Bell's palsy varies among physicians depending on their view on the benefit of steroids, acyclovir, and surgical decompression. Hughes published practical management guidelines in 1990 which he had presented to the Annual Meeting of the American Neurotology Society in San Francisco. Since maximal nerve injury occurs by 3 weeks after the onset of Bell's palsy, management depends on whether or not the patient is seen within this 3 week period. Management also depends on if the patient has palsy or paresis.

Hughes recommends all patients presenting with Bell's Palsy should receive a complete history, head and neck examination, screening audiologic testing, and baseline photography. Eye care is also discussed which usually includes eyedrops during the daytime, eyeglasses while outdoors, and eye ointment at night. If the audiogram indicates associated sensorineural hearing loss, then a CT or MRI scan is obtained to rule out an acoustic tumor.

If patients present within 21 days of onset of noticeable weakness and there are no contraindications, prednisone 1 mg/kg/day is given for 10 to 14 days followed by a taper. If palsy is mild, patient is followed up in one week but instructed to return sooner if palsy progresses rapidly. If palsy is severe, the patient is seen within 1 to 2 days. No topognostic, prognostic, or other diagnostic testing is indicated if the face is not paralyzed since this is the best sign of an excellent recovery within the upcoming weeks. Patients should be followed closely for the first 3 weeks to determine if surgery may be indicated. If paralysis does not occur within this period, the patient is reassured and asked to return when recovery is complete.

If the face becomes paralyzed, a CT or MRI scan is obtained to other causes for facial paralysis. If the clinician is willing to recommend surgical decompression, electroneurography (ENoG) is urgently obtained. Surgery is recommended if there is >90% CAP reduction. If ENoG shows <90% CAP reduction, it is repeated in 1 to 2 days. Patient follow-up is then scheduled every 3 months until full recovery is reached. Photodocumentation at each visit is recommended to better assess recovery.

If the patient initially presents after 21 days of onset, maximal nerve injury has usually taken place and no medical or surgical treatment is likely to improve the outcome. Diagnostic tests and eye care should be used as described earlier, but prognostic tests and steroids are not useful. Patients should receive follow-up periodically until they fully recover.

Bell's Palsy is an idiopathic facial paralysis and should only be considered as a diagnosis of exclusion. A complete history and physical examination and occasionally diagnostic testing such as audiogram, CT, or MRI are necessary to rule out other causes of facial paralysis. Management includes eye care, steroids if not contraindicated, and close follow-up. Prognostic testing is not necessary unless the face is paralyzed and the clinician is willing to recommend surgical decompression.