HistoryThe diagnosis of Bell palsy must be made on the basis of a thorough history and physical examination, as well as the use of diagnostic testing when necessary. Bell palsy is a diagnosis of exclusion. Clinical features of the disorder that may help to distinguish it from other causes of facial paralysis include the sudden onset of unilateral facial paralysis and the absence of signs and symptoms of CNS, ear, and cerebellopontine angle disease.

Symptoms of Bell palsy include the following:

Acute onset of unilateral upper and lower facial paralysis (over a 48-h period) Posterior auricular pain Decreased tearing Hyperacusis Taste disturbances Otalgia

Early symptoms include the following:

Weakness of the facial muscles Poor eyelid closure Aching of the ear or mastoid (60%) Alteration of taste (57%) Hyperacusis (30%) Tingling or numbness of the cheek/mouth Epiphora Ocular pain Blurred vision

Onset

The onset of Bell palsy is typically sudden, and symptoms tend to peak in less than 48 hours. This sudden onset can be frightening for patients, who often fear they have had a stroke or have a tumor and that the distortion of their facial appearance will be permanent.

Because the condition appears so rapidly, patients with Bell palsy frequently present to the emergency department (ED) before seeing any other health care professional. More people first notice paresis in the morning. Because the symptoms require several hours to become evident, most cases of paresis likely begin during sleep.

Facial paralysis

The paralysis must include the forehead and lower aspect of the face. The patient may report the inability to close the eye or smile on the affected side. He or she also may report increased salivation 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.

If a patient has gradual onset of facial paralysis, weakness of the contralateral side, or a history of trauma or infection, other causes of facial paralysis must be strongly considered. Progression of the paresis is possible, but it usually does not progress beyond 7-10 days. A progression beyond this point suggests a different diagnosis. Patients who have bilateral facial palsy must be evaluated for Guillain-Barré syndrome, Lyme disease, and meningitis.

Many patients report numbness on the side of the paralysis. Some authors believe that this is secondary to involvement of the trigeminal nerve, whereas other authors argue that this symptom is probably from lack of mobility of the facial muscles and not lack of sensation.

Ocular manifestations

Early ocular complications include the following:

Lagophthalmos (inability to close the eye completely)

Paralytic ectropion of the lower lid Corneal exposure Brow droop Upper eyelid retraction Decreased tear output/poor tear distribution Loss of the nasolabial fold Corneal erosion, infection, and ulceration (rare)

Late ocular manifestations include the following:

Mild, generalized mass contracture of the facial muscles, rendering the affected palpebral fissure narrower than the opposite one (after several months)

Aberrant regeneration of the facial nerve with motor synkinesis Reversed jaw winking (ie, contracture of the facial muscles with twitching of the corner of the mouth or

dimpling of the chin occurring simultaneously with each blink) Autonomic synkinesis (ie, crocodile tears—tearing with chewing) Permanent, disfiguring facial paralysis (rare)

Two thirds of patients complain about tear flow.[10] This results from the reduced function of the orbicularis oculi in transporting the tears. Fewer tears arrive at the lacrimal sac, and overflow occurs. The production of tears is not accelerated.

Posterior auricular pain

Half of the patients affected with Bell palsy may complain of posterior auricular pain.[10] The pain frequently occurs simultaneously with the paresis, but pain precedes the paresis by 2-3 days in about 25% of patients. Ask the patient if he or she has experienced trauma, which may account for the pain and facial paralysis.

One third of patients may experience hyperacusis in the ear ipsilateral to the paralysis, which is secondary to weakness of the stapedius muscle.

Taste disorders

While only one third of patients report taste disorders,[10] 80% of patients show a reduced sense of taste. Patients may fail to note reduced taste, because of normal sensation in the uninvolved side of the tongue. Early recovery of the sense of taste suggests that the patient will experience a complete recovery.

Facial spasm

Facial spasm, a very rare complication of Bell palsy, occurs as tonic contraction of 1 side of the face. Spasms are more likely to occur during times of stress or fatigue and may be present during sleep. This condition may occur secondary to compression of the root of the seventh nerve by an aberrant blood vessel, tumor, or demyelination of the nerve root.

Facial spasm occurs most commonly in patients in the fifth and sixth decades of life. Sometimes the etiology is not found. The presence of progressive facial hemispasm with other cranial nerve findings indicates the possibility of a brainstem lesion.

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 mouth or chin when the patient blinks or in eye closure with smiling. Crocodile tears can be observed; patients shed tears while they eat.

Cranial neuropathies

Some believe that other cranial neuropathies may also be present in Bell palsy; however, this is not uniformly accepted. The symptoms in question include the following:

Hyperesthesia or dysesthesia of the glossopharyngeal or trigeminal nerves Dysfunction of the vestibular nerve Hyperesthesia of the cervical sensory nerves Vagal or trigeminal motor weakness

DiagnosisExamination for Bell palsy includes the following:

Otologic examination: Pneumatic otoscopy and tuning fork examination, particularly if evidence of acute or chronic otitis media

Ocular examination: Patient often unable to completely close eye on affected side Oral examination: Taste and salivation often affected Neurologic examination: All cranial nerves, sensory and motor testing, cerebellar testing

Grading

The grading system developed by House and Brackmann categorizes Bell palsy on a scale of I to VI,[3, 4, 5] as follows:

Grade I: normal facial function

Grade II: mild dysfunction

Grade III: moderate dysfunction

Grade IV: moderately severe dysfunction

Grade V: severe dysfunction

Grade VI: total paralysis

See Clinical Presentation for more specific information on patient history and physical examination for Bell palsy.

Testing

Although there are no specific diagnostic tests for Bell palsy, the following may be useful for identifying or excluding other disorders:

Rapid plasma reagin and/or venereal disease research laboratory test or fluorescent treponemal antibody absorption test

HIV screening by enzyme-linked immunosorbent assay and/or Western blot Complete blood count Erythrocyte sedimentation rate Thyroid function Serum glucose CSF analysis Blood glucose Hemoglobin A1c

Antineutrophil cytoplasmic antibody levels Salivary flow Schirmer blotting test Nerve excitability test Computed tomography Magnetic resonance imaging

See Workup for more specific information on testing and imaging modalities for Bell palsy.

In many cases, the history and physical examination of the patient establish the diagnosis of Bell palsy. If the clinical findings are doubtful or if paralysis lasts longer than 6-8 weeks, further investigations should be considered.[11]

No specific diagnostic tests are available for Bell palsy, though the following may be useful for identifying or excluding other disorders:

Rapid plasma reagin (RPR) and/or venereal disease research laboratory (VDRL) test or fluorescent treponemal antibody absorption (FTA-ABS) test

HIV screening by means of enzyme-linked immunosorbent assay (ELISA) and/or Western blot Complete blood cell (CBC) count

Erythrocyte sedimentation rate measurement Thyroid function studies Serum glucose level Cerebrospinal fluid analysis

In addition to the above tests, blood glucose or hemoglobin A1c levels may be obtained to determine if the patient has undiagnosed diabetes. Persons with diabetes have a 29% higher risk of being affected by Bell palsy than do persons without diabetes.

Serum titers for herpes simplex virus (HSV) may be obtained. However, this test is usually not helpful, owing to the ubiquitous nature of this virus.

Antineutrophil cytoplasmic antibody (cANCA) levels are indicated, if applicable, to exclude Wegener granulomatosis. In areas where Lyme disease is endemic, serum titers (immunoglobulin M [IgM] and IgG) for Borrelia burgdorferi should be obtained.

Serum titers (IgM and IgA) for Mycoplasma pneumoniae may be obtained. A study in Germany measured titers in patients with Bell palsy and found that several patients had elevated titers for M pneumoniae, though only 2 of those who tested positive had respiratory symptoms.[37]

Salivary flow test

Salivary flow also may be tested. The physician places a small catheter into the paralyzed and normal submandibular glands. The patient is then asked to suck on a lemon, and the salivary flow is compared between the 2 sides. The normal side is the control.

Schirmer blotting test

The Schirmer blotting test may be used to assess tearing function. The use of benzene will stimulate the nasolacrimal reflex, and the degree of tearing can be compared between the paralyzed and normal sides.

Nerve excitability test

The nerve excitability test determines the threshold of the electrical stimulus needed to produce visible muscle twitching. This test is technically challenging and has very limited clinical availability.

Imaging considerations

If the history and physical examination lead to a diagnosis of Bell palsy, then immediate imaging is not necessary, because most patients with Bell palsy improve within 8-10 weeks. If the paralysis does not improve or worsens, imaging may be useful. If the patient has a palpable parotid mass, imaging may be necessary

9. CT Scanning and MRIImaging with CT scanning or other methods is indicated if there are other associated physical findings or if the paresis is progressive and unremitting. CT scanning demonstrates the architecture of the temporal bone and may be used if some other pathology is suspected.

MRI is useful as a means of excluding other pathologies as the cause of paralysis and is preferred for imaging the cerebellopontine angle.

MRI in patients with Bell palsy may show enhancement of the seventh cranial nerve (facial nerve) at or near the geniculate ganglion. Alternatively, MRI may demonstrate a neoplasm compressing the facial nerve. Tumors that compress or involve the facial nerve include schwannoma (most common), hemangioma, meningioma, and sclerosing hemangioma.

Perform gadolinium-enhanced MRI when findings are atypical or when the facial nerve paralysis appears central, to rule out a tumor or vascular compression.[38]Increased signal intensity of the premeatal or intratemporal segment of the facial nerve after administration of gadolinium has been noted in patients with Bell

palsy.[39, 40] Attempts to correlate outcome with quantification of signal intensity increases have yielded contradictory results.

Conduction Testing and EMGUseful tests for evaluation of the function of the facial nerve include nerve conduction testing and EMG. Nerve conduction velocities and EMG produce a graphic readout of the electrical currents, displayed by stimulating the facial nerve and recording the excitability of the facial muscles it supplies. These tests may aid in assessing the outcome of a patient who has persistent and severe Bell palsy.

This testing is not part of the acute workup; the tests are most useful when performed 3-10 days after the onset of paralysis. Note that most electromyographic/nerve conduction studies do not show an abnormality for 3 weeks following a peripheral nerve injury.

Comparison to the contralateral side helps to demonstrate the extent of nerve injury and has prognostic implications. Nerve conduction responses are abnormal if a difference of 50% in amplitude between the paralyzed and normal side is detected; a difference of 90% between the 2 sides suggests a poorer prognosis.

May et al demonstrated that prognosis may be favorable if the motor amplitude of the affected side is greater than 25% of that of the normal side. An incomplete recovery was observed in patients whose results demonstrated less than 25% amplitude on the paralyzed side.[41] Blink reflexes can be used to measure conduction across the involved segment, but they are commonly absent in Bell palsy.

ElectroneurographyElectroneurography is a physiologic test that uses EMG to objectively measure the difference between potentials generated by the facial musculature on both sides of the face in response to a supramaximal electrical stimulation of the facial nerve. Because all electrodiagnostic testing is performed on the nerve distal to the proposed site of injury, sufficient time is needed for wallerian degeneration to occur, usually 48-72 hours. Testing should begin 3 days from the onset of complete paralysis.

Electrodiagnostic testing measures the facial nerve degeneration indirectly. If a patient does not reach 90% degeneration within the first 3 weeks of the onset of paralysis, some studies suggest that the prognosis is excellent, with over 80-100% of the patients recovering with excellent function.

The patients who reach over 90% degeneration within the first 3 weeks of the onset of paralysis have a much more guarded prognosis, with only 50% having good recovery of facial motion. The rate of degeneration also predicts the prognosis. Patients who have 90% degeneration by 5 days have a worse prognosis than those with 90% degeneration at 14 days

Brainstem Auditory Evoked Response and AudiometryBrainstem auditory evoked response (BAER) may be obtained in patients with peripheral facial nerve lesions and other neurologic involvement. This test measures the transmission of response through the brainstem and is effective in detecting, notably, retrocochlear lesions.

Hendrix and Melnick evaluated the BAER of 17 patients with Bell palsy and found no evidence of retrocochlear lesions of the auditory system in any of the patients.[42] In study by Shannon et al, BAER was recorded in 27 patients with Bell palsy; only 6 patients had prolonged brainstem transmission but normal auditory function.[43]

These studies were small and do not support routine use of BAER in patients with Bell palsy. However, when a patient presents with multiple cranial neuropathies (eg, of the seventh and eighth cranial nerves), BAER may be useful.

If hearing loss is suspected, audiography and auditory evoked potentials (AEPs) should be pursued once an underlying structural lesion has been excluded. Typically, the hearing threshold is not affected by Bell palsy. Impedance testing may reveal an absent or diminished stapedial reflex because of paresis of the stapedial branch of the facial nerve.

Blepharokymographic Analysis

Blepharokymographic analysis, a high-speed eyelid motion-analysis system, has been used to evaluate movement of the eyelids. Computer-based analysis may prove helpful in diagnosing Bell palsy, predicting prognosis, and evaluating response to therapeutic measures such as placement of a gold weight in the affected upper eyelid (used in cases in which spontaneous recovery has been limited)

Histologic FindingsIn a review of 12 autopsy cases of patients with Bell palsy, most cases showed inflammatory changes around the mastoid cells and walls of the arteries.[44] The most common site of involvement was the geniculate ganglion. Surgical findings described constriction of the nerve at the stylomastoid foramen, with swelling of the nerve itself. Microscopic findings showed an inflammatory reaction with infiltration of macrophages on the nerve.

History: The most obvious symptom of Bell's palsy is an unexplained episode of unilateral facial weakness or paralysis. Individuals may report other symptoms, including a headache, tearing, changes in the amount of saliva and tears, drooling, difficulty eating and drinking, change in facial appearance, impairment of taste, and hearing loss. Some individuals report having a mild cold, influenza, or other upper respiratory tract infection within a week prior to the onset of Bell's palsy. The individual may report a history of diabetes or prior herpes infection with a recent outbreak. A complete history of current and prior illnesses is usually obtained.

Physical exam: The exam reveals facial asymmetry, drooling, increased distance between the top and bottom eyelids (palpebral fissure width), a smooth forehead, and a flattened crease between the nose and the upper lip (nasolabial fold). No other evidence of central nervous system signs is usually noted. The ear and neck will be examined fully for any conditions contributing to the symptoms. If the face is paralyzed except for the forehead, a central nervous system cause is sometimes suspected. The extent of facial dysfunction will be graded (grades I through VI) according to standard definitions.

Tests: No specific test confirms Bell’s palsy; the initial diagnosis is made through observation. Laboratory testing may include complete blood count (CBC), erythrocyte sedimentation rate (ESR), C-reactive protein, antinuclear antibodies, and blood chemistries to rule out underlying illness such as autoimmune or other immunologic disease, diabetes, neoplastic disease, or infectious disease. Serological laboratory tests may be done to rule out Lyme disease. An antineutrophil cytoplasmic antibody (cANCA) test may be performed if Wegener granulomatosis is a possible underlying diagnosis.

A careful cranial nerve examination is typically performed, including a tuning fork examination to test hearing and testing for corneal sensation. A simple test of taste should be performed. Audiometry may also be used to evaluate hearing. Nerve excitability testing may also be performed through the use of electromyography (EMG) for assessing facial paralysis by measuring voluntary motor activity, and electroneuronography for determining the extent of nerve fiber degeneration. EMG usually is not thought to be reliable sooner than 18 days after onset of the paralysis. Blepharokymographic analysis may be used to evaluate eyelid motion, which can confirm the diagnosis and help predict the prognosis. Imaging (x-ray, MRI, or CT) may be performed to evaluate other possible pressure sources such as infection, tumor, or skull fracture (“Bell’s Palsy”)