- Bell’s palsy is the most common cause of acute facial nerve paresis/paralysis, and the most common acute mononeuropathy.
- Patients may have impaired eye closure which may lead to eye injury.
- Not all patients with facial paresis/paralysis have Bell’s palsy. Alternative underlying etiologies must be considered.
When evaluating a patient with facial paresis/paralysis for Bell’s palsy, the following should be considered:
- Bell’s palsy is rapid in onset (<72 hours).
- Bell’s palsy is diagnosed when no other medical etiology is identified as a cause of the facial paresis/paralysis.
- Bilateral Bell’s palsy is rare.
- Currently, no cause for Bell’s palsy has been identified.
- Other conditions may cause facial paresis/paralysis, including stroke, brain tumors, tumors of the parotid gland or infratemporal fossa, cancer involving the facial nerve, and systemic and infectious diseases, including varicella zoster, sarcoidosis, and Lyme disease.
- Bell’s palsy is typically self-limited. Most patients with Bell’s palsy show some recovery without intervention within 2-3 weeks after onset of symptoms and completely recover within 3-4 months.
- Bell’s palsy may occur in men, women, and children but is more common in persons 15-45 years old; individuals with diabetes, upper respiratory ailments, or compromised immune systems; and during pregnancy.
Table 1. Abbreviations and Definitions of Common Terms
|Acute||Occurring in <72 h|
|Bell’s palsy||Acute unilateral facial nerve paresis/paralysis with onset in <72 h|
and without identifiable cause
|EMG testing||A test in which a needle electrode is inserted into affected muscles to record both spontaneous depolarizations and the responses to voluntary muscle contraction|
|ENoG testing (neurophysiologic studies)||A test used to examine the integrity of the facial nerve, in which surface electrodes record the electrical depolarization of facial muscles following electrical stimulation of the facial nerve|
|Facial paralysis||Inability to move the facial muscles|
|Facial paresis||Impaired ability to move the facial muscles|
Table 2. House-Brackmann Facial Nerve Grading System
Normal facial function in all areas
Slight paresis/paralysis noticeable only on close inspection
At rest: normal symmetry of forehead, ability to close eye with minimal effort and slight asymmetry, ability to move corners of mouth with maximal effort and slight asymmetry
No synkinesis, contracture, or hemifacial spasm
Obvious but not disfiguring difference between 2 sides, no functional impairment; noticeable but not severe synkinesis, contracture, and/or hemifacial spasm
At rest: normal symmetry and tone
Motion: slight to no movement of forehead, ability to close eye with maximal effort and obvious asymmetry, ability to move corners of mouth with maximal effort and obvious asymmetry
Patients who have obvious but no disfiguring synkinesis, contracture, and/or hemifacial spasm are grade 3 regardless of degree of motor activity
|4||Moderately severe dysfunction|
Obvious paresis/paralysis and/or disfiguring asymmetry
At rest: normal symmetry and tone
Motion: no movement of forehead; inability to close eye completely with maximal effort
Patients with synkinesis, mass action, and/or hemifacial spasm severe enough to interfere with function are grade 4 regardless of motor activity
Only barely perceptible motion
At rest: possible asymmetry with droop of corner of mouth and decreased or absence of nasal labial fold
Motion: no movement of forehead, incomplete closure of eye and only slight movement of lid with maximal effort, slight movement of corner of mouth
Synkinesis, contracture, and hemifacial spasm usually absent
Loss of tone; asymmetry; no motion; no synkinesis, contracture, or hemifacial spasm
Table 3. Etiologies and Clinical Features of Facial Paralysis
|Type||Condition||Etiologic Agent||Distinguishing Factors|
|Congenital||Mobius syndrome||Possibly viral||Young age, bilateral in nature, unable to move face or eyes laterally|
|Endocrine||Diabetes||Microvascular disease||Other signs and symptoms of diabetes, laboratory testing|
|Idiopathic||Acute facial nerve paresis/paralysis||Unknown||Classic Bell’s palsy with other etiologies excluded|
|Inherited||Heritable disorders||Autosomal dominant inheritance||Family history as high as 4%; may have other neurologic disorders|
|Neoplastic||Facial nerve tumor, skin cancer, parotid tumors||Multiple carcinomas of the head and neck||May involve only select branches of the facial nerve or other cranial nerves and present as multiple cranial neuropathies|
|Neurovascular||Stroke||Ischemia, hemorrhage||Forehead sparing most often, extremities often involved|
|Traumatic||Injury to facial nerve||Trauma, including forceps delivery||Timing of injury coincides with trauma|