Bell’s Palsy: Pearls and Pitfalls in Evaluation and Management

Authors: Drew A. Long BS (@drewlong2232, Vanderbilt University School of Medicine, US Army) and Brit Long MD (@long_brit, EM Chief Resident at SAUSHEC, USAF) // Edited by: Alex Koyfman, MD (@EMHighAK, EM Attending Physician, UT Southwestern Medical Center / Parkland Memorial Hospital) and Stephen Alerhand, MD (@SAlerhand)

A 32 year-old man presents to the Emergency Department complaining of facial drooping. He states that over the past two days, he has had increasing difficulty moving the right side of his face. He first noticed his mouth drooping on the right side along with difficulty closing his right eye. He has no history of any previous episode like this, no past medical history, and no history of trauma. His vitals are normal. Physical exam reveals complete paralysis of the right side of his facial muscles, though the rest of the neurologic exam is normal. What conditions are important to rule out? How do you treat this patient? What do you tell him when he asks if and how soon he will regain normal function?
BP face
32 year-old male presenting to E.D. with facial weakness


Bell’s palsy (BP) is a unilateral facial paralysis resulting from lower motor neuron involvement of Cranial Nerve VII.1 While the exact pathogenesis is unclear, BP is thought to occur from inflammation and swelling of the facial nerve at the geniculate ganglion, which can cause compression and ischemia or demyelination of the nerve.2,3 The exact etiology of BP is controversial; reactivated herpes simplex virus is thought to be the most probable cause followed by herpes zoster virus.3,4 It affects about 40,000 people in the U.S. every day,5 affects men and women equally, and has a median age of onset of 40.2 BP is more common in diabetics and pregnant women, with diabetics making up 5-10% of patients.6,7 The risk of developing BP increases threefold during pregnancy, especially the third trimester, which is thought to occur due to swelling of the facial nerve.8

How does BP present? The presentation can be linked to its involvement with the facial nerve. The facial nerve is a mixed nerve and has motor, sensory, and parasympathetic components. It has four major functions:3

  1. Voluntary facial movement (motor fibers)
  2. Lacrimal, submandibular, and sublingual gland secretions (parasympathetic fibers)
  3. Taste of anterior two-thirds of tongue (afferent fibers from taste receptors)
  4. Sensation of external auditory canal and pinna (somatic afferent fibers)

The classic presentation of BP is a patient with partial or complete weakness of the muscles on one half of the face. This results in an inability to raise eyebrows, wrinkle the forehead, or close the eyelid. Furthermore, the nasolabial fold is lost and the mouth will droop. These deficits all result from involvement of the motor component of the facial nerve. Involvement of the parasympathetic fibers leads to decreased tear production and salivation. Involvement of the afferent fibers from taste receptors leads to alterations and lack of taste sensation. Lastly, hyperacusis or ear pain may occur due to involvement of the somatic afferent fibers to the external auditory canal and pinna.1-4

Several factors set the presentation of BP apart from other conditions that can affect the facial nerve. The onset is acute, often occurring overnight.5 While acute, BP does not develop over a matter of minutes but instead progresses over hours, usually peaking within 72 hours.1 Additionally, a patient with BP should not complain of any facial pain and should not have any cranial nerve involvement other than the facial nerve. BP is usually unilateral, and bilateral facial palsy suggests a diagnosis other than BP.1-5

An important distinction to make during the exam is involvement of the forehead. The innervation of the upper facial muscles is bilateral and that of the lower facial muscles unilateral. If the patient has weakness of the lower half of his/her face but not the upper half, an intracranial process should be suspected.3,9 Thus a patient who has a drooping mouth but is able to wrinkle his/her forehead must be worked up immediately, with stroke at the forefront of consideration. Unfortunately, despite what we are taught, complete unilateral facial paralysis does not exclude an intracranial process, and if the history or presentation is concerning for an upper motor neuron process the patient should receive further evaluation.

BP innervation
Innervation of the upper and lower facial muscles


The differential for facial nerve palsy is broad. The main diagnoses to consider when a patient’s presentation is suspicious for BP can be grouped into infectious, inflammatory, neoplastic, and cerebrovascular categories.1 This grouping is shown in Table 1. Additionally, trauma can result in facial nerve palsy; this can be gathered from the history and will likely also be evident on exam. Ultimately, what every physician is worried about missing is stroke or an intracranial process.

Table 1. Differential Diagnosis of Bell’s Palsy.1,3

Infectious Ramsay-Hunt Syndrome, Otitis Media, Lyme Disease, HIV


Inflammatory Guillain-Barré syndrome, Sarcoidosis, Sjögren syndrome 
 Neoplastic  Tumor
 Cerebrovascular  Ischemic or Hemorrhagic Stroke


When considering the differential for BP, the history and physical will often be enough to exclude most of these conditions. A history of hypertension, diabetes, smoking, dyslipidemia, or cardiovascular disease calls for close evaluation of other deficits. Likewise, risk factors for HIV, such as IV drug use or risky sexual behavior, necessitates HIV testing. Any history of a prior cancer or of facial palsy that progresses over weeks or months is concerning for either brain metastasis or expansion of an intracranial tumor. The physical exam will be enough to rule out Ramsay-Hunt Syndrome (which will present with an erythematous vascular rash in the ear) and otitis media (facial paralysis is a potential complication). Facial nerve palsy is the most common cranial neuropathy associated with Lyme disease, and was found to occur in up to 63% of patients with Lyme meningitis in one study.10 However, Lyme disease often presents with other symptoms preceding the facial paralysis, such as erythema migrans, heart block, or arthritis.3 Unfortunately, patients often do not recall exposure to a tick. While Guillain-Barré syndrome can present with facial weakness in up to 50% of patients,11,12 it is most commonly bilateral and occurs with symmetric muscle weakness and absent or decreased deep tendon reflexes. Neurosarcoidosis can frequently result in cranial neuropathy including facial nerve palsy and should be considered in a patient with a history of sarcoidosis.3 While Sjogren’s syndrome can cause facial nerve palsy, it is uncommon to occur without other cranial neuropathies or skin, eye, and/or mouth dryness.13

When considering BP, a provider must evaluate for several red flags. These are detailed in Table 2. Presence of any of the factors warrants an evaluation for an underlying cause other than BP.

Table 2. Red Flags of Facial Nerve Palsy 1,2,9
Cranial Nerve involvement other than CN VII
Bilateral facial palsy
Step-wise progression of facial palsy or slowly progressive beyond 72 hrs
Recurrent facial palsy
Prolonged facial palsy (>4 months)
Sudden-onset complete facial palsy
Weakness or numbness of arms or legs
Unaffected upper facial muscles (forehead)
Headache, visual deficits, nausea or vomiting
History of travel through woods or tick bite
Ulceration or blisters near ear



Bell’s palsy is a clinical diagnosis, which depends on the presentation and not clinical studies. It is based on the following criteria:3

  • Diffuse involvement of the facial nerve, as seen by unilateral facial weakness, with or without loss of taste of the anterior two-thirds of the tongue or altered secretion from the salivary and/or lacrimal glands.
  • Acute onset, usually over a day or two; recovery occurs in less than 6 months.

The diagnosis depends on the history and physical exam. For BP, no other CN involvement, altered mental status, or signs of stroke/intracranial process should be present.1-5,9 The presence of any red flags in the history and physical (see Table 2) warrants additional diagnostic evaluation. If a red flag is present, further testing including a complete blood count with differential, sedimentation rate, Lyme titer, thyroid function studies, and electrolytes is warranted.4 Intracranial imaging with CT noncontrast of the head should be obtained. The best test for evaluation of intracranial processes is MRI, but this is often difficult to obtain in the ED.14

Perhaps the most worrisome mimic of BP is stroke. The possibility of stroke in a patient presenting with what looks like BP must be considered and ruled out immediately. Ischemic stroke is the second leading cause of unilateral facial paralysis, behind BP.15 As previously stated, a common rule of thumb is that upper motor neuron lesions spare the forehead, which receives bilateral upper motor neuron innervation. On the other hand, lesions that affect the facial nerve after it exits the brainstem (such as BP) result in weakness of the entire ipsilateral face. However, this rule does not always hold true, as rarely ipsilateral pontine pathology (such as ischemia or mass) can lead to a lower motor neuron pattern of facial weakness. In this case, dysfunction of the ipsilateral abducens nerve (resulting in lateral gaze palsy) will also be present, helping to differentiate a stroke of the ipsilateral pons from BP.1 In summary, when evaluating for stroke, take into account the overall clinical picture of the patient. Speak to the patient, perform a neuro exam, and look for any associated signs/symptoms, and if the possibility of a stroke is still a valid possibility, rule it out.16 CN involvement other than VII requires immediate imaging.  


Medical treatment for BP in the past has revolved around two medications: antivirals and steroids. Recent literature favors the use of steroids and not antivirals. Sullivan et al. in 2007 examined the treatment options for BP in a randomized control trial across 17 sites in Scotland. At three months, 83% of patients in the prednisolone group versus 63.6% of patients in the non-prednisolone group fully recovered while 71.2% in the acyclovir versus 75.7% in the non-acyclovir group fully recovered. Furthermore, recovery rates were lower in the group receiving prednisolone and acyclovir compared to the group receiving prednisolone alone.17 A meta-analysis in 2009 examining use of corticosteroids alone vs. antivirals alone found that treatment with steroids was associated with a reduced risk of unfavorable recovery, while treatment with antivirals alone was not.18 A second meta-analysis in 2009 determined there was no significant benefit of combined antiviral and steroid treatment compared to steroids alone.19 Currently, the recommended treatment regiment for BP is prednisone, 60 to 80 mg per day, for one week.20

In addition to medical treatment, eye care in BP patients is imperative. Severe BP can result in inability to completely close the eye in addition to decreased lacrimal secretions, leading to drying and/or tearing of the cornea. These patients should be given lubricating eye drops for use during the day in addition to a corneal lubricant to use at night.4 Furthermore, patches or taping the eyelid closed can be used at night. The patient should be referred to an ophthalmologist if they experience ocular pain or develop any ocular complications.

The prognosis of BP is good even without treatment. About 85% of patients without treatment will show signs of recovery within 3 weeks, with the other 15% recovering between 3-6 months later.21 The prognosis depends on the severity of the lesion, with less severe lesions recovering faster.20 If no facial function has returned within three to four months, the diagnosis of BP is doubtful and further investigations are warranted. Unfortunately, the recurrence rate of BP is estimated to be between 7%-15% of patients.22-25


Bell’s palsy is an idiopathic paralysis of the facial nerve and is the most common cause of lower motor neuron facial palsy. It is unilateral and acute in onset, progressing over a period of hours and reaching maximal intensity within several days. The signs and symptoms can be traced to the various functions of the facial nerve. Involvement of the forehead can be used as a baseline in differentiating lower versus upper motor neuron involvement. When evaluating BP, any features concerning for an intracranial process such as a tumor or stroke warrant further consideration. There are no tests for diagnosing BP, and the diagnosis is one of exclusion. Careful history and examination are paramount. Treatment consists of prednisone 60-80 mg per day for one week. In addition, eye care in patients with BP must be a priority. The prognosis of BP is excellent, with 85% of patients regaining function within three weeks.


References / Further Reading
  1. Eviston TJ, Croxson GR, Kennedy PGE, et al. Bell’s palsy: aetiology, clinical features, and multidisciplinary care. J Neurol Neurosurg Psychiatry. 2015;86:1356-1361.
  2. Fahimi J, Navi BB, Kamel H. Potential Misdiagnoses of Bell’s Palsy in the Emergency Department. Ann Emerg Med. 2014;63:428.
  3. Ronthal M. Bell’s palsy: pathogenesis, clinical features, and diagnosis in adult. UpToDate. October 2015.
  4. Billue JS. Bell’s Palsy: An Update on Idiopathic Facial Paralysis. Nurse Pract. 1997;22(8):88,97-100.
  5. Herbert M, Swadron S, Mallon B, Lex J. Bell’s Palsy: That was then, this is now. EMRAP. 2015;15:3-4.
  6. Mountain RE, Murray JA, Quaba A, Maynard C. The Edinburgh facial palsy clinic: a review of three years’ activity. J R Coll Surg Edinb. 1994;39(5):275.
  7. Adour KK, Byl FM, Hilsinger RL Jr, Zahn ZM, Sheldon MI. The true nature of Bell’s palsy: analysis of 1,000 consecutive patients. Laryngoscope. 1978;88(5)787.
  8. Hilsinger RL Jr, Adour KK, Doty HE. Idiopathic facial paralysis, pregnancy, and the menstrual cycle. Ann Otol Rhinol Laryngol. 1975;84(4 Pt 1):433.
  9. Toy EC, et al. Case Files: Emergency Medicine. McGraw Hill Medical: 2009. 2nd Ed.
  10. Ackermann R, Hörstrup P, Schmidt R. Tick-borne meningopolyneuritis (Garin-Bujadoux, Bannwarth). Yale J Biol Med. 1984;57(4):485.
  11. Verma R, Chaudhari TS, Giri P. Unilateral facial palsy in Guillain-Barre syndrome (GBS): a rare occurrence. BMJ Case Rep. 2012;2012.
  12. Kamihiro N, et al. Acute motor-sensory axonal Guillain-Barre syndrome with unilateral facial nerve paralysis after rotavirus gastroenteritis in a 2-year-old boy. J Infect Chemother.   2012 Feb;18(1):119-23.
  13. Mori K, et al. The wide spectrum of clinical manifestations in Sjögren’s syndrome-associated neuropathy. Brain. 2005;128(Pt 11):2518.
  14. Roob G, Fazekas Franz, Hartung Hans-Peter. Peripheral Facial Palsy: Etiology, Diagnosis and Treatment. Eur Neurol. 1999 Jan;41(1):3-9.
  15. Gilden DH. Clinical practice. Bell’s palsy. N Engl J Med. 2004;351(13):1323-1331.
  16. Mullen MT. Differentiating Facial Weakness Caused by Bell’s Palsy vs. Acute Stroke: Can you tell the difference? JEMS. 7 May 2014.
  17. Sullivan FM et al. Early treatment with prednisolone or acyclovir in Bell’s Palsy. N Engl J Med. 2007;357(1598-1607).
  18. de Almeida JR, et al. Combined corticosteroid and antiviral treatment for Bell palsy: a systemic review and meta-analysis. JAMA. 2009;302(9):985.
  19. Quant EC, et al. The benefits of steroids versus steroids plus antivirals for treatment of Bell’s palsy: a meta-analysis. BMJ. 2009;339:b3354.
  20. Ronthal M. Bell’s Palsy: Prognosis and treatment in adults. UpToDate. Oct 2015.
  21. Petersen E. The natural history of Bell’s palsy. Am J Otol. 1982:107-111.
  22. Cawthorne T, Haynes DR. Facial Palsy. Br Med J. 1956;2(5003):1197.
  23. Boddie HG. Recurrent Bell’s Palsy. J Laryngol Otol. 1972;86(11):117.
  24. Hallmo P, Elverland HH, Mair IW. Recurrent facial palsy. Arch Otorhinolaryngol. 1983;237(2):97.
  25. Pitts DB, Adour KK, Hilsinger RL Jr. Recurrent Bell’s Palsy: analysis of 140 patients. Laryngoscope. 1988;98(5):535.

One thought on “Bell’s Palsy: Pearls and Pitfalls in Evaluation and Management”

  1. My 6th episode of Bell’s Palsy started on 02/16/16. I have had once on the left side of my face and now the 5th on the right side. I have found that steroids nor anti-virals have done no good in my cases. I have had pain in the nerves near the salivary gland and my ear. I have heard of decompression surgery, but am not willing to go that route unless people are running away when they see me. Any idea why I seem to be so susceptible to this?

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