Bell's Palsy

Bell's palsy is an idiopathic LMN palsy involving the facial nerve accounting for up to 3/4 of all cases of unilateral facial paralysis. It is believed that inflammation and swelling of the facial nerve causes compression of the nerve which manifests as facial muscle weakness. However, the exact etiology is controversial. Reactivated herpes simplex virus is thought to be the most probable cause followed by herpes zoster virus.

The facial nerve consists of a:

• Motor component, which supplies all the muscle of facial expression
• Sensory branch that carries taste sensation from the anterior two thirds of the tongue through the chorda tympani nerve
• Parasympathetic fibres reach the lacrimal glands via the greater superficial petrosal nerve, and they reach the sublingual and submaxillary glands via the chorda tympani. 

Bell's palsy is diagnosed upon the abrupt onset of unilateral facial weakness or complete paralysis of all the muscles on one side of the face, dry eye, pain around the ear, an altered sense of taste, hyperacusis, or decreased tearing. On attempted closure, the eye rolls upward (Bell's phenomenon). The disease usually progresses from the onset of symptoms to maximal weakness within three days. 

The most wodely used classification to grade severity of the facial muscle weakness is House-Brackmann classification:

UMN and LMN facial palsy

Classically stroke presents with a UMN type of facial nerve palsy i.e. a supra nuclear lesion sparing of forehead/eyelid muscles (image on right) and lesions beloew the facial nerve nuclei presnet with involvement of upper as well as lower half of face i.e involving forehead/eyelid muscles as well. It is important to look for involvement of limb weakness and deficts in other cranial nerves fucntion as LMN palsy may reperesent a brainstem stroke. 

Diagnosis and Treatment 

Focus on the history and physical examination to identify the possible causes of LMN facial palsy such as:

• Otitis media
• Trauma
• Postsurgical complications
• Neoplasms
• Sarcoidosis
• Lyme Disease 
• Reactivation of VZV infection

Corticosteroids adminiatered within 3 days of the onset of synmptoms increase the likelihood of recovery and shorten time to recovery as well. Patients with Bell's palsy do not complain of any facial pain and don't have any cranial nerve involvement other than the facial nerve.

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. A meta-analysis in 2009 determined there was no significant benefit of combined antiviral and steroid treatment compared to steroids alone. Currently, the recommended treatment regiment for BP is prednisone, 60 to 80 mg per day, for one week or giving 25 mg twice daily for 10 days. 

Eye Care: Prescribe lubricating eye drops for use during the day in addition to a corneal lubricant to use at night. Furthermore, patches or taping the eyelid closed can be used at night. 

Severe disease can result in inability to completely close the eye in addition to decreased lacrimal secretions, leading to drying and tearing of the cornea. 

Summary

• Bell’s palsy is idiopathic paralysis of the facial nerve and is the most common cause of LMN facial palsy. DO a full neuro exam and look for other cranila nerve involvement to look for potential brainstem CVA.
• Bell's Palsy is unilateral and acute in onset, progressing over a period of hours and reaching maximal intensity within several days. 
• Treatment consists of corticosteroids and eye care. The prognosis of BP is excellent, with 85% of patients regaining function within three weeks. 

References:

1. Fahimi J, Navi BB, Kamel H. Potential misdiagnoses of Bell's palsy in the emergency department. Annals of emergency medicine. 2014 Apr 1;63(4):428-34.
2. Sullivan FM, Swan IR, Donnan PT, Morrison JM, Smith BH, McKinstry B, Davenport RJ, Vale LD, Clarkson JE, Hammersley V, Hayavi S, McAteer A, Stewart K, Daly F. Early treatment with prednisolone or acyclovir in Bell’s palsy. N Engl J Med. 2007 Oct 18;357(16):1598-607.
3. https://cks.nice.org.uk/bells-palsy#!scenario
4. 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 

Posted by:

              

     Lakshay Chanana

     

     Speciality Doctor

     Northwick Park Hospital

     Department of Emergency Medicine

     England

     @EMDidactic