Bell’s Palsy – Diagnosis, Symptoms, and Treatment

What is Bell’s Palsy?

Bell’s palsy is a neurologic disorder characterized by dysfunction of cranial nerve VII, the facial nerve.  Individuals typically develop one-sided facial weakness associated with altered saliva and tear production on the same side as a facial weakness.  Individuals may also experience loss of sensation in the anterior two-thirds of the tongue.  Most individuals experience a full recovery; however, a subset of patients have a permanent facial weakness.  This may lead to psychological symptoms and disability.  Eyelid involvement can result in the inability to close the eyelid.  Individuals often require frequent use of eye lubricants and referral an eye specialist.

Lower facial muscle involvement can lead to drooping of the mouth’s corner and slurred speech (dysarthria).  These symptoms are often mistaken for a stroke.  Patients often require referral to a speech and language therapist.

What Causes Bell’s Palsy?

The precise cause of Bell’s palsy is uncertain. However, there is some evidence to suggest that herpes simplex virus activation is related to its pathogenesis.  The virus is postulated to reactivate, spread across the facial nerve, multiply, and produce nerve inflammation and injury.  Herpes zoster virus infection is the second leading viral etiology.  Other viruses may also be responsible, including cytomegalovirus (CMV), Epstein-Barr virus (EBV), adenovirus, and rubella.

Alternative mechanisms may involve genetic factors or ischemia of the facial nerve.  The latter may occur in patients with diabetic microangiopathy.  Pregnancy may also result in facial nerve compression due to fluid retention.

How Common is Bell’s Palsy?

Bell’s palsy is a relatively uncommon disorder and is often evaluated in the primary care clinic or emergency department.  The most likely cause is the viral reactivation of herpes simplex virus.  The condition may require referral to a neurologist, ophthalmologist, and speech therapist, particularly if symptoms persist despite medical treatment.

The annual incidence of Bell’s palsy is approximately 13-34 cases per 100,000 people.  The condition accounts for about 60%-75% of cases of acute one-sided facial palsy.  The right side of the face is affected more often than the left.  The risk of Bell’s palsy is about 3 times higher during pregnancy, particularly in women in the third trimester of pregnancy.  Diabetes is found in 5%-10% of individuals with the disease.

Signs and Symptoms

Symptoms and signs of Bell’s palsy typically include:

• Difficulty closing the eyes
• Drooling from the corner of the mouth
• Slurred speech
• Difficulty swallowing
• Hyperacusis in the ipsilateral ear
• Altered secretion of the lacrimal and salivary glands
• Loss of taste on the anterior two-thirds of the tongue

Symptoms are typically acute and occur over 1-2 days, usually leading to maximal weakness at 3 weeks.  Most patients have symptomatic recovery within 6 months.  Patients often suffer from psychological distress due to the disabling features of the disease.

In contrast to individuals with stroke, patients with Bell’s palsy have a complete loss of facial muscle function, including the forehead’s involvement.  Individuals with stroke often have preserved forehead muscle function due to crossed innervation of the central nervous system.  This is a critical distinguishing feature between Bell’s palsy and facial paralysis due to stroke - sparing of the forehead muscles

On physical examination, your doctor will typically evaluate your ability to close the eye, furrow the forehead, smile, and puff out the cheeks.  They will also perform a detailed head-to-toe neurologic examination assessing muscle strength, tone, sensation, balance, coordination, and reflexes.  Close attention is usually made to the external ear to evaluate for vesicles (blisters) or scabbing, suggesting herpes zoster infection.  The parotid gland is also felt to assess for a parotid tumor.

Diagnosis

The diagnosis of Bell’s palsy is suggested based on symptoms and physical examination.  If the diagnosis is unclear or the clinical presentation is atypical, your doctor may recommend magnetic resonance imaging (MRI) and magnetic resonance angiography (MRA) of the head and neck to rule out a stroke or tumor. Occasionally they will recommend a high-resolution contrast-enhanced CT scan of the head.  Sometimes, electrodiagnostic studies are requested to help determine prognosis.  Your doctor will also frequently evaluate serologies for HIV infection and Lyme disease.

Bell's Palsy Medication and Treatment

Individuals with Bell’s palsy and poor eyelid closure require proper eye protection.  Reduced tearing and the inability to close the eye can lead to corneal drying and abrasion, leading to blindness.  Patients are often encouraged to use artificial tears in liquid, gel, or ointment formulations.  Liquids or gels are typically used during the day, while ointments are reserved for nighttime use.  Your doctor may recommend the use of protective glasses.  Patches are often performed at night.  On rare occasions, your doctor will temporarily implant a gold weight into the upper lid to facilitate eyelid closure.

Patients with idiopathic or viral Bell’s palsy are typically treated with oral glucocorticoids such as Deltasone (prednisone) within three days of symptom onset.  Individuals with severe cases often receive the combination of Deltasone (prednisone) plus Valtrex (valacyclovir).  Botox (botulinum toxin) injections can be beneficial for patients that do not completely recover.

References:

1. Gronseth GS, Paduga R, American Academy of Neurology. Evidence-based guideline update: steroids and antivirals for Bell’s palsy: report of the Guideline Development Subcommittee of the American Academy of Neurology. Neurology 2012; 79:2209. - https://www.ncbi.nlm.nih.gov/pubmed/23136264
2. Baugh RF, Basura GJ, Ishii LE, et al. Clinical practice guideline: Bell’s's palsy. Otolaryngol Head Neck Surg 2013; 149:S1. - https://www.ncbi.nlm.nih.gov/pubmed/24189771
3. Schwartz SR, Jones SL, Getchius TS, Gronseth GS. Reconciling the clinical practice guidelines on Bell’s's palsy from the AAO-HNSF and the AAN. Otolaryngol Head Neck Surg 2014; 150:709. - https://www.ncbi.nlm.nih.gov/pubmed/24789656