EBM Consult

Stroke vs. Bell's Palsy

    Anatomy Image

    Bells Palsy vs Stroke Anatomy Image


    If you have a patient come in complaining of new or acute onset of unilateral facial paralysis without any other sensory or motor deficits (i.e., no upper or lower extremity weakness) the next thing you need to do is determine which parts of the face are affected.  Have the patient attempt to raise both eyebrows as if surprised.  Then have the patient smile. 

    • If they cannot raise their eyebrows and cannot move the lower portion of their face they have Bell's palsy and should be given steroids +/- antivirals. 
    • If the lower portion of the face is paralyzed but the eyebrows rise symmetrically, then you have to be concerned for a stroke and should get imaging and further consideration of treatment (depending on time of presentation and cause). 
    Bell's Palsy vs. Stroke

    Bell's palsy (also called idiopathic facial paralysis) is the most common cause of unilateral facial paralysis.  It has the following features:

    • Acute onset of unilateral upper AND lower facial paralysis
    • Flattening of the forehead and inability to raise eyebrows on affected side
    • On smiling the face lateralizes to the opposite (normal side)
    • Hyperacusis
    • Changes in taste
    • Impaired eyelid closure

    The above symptoms are thought to occur as a result of the injury, swelling, and/or ischemia of the facial nerve (CN VII) as a result of compression as it passes through the facial canal.  While the exact cause is unknown, it appears that viral infection (herpes virus) is associated. 

    Bell's Palsy is a peripheral nerve effect whereas a ischemic stroke is a central process. As shown in the diagram, the forehead receives motor innervation from both hemispheres of the cerebral cortex. A stroke that compromised motor innervation of the face would therefore only result in paralysis of the lower half of the face - the forehead still receiving innervation from the unaffected hemisphere. A peripheral lesion, such as Bell's Palsy, interrupts the innervation after the motor commands from both hemispheres have joined, so that the forehead is paralyzed.

    Treatment of Bell's Palsy

    Therefore, the location of the lesion is important in differentiating the two clinical scenarios whose treatments are drastically different.  Patients with Bell's palsy should be given steroids within 72 hours of onset +/- antivirals, and +/- eye lubricant to prevent corneal abrasions or ulcers.  Dosing regimens include:

    • Prednisone 1 mg/kg in 2 divided doses by mouth daily x 5 days, then 5 mg by mouth twice a day for another 5 days for a total of 10 days of steroids.
    • Valacyclovir 500 mg by mouth twice a day x 5 days
      • Alternative option (due to compliance): Acyclovir 800 mg by mouth 5 times per day x 7-10 days
    • Erythromycin ophthalmic ointment 1/2 inch into the affected eye 2 - 4 times per day
    1. Baugh RF et al. Clinical Practice Guidelines: Bell's Palsy Executive Summary.  Otolaryngol Head Neck Surg 2013;149(5):656-63.
    2. Gronseth GS et al.  Evidenced-based guidelines update: steroids and antivirals for Bell palsy: report of the Guideline Development Subcommittee of the American Academy of Neurology. Neurology 2012;79(22):2209-13.  
    3. Sullivan FM et al.  Early treatment with prednisolone or acyclovir in Bell's palsy. N Engl J Med 2007;357:1598.
    Editors & Reviewers


    • Anthony J. Busti, MD, PharmD, FNLA, FAHA
    • Dylan Kellogg, MD

    Last Updated:  July 2015