Possible Causes of Facial Paralysis
What Caused My Facial Paralysis?
Most Likely
Reactivation of dormant virus (herpes simplex or varicella-zoster)
Virus causes facial nerve to swell inside narrow bone canal
Swelling compresses nerve = can't send signals to muscles
Risk Factors
Stress
Pregnancy (30% higher risk)
Diabetes
High blood pressure
Weakened immune system
Important
Less than 2% of cases affect both sides
If both sides affected, different cause likely—needs different workup
Other Possible Causes
Lyme Disease
Symptoms: Fatigue, joint pain and swelling, fever, potentially bullseye rash on the body
Sudden onset of facial weakness
Zoster Sine Herpete
Symptoms: Same symptoms as Ramsay Hunt except for blisters and swelling of ear, loss of taste or metallic taste, oftentimes pregnancy-related
Sudden onset of facial weakness
Acoustic Neuroma
Symptoms: Hearing loss and/or balance issues without sudden onset of facial weakness
Gradual facial weakness
Facial Nerve Tumor
Sudden onset of facial weakness
Usually not painful
Trauma
Bell's Palsy
Symptoms: Tooth ache, ear infection or ear ache, flickering of the eye, difficulty closing the eye, pregnancy
After facial droop the pain goes away
Is this Bell’s Palsy or Ramsay Hunt Syndrome?
This matters because treatment differs.
Ramsay Hunt Syndrome (RHS) signs
Extreme pain in/around ear
Blisters/rash in ear, on ear, or on face/tongue
Severe vertigo/dizziness
Hearing loss
Important facts
RHS is shingles attacking facial nerve
33% of RHS cases have NO blisters (zoster sine herpete)
RHS has worse prognosis than Bell's palsy
RHS needs aggressive antiviral treatment
Often misdiagnosed as Bell's palsy
If you have severe ear pain or any blisters
Tell your doctor immediately
Request blood test for varicella-zoster virus
Insist on extended antiviral treatment
Understanding the Causes of Facial Palsy
What causes facial palsy?
Facial palsy happens when the facial nerve—the nerve that controls the muscles on one side of your face—becomes damaged, inflamed, or compressed. There are many possible causes.
Breakdown of causes
Based on recent medical studies, here is how facial palsy cases are typically distributed:
60–75%
of cases
Bell's palsy (idiopathic)
Hearing loss
Likely related to herpes simplex virus (cold sore virus) reactivation
Comes on suddenly (within 72 hours)
7–15%
of cases
Ramsay Hunt syndrome (varicella zoster virus)
Caused by the same virus that causes chickenpox and shingles
Classic form: facial weakness with painful blisters in or around the ear
"Zoster sine herpete" (ZSH): facial weakness caused by the virus but WITHOUT any visible rash—this occurs in up to one-third of Ramsay Hunt cases and may initially look exactly like Bell's palsy
4–6%
of cases
Lyme disease
Bacterial infection spread by tick bites
More common in certain geographic areas (Northeast, Upper Midwest, Pacific Coast in the US)
May have other symptoms like rash, fever, or joint pain
3–7%
of cases
Tumors
Includes acoustic neuromas, parotid gland tumors, and cancers
Usually develops slowly over weeks to months
May be associated with facial pain, numbness, or tearing
5–10%
of cases
Other Causes
Ear infections
Autoimmune diseases (sarcoidosis, Guillain-Barré syndrome)
Trauma or surgery
Other infections
Why the distinction matters
Ramsay Hunt syndrome vs. Bell's palsy:
Ramsay Hunt syndrome tends to cause more severe facial weakness and has a lower chance of complete recovery compared to Bell's palsy. This is why your doctor may look carefully for any blisters in your ear or mouth.
Zoster sine herpete (ZSH):
This is an important condition to understand. Some patients have facial palsy caused by the varicella zoster virus (shingles virus) but never develop the typical rash. Studies suggest this "hidden" form of Ramsay Hunt syndrome may account for up to 29% of cases initially diagnosed as Bell's palsy. Patients with ZSH may have:
Worse hearing on the affected side
Lower rates of complete recovery compared to true Bell's palsy
Your doctor may test for this if your symptoms are severe or if you are not recovering as expected.
How does my doctor determine the cause?
For most people with sudden-onset facial weakness affecting the entire side of the face, Bell's palsy is the most likely diagnosis. Your doctor will:
- Ask about your symptoms: When did the weakness start? Did it come on suddenly or gradually? Do you have any other symptoms like rash, fever, hearing changes, or weakness elsewhere?
- Examine you: Your doctor will check your facial movements, look in your ears, and test your other nerves.
- Consider testing if needed: Most people with typical Bell's palsy do not need blood tests or imaging. However, your doctor may recommend:
Specialized tests for varicella zoster virus if ZSH is suspected
An MRI if your symptoms are unusual, if you have had facial palsy before on the same side, or if you are not improving after 3 months
Blood tests for Lyme disease if you live in or visited an area where Lyme disease is common
Warning signs that suggest a cause other than Bell's palsy
Tell your doctor right away if you have:
Weakness that developed slowly over days to weeks (rather than suddenly)
Hearing loss, ringing in your ears, or dizziness
Weakness on both sides of your face
Excessive tearing from the affected eye
No improvement after 3 months of treatment
A rash, especially near your ear
Weakness in your arms or legs
Numbness or pain in your face
A history of skin cancer or cancer of the salivary glands
The good news
Most people with Bell's palsy recover completely within a few weeks to months, especially with early treatment. Even when facial palsy has another cause, many conditions are treatable once identified.
REFERENCES
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Etiology, Diagnosis, and Management of Facial Palsy: 2000 Patients at a Facial Nerve Center. Hohman MH, Hadlock TA. The Laryngoscope. 2014;124(7):E283-93. doi:10.1002/lary.24542.
High Prevalence of Varicella-Zoster Virus Reactivation in Herpes Simplex Virus-Seronegative Patients With Acute Peripheral Facial Palsy. Furuta Y, Ohtani F, Kawabata H, Fukuda S, Bergström T. Clinical Infectious Diseases : An Official Publication of the Infectious Diseases Society of America. 2000;30(3):529-33. doi:10.1086/313721.
Characteristics of Patients With Acute Peripheral Facial Palsy Showing Varicella Zoster Virus DNA in Saliva. Chang DS, Lee J, Shin SA, Lee HY. Journal of Medical Virology. 2018;90(5):959-964. doi:10.1002/jmv.25030.
Multiple Cranial Neuropathy Due to Varicella Zoster Virus Reactivation Without Vesicular Rash: A Challenging Diagnosis. Stornaiuolo A, Iodice R, De Simone R, et al. Neurological Sciences : Official Journal of the Italian Neurological Society and of the Italian Society of Clinical Neurophysiology. 2023;44(10):3687-3689. doi:10.1007/s10072-023-06833-6.
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