Causes of Bell's (Facial) Palsy

 

Once thought to be of idiopathic origin, viral and bacterial infections, and autoimmune disorders such as AIDS have emerged as the most frequent common causes in the etiology of Bell¹s Palsy.

 

HERPES SIMPLEX 1

Herpes Simplex 1, was first believed to be  a cause of Bell's Palsy during the 1970's.  Although some causes Bells palsy are still considered idiopathic, over twenty years later, a 1995 study (Murakami, et al.) strongly linked the herpes simplex virus (HSV-1) as the most frequent cause of Bell's palsy, responsible for at least 60 - 70% of cases. Current research continues to reinforce his conclusion.

 

Exposure to HSV-1 has become increasingly common; a vast majority of the population has been exposed.

§       Most people are exposed during childhood.

§       Kissing between relatives is the most frequent source of exposure, but it may be possible that the virus is also spread while sharing towels, utensils, etc.

The active virus is commonly associated with cold sores, but the virus often runs its course without causing any blisters - blisters actually appear only 15% of the time.

§       HSV-1 is infectious for a short time following the incubation period.

§       This results in a large population of HSV-1 carriers are unaware they've been exposed to the virus.

§       It then enters a dormant state, residing on nerve tissue where several triggers can cause the dormant virus to reactivate.

As a normal function to remove harmful foreign bodies such as viruses and bacteria so that we can recover from illness and injuries, when the latent virus reactivates at the facial nerve, the immune system begins to produce antibodies.

§       The production of antibodies causes inflammation.

§       The nerve itself becomes inflamed, or the inflammation within the canal exerts pressure on the nerve.

If the location of the inflammation is within the fallopian canal, there is no room for the swelling to expand.

§       The result is that the nerve is compressed inside its bony tube.

§       Compression of the nerve is the injury that stops transmission of signals to muscles.

§       Unable to receive signals to contract and relax, the muscles become temporarily weakened or paralyzed.

 

The triggers for reactivation of the virus prior to the onset of Bell's palsy have not been proven conclusively However,  impaired immunity, due to temporary (stress, lack of sleep, minor illness, physical trauma, upper respiratory infection, etc.) or long-term stressors (autoimmune syndromes, chronic disease, etc.) are now strongly believed to be the most likely triggers.

 

OTHER CAUSES ...

Facial and surgical wounds, trauma due to a blunt force, temporal bone fractures, brain stem injuries, acoustic neuromas, cysts and tumors can result in facial palsy. Diabetes and thyroid conditions are also associated with facial palsy. Lupus, Sjogrens syndrome and congenital defects can, infrequently, cause facial paralysis.

 

Other  VIRAL LINKS

There has been research implicating other viruses, including cytomegalovirus, Epstein-Barr, rubella and mumps, in the etiology of Bell's palsy. As with the herpes virus, potential triggers appear to be related to conditions that affect the immune system. The internal process that would cause the nerve to become compressed and result in Bells palsy is currently thought to be the same as described above for the Herpes virus.