Bell's palsy

Bell's palsy is a specific type of facial paralysis. It causes a temporary inability to control facial muscles on one side of the face. In rare cases, it can affect both sides. This condition is significant because it is the most common cause of one-sided facial nerve paralysis. It accounts for 70% of such cases. While it can be startling, the weakness is usually temporary. Most people see significant improvement over several weeks.

The condition is caused by a dysfunction of cranial nerve VII, also known as the facial nerve. This nerve is responsible for many important facial functions. It controls blinking, closing the eyes, smiling, frowning, and raising the eyebrows. It also manages salivation and the flaring of nostrils. Additionally, the facial nerve carries taste sensations from the anterior two-thirds of the tongue. It also innervates the stapedius muscle in the middle ear. This muscle helps dampen loud sounds. When the nerve fails, sounds may seem too loud, a condition called hyperacusis.

Scientists are still studying the exact mechanism of how this happens. The precise cause remains unknown. However, many researchers believe a viral infection causes the nerve to swell. This is known as inflammation or edema. As the nerve swells, it creates pressure within a narrow bony canal called the stylomastoid foramen. This pressure restricts blood and oxygen to the nerve cells. This restriction can block neural signals or damage the nerve itself. Some research suggests that the herpes simplex virus type 1 may cause demyelination. Demyelination is the damage to the protective coating of the nerve.

There are several risk factors associated with Bell's palsy. These include diabetes, pregnancy, and recent upper respiratory tract infections. Some believe the reactivation of dormant viruses, such as the herpes family, triggers the swelling. This includes the varicella zoster virus and the Epstein–Barr virus. Other infections like HIV and Lyme disease have also been linked to facial palsy. In areas where Lyme disease is common, it accounts for about 25% of facial palsy cases. There is also a suspected association with migraines. Furthermore, familial inheritance has been found in 4% to 14% of cases.

History tells us that a Scottish surgeon named Charles Bell first described this condition. He lived from 1774 to 1842. He was the one who identified the connection between the facial nerve and this paralysis. Today, doctors use a specific process to diagnose Bell's palsy. It is considered a diagnosis of exclusion. This means doctors must rule out other serious conditions first. They look to ensure the weakness is not caused by a stroke, a brain tumor, or meningitis. A stroke is different because it often allows a person to still wrinkle their forehead.

The statistics for Bell's palsy show how common it is. It occurs in 1 to 4 people per 10,000 every year. About 1.5% of the population will be affected at some point in their lives. It most frequently occurs in people between the ages of 15 and 60. Males and females are affected at equal rates. While the condition is often straightforward, some people experience "myriad neurological symptoms." These can include facial tingling, headaches, neck pain, or even balance problems.

Treatment focuses on improving recovery and protecting the body. Corticosteroids, such as prednisone, are often used to reduce inflammation. These are most effective when given within three days of the symptoms starting. Antiviral medications are sometimes prescribed, though their benefit is debated. Protecting the eye is a critical part of management. If a person cannot blink properly, the eye may dry out. Patients use eye drops, ointments, or even an eyepatch to keep the eye safe. Physiotherapy can also help maintain muscle tone. Most people show signs of improvement within 14 days. Complete recovery usually happens within six months.