As they share common features, it's sometimes difficult to differentiate between the facial paralysis that results from Bell's Palsy and the more serious side effects of a stroke. They are in fact very different medical conditions, and are not related to each other.
Knowing the difference is important as a rapid diagnosis is often crucial in treating someone who has experienced a stroke.
So let's look in more detail at Bell palsy vs stroke.
Both conditions involve sudden distortions in the face. Facial features become noticeably asymmetrical; the sufferer may experience a sudden â€œdropâ€ in one side of their facial muscles, resulting in a droopy eye, or mouth.
Certain movements may become more difficult such as closing one eye or smiling properly. They can vary in their severity from person to person, but both generally appear "overnight".
Each side of the human face is controlled by its own set of nerves and muscles. The way these nerve fibers and muscles connect is also slightly different between the top and bottom half of the face.
The source of the nerves (which control the muscles' movements) is the brain stem. Messages are sent from the brain along the nerves to create appropriate changes in facial expressions.
These same nerves â€“ usually encased in a protective, bony shell â€“ also control other functions such the production of tears in the tear ducts and saliva in the mouth. They also collect taste sensations from the tongue.
The way the muscles and nerves interact with each other and the central cortex is complex and like much of neurological science, it's still relatively unexplained.
Bell's palsy is the most common cause of facial paralysis; usually only affecting one side of the face, it can sometimes create weakness in both sets of nerve-muscle configurations.
It's named after the person who first researched and documented the condition, 19th-century Scottish surgeon Sir Charles Bell.
Bell's palsy usually manifests itself as someone struggling to close one of their eyes or wrinkle their forehead. They may have twitching muscles, weakness or total paralysis.
With Bell's palsy, sufferers may also report impaired ability to taste or difficulties in eating and drinking. They may find one eye is â€œtearyâ€ or that they are drooling out of one side of their mouth.
Onset can be rapid - usually over 48 hours - but the effects are usually temporary. It indicates that facial nerves have suffered some form of damage or trauma. This has interrupted the way the nerves function, and they are not sending messages effectively.
As the causes of Bell's palsy are still not properly understood, medical science has not created ways to test for it accurately or treat the condition.
There is a body of opinion that its primary cause is a viral infection.
Milder cases are often left untreated and they disappear within a couple of weeks. If the paralysis is severe, the medical professional may carry out tests for underlying conditions such as permanent nerve damage from injury, or infections and diabetes which may affect nerve function.
It is also possible to use scans to check for structural damage to the face which may be putting pressure on the facial nerves.
As mentioned, strokes also manifest themselves in facial paralysis. In fact, it is not uncommon for this to be the first indication that a stroke has occurred.
An ischemic stroke is when a blockage or contraction interferes with the proper functioning of the artery that supplies blood to the brain. A haemorrhagic stroke is less common and is when a weakened blood vessel breaks, also reducing blood flow to the brain.
It's possible to have a â€œmini-strokeâ€ which is the term used for a brief interruption in the blood flow to the brain. The effects of this are temporary.
However, if the interruption is even a few seconds long, the brain is starved of oxygen it needs and brain cell damage can occur. The location of the damage and how severe it is varies from case to case.
It's common for strokes to lead to damage on one side of the brain. This then affects the way the brain controls the corresponding side of the body, including sending messages to the face on that side.
However, as strokes affect brain function (not just nerves), the symptoms often include more than facial weakness or paralysis. The patient usually reports problems with the arm and leg on that side of their body too. Cognitive abilities can be impaired. They may struggle to form words, lose consciousness or become easily confused.
This overview shows some of the ways to assess Bell's palsy vs strokes. But seeking professional help is always best.
Medical professionals can differentiate between the two conditions by taking a full medical history and a detailed medical examination.