Paralysis is a medical condition characterized by the inability to move one or more muscles. In most cases, a person experiencing this condition also loses all feeling in the affected area. It may be temporary or permanent, depending on the cause. If it is the result of damage to the nervous system, it is usually consistent. Sleep paralysis, on the other hand, only affects a person during the time that immediately precedes sleep or immediately after waking up.
There are many potential causes of paralysis. The two most common are stroke and trauma, particularly to the nervous system or the brain. Certain diseases or afflictions, such as poliomyelitis, peroneal dystrophy, spina bifida, Bell’s palsy, and multiple sclerosis may also cause paralysis. Botulism, paralytic shellfish poisoning, and certain types of poisons, particularly those that directly affect the nervous system, may also lead to this condition.
The precise type of paralysis a person experiences depends on the underlying cause. With Bell’s palsy, for example, the inability to move is usually localized, which means it only affects a small area of the person’s body. Typically, only one side of the person’s face becomes paralyzed as the facial nerve on that side becomes inflamed. When only one side of a person’s body is affected, the condition is considered unilateral. When it affects both sides, it is bilateral.
A person who has experienced a stroke, on the other hand, may experience weakness throughout his or her body. This is referred to as global paralysis. Conversely, the person may only experience weakness on one side of his or her body. Medically, this is known as hemiplegia.
Generally, the most severe form of paralysis is caused by damage to the spinal cord. A person who experiences trauma in his or her upper spinal cord may develop quadriplegia as a result. A person who is quadriplegic is unable to move his or her arms and legs. Injury to the lower spinal cord may cause paraplegia, which results in either the legs or the arms becoming paralyzed.