Paralysis

Overview
Paralysis is the complete loss of muscle function for one or more muscle groups. Paralysis often includes loss of feeling in the affected area.

Pathophysiology
Paralysis is most often caused by damage to the nervous system or brain, especially the spinal cord. Partial paralysis can also occur in the REM stage of sleep.

Differential diagnosis of causes of paralysis

 * Amyotrophic lateral sclerosis (ALS)
 * Botulism
 * Guillain-Barré syndrome
 * Multiple sclerosis
 * Poisons that interfere with nerve function, such as curare
 * Poliomyelitis
 * Spina bifida
 * Stroke
 * trauma

Variations
Paralysis may be localized, or generalized, or it may follow a certain pattern. For example, localized paralysis occurs in Bell's palsy where one side of the face may be paralyzed due to inflammation of the facial nerve on that side. Patients with stroke may be weak throughout their body (global paralysis) or have hemiplegia (weakness on one side of the body) or other patterns of paralysis depending on the area of damage in the brain.

Other patterns of paralysis arise due to different lesions and their sequelae. For example, lower spinal cord damage from a severe back injury may result in paraplegia, while an injury higher up on the spinal cord, such as a neck injury, can cause quadriplegia. Patients with paraplegia or quadriplegia often use equipment such as a wheelchair or standing frame for mobility and to regain some independence.

Most paralyses caused by nervous system damage are constant in nature; however, there are forms of periodic paralysis, including sleep paralysis, which are caused by other factors.