Paralysis

Paralysis, also known as plegia, is the loss of motor function in one or more muscles. This condition can also include sensory loss, which is a loss of feeling in the affected area. In the United States, approximately 1 in 50 people have been diagnosed with some form of paralysis. This condition can be permanent or transient, meaning it is temporary. The term itself comes from the Greek word "paralysis," which means "disabling of the nerves." If paralysis is accompanied by involuntary tremors, it is usually called palsy.

Most cases of paralysis result from damage to the nervous system. The spinal cord is a very common site for this type of damage. Many different medical conditions can cause these issues. These include stroke, cerebral palsy, and Parkinson's disease. Other causes include multiple sclerosis, ALS, and Guillain-Baré syndrome. Physical trauma can also lead to nerve injury. Common incidents include motor vehicle accidents, falls, industrial accidents, and sports injuries. Even certain drugs, such as curare, can interfere with nerve function and cause paralysis.

Paralysis can follow different patterns depending on the cause. Ascending paralysis begins in the lower limbs and moves toward the upper limbs. This pattern is associated with Guillain-Baré syndrome and tick paralysis. In contrast, descending paralysis moves from the top down. This type of movement is seen in conditions like botulism. Some paralysis is localized to one part of the body. Other forms are generalized, affecting much larger areas. There is also pseudoparalysis, which is a false paralysis. This is not actual muscular damage but a voluntary restriction of motion due to pain or mental stress.

Some individuals are born with conditions that lead to paralysis. Spina bifida is a congenital defect where the vertebrae fail to form properly. This allows the spinal cord to protrude from the spine. In extreme cases, the spinal cord function below the missing arches can cease. This often results in the paralysis of the lower extremities. It can even cause paralysis of the anal sphincter in newborns. If spina bifida is treated surgically within 72 hours of birth, many cases can be corrected.

In the animal kingdom, paralysis is often used as a tool for survival. Many species use paralyzing toxins to capture prey or to avoid being eaten. For example, the wasp genus Microbracon uses venom to paralyze the neuromuscular system of its prey. The wasp Philanthus gibbosus uses venom to paralyze bees. The female wasp coats the paralyzed bee in a thick layer of pollen. She then lays eggs on the insect, which the larvae eat after they hatch.

Vertebrates also produce powerful toxins that affect the nervous system. The pufferfish, known as Takifugu rubripes, produces tetrodotoxin. This toxin binds to sodium channels in nerve cells. By doing this, it inhibits the proper function of those cells. A nonlethal dose of tetrodotoxin results in temporary paralysis. This toxin is also found in other animals, including certain toads and nemerteans.

Pets can also suffer from neurological issues that cause paralysis. Certain dog breeds with short legs may have brittle intervertebral discs. If a disc ruptures, it can press on spinal nerves or enter the spinal canal. A major rupture can cut off circulation and require surgery within 24 hours. If surgery is delayed, the spinal cord tissue may deteriorate and die. Other breeds, like the German Shepherd, are prone to degenerative myelopathy. This is a deterioration of the nerves in the posterior part of the spinal cord.

Medical science also looks at how blood flow affects nerve health. A fibrocartilaginous embolism occurs when a tiny piece of disc material blocks a spinal artery. When an artery is blocked, the nerves it serves can die from a lack of blood. Similarly, cats with heart murmurs may develop blood clots. If a clot blocks the femoral arteries, it can cause paralysis in the hind legs. Understanding these complex connections between the blood, the nerves, and the spine is vital for modern medicine.