Causes of paralysis

Thefour most common causes of paralysis are stroke, head injury, spinal cord injury and multiple sclerosis.

Stroke

A stroke is a serious medical condition that occurs when the blood supply to your brain is disturbed.

Like all organs,the brain needs a constant supply of blood that containsoxygen and nutrientsto function properly.

If the blood supplyis restricted or stopped, brain cells will begin to die, whichcan lead to brain damage that often results in paralysis.

The brain's surface can tear or bruise as it bumps against the skull, damaging blood vessels and nerves.

Paralysis can occur if a part of the brain that controls specific muscles is damaged during a severe head injury.

Damage to the left side of the brain can cause paralysis on the right side of the body, and damage to the right side of the brain can cause paralysis on the left side of the body.

For example, the spinal cord passes nerve signals, such as hot or cold sensations, back to the brain.

Ifthe neck or spine is injured, thespinal cordcan also be damaged. This meansthe brain may no longer be able to transmit signals to the muscles, causing paralysis.

The exact locationwhere the spinal injury occurs can have a significant effect on how severe and wide-ranging the paralysis is. The higher up the spine the injury occurs, the worse the paralysis will be. For example, an injury in the middle of the spine will usually causeparaplegia (paralysis ofthe lower limbs).

Aneck injury, such as a broken neck, will usually result in tetraplegia(paralysis in all four limbs, also known as quadriplegia), as well as loss of normal lung function, which means the person will need to use a ventilator to breathe.

It is estimated that half of all spinal cord injuries occur in people who are16 to 30 years of age.

Multiple sclerosis

Multiple sclerosis (MS) is a condition wherenerve fibres in the spinal cord become damaged by the immune system (the body's natural defence against infection and illness).

The immune system mistakenly attacks a substance called myelin, which surrounds nerve fibres and helps with the transmission of nerve signals.

In MS, the myelin around thenerve fibres becomes damaged, which disturbs the messages coming to and from thebrain. Thiscan result inparalysis.

Less common causes of paralysis

There are also a number of less common causes,which are listedbelow.

Cancer

Cancers that develop in the brain, such as a high-grade Brain tumour, malignant (cancerous) , can cause paralysis, usually on one side of the body.

Alternatively, cancers can spread (metastasise) from other parts of the body into the brain or spinal cord, leading to paralysis.

Cerebral palsy

Cerebral palsy is a set of neurological conditions (those that affect the brain and nervous system)that affect a child's movement and co-ordination.

Cerebral palsy is caused by braindamage, which usually occurs before, during or soon after birth. Some possible causes of cerebral palsy include:

• infection duringearly pregnancy
• a difficult or premature birth
• bleeding in the baby's brain
• abnormal brain development in the baby

The most severe type of cerebral palsy is called spastic quadriplegia, where a person has such a high degree of muscle stiffness (spasticity) in all of their limbsthat they are unable touse them.

Itis caused by a mutation in a gene known as the GAA gene.

The mutation results in the body not producing enough of the protein frataxin. Frataxin is thought to play a role in the regulation of iron levels inside nerve cells.

Becauseofthe lack ofenough frataxin being produced, the level of iron and other toxic substances starts to build up inside the nerve cells, damaging them.

Many people with Friedreich's ataxia experience agradual increaseofparalysis in their legs. They will eventually need to use a wheelchair or another type of mobility aid.

Guillain-Barr syndrome

Guillain-Barr syndrome is a rare and poorly understood conditioncaused by peripheral nervous systemdamage. The peripheral nervous system is the network of nerves that controls the body's senses and movements.

In Guillain-Barr syndrome, the body's immune system attacks the nerves of theperipheral nervous system, which causes them to become inflamed.

This nerve damage results ina tingly, numb sensation in the arms and legs, which can eventually lead to temporary paralysis of the arms, legs and face.

Most people with Guillain-Barr syndrome make a full recovery in a few weeks or months and do not experience any other associated problems.

Lyme disease

Lyme disease is a bacterial infectionspread by infected ticks.

Ticks are smallarachnids that feed on the blood of mammals, including humans. The ticks release bacteria that can damage the nerves, leading to temporary paralysis of the face.

Motor neurones are specialised nerve cells that control voluntary muscle movements, such as walking. MND causes progressive muscle weakness, which eventually leads tototal body paralysis.

Spina bifida

Spina bifida is a term that describes a series of birth defects that affect development of the spine and nervous system.

Myelomeningocele is the most serious type of spina bifida, occurring in 1 in every 1,000 births. Itcauses extensive damage to the nervous system, whichcan often result in partial or total permanent paralysis of the lower limbs.

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