amyotrophy

Spinal muscular atrophy (SMA) is a group of genetic diseases that damages and kills motor neurons. Motor neurons are a type of nerve cell in the spinal cord and lower part of the brain. They control movement in your arms, legs, face, chest, throat, and tongue.

As the motor neurons die off, your muscles start to weaken and atrophy (waste away). The muscle damage gets worse over time and can affect speaking, walking, swallowing, and breathing.

There are different types of SMA. They are based on how serious the disease is and when the symptoms start:

• Type l is also called Werdnig-Hoffman disease or infantile-onset SMA. It is the most severe type. It is also the most common. Babies with this type usually show signs of the disease before 6 months of age. In more severe cases, the signs show up even before or just after birth (Types 0 or 1A). The babies may have trouble swallowing and breathing and may not move around a lot. They have chronic shortening of muscles or tendons (called contractures). They usually cannot sit up without help. Without treatment, many children with this type will die before 2 years of age.
• Type ll is a moderate to severe type of SMA. It usually first noticed between 6 and 18 months of age. Most children with this type can sit without support but cannot stand or walk without help. They may also have trouble breathing. They can usually live into adolescence or young adulthood.
• Type lll is also called Kugelberg-Welander disease. It is the mildest type that affects children. The signs of the disease usually show up after age 18 months. Children with this type can walk by themselves but may have trouble running, getting up from a chair, or climbing stairs. They may also have scoliosis (curvature of the spine), contractures, and respiratory infections. With treatment, most children with this type will have a normal lifespan.
• Type IV is rare and often mild. It usually causes symptoms after 21 years of age. The symptoms include mild to moderate leg muscle weakness, tremors, and mild breathing problems. The symptoms slowly get worse over time. People with this type of SMA have a normal lifespan.

Most types of SMA are caused by a change in the SMN1 gene. This gene is responsible for making a protein that the motor neurons need to be healthy and to function. But when part of the SMN1 gene is missing or abnormal, there isn't enough protein for the motor neurons. This causes the motor neurons to die off.

Most people have two copies of the SM1 gene - one from each parent. SMA normally only happens when both copies have the gene change. If only one copy has the change, there usually aren't any symptoms. But that gene could be passed down from parent to child.

Some of the less common types of SMA may be caused by changes in other genes.

Your health care provider may use many tools to diagnose SMA:

• A physical exam
• A medical history, including asking about family history
• Genetic testing to check for the gene changes that cause SMA
• Electromyography and nerve conduction studies and a muscle biopsy may be done, especially if no gene changes were found

Parents who have a family history of SMA may want to do a prenatal test to check to see whether their baby has an SMN1 gene change. An amniocentesis or in some cases a chorionic villi sampling (CVS) is used to get the sample for testing.

In some states, genetic testing for SMA is part of newborn screening tests.

There is no cure for SMA. Treatments can help manage symptoms and prevent complications. They may include:

• Medicines to help the body make more of the proteins that the motor neurons need
• Gene therapy for children under 2 years of age
• Physical, occupational, and rehabilitation therapy to help to improve posture and the mobility of the joints. These therapies may also improve blood flow and slow muscle weakness and atrophy. Some people may also need therapy for trouble speaking, chewing, and swallowing.
• Assistive devices such as supports or braces, orthotics, speech synthesizers, and wheelchairs to help people stay more independent
• Good nutrition and a balanced diet to help maintain weight and strength. Some people might need a feeding tube in order to get the nutrition they need.
• Breathing support for people who have muscle weakness in the neck, throat, and chest. The support may include devices to help with breathing during the day and to prevent sleep apnea at night. Some people might need to be on a ventilator.

NIH: National Institute of Neurological Disorders and Stroke

Charcot-Marie-Tooth disease (CMT) is a group of genetic nerve disorders. It is named after the three doctors who first identified it. In the United States, CMT affects about 1 in 2,500 people.

CMT affects your peripheral nerves. Peripheral nerves carry movement and sensation signals between the brain and spinal cord and the rest of the body. Symptoms usually start around the teen years. Foot problems such as high arches or hammertoes can be early symptoms. As CMT progresses, your lower legs may weaken. Later, your hands may also become weak.

Doctors diagnose CMT by doing a neurologic exam, nerve tests, genetic tests, or a nerve biopsy. There is no cure. The disease can be so mild you don't realize you have it or severe enough to make you weak. Physical therapy, occupational therapy, braces and other devices and sometimes surgery can help.

NIH: National Institute of Neurological Disorders and Stroke

Degenerative nerve diseases affect many of your body's activities, such as balance, movement, talking, breathing, and heart function. Many of these diseases are genetic. Sometimes the cause is a medical condition such as alcoholism, a tumor, or a stroke. Other causes may include toxins, chemicals, and viruses. Sometimes the cause is unknown.

Degenerative nerve diseases include:

• Alzheimer's disease
• Amyotrophic lateral sclerosis
• Friedreich ataxia
• Huntington's disease
• Lewy body disease
• Parkinson's disease
• Spinal muscular atrophy

Degenerative nerve diseases can be serious or life-threatening. It depends on the type. Most of them have no cure. Treatments may help improve symptoms, relieve pain, and increase mobility.

Neuromuscular disorders affect your neuromuscular system. They can cause problems with:

• The nerves that control your muscles
• Your muscles
• Communication between your nerves and muscles

These disorders can cause your muscles to become weak and waste away. You may also have symptoms such as spasms, twitching, and pain.

Examples of neuromuscular disorders include:

• Amyotrophic lateral sclerosis
• Muscular dystrophy
• Myasthenia gravis
• Spinal muscular atrophy

There can be different causes for these diseases. Many of them are genetic.This means they are inherited (run in families) or are caused by a new mutation in your genes. Some neuromuscular disorders are autoimmune diseases. Sometimes the cause is unknown.

Many neuromuscular diseases have no cure. But treatments may improve symptoms, increase mobility, and lengthen life.

Epilepsy is a brain disorder that causes people to have recurring seizures. The seizures happen when clusters of nerve cells, or neurons, in the brain send out the wrong signals. People may have strange sensations and emotions or behave strangely. They may have violent muscle spasms or lose consciousness.

Epilepsy has many possible causes, including illness, brain injury, and abnormal brain development. In many cases, the cause is unknown.

Doctors use brain scans and other tests to diagnose epilepsy. It is important to start treatment right away. There is no cure for epilepsy, but medicines can control seizures for most people. When medicines are not working well, surgery or implanted devices such as vagus nerve stimulators may help. Special diets can help some children with epilepsy.

NIH: National Institute of Neurological Disorders and Stroke

Nerves are like wires that carry messages back and forth between your brain and your body. Your peripheral nerves branch off from your brain and spinal cord and connect to all parts of your body, including your muscles and organs. Peripheral nerves carry messages from your brain that control your movement, breathing, heartbeat, digestion, and more. They also carry messages from your body to your brain, so you can feel things, such as pain, heat, and cold.

Peripheral nerve disorders happen when one or more peripheral nerves are damaged. Damaged nerves may not carry messages correctly, or they may not work at all. As a result, you may have pain, trouble walking, or a variety of other problems, depending on which nerves are involved.

Peripheral nerve disorders are very common. There are more than 100 different types.

Many things can damage nerves and lead to peripheral nerve disorders:

• Diabetes is the most common cause of peripheral nerve disorders. Most people with diabetes will develop diabetic nerve problems.
• Physical injury (trauma) that stretches, crushes, squeezes, cuts, or puts pressure on one or more nerves. Some examples of peripheral nerve disorders from physical injury include complex regional pain syndrome and brachial plexus injuries.
• Health conditions, including:
  • Certain cancers and their treatment (chemotherapy and radiation therapy).
  • Infections, such as HIV and Lyme disease.
  • Problems with blood or blood vessels.
  • Autoimmune diseases, such as rheumatoid arthritis and lupus.
  • Kidney or liver disease.
• Certain medicines.
• Contact with certain toxic substances, such as lead or mercury.
• Alcohol use disorder (AUD) and smoking.
• Vitamin imbalances, especially a lack of vitamin B12.
• Your genes, including changes in your genes or conditions that you inherit from your parents, such as Charcot-Marie-Tooth disease.

In certain cases, the cause of peripheral nerve disorder is not known.

The symptoms of peripheral nerve disorders depend on which nerves are affected, what is causing the damage, and how serious it is:

• Weak or aching muscles
• Problems with balance, walking, or using your arms and hands
• Cramps or twitching muscles
• Muscle shrinking

• Tingling, numbness, or pain often in the hands and feet
• Not being able to feel heat, cold, or pain, such as a cut on your foot
• Pain from even light touch

• A heartbeat that's too fast or too slow
• Trouble swallowing
• Sweating too much or too little
• Vomiting, diarrhea, or constipation
• Problems with urination or sexual function

Symptoms may range from mild to very strong. They may develop quickly over days or slowly over months and years. But they are rarely life-threatening.

To find out if you have a peripheral nerve disorder, your provider will:

• Ask about your medical history
• Ask about your family health history
• Do a physical exam
• Order tests, which may include:
  • Blood tests
  • Genetic tests
  • Nerve tests that measure:
    • Electrical activity in your nerves and muscles
    • How well your autonomic nerves are working
  • A biopsy of nerve or skin tissue
  • CT or MRI scan to see what may be pressing on your nerves

It's important to treat any conditions that are causing nerve damage. In certain cases, that will allow your nerves to heal over time.

Treatment for symptoms depends on the type of peripheral nerve disorder you have, where it is, and how severe. Treatment options include:

• Braces or splints
• Over-the-counter patches and skin creams
• Prescription medicines
• Non-drug pain management, such as electrical stimulation or relaxation therapy
• Surgery to relieve pressure on a nerve

You can help prevent peripheral nerve disorders by:

• Managing health conditions that may cause nerve damage, especially diabetes
• Preventing falls and accidents
• Avoiding toxic substances
• Being careful to avoid repeated motions and body positions that press on your nerves
• Eating a balanced diet, exercising, limiting alcohol, and not smoking

NIH: National Institute of Neurological Disorders and Stroke

Your spinal cord is a bundle of nerves that runs down the middle of your back. It carries signals back and forth between your body and your brain. It is protected by your vertebrae, which are the bone disks that make up your spine. If you have an accident that damages the vertebrae or other parts of the spine, this can also injure the spinal cord. Other spinal cord problems include:

• Tumors
• Infections such as meningitis and polio
• Inflammatory diseases
• Autoimmune diseases
• Degenerative diseases such as amyotrophic lateral sclerosis and spinal muscular atrophy

Symptoms vary but might include pain, numbness, loss of sensation and muscle weakness. These symptoms can occur around the spinal cord, and also in other areas such as your arms and legs. Treatments often include medicines and surgery.