KURSK STATE MEDICAL UNIVERSITY

DEPARTMENT OF NEUROLOGY

NEUROMUSCULAR DISEASES

Name: Aayupta Mohanty

Faculty : Medical

Group : No. 5

Course : 4th year, 1st semester

~ KURSK 2012 ~

Neuromuscular Disorders

Neuromuscular disorders affect the nerves that control your voluntary muscles. Voluntary muscles are the ones you can control, like in your arms and legs. Your nerve cells, also called neurons, send the messages that control these muscles. When the neurons become unhealthy or die, communication between your nervous system and muscles breaks down. As a result, your muscles weaken and waste away. The weakness can lead to twitching, cramps, aches and pains, and joint and movement problems. Sometimes it also affects heart function and your ability to breathe.

Examples of neuromuscular disorders include

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

Many neuromuscular diseases are genetic, which means they run in families or there is a mutation in your genes. Sometimes, an immune system disorder can cause them. Most of them have no cure. The goal of treatment is to improve symptoms, increase mobility and lengthen life.

Amyotrophic lateral sclerosis

Definition

Amyotrophic lateral sclerosis or ALS or often called Lou Gehrig's disease, after the famous baseball player who was diagnosed with it in 1939 is a serious neurological disease that causes muscle weakness, disability and eventually death.

It results from loss of motor neurons. This is most striking in the anterior horn cells of spinal cord with loss of lower motor neurons, marked initially by muscle fasciculations. ALS may also involve upper motor neurons including cranial motor nuclei and Betz cells of neocortex, evidenced by spasticity of muscles. The loss motor innervation eventually leads to muscle atrophy. Astrocytosis is seen in response to the loss of motor neurons. With loss of upper motor neurons there is lateral column degeneration with gliosis, the so-called "sclerosis" of the lateral columns of spinal cord

.

Worldwide, ALS occurs in 1 to 3 people per 100,000. In the vast majority of cases — 90 to 95 percent — doctors don't yet know why ALS occurs. About 5 to 10 percent of ALS cases are inherited.

ALS often begins with muscle twitching and weakness in an arm or leg, or with slurring of speech. Eventually, ALS affects your ability to control the muscles needed to move, speak, eat and breathe.The patients present in middle age with weakness of the extremities and may go on to develop bulbar signs and symptoms. Sphincter control, sensation, intellectual function are not affected by ALS. The course is usually 2 to 6 years after diagnosis, but patients presenting with bulbar signs and symptoms have a shorter life span because of swallowing difficulties and aspiration. The etiology is unknown.

Stephen Hawking(famous mathematician)

Symptoms

Early signs and symptoms of ALS include:

Difficulty lifting the front part of your foot and toes (footdrop)

Weakness in your leg, feet or ankles

Hand weakness or clumsiness

Slurring of speech or trouble swallowing

Muscle cramps and twitching in your arms, shoulders and tongueThe disease frequently begins in your hands, feet or limbs, and then spreads to other parts of your body. As the disease advances, muscles become progressively weaker until they're paralyzed. It eventually affects chewing, swallowing, speaking and breathing.

Causes

In ALS, the nerve cells that control the movement of your muscles gradually die, so your muscles progressively weaken and begin to waste away. Up to 1 in 10 cases of ALS is inherited. But the remainder appear to occur randomly

Gene mutation. Various genetic mutations can lead to inherited forms of ALS, which appear

nearly identical to the non-inherited forms.

Chemical imbalance. People who have ALS typically have higher than normal levels of

glutamate, a chemical messenger in the brain, around the nerve cells in their spinal fluid. Too

much glutamate is known to be toxic to some nerve cells.

Disorganized immune response. Sometimes a person's immune system begins attacking

some of his or her body's own normal cells, and scientists have speculated that this may trigger

the process that results in ALS.

Protein mishandling. There's evidence that mishandled proteins within the nerve cells can lead

to a gradual accumulation of abnormal forms of these proteins in the cells, eventually causing

the nerve cells to die.

Risk factors

Established risk factors for ALS include:

Heredity. Up to 10 percent of the people who have ALS inherited it from their parents. If you

have this type of ALS, your children have a 50-50 chance of developing the disease.

Age. ALS most commonly occurs in people between the ages of 40 and 60.

Sex. Before the age of 65, slightly more men than women develop ALS. This sex difference

disappears after age 70.

It may be that ALS, similar to other diseases, is triggered by certain environmental factors in people who already carry a genetic predisposition to the disease. For example, some studies examining the entire human genome (genome-wide association studies) found numerous genetic variations that people with ALS held in common, and that might make a person more susceptible to ALS.

Environmental factors under study that may modify a person's individual risk of ALS include:

Smoking. Smoking cigarettes appears to increase a person's risk of ALS to almost twice the

risk of nonsmokers. The more years spent smoking, the greater the risk. On the other hand,

quitting smoking can eventually lower this increased risk to that of a nonsmoker.

Lead exposure. Some evidence suggests that exposure to lead in the workplace may be

associated with the development of ALS.

Military service. Recent studies indicate that people who have served in the military are at

higher risk of ALS. Exactly what about military service may trigger the development of ALS is

uncertain, but it may include exposure to certain metals or chemicals, traumatic injuries, viral

infections and intense exertion.

Complications

As the disease progresses, people with ALS experience one or more of the following complications:

Breathing problemsALS eventually paralyzes the muscles needed to breathe. Some devices to assist your breathing are worn only at night and are similar to devices used by people who have sleep apnea (for example, continuous positive airway pressure, or CPAP, masks). In the latter stages of ALS, some people choose to have a tracheostomy — a surgically-created hole at the front of the neck leading to the windpipe (trachea) — to enable the full-time use of a respirator that inflates and deflates their lungs.

The most common cause of death for people with ALS is respiratory failure, usually within three to five years after symptoms begin.

Eating problemsWhen the muscles that control swallowing are affected, people with ALS can develop malnutrition and dehydration. They are also at higher risk of aspirating food, liquids or secretions into the lungs, which can cause pneumonia. A feeding tube can reduce these risks.

DementiaSome people with ALS experience problems with memory and making decisions, and some are

eventually diagnosed with a form of dementia called frontotemporal dementia

neurologist checks patient’s neurological health by testing: Reflexes

Muscle strength

Muscle tone

Senses of touch and sight

Coordination

BalanceTests and diagnosisAmyotrophic lateral sclerosis is difficult to diagnose early because it may appear similar to several other neurological diseases. Tests to rule out other conditions may include:

Electromyogram. This test measures the tiny electrical discharges produced in muscles. A fine

wire electrode is inserted into the muscles that your doctor wants to study. An instrument

records the electrical activity in your muscle as you rest and contract the muscle. Generally, this

test is mildly uncomfortable.

Nerve conduction study. For this test, electrodes are attached to your skin above the nerve or

muscle to be studied. A small shock, which may feel like a twinge or spasm, is passed through

the nerve to measure the strength and speed of nerve signals.

MRI. Using radio waves and a powerful magnetic field, MRI can produce detailed images of

your brain and spinal cord. It involves lying on a movable bed that slides into a tube-shaped

machine that makes loud thumping and banging noises during operation. Some people feel

uncomfortable in the confined space.

Blood and urine tests. Analyzing samples of your blood and urine in the laboratory may help

your doctor eliminate other possible causes of your signs and symptoms.

Muscle biopsy. If your doctor believes you may have a muscle disease rather than ALS, you may undergo a muscle biopsy. In this procedure, a small portion of muscle is removed while you're under local anesthesia and is sent to a lab for analysis.

Multiple sclerosis

Multiple sclerosis (MS) is a potentially debilitating disease in which your body's immune system eats away at the protective sheath that covers your nerves. This interferes with the communication between your brain and the rest of your body. Ultimately, this may result in deterioration of the nerves themselves, a process that's not reversible.Symptoms vary widely, depending on the amount of damage and which nerves are affected. People with severe cases of multiple sclerosis may lose the ability to walk or speak. Multiple sclerosis can be difficult to diagnose early in the course of the disease because symptoms often come and go — sometimes disappearing for months.

There's no cure for multiple sclerosis. However treatments can help treat attacks, modify the course of the disease and treat symptoms.

Symptoms

Signs and symptoms of multiple sclerosis vary widely, depending on the location of affected nerve fibers. Multiple sclerosis signs and symptoms may include:

Numbness or weakness in one or more limbs, which typically occurs on one side of your body at

a time or the bottom half of your body

Partial or complete loss of vision, usually in one eye at a time, often with pain during eye

movement (optic neuritis)

Double vision or blurring of vision

Tingling or pain in parts of your body

Electric-shock sensations that occur with certain head movements

Tremor, lack of coordination or unsteady gait

Fatigue

DizzinessMost people with multiple sclerosis, particularly in the beginning stages of the disease, experience relapses of symptoms, which are followed by periods of complete or partial remission. Signs and symptoms of multiple sclerosis often are triggered or worsened by an increase in body temperature.Causes

The cause of multiple sclerosis is unknown. It's believed to be an autoimmune disease, in which the body's immune system attacks its own tissues. In multiple sclerosis, this process destroys myelin — the fatty substance that coats and protects nerve fibers in the brain and spinal cord.

Myelin can be compared to the insulation on electrical wires. When myelin is damaged, the messages that travel along that nerve may be slowed or blocked.

Doctors and researchers don't understand why multiple sclerosis develops in some people and not others. A combination of factors, ranging from genetics to childhood infections, may play a role.

Risk factors

These factors may increase your risk of developing multiple sclerosis:

Being between the ages of 20 and 40. Multiple sclerosis can occur at any age, but most

commonly affects people between these ages.

Being female. Women are about twice as likely as men are to develop multiple sclerosis.

Having a family history. If one of your parents or siblings has had multiple sclerosis, you have

a 1 to 3 percent chance of developing the disease — as compared with the risk in the general

population, which is just a tenth of 1 percent. But the experiences of identical twins show that

heredity can't be the only factor involved. If multiple sclerosis was determined solely by

genetics, identical twins would have identical risks. However, an identical twin has only a 30

percent chance of developing multiple sclerosis if his or her twin already has the disease.

Having certain infections. A variety of viruses have been linked to multiple sclerosis. Currently

the greatest interest is in the association of multiple sclerosis with Epstein-Barr virus, the virus

that causes infectious mononucleosis. How Epstein-Barr virus might result in a higher rate of

MS remains to be clarified.

Being white. White people, particularly those whose families originated in northern Europe, are

at highest risk of developing multiple sclerosis. People of Asian, African or Native American

descent have the lowest risk.

Living in countries with temperate climes. Multiple sclerosis is far more common in Europe, southern Canada, northern United States, New Zealand and southeastern Australia. The risk seems to increase with latitude.

A child who moves from a high-risk area to a low-risk area, or vice versa, tends to have the risk level associated with his or her new home area. But if the move occurs after puberty, the young adult usually retains the risk level associated with his or her first home.

Having certain other autoimmune diseases. You're very slightly more likely to develop

multiple sclerosis if you have thyroid disease, type 1 diabetes or inflammatory bowel disease.

Complications

In some cases, people with multiple sclerosis may also develop:

Muscle stiffness or spasms

Paralysis, most typically in the legs

Problems with bladder, bowel or sexual function

Mental changes, such as forgetfulness or difficulties concentrating

Depression

Epilepsy

Tests and diagnosis

There are no specific tests for multiple sclerosis. Ultimately, the diagnosis relies on ruling out other conditions that might produce similar symptoms. Your doctor may base a multiple sclerosis diagnosis on the following:

Blood testsAnalysis of your blood can help rule out some infectious or inflammatory diseases that have symptoms similar to multiple sclerosis.

Spinal tap (lumbar puncture)In this procedure, a doctor or nurse removes a small sample of cerebrospinal fluid from within your spinal canal for laboratory analysis. This sample can show abnormalities associated with multiple sclerosis, such as abnormal levels of white blood cells or proteins. This procedure can also help rule out viral infections and other conditions that can cause neurological symptoms similar to those of multiple sclerosis.

MRIThis test uses a powerful magnetic field and radio waves to produce detailed images of internal organs. MRI can reveal lesions, indicative of the myelin loss on your brain and spinal cord. However, these types of lesions can also be caused by other conditions, such as lupus or Lyme disease, so the presence of these lesions isn't definitive proof that you have multiple sclerosis.

During an MRI test, you lie on a movable table that slides into a large, tube-shaped machine, which makes loud tapping or banging noises during the scans. Most MRIs take at least an hour. While the test is painless, some people feel claustrophobic inside the machine. Your doctor can arrange for a sedative if necessary.

You may also receive an intravenous dye that may help highlight "active" lesions. This helps doctors know whether your disease is in an active phase, even if no symptoms are present. Newer MRI techniques can provide even greater detail about the degree of nerve fiber injury or permanent myelin loss and recovery.

Newer MRI techniques may help with diagnosing multiple sclerosis. They include:

Magnetic resonance spectroscopy (MRS). This provides information about the brain's

biochemistry.

Magnetization transfer imaging (MTI). MTI can detect abnormalities before lesions are visible

on standard MRI scans.

Diffusion tensor imaging (DTI). This technology provides 3-D images of demyelinated areas

of the brain, which are useful in determining disease progression.

Functional MRI (fMRI). This is used during cognitive performance tests.

Evoked potential testThis test measures the electrical signals sent by your brain in response to stimuli. An evoked potential test may use visual stimuli or electrical stimuli, in which short electrical impulses are applied to your legs or arms.

Muscular dystrophyMuscular dystrophy is a group of genetic diseases in which muscle fibers are unusually susceptible to damage. These damaged muscles become progressively weaker. Most people who have muscular dystrophy will eventually need to use a wheelchair.There are many different kinds of muscular dystrophy. Symptoms of the most common variety begin in childhood, primarily in boys. Other types of muscular dystrophy don't surface until adulthood.People who have muscular dystrophy may have trouble breathing or swallowing. Their limbs may also draw inward and become fixed in that position — a problem called contracture. Some varieties of the disease can also affect the heart and other organs.While there is no cure for muscular dystrophy, medications and therapy can slow the course of the disease.

SymptomsProgressive muscle weakness is the main feature of muscular dystrophy. Each separate form of muscular dystrophy varies a bit in terms of the age at which the signs and symptoms usually begin and the sequence in which different muscle groups are affected.Duchenne muscular dystrophyAbout half of all muscular dystrophy cases are the Duchenne variety, which most commonly occurs in boys. Signs and symptoms typically first surface when the child begins to walk and may include:

Frequent falls

Difficulty getting up from a lying or sitting position

Trouble running and jumping

Waddling gait

Large calf muscles

Learning disabilitiesBecker muscular dystrophyThis variety has signs and symptoms similar to Duchenne muscular dystrophy, but they typically are milder and progress more slowly. Symptom onset is generally in the teens but may not occur until the mid-20s or even later.Other types of muscular dystrophy Certain other types of muscular dystrophy are defined by a specific feature or the location of the body where symptoms first begin. Examples include:

Myotonic. Also known as Steinert's disease, this form of muscular dystrophy also features an

inability to relax muscles at will. It most often begins in early adulthood. Muscles of the face are

usually the first to be affected.

Limb-girdle. The hip and shoulder muscles are usually the first affected in this type of muscular

dystrophy. In some cases, it becomes difficult to lift the front part of the foot, so frequent tripping

may occur. Signs and symptoms may begin from early childhood to adulthood.

Congenital. This category of muscular dystrophy is apparent at birth or becomes evident before

age 2. Some forms progress slowly and cause only mild disability, while others progress rapidly

and cause severe impairment.

Fascioscapulohumeral (FSHD). One of the most striking signs of this variety of muscular

dystrophy is that the shoulder blades might stick out like wings when the person raises his or

her arms. Onset usually occurs in teens or young adults.

Oculopharyngeal. The first sign of this type of muscular dystrophy is usually drooping of the

eyelids. Weakness of the muscles of the eye, face and throat often results in swallowing

difficulties. Signs and symptoms first appear in adulthood, usually in a person's 40s or 50s.When to see a doctorSeek medical advice if you notice signs of muscle weakness — such as increased clumsiness and falling — in yourself or your child.CausesHundreds of genes are involved in making proteins that protect muscle fibers from damage. Muscular dystrophy occurs when one of these genes is defective. Each form of muscular dystrophy is caused by a genetic mutation that's particular to that type of the disease. Many of

these mutations are inherited, but some occur spontaneously in the mother's egg or the developing embryo.Risk factorsMuscular dystrophy occurs in both sexes and in all ages and races, but the most common variety usually occurs in young boys. People who have a family history of muscular dystrophy are at higher risk of developing the disease or passing it on to their children.ComplicationsSome types of muscular dystrophy shorten the person's lifespan, often by affecting the muscles associated with breathing. Even with improved mechanical breathing assistance, people who have Duchenne muscular dystrophy — the most common type of muscular dystrophy — usually die of respiratory failure before they reach age 40.Many types of muscular dystrophy can also reduce the efficiency of the heart muscle. If the muscles involved with swallowing are affected, nutritional problems may develop.As muscle weakness progresses, mobility becomes a problem. Many people who have muscular dystrophy will eventually need to use a wheelchair. However, the prolonged immobility of joints associated with wheelchair use can worsen contractures, in which the limbs draw inward and become fixed in that position.Contractures may also play a part in the development of scoliosis, a sideways curvature of the spine that further reduces lung efficiency in people who have muscular dystrophy.

Tests and diagnosis

In addition to a medical history review and physical examination, your doctor may suggest some of the following tests:

Enzyme tests. Damaged muscles release enzymes, such as creatine kinase (CK), into your

blood. In the absence of traumatic injuries, high blood levels of CK suggest a muscle disease —

such as muscular dystrophy.

Electromyography. This test involves inserting an electrode needle through your skin and into

the muscle to be tested. Electrical activity is measured as you relax and as you gently tighten

the muscle. Changes in the pattern of electrical activity can confirm a muscle disease.

Muscle biopsy. A small piece of muscle can be removed through a small incision or with a

hollow needle. The analysis of the sample can distinguish muscular dystrophies from other

muscle diseases.

Genetic testing. Blood samples can be examined for mutations in some of the genes that

cause different types of muscular dystrophy.

Myasthenia gravisMyasthenia gravis is characterized by weakness and rapid fatigue of any of the muscles under your voluntary control. The cause of myasthenia gravis is a breakdown in the normal communication between nerves and muscles.

There is no cure for myasthenia gravis, but treatment can help relieve signs and symptoms — such as weakness of arm or leg muscles, double vision, drooping eyelids, and difficulties with speech, chewing, swallowing and breathing.While myasthenia gravis can affect people of any age, it's more common in women younger than 40 and in men older than 60

. SymptomsMuscle weakness caused by myasthenia gravis worsens as the affected muscle is used repeatedly. Since symptoms typically improve with rest, your muscle weakness may come and go. However, the symptoms of myasthenia gravis tend to progress over time, usually reaching their worst within a few years after the onset of the disease.Although myasthenia gravis can affect any of the muscles that you control voluntarily, certain muscle groups are more commonly affected than others.Eye musclesIn more than half the people who develop myasthenia gravis, their first signs and symptoms involve eye problems, such as:

Drooping of one or both eyelids (ptosis)

Double vision (diplopia), which may be horizontal or verticalFace and throat musclesIn about 15 percent of people with myasthenia gravis, the first symptoms involve face and throat muscles, which can cause difficulties with:

Altered speaking. Your speech may be very soft or may sound nasal, depending upon which

muscles have been affected.

Difficulty swallowing. You may choke very easily, which makes it difficult to eat, drink or take

pills. In some cases, liquids you're trying to swallow may come out your nose.

Problems chewing. The muscles used for chewing may wear out halfway through a meal,

particularly if you've been eating something hard to chew, such as steak.

Limited facial expressions. Family members may note that you've "lost your smile" if the

muscles that control your facial expressions are affected.Neck and limb musclesMyasthenia gravis can cause weakness in your neck, arms and legs, but this usually happens in

conjunction with muscle weakness in other parts of your body — such as your eyes, face or throat. The disorder usually affects arms more often than legs. However, if it affects your legs, you may waddle when you walk. If your neck is weak, it may be hard to hold your head erect.When to see a doctorTalk to your doctor if you have trouble:

Breathing

Seeing

Swallowing

Chewing

Walking

Using your arms or hands

Holding up your headCauses

Illustration showing receptors for neurotransmitters

Thymus gland

Your nerves communicate with your muscles by releasing chemicals, called neurotransmitters, which fit precisely into receptor sites on the muscle cells. In myasthenia gravis, your immune system produces antibodies that block or destroy many of your muscles' receptor sites for a neurotransmitter called acetylcholine. With fewer receptor sites available, your muscles receive fewer nerve signals, resulting in weakness.It's believed that the thymus gland — a part of your immune system situated in the upper chest beneath the breastbone — may trigger or maintain the production of these antibodies. Large in infancy, the thymus is small in healthy adults. But, in some adults with myasthenia gravis, the thymus is abnormally large. Some people also have tumors of the thymus. Usually, thymus gland tumors are noncancerous.Factors that can worsen myasthenia gravis

Fatigue

Illness

Stress

Extreme heat

Some medications — such as beta blockers, calcium channel blockers, quinine and some

antibioticsComplicationsComplications of myasthenia gravis are treatable, but some can be life-threatening.Myasthenic crisisMyasthenic crisis is a life-threatening condition, which occurs when the muscles that control breathing become too weak to do their jobs. Emergency treatment is needed to provide mechanical assistance with breathing. Medications and blood-filtering therapies help people recover from myasthenic crisis, so they can again breathe on their own.

Thymus tumorsAbout 15 percent of the people who have myasthenia gravis have a tumor in their thymus, a gland under the breastbone that is involved with the immune system. Most of these tumors are noncancerous.Other disordersPeople who have myasthenia gravis are also more likely to have the following problems:

Underactive or overactive thyroid. The thyroid gland, which is in the neck, secretes hormones

that regulate your metabolism. If your thyroid is underactive, your body uses energy more

slowly. An overactive thyroid makes your body use energy too quickly.

Pernicious anemia. This is a condition in which vitamin B-12 is not properly absorbed from the diet, leading to anemia or neurological problems

doctor will want a detailed description of your symptoms and your medical history. In addition to a physical exam, your doctor may also check your neurological health by testing your:

Reflexes

Muscle strength

Muscle tone

Senses of touch and sight

Coordination

Balance

Tests and diagnosis

The key sign that points to the possibility of myasthenia gravis is muscle weakness that improves with rest. Tests to help confirm the diagnosis may include:

Edrophonium testInjection of the chemical edrophonium (Tensilon) may result in a sudden, although temporary, improvement in your muscle strength — an indication that you may have myasthenia gravis. Edrophonium acts to block an enzyme that breaks down acetylcholine, the chemical that transmits signals from your nerve endings to your muscle receptor sites.

Blood analysisA blood test may reveal the presence of abnormal antibodies that disrupt the receptor sites where nerve impulses signal your muscles to move.

Repetitive nerve stimulationThis is a type of nerve conduction study, in which electrodes are attached to your skin over the muscles to be tested. Small pulses of electricity are sent through the electrodes to measure the

nerve's ability to send a signal to your muscle. To diagnose myasthenia gravis, the nerve will be tested many times to see if its ability to send signals worsens with fatigue.

Single-fiber electromyography (EMG)Electromyography (EMG) measures the electrical activity traveling between your brain and your muscle. It involves inserting a fine wire electrode through your skin and into a muscle. In single-fiber EMGs, a single muscle fiber is tested. Most people find this test to be somewhat uncomfortable.

Imaging scansYour doctor may order a CT scan or an MRI to see if there's a tumor or other abnormality in your thymus.

Spinal muscular atrophy (SMA)

Types I, II, and III belong to a group of hereditary diseases that cause weakness and wasting of the voluntary muscles in the arms and legs of infants and children.

The disorders are caused by an abnormal or missing gene known as the survival motor neuron gene (SMN1), which is responsible for the production of a protein essential to motor neurons. Without this protein, lower motor neurons in the spinal cord degenerate and die.

The type of SMA (I, II, or III) is determined by the age of onset and the severity of symptoms. Type I has the earliest onset, usually at birth, and the most severe symptoms. Type II usually happens in early childhood and is less severe but still disabling. Type III can happen as late as adolescence and may be only moderately disabling.

There are other types of SMA disorders with similar symptoms, but different causes. Infantile SMA disorders, such as X-linked infantile SMA, SMA with cerebellar hypoplasia, diaphragmatic SMA, and SMA with congenital bone fractures are linked to genes other than SMN1. Kennedy syndrome (X-linked spinal and bulbar muscular atrophy, SMAX1), a disease of adult males, has symptoms similar to the childhood SMAs, but is caused by a different gene

and genetic mutation.

symptoms of SMA in children

SMA Type I, also known as Werdnig-Hoffman disease, or infantile-onset SMA, is evident at birth or within the first few months. Symptoms include floppy limbs and trunk, feeble movements of the arms and legs, swallowing difficulties, a weak sucking reflex, and impaired breathing. A baby with SMA Type I will not be able to sit without support. The majority of babies with SMA Type I die of respiratory failure within the first two years.

SMA Type II, also known as juvenile SMA, intermediate SMA, or chronic SMA, has an onset between 6 and 18 months. Legs tend to be more impaired than arms. The first indication that a baby may have the disease is when he or she fails to crawl or walk. Children with Type II are usually able to sit without support if placed in position. Some may be able to stand or walk with help. Although children with SMA Type II may not need artificial assistance to breathe, they are still at an increased risk for respiratory infections. These children often survive into adulthood, but with significant motor disability.

SMA Type III, also called Wolhlfart-Kugelberg-Welander disease, or mild SMA, can begin as early as the toddler years or as late as adolescence. Children can stand alone and walk, but may have difficulty getting up from a sitting position. Their fingers may tremble. Children with SMA Type III usually remain mobile well into adulthood. Like children with Type II, they are at an increased risk for respiratory infections.

COMPLICATIONS

Breathing issues: Babies with SMA (especially those with Type I) may need help breathing, especially at night, using non-invasive methods that include negative pressure ventilators and bi-level positive airway pressure support, which direct air through the nostrils via a small, gently-fitted mask. Children who survive their first two years are at risk for complications involving the lungs, which may not be fully developed. A regular program of respiratory therapy and breathing exercises is helpful. Parents should be instructed in

chest physiotherapy (CPT), a series of physical maneuvers that clear the lungs and airway.

Failure to thrive: Infants with SMA I may have difficulties getting adequate nutrition because they have a weak sucking reflex and tendency to tire easily. Their unprotected air passage makes it difficult for older babies to chew and swallow; they may inhale and choke on their food. Some babies may require feeding with naso-gastric or gastric tubes.

Weak arms and legs: Children with SMA Types I and II are not likely to stand or walk on their own. They can be taught to operate a power wheelchair at two to three years of age. Less handicapped children may benefit from a standing frame, vertical stander, or standing wheelchair. Physical therapy and exercise may also help improve mobility and joint movement, brighten mood, and improve sleep patterns. Stretching exercises can preserve and increase flexibility.

Orthopedic complications. Scoliosis (curvature of the spine) occurs at some point in the majority of children with SMA Types I and II, and some with Type III. Custom seating systems, seating aids, and a body jacket can be used to prevent severe scoliosis. Spinal fusion surgery may be necessary for some children.