Spinal Muscular Atrophy

Description

Other Names

Werdnig-Hoffman disease, Kugelberg-Welander disease, SMA, anterior horn cell disease

Diagnosis Coding

ICD-10

G12.0, spinal muscular atrophy, type I; Werdnig-Hoffman

G12.1, other inherited spinal muscular atrophy

G12.9, spinal muscular atrophy, unspecified

ICD-10 for Spinal Muscular Atrophy and Related Syndromes provides further coding details.

Description

Face of a child with spinal muscular atrophy (SMA) in wheelchair and smiling - diagnosis and management info
Image courtesy of Cure SMA
Spinal muscular atrophy (SMA) is an autosomal recessive disorder that causes decreased survival of the anterior horn cells in the spinal cord (lower motor neurons), which innervate voluntary muscles. This results in progressive muscle atrophy and weakness. As more is learned about SMA, it is becoming clear that motor neurons are not the only part of the body affected, and SMA may actually be a multi-system disorder. [Shanmugarajan: 2007] [Hamilton: 2013] SMA is traditionally classified by age of onset and severity. Classification by maximal motor function (non-sitters, sitters, and walkers) may correlate with clinical care needs better than the traditional classifications. [Wang: 2007] Children with type I SMA never achieve independent sitting. Children with type II sit but do not walk, and those with type III ambulate independently, if only for a brief time.

Prevalence

SMA is one of the most common recessively inherited disorders (second only to cystic fibrosis) and occurs in about 1:6,000 births. [Jones: 2015] Approximately 1:40 people are genetic carriers for type I SMA. [Cusin: 2003] SMA type I is the leading inherited cause of infant mortality.

Genetics

Missing or defective motor neuron survival protein (SMN protein) results in SMA. This protein is coded for by the SMN1 gene, which is located on the long arm of chromosome 5. Most cases of SMA contain deletions in various combinations of exons 7 and/or 8. SMN2  is a pseudogene, similar to SMN1, but not functional. SMN2 is also located on chromosome 5q and may be present in multiple copies. Copy number of the SMN 2 gene appears to control severity of SMA by a complex mechanism allowing some production of the survival motor neuron protein from the defective SMN2 gene. The SMN protein complex appears to be involved in the biogenesis of specific ribonucleoproteins that control regulation of gene transcription. [Kolb: 2007] [Sumner: 2007] For further details, please see Genetics of Spinal Muscular Atrophy.

Prognosis

Prognosis is variable and depends on SMA subtype. Most children with type I SMA who do not receive ventilatory support die in early infancy. [Cobben: 2008] [Bach: 2007] Families of children with type I SMA are increasingly choosing ventilation (either invasive or non-invasive) as palliative treatment. Ventilation results in prolonged survival, but most children with type I SMA succumb to respiratory failure in the setting of infection before the end of their second year. [Finkel: 2014] Individuals with type II and type III SMA can have a normal life span, but experience significant disability and respiratory or other complications. Anticipatory care that includes careful attention to respiratory, nutritional, and orthopedic issues can significantly prolong survival. Although Cochrane studies have concluded that there are no statistically proven treatments for types I, II, or III SMA [Wadman: 2012] [Wadman: 2012], treatments targeting genetic mechanisms are prompting new hope that approved treatments will be forthcoming. [Wertz: 2016] [Faravelli: 2015]

Roles Of The Medical Home

Optimally, care of children with SMA should take place in a multi-disciplinary clinic (see all Muscular Dystrophy Clinics services providers (3) in our database). If one is not available, it is essential that the medical home helps families organize specialty care, remains watchful for changes in function, understands current treatment for acute illnesses, and advocates throughout the life of the child. Children with SMA will need surveillance of respiratory adequacy (awake and asleep), GI/nutritional balance, musculoskeletal status, dental hygiene, and individual and family functioning.
Children with SMA Types I, II, and III
Left image: Five-month old girl with SMA type I

Middle image: Boy with SMA type II with turtle shell and ankle-foot orthoses

Right image: Boy with SMA type III being checked for hip weakness

Photo permissions on file

Practice Guidelines

The standard of care guideline (below) represents expert consensus, but lacks well-designed clinical trials to validate recommendations. It is expected that the standards of care will be updated in the near future to reflect new data from the increasing amount of ongoing studies.

Wang CH, Finkel RS, Bertini ES, Schroth M, Simonds A, Wong B, Aloysius A, Morrison L, Main M, Crawford TO, Trela A.
Consensus statement for standard of care in spinal muscular atrophy.
J Child Neurol. 2007;22(8):1027-49. PubMed abstract / Full Text

Helpful Articles

PubMed search for spinal muscular atrophy in children, last 2 years.

Kolb SJ, Kissel JT.
Spinal Muscular Atrophy.
Neurol Clin. 2015;33(4):831-46. PubMed abstract / Full Text

Tisdale S, Pellizzoni L.
Disease mechanisms and therapeutic approaches in spinal muscular atrophy.
J Neurosci. 2015;35(23):8691-700. PubMed abstract / Full Text

Darras BT.
Spinal muscular atrophies.
Pediatr Clin North Am. 2015;62(3):743-66. PubMed abstract

Viollet L, Melki J.
Spinal muscular atrophies.
Handb Clin Neurol. 2013;113:1395-411. PubMed abstract

García-Salido A, de Paso-Mora MG, Monleón-Luque M, Martino-Alba R.
Palliative care in children with spinal muscular atrophy type I: What do they need?.
Palliat Support Care. 2015;13(2):313-7. PubMed abstract

Lin CW, Kalb SJ, Yeh WS.
Delay in Diagnosis of Spinal Muscular Atrophy: A Systematic Literature Review.
Pediatr Neurol. 2015;53(4):293-300. PubMed abstract

Clinical Assessment

Overview

Clinicians should suspect SMA in infants and children with proximal muscle weakness (shoulder and hip girdles) and absent or very reduced deep tendon reflexes. In young infants, respiratory difficulties (e.g., bell-shaped chest or weak cough or cry) and feeding problems may be present from very early in the course.

Screening

Of Family Members

Siblings of a person with SMA have a 1:4 chance of being born with the condition and a 2:4 chance of being a carrier. Carrier testing is available for adults and siblings over age 18. [Carré: 2016] Although testing at-risk younger siblings who are asymptomatic for SMA is controversial, many experts feel that early identification of children with SMA may improve clinical outcome, so such testing is recommended if desired by the family. [Wang: 2007] The American College of Medical Genetics endorses offering SMN1 gene testing for all couples considering pregnancy or early in pregnancy. [Prior: 2008]

Presentations

Presentations and clinical characteristics vary by SMA subtypes.
  • Type I SMA (Werdnig-Hoffman) presents near birth. Children never learn to sit or walk and have severe respiratory and swallowing problems, including difficulty handling oral secretions, and a significantly shortened life span. Other features include poor head control, a bell-shaped chest, weak cry and cough, tongue atrophy and fasciculation, and paradoxical breathing.
  • Type II SMA presents later in the first year of life or up to about 2 years of age. Children usually learn to sit, but do not walk. Fine tremor-like movements in the hands and fingers may be noted from early in the course. As weakness progresses, children often have respiratory and swallowing problems, including difficulty gaining weight due to bulbar muscle weakness, weak cough, and night-time hypoventilation. Swallowing problems and difficulties opening the jaw widely have been shown to contribute to malnutrition. [Messina: 2008] Joint contractures and scoliosis develop over time in nearly all affected children and warrant proactive intervention.
  • Type III SMA (Kugelberg-Welander) is much more variable in onset than types I and II, but usually presents in childhood or early adolescence. Children can sit and walk (although some may lose this ability over time). As with type II SMA, children with type III SMA may have fine tremor-like movements in the hands and fingers. Quadriceps atrophy may be pronounced. Children with type III SMA may have fewer problems with respiratory function and swallowing than children with type I or II SMA. Scoliosis, contractures, and joint pain are often noted in older children.
  • Type 0 SMA presents before birth with decreased fetal movement noted around 30 weeks of age. Newborns are severely hypotonic at birth with congenital contractures, swallowing problems, and respiratory failure.
  • Type IV SMA presents in adults and will not be discussed further here.

Diagnostic Criteria

Diagnosis is made by genetic testing for the common deletion of exon 7 of the SMN1 gene in children with appropriate clinical features. This testing is inexpensive and readily available; laboratories offering testing can be found at Testing for SMA (GeneTests) or Testing for SMA (Genetic Testing Registry).

Identification of the copy number of the SMN2 gene assists in prognosis and is becoming a standard feature of genetic testing for SMA. While most patients will have the common deletion of exon 7, about 5% of children who present with SMA have negative genetic testing due to presence of a deletion on 1 allele and a point mutation on the other. Clinical suspicion and electromyography (EMG) play important roles in diagnosis in these cases.

Differential Diagnosis

SMA is usually readily identified by clinical features and confirmed by genetic testing. Differential diagnoses for a child with newly presenting progressive muscle weakness are described below.

Infant botulism
occurs in children up to 12 months of age. Symptoms start with constipation in a previously normal baby and are followed by decreased facial expression, poor swallowing, a weak cry, and decreased movement. Over time, the course is more acute than SMA. Diagnosis is made by recognition of clinical features and demonstration of botulinum toxin in the infant's stool. EMG can help to exclude other diagnoses.

Neuropathies
are a wide spectrum of syndromes with various time courses. Sensory nerves are usually involved. Family history is often positive (e.g., Charcot-Marie-Tooth disease or hereditary motor sensory neuropathy). Acquired polyneuropathies, such as Guillain-Barre syndrome, have a rapid onset over a few days to a week. These are exceedingly rare in children under 2 years old. Diagnosis is confirmed by EMG and/or tests showing elevated cerebrospinal fluid (CSF) protein.

Metabolic myopathy (e.g., mitochondrial myopathy, Pompe disease) is much less common than SMA, but early features can be a clinically similar. Infants with Pompe disease have severe progressive cardiac dysfunction not seen in SMA.

Duchenne muscular dystrophy
occurs in boys only. In this condition, calves are large, creatine kinase (CK) is extremely high, and developmental delay is often present. It is diagnosed by genetic testing for mutations in the DMD gene.

X-linked SMA and SMA with respiratory distress (SMARD)
may appear clinically similar to SMA, but they have different genetic etiologies. SMARD1 presents as distal (not proximal) muscle weakness, with foot deformities as well as respiratory failure that often occurs suddenly. This condition is due to mutations in the IGHMBP2 gene on chromosome 11q13.3, which encodes the immunoglobulin micro-binding protein 2. [Kaindl: 2008] Infants with X-linked SMA may have a family history showing X-linked inheritance and will have negative SMN1 testing. An increasing number of new genes are being associated with these phenotypes and suspicion should prompt referral to a sub-specialty clinic for assessment.

Congenital myopathy presents with non-progressive weakness and is diagnosed by muscle biopsy.

Pearls & Alerts

Address possibility of respiratory failure

Infants with type I SMA are susceptible to respiratory failure due to infection or aspiration. Addressing this possibility early with the family and implementing proactive measures (e.g., non-invasive ventilation, cough assist, and G-tube placement) can prevent emergency situations. Frequent pneumonias or respiratory illnesses may signal impending respiratory failure or aspiration.

History & Examination

Early recognition of weakness is critical to the initial evaluation. Assessment of weakness can be difficult in young children, but close attention to functional ability allows a good assessment of strength. Video of children with and without weakness are available at the Child Muscle Weakness Organization and can be helpful in identifying subtle weakness.

Family History

SMA is an autosomal recessive disorder usually occurring with no family history; yet, providers should ask about infant and childhood deaths and consanguinity.

Pregnancy Or Perinatal History

Although there is no specific pregnancy history, sometimes mothers of children with type I SMA will report decreased fetal movement in late pregnancy. Children with type 0 and type I SMA may also have arthrogryposis at birth, difficulties with early feeding, and bell-shaped chests.

Current & Past Medical History

Nutrition/GI: Has weight gain been adequate? Ask about GI issues such as reflux, stomach pain, and constipation. Children with any neuromuscular disorder, including SMA, are osteopenic. Is calcium and vitamin D intake adequate? Any fractures? [Khatri: 2008]

Respiratory: Ask about breathing problems while awake, including while eating, for infants. Ask about history of pneumonia, strength of cough, reactive airway disease, recent pulmonary testing (oximetry), use of respiratory support (noninvasive respiratory support such as CPAP and BiPAP and nighttime or continuous ventilation), and use of a cough assist machine. Ask also about sleep, results of previous sleep studies, snoring as evidence of obstructive sleep apnea and hypoventilation, frequency of night awaking, daytime sleepiness, and morning headaches. Check immunization history, including pneumococcal and flu vaccines. 

Swallowing problems: Ask about coughing or choking while eating and drinking (especially thin fluids) and strength of cough. Ask if the family has a suction machine at home.

Musculoskeletal: Ask about recent change in muscle strength, fatigability, and functional abilities. Ask about fit and maintenance of the wheelchair, stander, or other equipment. Ask if the family has a license plate or placard for individuals with disabilities.

Orthopedic: Ask about orthotics use, joint pain, range of motion, and history of fractures.

HEENT: Ask about chronic ear infections.

Dental: Ask about dental history and the ability to open and close jaw.

Developmental & Educational Progress

Early motor milestones, such as development of head control, will often be delayed. Babies may lie in the classic frog position when supine. Speech and language skills will not be delayed. Developmental testing will show profound delays in gross motor abilities, but cognitive abilities are spared. Measures of daily functioning, such as the Pediatric Evaluation of Disability Inventory (PEDI) (available for a fee), can help evaluate the child's functional abilities over time and are often available from the child's therapists. Ideally, these assessments should be part of the medical home record. Families should sign releases of information to obtain these records or bring copies of them to their appointments. A quick look at changes in the functional abilities of the child will help guide assessment of progression.

Social & Family Functioning

Ask about family and community supports, access to resources, and any social issues for the child and family. Are necessary accommodations being made at school? Do the parents have anyone to stay with their child while they take a break? If the child with SMA is having difficulty with breathing, whether unaided or using BiPAP, how is that impacting the family, and what are their feelings concerning the next step? Is there a plan for an acute respiratory illness?

Physical Exam

General

Babies with SMA are often alert and interactive, and children with SMA are often bright and quite social.

Vital Signs

RR | HR may be elevated in children with weak respiratory muscles.

Growth Parameters

Wt | Ht | BMI: Due to feeding problems, infants with SMA may be underweight or overweight (particularly when using a G-tube to augment feedings). Careful attention to feeding and growth patterns is important. With decreased muscle mass, a relatively low weight for length may be ideal. Growth charts for normal children may be inappropriate.

Skin

Is there evidence of breakdown, cool extremities, mottling of skin, or yeast infection (tongue, body creases)?

HEENT

Check ability to open jaw and the size of tonsils.

Mouth/Teeth

Check for bad breath, dental caries, and drooling that may be caused by swallowing problems.

Chest

The chest wall may appear bell-shaped. Listen to lungs and observe for evidence of breathing difficulties. Check respiratory rate and look for paradoxical abdominal/chest wall movements. Observe cough or cry if possible. Consider spot oximetry, peak flow, and forced vital capacity measures. Measure chest circumference at the nipple line and follow growth. Chest and head circumference should be fairly equal in the first year. If the chest isn’t growing, the child is at a higher risk of respiratory compromise.

Abdomen

Non-tender mobile masses may represent hard, backed-up stool.

Extremities/Musculoskeletal

Check for progression of joint contractures. Perform muscle strength and functional ability exams. Sensation should be completely preserved. Evaluate for clinical scoliosis and hip dislocation.

Neurologic Exam

Check for tone, proximal muscle strength, and reflexes. Central nervous system function should be normal.

Testing

Sensory Testing

Vision and hearing screening should be performed as appropriate for age.

Laboratory Testing

No routine testing is needed. Consider labs to evaluate for nutritional inadequacies, carnitine deficiency, hypercalcemia, and iron deficiency anemia. A urinalysis will detect urinary tract infection, etc. In the setting of illness, check for acidosis or electrolyte disturbances. Creatinine levels are normally low. Elevated CK levels are usually considered in those with muscle disorders such as Duchenne muscular dystrophy; however, CK levels can be elevated in patients with SMA undergoing active denervation.

Imaging

Consider a video swallow study to look for aspiration or for children who take a long time to eat, have poor weight gain, or swallowing problems. Since the study is performed with a speech therapist present, strategies for safer feeding (e.g., thickening fluids) may be explored. A chest X-ray will help diagnose chronic aspiration or acute pneumonia; spine and hip x-rays will help diagnose scoliosis or hip dislocation.

Genetic Testing

Definitive diagnosis is based on molecular genetic testing for SMN1 mutations and SMN2 copy number. Results are usually available within a few weeks. A small percentage of children with SMA will be negative for the common exon 7 deletion, but when more detailed testing is performed, the child will have SMA with a mutation not included in the routine genetic testing. See Testing for SMA (GeneTests), Testing for SMA (Genetic Testing Registry), and the Medical Home Portal page about Genetics of Spinal Muscular Atrophy.

Other Testing

Other possible testing:
  • Electromyography (EMG) can indicate probable SMA, in which case, genetic testing should follow.
  • Muscle biopsy is performed by some clinicians for various reasons. A biopsy consistent with SMA should still be followed by genetic testing, which gives a definitive diagnosis.
  • Pulmonary function tests and sleep studies are used to evaluate respiratory status as needed.
  • Nutritional assessments are helpful for evaluation of children who are underweight or overweight.
  • DEXA scan are performed if the child has a history of fractures or, as a baseline if the child has been immobile and confined to a wheelchair for an extended period, especially if the child is on valproic acid or proton pump inhibitors.

Subspecialist Collaborations & Other Resources

When available, an SMA-specific clinic for children is preferred for evaluation and management. Depending on the location, additional involvement of sub-specialists, such as those in physical medicine & rehabilitation and pulmonology, can be helpful.

Muscular Dystrophy Clinics (see Services below for relevant providers)

Multidisciplinary care for children with SMA and other neuromuscular disorders is often available through clinics sponsored by the Muscular Dystrophy Association. In partnership with the primary care team, these clinics can coordinate anticipatory care and subspecialty referrals.

Pediatric Genetics (see Services below for relevant providers)

Genetics and genetic counseling may be available in an SMA-specific or neuromuscular clinic. If not, an initial visit for genetic testing and discussion of test results, and periodic visits to address new issues, may be helpful.

Pediatric Pulmonology (see Services below for relevant providers)

Referral is particularly important for children with type 0 and type I SMA because of the risk for respiratory compromise. Night-time ventilation is often affected first; deterioration may be subtle. Early pulmonology consultation is recommended, even for children with SMA that are doing well.

Pediatric Gastroenterology (see Services below for relevant providers)

Referral may be helpful for evaluation and management of eating and nutrition problems. Swallowing difficulty, reflux, constipation, or failure to gain weight appropriately should also prompt consideration of referral.

Pediatric Orthopedics (see Services below for relevant providers)

Most children with SMA of any type will benefit from periodic referrals for evaluation and management of musculoskeletal complications. If the child with SMA has been born with arthrogryposis, early involvement is critical.

Pediatric Physical Medicine & Rehab (see Services below for relevant providers)

Referral can help optimize mobility and the activities of daily living, and it usually includes physical, occupational, and speech therapy.

Pediatric Otolaryngology (see Services below for relevant providers)

Consider a referral if obstructive sleep apnea is a concern.

Treatment & Management

How should common problems be managed differently in children with Spinal Muscular Atrophy ?

Growth Or Weight Gain

Standard growth charts often are not appropriate for children with SMA. Children who are following “normal” growth curves may be functionally obese and at risk for insulin resistance and complications of a metabolic syndrome. Muscle atrophy complicates management of nutritional issues; close monitoring is essential. Children with type I SMA have early dysphagia and early placement of G-tube with Nissen fundoplication is often necessary to prevent aspiration and pneumonia.

Development (cognitive, motor, language, social-emotional)

Cognitive and emotional development is normal in children with SMA. While language is normal from a neurologic perspective, communication, especially with type I SMA, can be difficult due to weakness. Children may need adaptive devices to assist communication.

Viral Infections

Due to weakness of respiratory muscles and poor cough, children with SMA are at risk for significant upper respiratory infections. Families should be encouraged to take appropriate precautions (e.g., handwashing and limiting exposure to sick individuals). Patients should receive annual flu vaccine; RSV prophylaxis is appropriate in infants with type I SMA.

Bacterial Infections

Children with SMA are at risk for bacterial pneumonia as a primary feature or as a complication of viral upper respiratory infection or aspiration. Age-appropriate pneumococcal vaccination is recommended. Early use of non-invasive ventilation and Cough Assist are appropriate preventive measures.

Pearls & Alerts

Expectant management during hospital visits improves outcomes

Expectant management includes increased nutritional management and attention to respiratory status before and after surgery and during acute hospital visits. Temporary supplementation with nasogastric tubes or nasojejunal tubes, or peripheral or total parental nutrition, may be helpful.

Written care plans facilitate emergency care

Emergency room visits for families of children with SMA, as for any child with a complex condition, are challenging because of the need for families to detail their histories and preferences, as well as the reason for their visit. Plans for what to do in case of respiratory failure should be made and revised at non-acute medical home visits. Provide families with documentation so their resuscitation desires can be shared with other clinicians.

Early post-operative ambulation helps maintain strength

Required inactivity following major surgery (e.g., for scoliosis or hip dislocation) may precipitate the loss of ambulation. Early re-institution of ambulation in these settings can help significantly in maintaining strength.

Systems

Neurology

The clinical course of SMA is variable and difficult to predict. Proactive management of complications has led to increased quality of life and prolonged life expectancy. Although no medication definitively treats SMA, several clinical trials are in progress. [Wertz: 2016] [Faravelli: 2015]

Subspecialist Collaborations & Other Resources

Muscular Dystrophy Clinics (see Services below for relevant providers)

Muscular Dystrophy Association (MDA) clinics are available in many locations throughout the United States and Canada. These clinics specialize in managing people with neuromuscular disorders and offer visits at no cost to the patient. Clinical trials may also be available in these clinics.

Pediatric Neurology (see Services below for relevant providers)

In areas without specialty clinics, pediatric neurologists with expertise in neuromuscular disorders should be involved in the management of children with SMA.

Respiratory

Non-sitters, and sometimes sitters, may have severe respiratory problems. Bell-shaped chests and paradoxical breathing reflect weak respiratory musculature (sparing the diaphragm). Difficulties with swallowing and chronic aspiration exacerbate this situation. A weak cough makes clearing of secretions difficult. Scoliosis may add to respiratory problems.

SMA Type I infant with BiPAP device
Pulmonary referral should occur soon after diagnosis for both non-sitters and sitters. General guidelines for respiratory care in type I and many type II SMA patients includes airway clearance techniques, such as Cough Assist, and nocturnal non-invasive ventilation, such as BiPAP. [Schroth: 2009]

Photo, left: Infant with SMA type I using a BiPAP device (photo permission on file)

Consider a sleep study for identification of obstructive sleep apnea and central hypoventilation. These problems may occur early, before the child has obvious daytime problems. Nighttime BiPAP is usually necessary when the vital capacity is less than 40% of the predicted value. BiPAP can also be used in daytime during periods of increased need, such as with a respiratory illness or following surgery. The Medical Home Portal's CPAP and Bilevel PAP topic provides more information about indications for use and follow-up care.

Optimal preventive treatment includes nutritional optimization, especially with surgeries and illnesses. For some children, breath stacking methods and incentive spirometry can be taught, usually by staff at the pulmonology clinic. Breath stacking involves repetitions of taking a breath and holding it. Daily practice can be helpful for children who are losing lung capacity, but adherence is difficult.

If the child has a weak cough, percussion and postural drainage should be initiated; management of secretions is further improved by use of a cough-assist device. [Fauroux: 2008] Respiratory secretions should be managed with the help of an ENT if necessary. Consider medications to reduce secretions, botulinum toxin injections, and salivary gland ligation for children who can't manage secretions. Swallowing problems should be managed optimally, for example with thickened liquids and G-tube feeds; Nissen fundoplication may be helpful when reflux is present.

Ensure that immunizations, especially pneumococcal and yearly flu vaccines, are up to date. RSV prophylaxis should be given to non-sitters and most sitters. Respiratory infections and symptoms of reactive airway disease should be treated early and aggressively. If hospitalization is necessary for acute, severe respiratory illness, consider the use of non-invasive ventilation; children with SMA often have difficulty weaning from a ventilator. Supplemental oxygen without mechanical ventilation should be used with care as it may decrease respiratory drive, leading to hypercarbia and atelectasis.

Subspecialist Collaborations & Other Resources

Pediatric Pulmonology (see Services below for relevant providers)

Pulmonology should manage most children with SMA concurrently with the medical home. Children should be referred at diagnosis and periodically for management.

Pediatric Sleep Medicine (see Services below for relevant providers)

Children with SMA may need breathing assistance during sleep before they demonstrate problems while awake; refer for sleep evaluations and management as needed.

Pediatric Otolaryngology (see Services below for relevant providers)

Consider referral for drooling, swallowing problems, or sleep apnea.

Nutrition/Growth/Bone

If nutrition is oral, malnutrition may occur. Risk factors include being easily fatigued at meal time, needing excessive time to eat, and choking or coughing often while eating. Standard weight charts are not applicable due to the reduced muscle mass that occurs despite caloric supplementation. BMI, weight for height, or skinfold measurements of the triceps area are often available as part of a nutritional assessment and may be helpful in determining nutritional reserve. Maximize Calcium and Vitamin D intake, and consider bisphosphonates with a history of fractures.

Poor weight gain is common and often attributed to the decreased intake of food and the increased energy demands required for the work of breathing. Registered dieticians should be involved when infants are grossly underweight. Increasing calories may involve Power Packing, pureeing foods, or gastrostomy feeds (either exclusively or in addition to oral feeding). Although the decision to proceed with G-tube placement can be difficult, prolonged feeding time may make the logistics of caring for non-sitters with SMA very difficult. Families may prefer to start with a nasogastric tube before proceeding with G-tube placement. For an introduction to various kinds of feeding tubes and an overview of the role of the medical home in feeding tube care, see Feeding Tubes and Gastrostomies.

Excessive weight gain can also occur in sitters and walkers and can make mobility even more difficult; preventing excessive weight gain is easier than losing weight. Nutrition experts should be involved when a trend toward becoming overweight is first noted.

Subspecialist Collaborations & Other Resources

Nutrition/Dietary (see Services below for relevant providers)

Referral may be helpful in underweight and overweight children with SMA.

Pediatric Endocrinology (see Services below for relevant providers)

Consider referral for children who have low bone mineral density on Dexascan and have a history with fractures.

Musculoskeletal

Preventive and ongoing management for musculoskeletal problems, including joint contractures, hip dislocation, and scoliosis, should be initiated at time of diagnosis. Refer to early intervention services, physical therapy, physiatry, and orthopedics depending on preferences and local expertise.

Devices for upright positioning are prescribed for non-sitters to help with lung function, gastrointestinal function, and developmental goals. For sitters and non-sitters, standing equipment should be prescribed and used for a goal of 1 to 2 hours a day. This can help with lung and gastrointestinal function, decrease fracture risk, and delay scoliosis and contracture development. Orthotics and walking equipment should be provided, even if functional walking for all activities isn't a practical goal. Prescribe scooters, wheelchairs (manual and/or powered), or other equipment, as necessary, for all children with SMA to allow participation in age-appropriate community activities. To avoid progression of contractures, implement daily range of motion exercises and early return to weight bearing activities after surgeries.

Scoliosis assessment - SMA Type III boy
Scoliosis develops in more than half of children with SMA, and many of these children will require surgery. Optimal timing for surgery will depend on the respiratory status, progression of the curve, and growth of the child. Bracing is sometimes used to postpone surgery as long as possible and allow more linear growth before fusion; however, bracing can compromise respiratory function and should be used with caution, particularly in weaker children. Respiratory function should be monitored routinely; scoliosis surgery should be performed before respiratory function significantly declines. Surgery is performed before or when the scoliosis curve has reached approximately 40 degrees. Problems with surgery include blood loss, difficulty weaning the child from the ventilator, and prolonged rehabilitation time.

Photo, left: Boy with SMA type III being checked for scoliosis (photo permission on file)

Hip subluxation and dislocation are common problems for non-sitters, sitters, and, occasionally, walkers. Imaging of the hip should be performed biannually or annually. Hip dislocation can make sitting balance difficult, interfere with already compromised respiratory function, and lead to chronic pain. The risks and benefits of surgery for hip subluxation should be weighed by the family who is consulting with an experienced orthopedic surgeon. When surgery is being considered for walkers, be aware that the period of inactivity may lead to contractures or changes in a functional walking patterns.

Subspecialist Collaborations & Other Resources

Pediatric Orthopedics (see Services below for relevant providers)

Refer early for evaluation and management of hip dislocation, scoliosis, and joint contractures; ideally, the sub-specialist will have experience treating children with SMA.

Hospitals (see Services below for relevant providers)

Shriners Hospitals offer orthopedic care to children with SMA. For a map of locations, see Shriners Hospitals for Children.

Pediatric Physical Medicine & Rehab (see Services below for relevant providers)

Refer to optimize functional abilities, including activities of daily living and mobility.

Physical Therapy (see Services below for relevant providers)

Consider early referral to assist with range of motion, strengthening, mobility equipment, and prevention of contractures.

Early Intervention Programs (see Services below for relevant providers)

Young children are usually eligible for different types of therapies (physical, occupational, speech, etc.) through Early Intervention or programs administered at the local community level.

Nose/Throat/Mouth/Swallowing

Swallowing problems are common in non-sitters and sitters and may cause aspiration of oral secretions and food, bad breath, dental caries, and drooling. Feeding specialists (who may be occupational therapists or speech therapists) should optimize feeding methods. If children have difficulty with chewing and swallowing foods, pureed foods may be helpful. For children who cough, choke, silently aspirate thin liquids, or have lung problems consistent with aspiration, thickening liquids with an agent, such as Simply Thick or Thick It, may be helpful (see Thickening Liquids & Pureeing Foods). Ultimately, particularly in non-sitters and sitters, placement of a feeding tube, nasogastric, nasojejunal, or G-tube may be necessary. Note that while G-tubes are able to deliver sufficient calories, they do not protect the airway against aspiration of oral secretions. Feeding Tubes and Gastrostomies provides further clinical details.

Subspecialist Collaborations & Other Resources

Pediatric Gastroenterology (see Services below for relevant providers)

Referral may be helpful for children who are underweight, aspirating, or who are having difficulty swallowing. Placement of a G-tube may be beneficial.

General Pediatric Surgery (see Services below for relevant providers)

Referral may be helpful for G-tube insertion, especially if a fundoplication is also being considered.

Gastro-Intestinal & Bowel Function

Gastrointestinal problems such as reflux, delayed gastric emptying, and constipation are common. See Gastroesophageal Reflux (general) for medications that may be useful in treatment. In non-sitters, Nissen fundoplication may be needed for airway protection, especially if inadequate oral intake and aspiration are problems as well. Constipation should be treated aggressively as it may lead to discomfort, more problems with gastric emptying, decreased appetite, and reflux. See Constipation Treatment (general).

Subspecialist Collaborations & Other Resources

Pediatric Gastroenterology (see Services below for relevant providers)

Consider referral for children who do not respond to typical management.

General Pediatric Surgery (see Services below for relevant providers)

Depending on local expertise, children requiring G-tube placement may be referred.

Developmental Pediatrics (see Services below for relevant providers)

Depending on local expertise, behavioral and medical management of constipation may benefit from referral.

Dental

Due to contractures, many children with SMA have difficulty opening their mouths wide. This often causes problems with eating and can complicate dental care. Children with SMA need early referral and treatment to pediatric dentists. If children with SMA need surgery for other reasons, such as G-tube placement, piggy-backing dental cleaning, sealant application, and cavity treatment should be considered. If sedation is necessary for procedures, providers should be aware of increased risk due to respiratory problems in children with SMA.

Subspecialist Collaborations & Other Resources

Pediatric Dentistry (see Services below for relevant providers)

Children with SMA should be referred early and visit at least every 6 months for ongoing care.

General Dentistry for Children (see Services below for relevant providers)

The dentists in this list have expressed interest and experience in treating CSHCN.

Recreation & Leisure

Children with SMA need opportunities to participate in recreational activities, and adaptive sports are one of the fastest growing leisure activities in the US. Toys and games can be modified to suit a child’s abilities; driver education alternatives can be considered for older children with SMA. The Portal's page Switches has information about adapting toys. Recreation Activities provides more ideas for activities. Play (Cure SMA) has tips about play and care packages available with toys that other families affected by SMA have recommended based on their personal experience.

Subspecialist Collaborations & Other Resources

Recreation Programs/Activities (see Services below for relevant providers)

Encourage families to seek out recreational outlets for their child.

Funding & Access to Care

Families may have difficulty assessing resources, but can find help from organizations, such as Cure SMA. Since resources will differ somewhat between states, families should also contact their local Division of Services for People with Disabilities or a similar state agency for information. Muscular Dystrophy Association (MDA) clinics, found in many cities nationally, are great resources for children and adults with SMA. At these clinics, the doctor visits are funded by the MDA, and there is some financial help for consult visits and wheelchair purchases. See Muscular Dystrophy Association. Families should ask about eligibility for supplemental security income (SSI) by either contacting the government directly or by working with coordinators through early intervention or education services. See Financing Your Child's Healthcare for other helpful ideas.

Family

Refer families to support organizations, such as Cure SMA and the Muscular Dystrophy Association, which can connect them with others who have children with SMA. Families should also be referred to Wish Granting Organizations, such as the Dream Factory, Make a Wish Foundation, and Starlight Foundation, when children are between 2 1/2 and 18 years of age.

Appropriate care for children with SMA encompasses many options, and open discussions of alternatives are very helpful for families. Some families will choose to forego diagnostic and therapeutic interventions that they feel are invasive, whereas others will choose to proceed aggressively with interventions that might prolong life. All caregivers need to understand the family’s preferences. Discussions are best accomplished over time and in non-acute settings, rather than in the midst of an emergency room visit for pneumonia requiring intubation, for example. Preventive management, such as early implementation of non-invasive ventilation, will help avoid crises. The decision to aggressively manage SMA is a dynamic one that can be reconsidered whenever appropriate. Offer pediatric hospice in situations where aggressive intervention is not chosen. A Family Guide to the Consensus Statement for Standard of SMA Care (ICC) (PDF Document 267 KB) can assist families in understanding care possibilities.

Subspecialist Collaborations & Other Resources

Hospice & Palliative Care (see Services below for relevant providers)

Hospice services that have expertise in the care of children should be involved when necessary.

Wish Foundations (see Services below for relevant providers)

Refer, as appropriate, when children are between 2 1/2 and 18 years of age.

Pediatric Genetics (see Services below for relevant providers)

Families can benefit from periodic visits to review issues and address new questions (e.g., progress in genetic studies, options for prenatal and preimplantation diagnosis to help with reproductive planning, or risks for siblings of a child with SMA).

Frequently Asked Questions

What are the earliest signs of SMA?

Signs and symptoms will differ depending on a patient’s age and SMA subtype. Classically, children present with hypotonia, proximal weakness (shoulders and hips), feeding difficulties, and/or complications of respiratory insufficiency. Early signs of weakness include:

  • Abdominal breathing or accessory muscle use
  • A feeling of “slipping through hands” when held suspended by examiner under armpits
  • Inability to voluntarily flex neck when supine or head lag when pulled to sit
  • Difficulty rising from floor (including Gowers maneuver, full or modified)
Video of relevant examination features in children with early weakness, including SMA patients, can be reviewed on Child Muscle Weakness Organization.

What are the most pertinent issues to focus on during a routine well-child visit for a patient with SMA?

Ongoing proactive assessment of sitting status, joint range of motion, feeding ability, weight, and respiratory status can enhance quality of life and life span for children with SMA. Asking about family and community supports and access to resources that may affect the care of a child with SMA is also critical.

How does SMA affect growth and development?

Children with SMA are at risk for nutritional deficiencies and being underweight. Non-sitters, in particular, are commonly underweight secondary to decreased intake and the increased energy expenditure for the work of breathing. Standard weight charts are not applicable due to reduced muscle mass despite caloric supplementation. Children with SMA that are following the “normal” growth curves may be functionally obese and at risk for complications of metabolic syndrome.

Issues Related to Spinal Muscular Atrophy

Gastro-Intestinal & Bowel Function

Constipation Treatment
Gastroesophageal Reflux

Resources

Information for Clinicians

Feeding Tubes and Gastrostomies
Provides an introduction to various kinds of feeding tubes and the role of the medical home in feeding tube care.

Medical Issues (Cure SMA)
Excellent resources covering respiratory, orthopedic, nutrition, and rehabilitation needs for SMA patients.

Acute Respiratory Illness Care Guidelines (Cure SMA) (PDF Document 32 KB)
Two-page guideline for care of the intubated and non-intubated child with SMA during periods of acute respiratory illness.

Nutritional Care Guidelines (Cure SMA) (PDF Document 68 KB)
Proactive nutritional management tips for children with SMA.

Pediatric Motor Disorders Research Program (University of Utah)
Diagnostic and management information about SMA and other disorders.

Child Muscle Weakness Organization
Information and videos to help increase clinicians’ awareness of peripheral neuromuscular disease as a cause of developmental delay in young children and the early symptoms of neuromuscular disorders; National Task Force for the Early Identification of Childhood Neuromuscular Disorders.

Spinal Muscular Atrophy (GeneReviews)
An expert-authored, peer-reviewed, current disease description that applies genetic testing to diagnosis and management information; U.S. National Library of Medicine.

SMA Type I (OMIM)
Provides information about genetics, diagnosis, management, and studies; Online Mendelian Inheritance in Man, hosted by Johns Hopkins University.

SMA Type II (OMIM)
Provides information about genetics, diagnosis, management, and studies; Online Mendelian Inheritance in Man, hosted by Johns Hopkins University.

SMA Type III (OMIM)
Provides information about genetics, diagnosis, management, and studies; Online Mendelian Inheritance in Man, hosted by Johns Hopkins University.

Genetics in Primary Care Institute (AAP)
The goal of this site is to increase collaboration in the care of children with known or suspected genetic disorders. Includes health supervision guidelines and other useful resources; a collaboration among the Health Resources & Services Administration, the Maternal and Child Health Bureau, and the American Academy of Pediatrics.

Helpful Articles

PubMed search for spinal muscular atrophy in children, last 2 years.

Darras BT.
Spinal muscular atrophies.
Pediatr Clin North Am. 2015;62(3):743-66. PubMed abstract

García-Salido A, de Paso-Mora MG, Monleón-Luque M, Martino-Alba R.
Palliative care in children with spinal muscular atrophy type I: What do they need?.
Palliat Support Care. 2015;13(2):313-7. PubMed abstract

Kolb SJ, Kissel JT.
Spinal Muscular Atrophy.
Neurol Clin. 2015;33(4):831-46. PubMed abstract / Full Text

Lin CW, Kalb SJ, Yeh WS.
Delay in Diagnosis of Spinal Muscular Atrophy: A Systematic Literature Review.
Pediatr Neurol. 2015;53(4):293-300. PubMed abstract

Tisdale S, Pellizzoni L.
Disease mechanisms and therapeutic approaches in spinal muscular atrophy.
J Neurosci. 2015;35(23):8691-700. PubMed abstract / Full Text

Viollet L, Melki J.
Spinal muscular atrophies.
Handb Clin Neurol. 2013;113:1395-411. PubMed abstract

Clinical Tools

Assessment Tools/Scales

Pediatric Evaluation of Disability Inventory (PEDI)
Helps evaluate functional disabilities of children ages 6 months to 7 years old; completion time of 45-60 minutes; manual scoring; purchase required.

Patient Education & Instructions

Living with SMA (Cure SMA)
Excellent resource for families dealing with the day-to-day issues related to SMA. Contains information about standards of care, school, home, equipment needs, and community resources.

Information & Support for Families

Family Diagnosis Page

Information on the Web

A Family Guide to the Consensus Statement for Standard of SMA Care (ICC) (PDF Document 267 KB)
Assists families in understanding clinical care guidelines; prepared by the Patient Advisory Group of the International Coordinating Committee for SMA Clinical Trials.

SMA Foundation
The mission of the SMA Foundation is to accelerate treatment for children with SMA. Families will find detailed information about SMA, up-to-date information about drugs in development, and support.

Play (Cure SMA)
Tips for finding and making toys, getting involved in sports, and traveling. Care packages with toys that other families affected by SMA have recommended based on their personal experience are available.

Spinal Muscular Atrophy (MedlinePlus)
A brief description of SMA, along with numerous links to further information; sponsored by the National Library of Medicine.

Spinal Muscular Atrophy (Genetics Home Reference)
Excellent, detailed review of condition for patients and families; U.S. National Library of Medicine.

Support National & Local

Cure SMA
Offers information about research in SMA, access to support and local chapters, and opportunities for fundraising.

Rainbow Kids Palliative Care (Primary Children's Hospital)
A consultation service available to any child who is experiencing a life-threatening illness. The program helps both the child and family deal with feelings, symptoms, and concerns during a time that may be confusing and overwhelming.

Children's Hospice International
An organization that supports the idea that critically ill children should have access to hospice/palliative care along with curative care from the time their life threatening illness has been diagnosed.

Fight SMA
Nonprofit organization that engages in leading scientists and policymakers to create treatments and a cure for SMA.

SMA Coalition
A coalition of SMA-focused nonprofits working toward increased awareness and help for those with SMA.

Services for Patients & Families

Adaptive Recreation

See all Adaptive Recreation services providers (64) in our database.

Assistive Technology

See all Assistive Technology services providers (104) in our database.

Camps

See all Camps services providers (101) in our database.

Developmental Pediatrics

See all Developmental Pediatrics services providers (5) in our database.

Early Intervention Programs

See all Early Intervention Programs services providers (52) in our database.

General Dentistry for Children

See all General Dentistry for Children services providers (151) in our database.

General Pediatric Surgery

See all General Pediatric Surgery services providers (2) in our database.

Hospice & Palliative Care

See all Hospice & Palliative Care services providers (69) in our database.

Hospitals

See all Hospitals services providers (62) in our database.

Muscular Dystrophy Clinics

See all Muscular Dystrophy Clinics services providers (3) in our database.

Nutrition/Dietary

See all Nutrition/Dietary services providers (53) in our database.

Occupational Therapy, Pediatric

See all Occupational Therapy, Pediatric services providers (42) in our database.

Pediatric Dentistry

See all Pediatric Dentistry services providers (57) in our database.

Pediatric Endocrinology

See all Pediatric Endocrinology services providers (2) in our database.

Pediatric Gastroenterology

See all Pediatric Gastroenterology services providers (3) in our database.

Pediatric Genetics

See all Pediatric Genetics services providers (5) in our database.

Pediatric Neurology

See all Pediatric Neurology services providers (10) in our database.

Pediatric Orthopedics

See all Pediatric Orthopedics services providers (18) in our database.

Pediatric Otolaryngology

See all Pediatric Otolaryngology services providers (9) in our database.

Pediatric Physical Medicine & Rehab

See all Pediatric Physical Medicine & Rehab services providers (8) in our database.

Pediatric Pulmonology

See all Pediatric Pulmonology services providers (4) in our database.

Pediatric Sleep Medicine

See all Pediatric Sleep Medicine services providers (3) in our database.

Physical Therapy

See all Physical Therapy services providers (62) in our database.

Recreation Programs/Activities

See all Recreation Programs/Activities services providers (249) in our database.

Social & Recreational Opportunities

See all Social & Recreational Opportunities services providers (27) in our database.

Speech/Language Therapy

See all Speech/Language Therapy services providers (80) in our database.

Swallow Studies

See all Swallow Studies services providers (1) in our database.

Wish Foundations

See all Wish Foundations services providers (19) in our database.

For other services related to this condition, browse our Services categories or search our database.

Authors

Authors: Kathy Swoboda, MD - 7/2013
Lynne M Kerr, MD, PhD - 7/2013
Reviewing Authors: Meghan Candee, MD - 8/2016
Russell Butterfield, MD, PhD - 8/2016
Content Last Updated: 8/2016

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Spinal muscular atrophies.
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Spinal muscular atrophy--recent therapeutic advances for an old challenge.
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García-Salido A, de Paso-Mora MG, Monleón-Luque M, Martino-Alba R.
Palliative care in children with spinal muscular atrophy type I: What do they need?.
Palliat Support Care. 2015;13(2):313-7. PubMed abstract

Hamilton G, Gillingwater TH.
Spinal muscular atrophy: going beyond the motor neuron.
Trends Mol Med. 2013;19(1):40-50. PubMed abstract

Jones C, Oskoui M, Zielinski D, Vinikoor L, Farwell W.
Systematic review of incidence and prevalence of spinal muscular atrophy (SMA).
European Journal of Paediatric Neurology. 2015; 19(1):oral presentation. Elservier Ltd.; http://www.sciencedirect.com/science/article/pii/S1090379815302130
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Molecular functions of the SMN complex.
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Kolb SJ, Kissel JT.
Spinal Muscular Atrophy.
Neurol Clin. 2015;33(4):831-46. PubMed abstract / Full Text

Lin CW, Kalb SJ, Yeh WS.
Delay in Diagnosis of Spinal Muscular Atrophy: A Systematic Literature Review.
Pediatr Neurol. 2015;53(4):293-300. PubMed abstract

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Feeding problems and malnutrition in spinal muscular atrophy type II.
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Disease mechanisms and therapeutic approaches in spinal muscular atrophy.
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Viollet L, Melki J.
Spinal muscular atrophies.
Handb Clin Neurol. 2013;113:1395-411. PubMed abstract

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