Each of the following sections contains information to help manage spinal muscular atrophy.
Since respiratory management can impact lifespan considerably, physicians should support families in implementing a proactive approach. While pulmonary management is often demanding, it is also the therapeutic modality that will most likely enhance quality of life and prolong lifespan. Pulmonary medicine consultation is recommended to assist in making decisions regarding long-term respiratory management.
Exercises & Aids
To maintain lung capacity, breathing exercises and supplementary aids may be helpful. Incentive spirometry and “breath-stacking” can be implemented at an early age but require discipline to perform on a daily basis. Aerosol therapy with nebulizers may be helpful in some settings and can be initiated at the onset of respiratory symptoms.
Steroid treatments, cough assist devices, vest therapy, manual percussion
Benefit from the routine use of mucolytics, bronchodilaters or steroid treatments is unclear and should be dictated by individual circumstances. Cough assist devices, such as the inexsufflator (cough machine), are essential when ineffective cough inhibits adequate removal of bronchial secretions in the lower airways. Vest therapy or manual percussion techniques to help mobilize secretions, when used in conjunction with the cough assist machine, can be additionally helpful in some patients. Regular use of such therapies, most importantly the cough assist machine, are invaluable in the setting of a superimposed respiratory illness and can help prevent a simple cold or bronchitis from evolving into pneumonia or a collapsed lung resulting in respiratory crisis. Even when children are well, daily use of such a regimen can help minimize atelectasis and chest wall contractures and deformity. In many children and young adults, nocturnal hypoventilation with and without obstructive apnea necessitates assisted ventilation.
BiPAP is recommended whenever the vital capacity falls to less than 40 percent. However, in infants and young children who can’t cooperate with formal pulmonary function testing, doctors must use other signs and symptoms to help decide when a child might benefit from BiPAP support. Recurrent nighttime awakenings are often an indication that patients may not be optimally breathing during sleep. A sleep study may help to determine whether or not there is an obstructive component (due to low muscle tone or enlarged tonsils or adenoids), or whether nocturnal hypoventilation (shallow-breathing resulting in low oxygen levels or increased carbon dioxide levels) is present. BiPAP is often recommended for use only at night, but can be invaluable to use for longer periods of time when an upper respiratory infection or other illness results in increased work of breathing and fatigue.
Flu prophylaxis is recommended annually. In younger infants and children with significant intercostal weakness (all type I and weak type II subjects), prophylaxis for respiratory syncytial virus (RSV) is also recommended.
Oxygen therapy should only be used in conjunction with assisted ventilation in such patients as it can suppress respiratory drive, resulting in atelectasis and hypercarbia.
Aggressive treatment of respiratory infection is essential. Antibiotic use is of value when symptoms arising from a presumed viral upper respiratory infection persist longer than expected or new fever or altered secretions appear in the midst of an apparent viral illness. Since recurrent or prolonged antibiotic treatment can predispose patients to yeast infections or even enterocolitis, a balanced approach is needed.
In the severely compromised infant or child, a lower threshold for administering antibiotics may be warranted. If illness results in persistent hypoxemia below 93 percent, the need for hospitalization and potential intubation should be discussed, although many such patients can be managed effectively in hospital using a non-invasive respiratory protocol.
Mary Schroth, MD, associate professor of pediatric pulmonology at the University of Wisconsin School of Medicine and Public Health. She has written several booklets funded by Families of SMA, regarding SMA respiratory care for parents, families and health care providers involved in SMA care.
Nutrition is critically important for maintaining muscle mass and strength and minimizing fatigue in SMA patients. Intermittent monitoring of dietary intake in consultation with a dietician experienced in management of patients with neuromuscular conditions or metabolic disorders can be extremely helpful. Children may be deficient in carnitine due to decreased intake of meat related to jaw contractures interfering with chewing. Swallowing problems sometimes be difficult to detect, and in weaker children or in those with borderline nutritional status or frequent respiratory illness, swallowing studies should be performed on a regular basis to ensure that silent aspiration isn’t contributing to respiratory problems.
Maintenance of appropriate nutrition is especially critical during illness. SMA subjects have diminished lean body mass and a secondary defect in fatty acid oxidation that limits their reserve in the setting of prolonged fasting. Thus, when concerns regarding the ability to safely administer oral feeds develop, alternative forms of nutrition should be considered. Options include temporary nasogastric or nasojejunal feeds, or peripheral or total parenteral nutrition (PPN or TPN).
See also Infants for more information about special considerations in SMA type I infants.
Physical therapy on a daily basis, performed by parents with appropriate direction from a physical therapist, can help to minimize joint contractures and maintain mobility. The use of standing devices, appropriate orthotics, bracing, and facilitated ambulation can help significantly in this regard. Weight bearing on a daily basis, instituted as early as possible in non-ambulatory children for a minimum of two hours per day, can help to delay onset of scoliosis, limit contractures and improve circulation and gastrointestinal motility.
Daily exercise should be encouraged, to include the upper extremities in those children with severely impaired lower extremity function, to help maintain motor function and promote cardiovascular health. A daily exercise program could include part-time use of manually propelled mobility devices, including manual wheelchair, manual stander or gait trainer.
The major orthopedic problems these children face include scoliosis, hip dislocation and an increased risk of fracture due to decreased bone density and propensity for falls. The age of onset and rate of progression of such complications are directly related to the severity of muscle weakness, but early intervention can minimize the impact and severity of such problems.
Contractures can develop quite rapidly in the setting of illness, excessive time spent in a wheelchair, decreased activity, or recovery after scoliosis surgery or other orthopedic procedures. Daily range of motion and early return to supported weight bearing can help maintain function in these children.
Scoliosis almost invariably begins in the first decade of life in SMA type II and in a substantial proportion of children with SMA type III. The curves progress over time, sometimes quite rapidly during transition to increased wheelchair use or in conjunction with a growth spurt. In non-ambulatory patients, spinal bracing may improve sitting stability, as long as care is taken not to compromise abdominal movement in those with intercostal muscle weakness. However, continuous use of such bracing should be limited if possible in order to maintain trunk strength and mobility. Periodic pulmonary function studies help to establish a profile for the individual patient, allowing design of the most appropriate care plan surrounding respiratory care in the post-surgical period. Since worsening is inevitable in most children, once the curve reaches 40 degrees a decision to intervene may be warranted. When very young patients develop scoliosis, bracing can sometimes help to defer surgery for variable periods of time, and “growth rods” or other means of accommodating growth may be indicated.
Proximal muscle weakness predisposes patients to progressive subluxation and dislocation of the hip. Subsequent hip degeneration can result in significant chronic pain. In non-ambulatory patients, it is important to prevent the hips from dislocating for reasons of comfort, good sitting balance and maintenance of pelvic alignment.
To achieve an optimal result, operative intervention may be required in some cases. Patients who have type III SMA and are still able to walk present a difficult management problem. These patients are also prone to subluxation of the hip due to significant proximal muscle weakness. However, because surgical intervention with proximal femoral varus osteotomy may result in additional weakening of the abductor muscles, the physician should be cautious in recommending such surgical procedures in an ambulatory patient.
Since these patients rely to a great extent on lumbar lordosis and a side-to-side waddle to walk, bracing or spinal arthrodesis may worsen their gait. It is not uncommon for SMA type III patients to become non-ambulatory following spinal surgery, particularly if a rehabilitation plan is not instituted immediately in the post-operative period. Joint contractures can progress quite rapidly in this setting without dedicated prevention. In a subset of cases in which ambulatory status is considered at risk, postponement of surgery may be the best choice. Special consideration of nutritional support in the perioperative period can help ensure a good outcome.
Children should be screened by a pediatric dentist as soon as possible following diagnosis.
Regular Dental Visits
For cleaning, consultations, cavity monitoring and protection, such as sealants, we recommend regular dental visits. Poor oral hygiene increases the risk for pneumonia. Institute the prevention of jaw contracture with the Therabyte system at the earliest indication of tightness. Early referral to an orthodontist as indicated is important to help utilize palate expanders for narrow high arched palates and teeth crowding.
Proactive dental hygiene and prevention of jaw contracture
Significant jaw contractures ultimately develop in a majority of adults with type II SMA. Some children with SMA type II and virtually all children with type I who survive to later childhood and adulthood also manifest this problem. Jaw contractures can result in inadequate oral hygiene and increase the risk for serious dental complications over time. Because of discomfort experienced during routine dental care due to this issue, many individuals choose to avoid going to the dentist at all rather than address the primary issue. This sets up a vicious cycle of poor dental care and hygiene and, ultimately, tooth decay. Subjects with tooth decay and gingivitis are at an increased risk for pneumonia as well as more serious medical problems such as endocarditis (inflammation and infection on heart valves). Thus, it is critical to avoid these problems in the first place by being proactive from early childhood. We recommend dental visits at least every six months beginning at three years of age for all individuals with SMA. Early consultation with an orthodontist for consideration of a retainer or palate expander can help prevent jaw and facial deformity and abnormal bit alignment due to decreased use of mandibular muscles.
Anticipatory jaw stretching is one possible solution to help avoid this problem. The Therabyte System is one solution. In subjects whom significant jaw contracture has already developed and who require dental or oral surgery or other medical procedures requiring significant mouth opening, a gradual increase in the width of jaw opening over a period of several weeks can increase access. However, this needs to done gently and carefully to avoid damage to the temporomandibular joint and surrounding muscles. If a dental, endodontal or oral surgery is recommended and the infant hasn’t had adequate ongoing mouth care, standard antibiotic prophylaxis should be considered prior to such a procedure.
Most individuals with significant jaw contracture have respiratory impairment, which warrants an anesthesiology consult if any type of sedation is planned. To avoid serious muscle damage and chronic temporomandibular joint pain, intubation using a laryngeal mask airway (LMA, which doesn’t require visualization of vocal cords) or fiber optic intubation via placement of an endotracheal tube over a bronchoscope can ensure adequate ventilation during and after the procedure. Sometimes, use of muscle relaxants or even paralysis are necessary to enable adequate jaw-opening to extract teeth or perform dental or oral surgery procedures. Where such a procedure is performed depends on how fragile their respiratory status is. Most individuals will need to be in a place where they can get appropriate post-procedure care and support until they have recovered their baseline state with regard to airway protection.
When dental issues have not been addressed in a proactive fashion, individuals who suffer gingivitis, tooth decay, abscesses or severe temporomandibular joint restriction can develop significant and chronic pain. While addressing the primary issue is desirable, sometimes individuals are fearful of aggressive interventions and may need time to fully consider the risks and benefits of more invasive procedures. It is important not to overlook the importance of adequate pain control or less invasive interim solutions in such patients, including palliative care interventions.
Special Considerations in SMA Infants
Before and after confirmatory genetic testing is completed in an obviously severely affected infant, it is essential to work closely with parents to ensure that they understand what they may face in the months following the diagnosis, fully reviewing their options regarding supportive nutritional and respiratory interventions. This is particularly important to address early, since these infants are often diagnosed in the setting of an initial respiratory event and may already have bulbar insufficiency and respiratory insufficiency.
It is important that families be presented with a range of options and that quality of life for the entire family be preserved as much as possible. Many parents, when presented with options, choose to forgo invasive diagnostic and therapeutic procedures. However, others are anxious and willing to embrace a very proactive care plan if it means extending the life of their child.
It is vital to maintain open communication so that all caregivers are aware of choices already made as well as areas of continuing uncertainty regarding interventions to be considered. Proper positioning, daily passive range of motion and use of alternative mattress systems or seating devices can enhance quality life. A flat-car bed rather than a car seat is advisable for infants who rely primarily on abdominal breathing. If swallowing problems are mild, thickening the formula and positioning the infant properly can help to avoid aspiration of formula into the lungs.
However, families of type I infants will almost certainly need to consider some alternative means of providing nutrition at some point. A nasogastric or nasojejunal tube (a slender tube which goes through the nose and down to the stomach or to the first part of the intestine) is often sufficient for prolonged periods of time, allowing the family time to consider the range of options.
More permanent options include gastrostomy or a combined Nissan/gastrostomy procedure. While surgery and general anesthesia clearly carry some potential risks, laparoscopic techniques are available that allow a more rapid recovery. In severely weak infants in whom general anesthesia is a concern, percutaneous gastrostomy with local anesthesia is an option. Given the SMA child’s need to eat regularly, limiting fasting prior to such procedures and providing nutritional support immediately afterward will help to enhance recovery.
Respiratory management is a challenge, presenting the greatest risk of death or serious disability in the weakest infants and children. The most aggressive approach, including tracheotomy and mechanical ventilation, does nothing to prevent disease progression. Complications such as tracheitis (infection involving the windpipe), sepsis (life-threatening infection in the blood) and ongoing respiratory complications can compromise quality of life.
Families may be pressured to make quick long-term decisions without adequate preparation when infants are intubated emergently due to respiratory crisis. However, the increasing availability of noninvasive ventilation techniques including bilevel positive pressure support (BiPaP), inexsufflator treatments (cough assist machine), percussion, postural drainage and suction can help allow such infants to be extubated more readily than in the past, providing an intermediary between tracheostomy and withdrawal of support. Perhaps more important, however, it offers families additional options for ongoing respiratory support on a daily basis at home, thus minimizing emergency room and hospital visits and potentially extending lifespan in more moderately affected infants.
An individualized approach to respiratory infection or compromise should be developed with the child’s family and updated regularly with regard to choices surrounding a need for intubation. If the family chooses palliative care, hospice provides compassionate support for such families. The use of narcotic medication in this setting to reduce discomfort, along with proper positioning and a less aggressive respiratory support regimen, in concert with the family’s wishes can minimize discomfort for the infant. It may be beneficial to have the family communicate with others who have experienced the loss of an infant with SMA type I during this difficult period.
Pediatric Intensive Care Unit (PICU)
A standardized approach to treatment when in the Pediatric Intensive Care Unit (PICU) can be very helpful in the treatment of children with SMA. Below are treatment guidelines used in the PICU units at the University of Utah Medical Center and Primary Children’s Medical Center.