In its most severe form, spinal muscular atrophy (SMA) presents at birth or soon after, progresses rapidly and is fatal by or before the child reaches toddlerhood. Children with less severe types of SMA can live to adulthood.
But even within an SMA “type,” there are variations in function, progression and life expectancies — and therefore, variations in the types of seating and wheeled mobility needed. Nusinersen, a promising new drug therapy shown to slow SMA progression, could introduce additional variables as seating and mobility teams seek out the best equipment for kids today and going forward.
Understanding Spinal Muscular Atrophy
Cure SMA (curesma.org), an advocacy group that supports families living with SMA and funds and directs research for treatments, noted that SMA is the number one genetic cause of death in infants around the world. Because SMA affects the muscles needed for breathing, eating, talking and moving, complex rehab technology (CRT) professionals can play a major role in supporting children with SMA and their families.
Missy Ball, MT, PT, ATP, explained that SMA “is an autosomal recessive disease (one copy from each parent) caused by a defect in the SMN 1 gene, which is necessary for production of SMN protein needed for effective motor neuron function. Human chromosome 5 contains two genes (SMN1 and SMN2) at location 5q13. SMA is a genetic defect in the SMN1 gene, but all patients retain at least one copy of SMN2 (some have two to four copies). SMN2 can code small amounts (10-20 percent) of the SMN protein, explaining variations in the severity of this disease.”
Cure SMA recognizes four types of SMA, the first three of which present at various stages of childhood. (Some healthcare organizations, such as the National Organization for Rare Disorders, have discussed an additional type — Type 0 — that is the most severe form of SMA and is typically fatal by the time an infant is 6 months old.)
“In general,” Ball said, “the clinical manifestations [of SMA] are areflexia (absence of reflexes) for most extremities; global muscle weakness; low tone; feeding/swallowing difficulties; tongue fasciculations; degrees of respiratory compromise; and developmental delay.”
SMA type 1, also known as Infantile or Werdnig-Hoffmann disease, “has an early onset, birth to 6 months,” Ball said. “Clinically, they present with ‘floppy baby syndrome,’ lacking head and trunk control, completely dependent, with respiratory compromise requiring mechanical ventilation soon if not immediately following birth. Their intellect can be quite normal, with the child expressing themselves through facial changes. Life expectancy is short, usually 2 years, but 10 percent at least can live to adolescence-adulthood.”
SMA Type II, Ball said, is known as Intermediate or Dubowitz disease, and “has an onset between 6 and 18 months of age, displaying global weakness with an inability to stand or walk, but some ability to sit independently or with assistance, respiratory compromise with or without need for mechanical ventilation, and life expectancy usually to adulthood.”
Supportive Seating & Mobility
Children with different types of SMA have very different assistive technology needs, said Darlene Hawthorne, Thomashilfen’s president of North America.
“There is a big difference in the main seating, positioning and mobility-related presentations between children with Type 1 and Type 2 SMA,” she noted. “In addition, within each group there is a range in strength from relatively strong to very weak, so it is hard to pinpoint the main presentations for each group. Children with Type 1 often present with pronounced scoliosis that must be assessed with the child in a fully reclined position, as this is indicated by their respiratory needs. Most are completely without head control.
“Children with Type 2 can present from quite strong, with head control, and the ability to sit in an upright position. Trunk stability must be considered, as many are stabilized by a TLSO [thoracolumbosacral orthosis].”
“SMA Type 1 needs full support to maintain head, trunk and extremities upright against gravity, since they are completely dependent,” Ball said. She recommended the following for children with Type 1 SMA:
- Supportive seat and back (hip and pelvic support) to maintain the pelvis in a more neutral position, maintain natural spinal curves, and prevent scoliosis.
- Width- and height-adjustable lateral supports and chest vest to prevent scoliosis and maintain trunk upright against back.
- Head support, which may include anterior and lateral support to maintain head upright for functional tasks, socialization, school work.
- Foot supports with either ankle straps or ankle huggies.
- Age-appropriate system that can provide position changes (tilt in space and recline) for feeding, trach care, pressure relief, diapering, postural control for functional activities, venous return insufficiency and that can accommodate a ventilator, battery, suction machine, and all the other respiratory essentials.
- The system should also be crash tested and approved for travel in automobiles for child safety and caregiver ease. The lighter the system, the easier for the caregiver to use it to get to multiple doctor appointments, as well as to allow inclusion in family outings.
- Power mobility can be considered at about 1 year of age if patient health status warrants and family has necessary transportation (van with lift) to accommodate its transport. A micro joystick using mobile arm supports could possibly allow independent operation on a power wheelchair with tilt in space and minimal-shear recline.
For children with Type 2, Ball said, “Some could be independent in power mobility with an effective input device and possibly mobile arm supports or tray for upper-extremity support while accessing the joystick/input device. This system would need tilt in space and maybe recline, if the client is ventilator dependent. If the client is not vent dependent, then tilt in space would be sufficient to position for functional tasks, provide pressure relief, and position changes throughout the day to tolerate sitting long periods.”
“The top priority for children with Type 1 is for the seating equipment to fully recline while at the same time providing the needed postural support and regular position changes,” Hawthorne said. “The equipment must be able to fully recline. It is also helpful if the equipment can be tilted beyond flat to a position that can be used for postural drainage. For children with Type 1, who must remain in the reclined position, the seating should also offer adequate contouring for comfort. It is important not to have their sight lines blocked if the child’s head is turned to one side or another.
“The top priority for children with Type 2 is seating that offers a variety of positions in order to support them from upright sitting to recline. The degenerative nature of SMA must be taken into consideration. Seating and positioning needs can change even in a single day, as the child with Type 2 fatigues or requires different positions in order to function well at school and therapy.”
And as typical with CRT clients, Hawthorne noted the individuality of children’s abilities.
“Seating and positioning goals for children with SMA cannot be stated generally,” she said. “This is because the children range from being able to sit upright with head control (strong Type 2) to being only able to lie in a fully reclined position (weak Type 1).”
Getting Out & About
Cure SMA noted that SMA typically doesn’t impact cognitive function or intelligence — and anecdotally, many healthcare professionals have noted that kids with SMA seem brighter than average typically developing kids. In fact, a 2002 study called “Intelligence and cognitive function in children and adolescents with spinal muscular atrophy” and cited by the U.S. National Library of Medicine actually sought to disprove the notion that older children and teens with SMA were smarter than their able-bodied peers.
The study’s result: The kids with SMA had higher mean IQ scores than their siblings and other unrelated kids, though not dramatically higher. Verbally, though, the kids with SMA significantly outscored able-bodied peers. The study’s conclusion: “It could be speculated that the development of cognitive skills and knowledge is a creative way to compensate the many restrictions due to their physical handicap.”
Regardless of whether kids with SMA are organically “smarter” than their peers or whether their skills are environmentally based, it’s obvious that inclusion — in school, family activities, outings and their communities — should be a major goal.
“To set seating and positioning goals, each child’s strength and educational/activity needs must be assessed,” Hawthorne said. “Most children with SMA do not have cognitive impairment. Therefore, how they are being educated should be considered. Are they home schooled or do they attend school? Are they using special mounts in order to use iPads, Eyegaze and other assistive devices? Can the equipment adjust to help them access these tools?
“Ideally, it is great if the seating system can be easily moved to an alternative base, so that the child can be positioned for peer group inclusion.”
On the mobility side, Hawthorne said, “Whether they are using a power wheelchair, a stroller-type wheelchair or both, their respiratory needs must be the first priority. Many children have had a tracheotomy to assist their breathing. Others use BiPAP, so when considering mobility equipment, it must be able to transport the necessary respiratory equipment.
“In both Type 1 and 2, whether the child will be transported by adapted van or school bus and how the child can ride safely must be considered. The mobility equipment must be equipped with the correct tie-down system to ensure this.”
Transportation becomes more complicated when additional equipment, such as ventilators, must be included in addition to the wheelchair and its seating.
“It is very challenging to create vent trays large enough to carry all the respiratory equipment,” Hawthorne said. “The regulations for transporting children by bus or van require crash testing at specific weight limits. When you consider that the respiratory Tech Perspectives for SMA equipment can weigh in excess of 20 lbs., very careful weights and measurements must be taken. It is crucial when building custom vent trays that the seating clears the equipment on the vent tray and at the same time allows the child to be fully reclined.
“Placement of the respiratory gear takes some creative strategy, as it is important not to unbalance the overall system while it is in motion.”
Something Quite Special
Hawthorne said the progressive nature of SMA makes it difficult to determine if optimal seating and mobility equipment can improve a child’s function.
“Whether the equipment can actually improve respiration is a very large question,” she said. “SMA is degenerative and children become weaker, with a great loss of both muscle and respiratory function over time. That said, the seating, positioning and mobility equipment can contribute a great deal to helping children maintain better function when their equipment works well for them.”
And that can make a big difference to children with SMA and their families.
“For example,” Hawthorne said, “if they can more easily access their schoolwork, have peer group and family interaction, and be transported because their seating is comfortable, then you are offering them something quite special: An opportunity to participate in everyday life.”