Spinal Muscular Atrophy Type 2
The child with type 2 spinal muscular atrophy poses a similar set of medical and ethical questions posed by the type 1 child. However the child with type 2 SMA has a more benign clinical presentation and as a rule, a different long term medical prognosis. The child with type 2 SMA usually comes to medical attention before the age of 18 months. Early motor milestones, such as achieving head control, turning and rolling in the crib, are oftentimes passed on time. The acquisition of independent sitting is oftentimes delayed, but doesn’t promote the type of medical concern that brings the child to the pediatrician or to the neurologist. Not as severe as the Type 1‘s but not as benign as the Type 3 or Type 4 patient.
The molecular genetic underpinning of Type 2 SMA is very similar to that which underscores Type 1 and Type 3: a defect in the survival motor neuron protein, necessary in some way for the care and well being of the motor neurons of our anterior horn cells. Many of the problems that an SMA child faces are common to Type 1 and Type 2 SMA, but the Type 2 child has a definite advantage. Firstly, feeding problems and aspiration are much less common in Type 2 SMA children. Secondly, respiratory muscles, although usually somewhat compromised, are generally nowhere near as severely involved as the type 1 SMA child. The child with type 2 spinal muscular atrophy may suffer with some degree of respiratory insufficiencies, some weakness of the chest wall, but typically the breathing problems are nowhere as severe as the child afflicted with Type 1 SMA.
But remember, this is a spectrum and the borders that we define between type 1, type 2, type 2 to type 3, are sort of fuzzy and we don’t have a one description that’s all for any of the type SMA patterns observed in infants, toddlers, and young adults.
What are the needs of the child with type 2 SMA? Again very similar to the child with Type 1 SMA, there really is a need for a multi-disciplinary team approach. A team captain of the medical community usually either a neurologist or a physical medicine and rehabilitation specialist. A pulmonist and a respiratory therapist to monitor, and when necessary intervene, because of respiratory insufficiency – an inability to breathe deeply enough and forcefully enough to support the oxygen needs, to clear secretions during infections, to clear the secretions we all have (our own saliva), and very often during sleep when there will be shallow breathing, which is dysfunctional, not supporting adequate oxygen to the tissues and allowing the buildup of carbon dioxide which may then in fact impinge on a child’s day to day activities making a child very sleepy and less functional during the daytime. In sleep especially, the risks of respiratory insufficiency become apparent, which prompts many pulmonists to obtain what are called “sleep studies,” an observation of the child’s sleeping pattern, making sure that adequate oxygenation and adequate exchange of carbon dioxide occurs.
An orthopedic consult becomes very important in conjunction with physical and occupational therapy to address the orthopedic deformities which oftentimes evolve in Type 2 SMA children. The physical and occupational therapists will be instrumental in instructing you and other caregivers as to range of motion to help prevent contractures from occurring; the fashioning of orthotics, such as wrist splints or ankle splints, to prevent contractures of the wrist joints, the finger joints, and the ankle joints. These can be tremendously effective in preventing those complications. The orthopedic surgeon may need to be involved when contracture reaches the point where it no longer responds to a physical therapy program or simple bracing. And, very importantly as children with SMA type 2 reach their 7th, their 8th, their 12th, their 15th birthdays, scoliosis, a curvature of the spine, may evolve which can be uncomfortable and may, if left untreated, cause additional problems with breathing.
A nutrition consult is oftentimes important from two factors: number one, occasionally, children with SMA type 2 do have difficulty handling their oral contents, have difficulty with swallowing food, making them at risk for aspiration. And, the diet itself must be carefully monitored to provide adequate protein and calories for growth. There must be a game plan if a child has an intercurrent illness to ensure that prolonged periods of fasting do not go on. Prolonged fasting may result in metabolic problems which can be very, very serious and potentially life-threatening. And, as a child gets older still, the children may, because of limited caloric expenditure (a big word for saying that the child doesn’t burn off calories that he takes in) may culminate in excessive weight gain. Children may become plump or in some cases, obese, even though their caloric intake is really no more than another child their age. This weight gain is because of the failure of their bodies to burn the calories. Excessive weight gain may, in point of fact, then further limit the function of these children. It’s a lot easier to function with the muscles that we have, if we’re not carrying an additional 5 or 10 or 20 pounds of body weight, which our weakened muscles really cannot handle.
Another issue we face with a child with type 2 SMA is how we get that youngster involved quickly and effectively into the family community, into the school community. The child will need early instruction in the use of a power wheelchair so that he or she can accompany her parents on outside activities and so the child will be able to enter school able to keep up with classmates in the classroom and to participate in extracurricular activities. We have found that children as young as two years of age are perfectly capable of managing power wheelchairs, oftentimes to the delight of their other siblings. The child with SMA 2 presents a formidable list of medical problems, however, properly addressed, we can fully anticipate very long term survival and a high-quality of life for these youngsters.
I invite you to peruse other sites here on this website, to send in your comments and questions. We don’t have all the answers to assist parents and caregivers as to managing their children with type 2 SMA. But, I promise that we’ll try to answer your questions to the best of our abilities. Thank you very much.
Although the preceding classification of SMA is useful to patients, families, and the medical team working with them, it must be emphasized that SMA Types I, II, and III (and in some cases SMA Type – IV) represent a continuum. Additional understanding of the gene defects will undoubtedly explain the tremendous clinical variation that children and young adults with SMA demonstrate.
The above was prepared for FightSMA by: Robert T. Leshner, M.D., Professor, Neurology and Pediatrics, Children’s National Medical Center. Special thanks to Metro Productions for the pro bono production of Dr. Leshner’s video.