Walking ability in type 3 SMA patients is significantly impaired during adolescence, according to recent research. Type 3 SMA, also known as Kugelberg-Welander disease, is a milder form of SMA. Muscle weakness in type 3 SMA mainly affects patients’ limb movements, and children are generally able to stand and walk. These abilities decrease over time, however. Symptoms usually appear between 18 months and early teens. Symptom onset before age 3 is classified as type 3A SMA, and onset at later ages as type 3B — considered a milder SMA subtype. However, while SMA is thought to be a largely stable disorder, recent studies have highlighted different rates of progression based on age and function. In patients who cannot walk, gross motor function improves until about age 5, then worsens until about age 15, followed by a relatively stable phase in late adolescence and adulthood. While ambulatory patients have a similar disease progression to that of non-ambulatory patients, a more specific assessment may be necessary to identify changes in walking function. Researchers used data from three prospective natural history studies to evaluate changes in walking ability in 73 individuals with type 3 SMA who were able to walk without support for at least 10 meters. The team used the the six-minute walk test, a valid and reliable functional assessment that measures the distance a person can walk in six minutes. While the 6MWT was initially developed to evaluate functional exercise capacity in heart- and lung-associated diseases, it has become a valuable and reliable test to measure functional walking ability in SMA patients. The study showed that the ability to walk strongly deteriorated during adolescence with a loss of 20.8 meters per year, and slowly declined again through adulthood with a loss of 9.7 meters per year. The age around puberty appeared to be the most vulnerable period in ambulant patients, with researchers hypothesizing that weight gain and growth associated with puberty could contribute toward a greater decline in walking capacity. The study authors emphasized that when designing future clinical trials with SMA patients, it is important to understand the natural history of the disease and identify disease trajectories as measured by the 6MWT to better interpret patients' response to treatment.
News
Taking care of a child with spinal muscular atrophy (SMA) significantly affects several aspects of families’ lives, including finances, career choices, social life, and mental health, according to an Australian study. The study, “Financial, opportunity and psychosocial costs of spinal muscular atrophy: an exploratory qualitative analysis…
Reldesemtiv improved muscle strength for walking and respiration in a dose-dependent manner in spinal muscular atrophy (SMA) patients, data from a Phase 2 clinical trial show. As a fast muscle activator, reldesemtiv will not treat the underlying causes of SMA — a lack of the SMN protein to nourish muscles…
A new way of restoring potentially adequate levels of survival motor neuron (SMN) — the protein missing in spinal muscular atrophy (SMA) — uses small molecules that target the structure of an intermediate player in this protein’s production. The study on this approach, “Targeting RNA structure in SMN2…
A pathway known as the cell’s “cleaning system” may be a promising target of alternative approaches to treating spinal muscular atrophy (SMA) — ones that look beyond the disease-causing mutation. This possibility is the focus of the perspective article, “Autophagy inhibition: a…
Two specific mutations may help in identifying people who are carriers of spinal muscular atrophy (SMA) — those who do not have the disease but can pass it to children — and should be aware before starting a family, a study from Spain reports. The study, “Utility…
Neurological health depends as much on signals sent by the body’s leg muscles to the brain as it does on those sent from the brain to the muscles, according to a recent study. These results offer new clues as to why patients with neurological diseases such as spinal muscular atrophy (SMA)…
Exicure’s gene c prolongs survival, increases the amount of SMN proteins, and shows limited toxicity in a mouse model of the disease, study data show. The investigational compound is a spherical nucleic acid (SNA) formulation of nusinersen, the active substance in Spinraza, made by Biogen and approved to treat all…
Decreased levels of an enzyme lead to cellular dysfunction and neuronal degeneration involved in the development of spinal muscular atrophy (SMA), a new mouse study suggests. The study, “Neuronal activity regulates DROSHA via autophagy in spinal muscular atrophy,” was published in Scientific Reports. An enzyme called DROSHA regulates the…
Targeted therapies or dietary supplements that work to improve the metabolism of certain molecules in muscle cells may slow the progression of spinal muscular atrophy (SMA), results of an early study in mice show. The study, “Interventions Targeting Glucocorticoid-Krüppel-like Factor 15-Branched-Chain Amino Acid Signaling Improve Disease Phenotypes…
