3 SMA type 1 patients show better finger, facial control with Spinraza
Three young people with severe spinal muscular atrophy (SMA) type 1 and treated with Spinraza (nusinersen) after their disease had already significantly advanced were seen by their caregivers to better control their finger and face movements, according to a Japanese report.
The gains helped the patients, who depended on a breathing tube, communicate better with their caregivers. The patients also tended to have increases in the electrical activity of their motor neurons, the specialized nerve cells that communicate with muscles and are progressively lost in SMA.
The study, “Nusinersen induces detectable changes in compound motor action potential response in spinal muscular atrophy type 1 patients with severe impairment of motor function,” was published in Brain and Development.
SMA type 1 is a severe, infantile-onset form of the disease. Left untreated, patients typically die by age 2. Those who survive beyond that fail to meet motor milestones and are reliant on medical interventions such as a breathing tube, or tracheostomy.
Spinraza, a disease-modifying therapy approved for all types of SMA, has improved patients’ motor function in clinical trials, but most studies have been with younger patients who weren’t severely affected, according to the authors.
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Spinraza’s effects on older patients with advanced disease
Studies of Spinraza on older SMA type 1 patients who depend on a breathing tube are lacking, leading scientists in Japan to retrospectively analyze responses to the therapy by three SMA type 1 patients with severe motor impairments who didn’t start it until after age 2.
The patients were ages 3, 4, and 16 when they started treatment. All had severely impaired motor function and couldn’t control their heads or roll over. They could only move their fingers or toes, and their faces slightly. They were all dependent on breathing and feeding tubes and remained on Spinraza for more than three years without having any significant side effects.
Motor function was monitored using the the Children’s Hospital of Philadelphia infant test of neuromuscular disorders (CHOP-INTEND). While CHOP-INTEND scores didn’t improve significantly by the last follow-up, some motor benefits were noted by caregivers, specifically, all the children showed improved finger or facial muscle movements.
This enabled them to more clearly communicate with their caregivers. One patient who used her fingers to control a communication tool was now able to do so more accurately. Another could more easily give their caregiver a thumbs-up sign to communicate.
Improved function of facial muscles made it easier for caregivers to understand patients’ intentions. Facial and finger movements aren’t well captured by CHOP-INTEND scores, which may not be “sensitive enough to evaluate treatment efficacy,” the researchers said.
“All the caregivers were highly satisfied with the improvement, even if it was slight, which could not have happened in the natural course of the disease,” they said.
The health of motor neurons was also monitored by measuring compound motor action potentials, or CMAPs, which measure electrical activity when motor neurons fire and elicit a muscle contraction.
As is common in SMA, CMAPs were markedly diminished before treatment started and were often undetectable. After two months of treatment, some CMAPs that had been undetectable showed trace responses, indicating increased motor neuron activity, which generally improved over time.
While these changes are not substantial enough to “recover gross motor function,” as has been associated with Spinraza in earlier-treated patients, the finding still indicates benefits to the motor neurons of those treated later, the researchers said.
Given the small nature of the study, “collaboration with other facilities is desired and further investigations … are needed to objectively evaluate the efficacy of therapeutic interventions,” for late-treated patients, they said.
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