Case Series: Spinraza Improves Hand Dexterity in SMA Type 2 Children

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by Steve Bryson PhD |

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Spinraza (nusinersen) improved fine manual dexterity — the ability to make coordinated finger movements to grasp and manipulate objects — in both hands of five children with spinal muscular atrophy (SMA) type 2 over 1.5 years of treatment, a case series study showed.

This study “is the first to investigate and demonstrate the effect of [Spinraza] on fine manual dexterity in patients with SMA type 2,” the researchers wrote.

“Further studies including larger numbers of patients are required to verify our findings,” the team wrote, but added that it is possible that Spinraza may be able “to reduce the gap with the normal fine motor milestone” in infants with SMA type 2.

The researchers noted that manual dexterity was measured using the Purdue Pegboard (PP) test, which can be added to existing motor assessment tools to provide a more thorough motor evaluation of SMA patients.

The study, “Improvement in Fine Manual Dexterity in Children with Spinal Muscular Atrophy Type 2 after Nusinersen Injection: A Case Series,” was published in the journal Children.

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Spinraza is a disease-modifying therapy approved to treat all types of SMA. It works by increasing the amounts of SMN, a protein necessary for the health of motor neurons, or nerve cells that control voluntary movements. A lack of SMN leads to progressive muscle weakness and atrophy (shrinkage).

Although Spinraza treatment has consistently been shown to improve both gross (overall) and upper extremity motor function, tools for assessing the therapy’s impact on fine manual dexterity are limited in scope.

The Purdue Pegboard (PP) test is a standardized tool to measure fine manual dexterity in both hands of people with neurological impairments or developmental delays.

The PP test involves picking up pegs one at a time from a cup on top of a pegboard and inserting them into the available holes as quickly as possible. The number of pegs inserted in 30 seconds is considered a measure of fine manual dexterity.

Investigators at the Chungbuk National University Hospital, in Korea, applied the PP test to a group of five girls treated with Spinraza who had SMA type 2, also called chronic infantile SMA, which usually is detected between ages 6–18 months.

“This study is meaningful in that it is the first to report improvements in fine manual dexterity after [Spinraza] administration in patients with SMA type 2,” the team wrote.

In this group, the age at SMA symptom onset ranged between 12 and 14 months, and the age at diagnosis varied from 2 months to 2 years. The girls were anywhere from 3 years old to nearly 7 when they began taking Spinraza.

Spinraza was given by injection into the fluid surrounding the spinal cord at a dose of 12 mg on days 0 (first), 14, 28, and 63 (about two months). Following the initial dosing, it was given once every four months for maintenance.

Before applying the PP test, the team examined the children’s gross motor function using the Hammersmith Functional Motor Scale – expanded version (HFMSE), before treatment (baseline) and after 18 months of Spinraza therapy, or at 1.5 years.

HFMSE is a 33-item assessment with scores for each item spanning from 0 (no response) to 2 (full response), and a total score from 0 to 66. Higher scores reflect improved gross motor function.

At baseline, HFMSE scores ranged from 10 to 40 points. After 18 months of Spinraza treatment, scores improved in all patients — from a minimum increase of 3 points to a maximum of 10 points.

Although little or no changes were found in standing, walking, running, or jumping ability, improvements in gross motor function were found. These improvements related to more control of the trunk region, including rolling, lying, sitting, crawling, and kneeling.

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In applying the PP test to the dominant (preferred) hand before treatment, the children’s scores ranged from 2 to 7. Compared with others of the same age and sex before Spinraza, the scores were lower in all patients except for one.

After 18 months of treatment, the PP scores in the dominant hand varied from 6 to 14, representing a relative improvement of 80 to 225% compared with the girls’ baseline scores.

Before treatment, PP scores in the non-dominant hand ranged from 1 to 6, but improved to 6 to 13 after Spinraza treatment. Those changes reflect a relative increase from 60 to 500% compared with baseline.

“Changes in PP scores from baseline to 18 months confirmed that [Spinraza] treatment improved fine manual dexterity in patients with SMA type 2,” the researchers concluded, also noting these skills were easy to assess with this test.

“Simply adding the PP test to the existing battery of evaluation tools may help to provide a more thorough assessment of the fine manual dexterity essential for daily living activities in patients with SMA type 2,” the researchers concluded, noting that additional studies with larger patient groups are needed to confirm these findings.

The researchers also noted that, because the study only included children with SMA type 2, there is no data on Spinraza’s effect on fine manual dexterity in patients with other SMA subtypes.

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