Spinal muscular atrophy (SMA) is a neuromuscular disease that, if left untreated, causes a progressive decline in abilities and functions — including sitting, standing, walking, eating, swallowing, and breathing. Over the past few years, new treatments for SMA have been introduced that appear to be effective in slowing the progression of the condition.
Because SMA causes progressive muscle weakness, some doctors recommend assessments called motor function tests about every six months. Repeating these tests over time helps to ensure that the person living with SMA is getting the most appropriate treatment and assistance available to them at every stage, maximizing their quality of life.
Motor function refers to our central nervous system’s ability to control our muscles. It is a complex process that involves different parts of the brain, the spinal cord, and specialized nerve cells called motor neurons. Healthy motor neurons transmit the brain’s instructions for movement to our muscles. In people with SMA, motor neurons can become degraded over time. This leads to loss of muscle strength and control.
Doctors use many different tests to assess motor function. These tests have been developed and refined to better assess different conditions, including muscular dystrophy, amyotrophic lateral sclerosis, multiple sclerosis, and others. All motor function tests measure muscle movement and control, such as the ability to crawl, kick, rise to standing, grip, walk, and more. The tests are not invasive.
Your neurologist, physical therapist, or other health care specialists may use a variety of methods to track you or your child’s physical progress and achievement of motor milestones.
The following tests have been adapted to be accessible and meaningful for those with SMA in particular. This means they factor in possible energy loss and other changes that could affect performance as someone completes the assessment. Ask your specialist if you have any questions or concerns about the appropriateness of any test they recommend.
Short for “Children’s Hospital of Philadelphia Infant Test of Neuromuscular Disorders,” CHOP INTEND is the most widely used scale worldwide to assess those with SMA. The test was introduced in 2010 by researchers at the Children’s Hospital of Philadelphia to more quickly and simply assess motor function in infants and children with diminished abilities and stamina. The exam often takes between 10 and 15 minutes. It assesses things like head movement, rolling, and grip strength.
Read more about the CHOP INTEND motor test.
The Hammersmith Infant Neurological Examination (HINE) was developed to track developmental milestones in the general population. It includes movement abilities and also examines posture, muscle tone, and reflexes.
The HINE was later refined for the SMA population to measure smaller increments of improvement. This refined HINE is called the Hammersmith Infant Neurological Examination — Part 2 (HINE-2). This tool works on a point system. It includes additional tests of ability to kick, crawl, and roll. This tool and points system is commonly used to numerically measure and track someone’s progress over time.
Read more about the HINE-2 motor test.
The Hammersmith Functional Motor Scale (HFMS) was introduced in 2003. It assesses someone’s ability to walk unaided for a short time. It can also be used by orthopedic specialists to assess someone’s ability to use different kinds of mobility aids.
The HFMS has been modified over time. Its expansions and refinements include:
Read more about the Hammersmith Functional Motor Scale.
The Motor Function Measure (MFM) was developed to assess people with a variety of conditions. In its original form, it was too strenuous for many people with SMA. It has been adapted for those with SMA as two assessments: the Motor Function Measure-20 (MFM-20) and the Gross Motor Function Measure (GMFM).
The MFM-20 removed some assessments that many people with SMA found difficult. It now includes 20 measures with some specialized for the SMA population, like transferring from a bed to a wheelchair.
The GMFM measures 88 abilities, including rolling, walking, running, and jumping (if applicable). This assessment takes longer to perform than many others, but it includes specific measures that other assessments don’t. It also measures smaller increments of change to create a more precise snapshot of abilities.
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Clinicians use the Six-Minute Walk Test (or 6MWT) to measure someone’s ability to walk continuously for six minutes. Participants may rest by standing still, but they may not sit. Because this test measures muscle strength and muscle control as well as aerobic capacity and endurance, it is not applicable to some people with SMA. The test also may not be appropriate for people with conditions affecting their heart and lungs, as people with these conditions can have reduced aerobic endurance.
Quantitative Muscle Testing uses a mechanical device called a dynamometer to measure the force produced by actions like gripping or pulling. Participants are asked to hold certain motions for a period of time (isometric exercises). Since this test requires close attention and cooperation, it may not be suitable for small children.
The Neuromuscular Gross Motor Outcome includes 50 assessments, including finger movement and fast walking (if applicable). This comprehensive test was designed to measure the strength of the entire body.
The Revised Upper Limb Module was developed to accommodate those living with SMA who have stiffened muscles or significant weakness, especially in their arms and hands. It involves precise tasks such as tracing a path on paper, lifting weighted tokens, and more.
As treatments for SMA continue to improve, it becomes even more crucial to measure people’s progress over time — especially children with SMA. Regular testing helps researchers and practitioners better understand what is working and what is not, leading to improvements in treatment for everyone. The development and improvement of motor function scales is an important part of that process.
This is just one of many reasons why it is important to keep regular appointments with your medical providers and specialists. Doing so will not only help to ensure that you or your loved ones are getting the most up-to-date treatments; it will also help everyone better understand how to best treat those living with SMA.
On mySMAteam, the social network for people with spinal muscular atrophy and their loved ones, more than 1,300 members come together to ask questions, give advice, and share their stories with others who understand life with SMA.
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