For parents and caregivers of children with spinal muscular atrophy (SMA), every milestone is momentous. Measuring motor function — how well a child is able to move and control their muscles — is also a vital aspect of diagnosing and treating pediatric SMA.

Doctors use a variety of tests to measure motor function accurately, since the results help determine how severe the disease is. The Children’s Hospital of Philadelphia Infant Test of Neuromuscular Disorders (CHOP INTEND) examination is a tool designed to help measure motor abilities in children with SMA.

What Is the CHOP INTEND Motor Test?

CHOP INTEND provides information about how strong a child’s muscles are and how well the child can control these muscles. The outcome measures motor milestones (specific physical skills usually achieved at certain points during development). It’s the most popular test used to assess motor function in people with SMA.

CHOP INTEND was originally designed as a test for infants with SMA type 1 (Werdnig-Hoffmann disease). This type of SMA is usually diagnosed within the first six months of life and leads to many muscle problems. In more recent years, however, studies have found that CHOP INTEND may help measure muscle function for adults with SMA type 2 who are experiencing severe muscle weakness.

Researchers developed CHOP INTEND after studying how SMA progresses over time when left untreated. CHOP INTEND is based on older motor skills tests, including the Test of Infant Motor Performance.

How Do Doctors Use CHOP INTEND?

CHOP INTEND is often used during regular doctors’ visits. It’s also useful within clinical trials where it helps researchers measure baseline motor function and assess the effectiveness of SMA treatments.

Measuring Motor Function Over Time

Doctors can use CHOP INTEND to assess motor skills when a person is first diagnosed with SMA. Then the test can be performed regularly to see how their physical function is changing over time.

Doctors may also use other tests to measure motor function, such as the Hammersmith Infant Neurological Examination, the Hammersmith Functional Motor Scale, and the Motor Function Measure. The tests that a child receives depend on their age, type of SMA, and whether they are able to sit or walk. CHOP INTEND is most useful for very young infants or children, as well as for older children or adults experiencing extreme muscle weakness.

Using CHOP INTEND in Clinical Trials

This assessment is also useful when evaluating potential new SMA treatments. For example, if a new therapy is effective, people receiving it may see an increase in their CHOP INTEND scores.

This test has been used in several clinical trials and studies for medications including:

• Nusinersen (Spinraza) — CHOP INTEND scores increased for infants who took this drug.
• Abeparvovec-xioi (Zolgensma) — This gene therapy led to a large improvement in CHOP INTEND scores.
• Risdiplam (Evrysdi) — Infants given risdiplam had much higher CHOP INTEND scores than untreated infants.

How Is a CHOP INTEND Test Conducted?

Doctors often perform motor function tests every six months for children with SMA. In certain cases, a doctor may recommend that these tests be carried out more or less often.

The CHOP INTEND test is given by a doctor or physical therapist and typically takes 10 to 15 minutes. During this time, the health care provider will work with the caregiver to test different motor skills. To get the most accurate results, the person being tested should be relatively comfortable — they shouldn’t be tired or hungry.

During CHOP INTEND, the health care provider measures 16 types of muscle movements, including head control (keeping the head upright), elbow flexion and knee extension (bending the joints), arm and leg mobility, and hand grip. Each of the 16 motor skills is given a score from zero to 4:

• A zero indicates that the person can’t complete the movement.
• A midrange score of 1, 2, or 3 means the person can partially perform the motor skill.
• A 4 means that the person can complete the movement on their own, without assistance.

All these scores are added to give one total score. The highest possible CHOP INTEND score is 64.

What Does the CHOP INTEND Score Mean?

Infants with SMA generally have a lower CHOP INTEND score than children without SMA. A low score may indicate that a child is experiencing muscle weakness from SMA. Other factors, such as age and developmental status, may also affect the final score.

If a person’s SMA is left untreated, their CHOP INTEND score will decrease as their condition progresses and their muscle weakness worsens. CHOP INTEND scores also tend to drop gradually after diagnosis.

A person’s genetics also affects their SMA score. SMA develops when people don’t have a working survival motor neuron 1 (SMN1) gene. As a result, the cells don’t make enough survival motor neuron (SMN) protein. This protein is important for healthy motor neurons — nerve cells that connect the brain to the muscles.

Another SMN gene, SMN2, also makes SMN protein, although not as much as SMN1. People with more copies of the SMN2 gene make more SMN protein. Studies have found that people with fewer copies of SMN2 tend to have more severe disease and lower CHOP INTEND scores.

Talk With Others Who Understand

On mySMAteam, the social network for people with spinal muscular atrophy and their loved ones, more than 2,000 members come together to ask questions, give advice, and share their stories with others who understand life with SMA.

Have you or your child had your motor function assessed using the CHOP INTEND motor test? Share your experiences in the comments below, or start a conversation by posting on your Activities page.