In brief
- The Trunk Impairment Scale (TIS) is a standardized clinical assessment that measures trunk motor control in a seated position. It was originally developed for adults after stroke. Studies in children and young people with cerebral palsy have found it reliable and valid, but a 2016 study that tested whether it detects change after therapy found that it did not.
- It assesses three things: static sitting balance (can the child stay upright), dynamic sitting balance (can they move and return to center), and trunk coordination (can they rotate their trunk in a controlled way).
- The TIS was one of three primary outcome measures in the completed clinical trial comparing DMI to the Bobath approach in children with spastic cerebral palsy. The others were the GMFM-88 and the Shoaib Sensorimotor Development Tool.
- Trunk control is the foundation for nearly every gross motor skill DMI targets. An assessment that measures it directly tells you something the GMFM-88 alone does not.
- If your child is being evaluated for DMI or any intensive motor program, the TIS is a reasonable assessment to ask about.
If you have read the cerebral palsy guide on this site, you have seen the Trunk Impairment Scale listed among the outcome measures in the completed clinical trial comparing DMI to the Bobath approach. This post explains what the TIS is, how it complements the GMFM-88, and why trunk control matters specifically when evaluating DMI.
What is the Trunk Impairment Scale?
The Trunk Impairment Scale (TIS) is a standardized clinical assessment of trunk motor control. It was developed by Geert Verheyden and colleagues at Katholieke Universiteit Leuven in Belgium and first published in 2004 in Clinical Rehabilitation. The original TIS was designed for adults who had experienced a stroke. It has since been studied in children and young people with cerebral palsy, as described below.
The key insight behind the TIS is that trunk control is a distinct domain of motor function. A child may improve in mobility (as captured by the GMFM-88) without necessarily improving in trunk stability, or vice versa. Measuring trunk control directly gives a more complete picture than measuring gross motor function alone.
This is especially relevant for DMI. DMI targets automatic postural responses against gravity, and those responses depend heavily on trunk control. An assessment that isolates trunk function can capture changes that a general gross motor measure might miss or show only indirectly.
The three subscales
The TIS has 17 items grouped into three subscales, all assessed with the child sitting:
Static Sitting Balance (3 items, max 7 points)
Can the child hold an upright sitting position? This is the most basic level of trunk control on the scale. The three items test sitting balance with the feet supported, sitting balance with the legs crossed for the child, and sitting balance while the child crosses their own legs. Items are scored 0 to 2 or 0 to 3.
Dynamic Sitting Balance (10 items, max 10 points)
Can the child actively move their trunk while staying seated? The child touches the seat with their elbow on each side and lifts the pelvis from the seat on each side. Several items repeat the same movement so the assessor can score how the trunk moves and whether the child uses compensation strategies. Each item is scored 0 or 1. This subscale directly measures the kind of active postural control DMI is designed to build.
Coordination (4 items, max 6 points)
Can the child rotate their upper trunk and lower trunk separately? The child rotates the shoulder girdle six times and the pelvic girdle six times, each first without and then within a six-second time limit. Items are scored 0 to 1 or 0 to 2.
The total TIS score ranges from 0 to 23, with higher scores indicating better trunk control. Items are not all scored on the same range. Some are scored 0 or 1, others 0 to 2 or 0 to 3, which is why the three subscales have maximum scores of 7, 10 and 6 rather than simply twice the number of items.
What does the TIS tell you that the GMFM-88 does not?
The GMFM-88 measures gross motor function across five dimensions. Its sitting dimension (Dimension B) captures whether a child can sit independently, reach while sitting, and sit up from lying down. But it does not isolate trunk control. A child who sits independently but with poor stability may score the same as a child with good trunk control on the GMFM-88 sitting items, because the GMFM-88 scores completion of the movement rather than quality or stability of the posture.
The TIS captures that difference. Two children may both achieve a 3 (full completion) on a GMFM-88 sitting item such as "sit on mat: maintains, arms free, 3 seconds," but one of them is wobbling, bracing, or using compensatory trunk strategies while the other is stable and efficient. The TIS tells you which is which.
In the DMI trial, the GMFM-88 and the TIS together give a more complete picture than either alone. The GMFM-88 shows whether the child progressed through broad motor categories (sitting, crawling, standing, walking). The TIS shows whether the underlying trunk control improved enough to support that progression.
Psychometric properties in children with cerebral palsy
Four published studies have examined the TIS in children with cerebral palsy. Sæther and Jørgensen (2011) filmed 20 children with CP aged 5 to 12 and found very high agreement between and within observers, with intraclass correlations of 0.94 to 1.00. A follow-up by Saether and colleagues (2013) found high reliability in adolescents aged 13 to 19, and in 37 children and adolescents at GMFCS levels I to IV, TIS scores correlated strongly with GMFM dimension scores (Spearman's rho 0.80 to 0.87), which supports it as a valid measure of trunk control.
A 2022 Rasch analysis by Jung and Choi, published in Children, studied 60 children aged 6 to 12 at all five GMFCS levels, using a modified Korean version of the TIS. It supported the scale measuring a single underlying construct, but identified five items that did not fit the model well — two static sitting balance items, two dynamic sitting balance items, and one coordination item — and of the three subscales, only static sitting balance failed to meet the rating scale criteria.
A 2016 study that tested whether the TIS detects change after therapy found that it did not. Pham and colleagues assessed 26 people with CP aged 8 to 29 before and after three weeks of intensive physical training. Their gross motor scores on the GMFM-66 improved, but there were no significant changes on the TIS, and the authors concluded that its responsiveness could not be documented. None of these four studies included children younger than 5, and the DMI trial enrolled children aged 2 to 4.
What the TIS does not tell you
The TIS measures trunk control in sitting only, in a controlled clinical setting. It does not measure trunk control while standing or walking, or in real-life situations such as sitting in a classroom chair, on a car seat, or on the floor during play. It also does not measure how much effort the child expends to maintain trunk stability. A child who scores well on the TIS but uses visible compensatory tension or fatigues quickly may have different therapy needs from a child who achieves the same score with ease.
Like all standardized assessments, the TIS captures what a child does on demand in a testing situation, not what they do spontaneously at home.
As described above, the 2016 study that tested whether the TIS detects change after therapy found no significant change on it, even though gross motor scores improved. The TIS has also not been studied in children younger than 5.
Why it matters for the DMI clinical trial
The completed trial comparing DMI to the Bobath approach (NCT07238634) listed three primary outcome measures: the GMFM-88, the Trunk Impairment Scale, and the Shoaib Sensorimotor Development Tool. The inclusion of the TIS tells us the researchers considered trunk control a relevant and separable domain of motor function worth measuring independently.
DMI targets antigravity postural responses, and those responses depend on trunk control. Keep the 2016 responsiveness finding in mind when the results appear. A change on the TIS would be notable, because the scale has not previously been shown to detect change after therapy. No change on the TIS would be harder to interpret, because it could mean trunk control did not improve or that the scale did not pick up an improvement.
When the trial results are published, looking at the TIS scores alongside the GMFM-88 scores will give you a more specific picture of what changed and for whom.
What you can do with this information
If your child has cerebral palsy and you are considering DMI, you can ask the therapist whether they assess trunk control and what they use. Not every clinic uses the TIS, and that is not necessarily a problem — some use alternative trunk assessments or rely on clinical observation. But a therapist who can describe how they measure trunk control, or who is willing to use the TIS, is demonstrating a systematic approach to evaluation.
You can also ask: what specifically about your child's trunk control makes DMI a good fit? A therapist who can point to sagging in sitting, poor lateral weight shift, or inability to rotate the trunk is telling you something specific. A therapist who says only that your child needs "better core strength" is being less specific than the evidence warrants.
Where it appears on this site
The Trunk Impairment Scale is listed as a primary outcome measure on our cerebral palsy guide, alongside the GMFM-88 and the Shoaib Sensorimotor Development Tool. It is also relevant to our GMFM-88 explainer, which covers the other main outcome measure from the same trial.
Sources
- Verheyden G, Nieuwboer A, Mertin J, Preger R, Kiekens C, De Weerdt W. The Trunk Impairment Scale: a new tool to measure motor impairment of the trunk after stroke. Clinical Rehabilitation. 2004;18(3):326-334. Sage Journals PubMed
- Jung H, Choi YE. The Psychometric Properties of the Trunk Impairment Scale in Children with Cerebral Palsy. Children. 2022;9(3):435. PMC PubMed
- Sæther R, Jørgensen L. Intra- and inter-observer reliability of the Trunk Impairment Scale for children with cerebral palsy. Research in Developmental Disabilities. 2011;32(2):727-739. PubMed
- Saether R, Helbostad JL, Adde L, Jørgensen L, Vik T. Reliability and validity of the Trunk Impairment Scale in children and adolescents with cerebral palsy. Research in Developmental Disabilities. 2013;34(7):2075-2084. PubMed
- Pham HP, Eidem A, Hansen G, Nyquist A, Vik T, Sæther R. Validity and responsiveness of the Trunk Impairment Scale and Trunk Control Measurement Scale in young individuals with cerebral palsy. Physical & Occupational Therapy in Pediatrics. 2016;36(4):440-452. PubMed
- ClinicalTrials.gov. Effects of DMI vs Bobath on Neuromuscular Development in CP (NCT07238634). ClinicalTrials.gov
Nothing here is medical advice, and no single assessment or score should change your child's care on its own. Discuss anything you read here with your child's pediatrician or therapist.