Table 2 Description of GMFC-MLD category definitions, with illustrative quotes from caregivers

0: Walking without support with quality of performance normal for age

• Yes, I’d say he was walking and normal for age up until 18 months (Interview 9)

• Yeah, so, with the walking without support, she was not … she was not able to do 0. So, I would say 0, she couldn’t do (Interview 11)

• She probably was at that level for 5 months (Interview 1)

• Yes. She hit all of her milestones, walking all the way up to two and a half would be … was normal for her (Interview 3)

1: Walking without support but with reduced quality of performance (e.g., instability when standing or walking)

• Yes, the age for that would have been … that winter, she would have been 2 [years old]. That would have been during the third … the start of the second month and into about the fourth month (Interview 3)

• Yeah, number 1 definitely had applied. I would say he was about a year and a half to two and a half. Two or two and a half (Interview 7)

• Walking without support was reduced. I would say no, because she never really could do … besides like cruising, she couldn’t really do 1 either. Walking with support. So, I would say with support maybe, but that would have to be like with one of us holding her hands to kind of help her (Interview 11)

2: Walking with support. Walking without support not possible (fewer than 5 steps)

• Support, that’s with his walker, so he was doing that through [date removed]. Or not all the way through [date removed], but I know through [date removed], so 28 months. 28, 29 months (Interview 9)

• She was able to for every so often. It would have been around [date removed], so I guess that would be two and a half years old, she was still able to, but she depended on us for help, and that pretty much lasted until … I would say until about [5 months later] (Interview 3)

3: Sitting without support and locomotion such as crawling or rolling. Walking with or without support not possible

• That I would say, she could really only sit without positioning with pillows and things like that from maybe 3 … the first 3 months of diagnosis, maybe like 3 months from diagnosis (Interview 5)

• Sitting without support, he did that … he only did that through [date removed], so that was only 1 more month, so 30 months (Interview 9)

4a: Sitting without support but no locomotion

OR

4b: Sitting without support not possible, but locomotion such as crawling or rolling

• [4a] Yeah. Yeah, I’d say that, probably did for a period of time. I’d say she probably did that for like maybe through May possibly June (Interview 1)

• [4a] Yeah. And again, that would have been like right around the same time because that sort of progression was really rapid (Interview 11)

• [4b] No, I would say that once the ability went, there was really no more, trying to move her body on the floor after that (Interview 11)

• I would say 4b is relevant. Probably 6 months (Interview 1)

• [4a] No. I don’t think so. I think she needed… still crawl or roll around when she could sit unsupported (Interview 8)

5: No locomotion nor sitting without support, but head control is possible

• That was definitely relevant. That was kind of the last thing she could move was her head. And I would say that brings her up to about 6. Maybe another 6 months or so, she could still kind of turn her head back and forth (Interview 1)

• So that was pretty much, that was pretty much [date removed], yeah, that was by her [event removed] so 5 or 6 months out (Interview 5)

• 5 I think is where he’s at now, and then 6, not yet (Interview 7)

6: Loss of any locomotion as well as loss of any head and trunk control

• Head and trunk control were just the steady decline like she couldn’t … yes she had lost her control but she has lost more and more of her control. Like in the beginning, she used to kind of rock teeter-totter and rock to try to hold herself up, you know her head, now she might be able to turn her head slightly, definitely can’t hold it up (Interview 5)

• I’d say it was probably by about [date removed], she really needed full support on her body. She was, by then, she had a neck brace to support … to help hold her head up (Interview 8)

• He is a 100% dependent on somebody to move him, move his arms, move his head for positioning. He hasn’t smiled for me since [date removed]. His eyes are still … he twinkles with his eyes (Interview 9)