[Yahoo! Chiebukuro Best Answer] What was the name of my younger brother's disability?

Q. To those knowledgeable about disabilities: My younger brother was disabled. He has passed away, but I would like to remember and know what the name of his disability was. Please tell me.

It is difficult to bring up the topic with my parents, so I cannot ask them.
He passed away around the age of 6, but I do not know the cause of death.
He could not stand or speak on his own.
He required assistance with both eating and excretion.
Even as he got older, he moved around in a stroller.
He often wore a helmet to prevent falls.
Sometimes he had symptoms like seizures? It felt like his breathing stopped and his whole body would shake.
Was speech completely impossible? Or rather, it was like 'ah' or 'ya'.
I searched until I thought it might be Down syndrome, but even with Down syndrome, it seems they can stand on their own or speak to some extent...
My brother couldn't do those things either, so I was curious about the name of the condition.
I would appreciate it if someone knowledgeable could tell me.
Thank you.
My father and mother do not have any physical or mental disabilities.
My own body is a little different from normal, but not to the extent of receiving a disability certificate.
Physical disability

A. It is thought to be for minimizing head injuries when falling while walking alone due to an illness or disability.

I cannot definitively state what illness or disability it was, but muscular dystrophy, spinocerebellar degeneration, amyotrophic lateral sclerosis, or cerebral palsy might be possibilities. However, in children, I have the impression that those with muscular dystrophy wear headgear more often.