What did dr. mckhann observe in the children in beijing and why did this observation lead him to question the original diagnosis of guillain-barrã© syndrome?

I believe the answer is Children were not able to move but they did have sensory function.
The main cause of the Guillain-barra syndrome is the fact that patient's own immune system is attacking his/her own peripheral nervous system. 
The original diagnosis stated that the damage in sensory function would cause patient unable perceive sensations properly, but still able to make little movement.