Suggest Treatment For Developmental Delay In A Child

Hello sir/madam, one child showing developmental delay, like at the age of 14 months it cannot sit, cannot hold things etc. after getting brains MRI, one of doctor told continue physical excercise, and other relative in medical field told brain cells are not active(dead), so transplantation of bone marrow cells is needed. so could be the problem n how can one diagnose it better.