A7-month old female client presents to the clinic to establish care. during the visit, the parents report that their daughter was developing as expected during the first 5 months of life, but they fear that her development has plateaued. over the last two months she has become withdrawn and has lost skills previously performed like partial hand skills and acquired spoken language. the provider notes on exam excessive bruxism, periods of apnea followed by hyperpnea, hand wringing, and spastic paraparesis. what is the most likely diagnosis?