An 11 year old girl has a 4 month history of abnormal behavior in the form of repeated crying and abnormal movements. On the examination she has jerky involuntary, arrhythmic movements especially in the upper limbs. No history of previous drug intake. The rest of neurological examination is normal.

A 4 year old boy's parents complain that their child has difficulty walking. The child first walked at 13 months of age. On examination, the child is oriented and has enlargement of his calves has been noticed. Family history revealed that the elder son of his aunt has the same condition.

A 7 year old female presents to the emergency room with lower limbs weakness One week prior, she had a fever of 38.5 with vomiting and diarrhea that resolved within 3 days. Neurological examination revealed bilateral symmetrical weakness of the lower limbs.

A 3-year-old boy is brought to you, as his mother is concerned about his attention span. You note that he has very poor eye contact and poor verbal skills (having only a four-word vocabulary). His weight and height are appropriate for his age.