last week my son got fall on back of his head from a chair..he fall quite hard but no bump/swollen visible..go to clinic doc says ok..so i assume he is ok la..then 2 days after the incident he vomitting 3 times n complaining got headache..he cannot sleep..bring  to GH but the doc also says ok..then the next morning he still complaining about the headache.then i went to paeditrician let the doc check throughly n give a referral letter to GH..at GH they suggest to do MRI to scan my son's head..to make story short they sedate my son with ketamine n do the MRI..luckily my son's head is fine but my concern rite now is after the MRI process my son being stutter,something that i didnt notice b4 this..not sure its the adverse effect of ketamine or he just being fooling around..do ketamine is a neurotoxic substance that can make a child/toddler be stutter?