You should be working in close concert with his therapist(s) so you can best help this child in all relevant areas (emotional, social, cognitive). To give you a better understanding of this disorder, take a look at the following websites:
http://www.anxietynetwork.com/spsm.html
http://www.comp-acc.com~diverse/smg/index10.html
http://www.journals.uchicago.edu/CDAB/journal/69/69-1089.htm
http://www.flinet.com/~diverse/smg/abstract.htm
http://www.comp.acc.com/~diverse/smg/links500.htm
Thanks for taking the time to find out how you can help this youngster. Good luck.