[1] St Michaels Hosp, Div Neurosurg, Toronto, ON M5B 1W8, Canada
[2] Univ Toronto, Fac Med Educ & Publ Hlth, Toronto, ON, Canada
[3] St Michaels Hosp, Dept Pathol, Div Endocrinol, Toronto, ON M5B 1W8, Canada
[4] St Michaels Hosp, Dept Otorhinolaryngol & Head & Neck Surg, Toronto, ON M5B 1W8, Canada
[5] Cairo Univ Hosp, Div Neurosurg, Cairo, Egypt