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Midline location of tumour is a risk factor for postoperative vomiting in children requiring posterior fossa tumour resection.

Children requiring posterior fossa brain tumour surgery form a unique and significant neuro-oncology population. Postoperative vomiting (POV) is a problem for these children. Also, severe vomiting that is refractory to treatment has been seen clinically in these children, but it is not well described in the literature. A subgroup of children requiring surgery for posterior fossa brain tumours (n=153) from a larger six-year retrospective chart audit (n=249) at two Canadian children's hospitals were reviewed for the presence of no, mild, moderate, and severe POV. Inter-rater reliability was established at 94% following a blinded process of comparing POV severity rankings between two data collector/researchers. Discrepancies were resolved through discussion in order to establish a consensus severity score. Findings from multivariable logistic regression analyses indicated that when age and intraoperative use of ondansetron were controlled for, the location of a tumour in a midline location had no overall effect (adjusted OR=1.37, 95% confidence interval: 0.64-2.96, p=0.43), but greater odds of severe vomiting (adjusted OR=7.08, 95% confidence interval: 2.56-19.64, p<0.001). These results support theories of modulation of vomiting by the medullary midline and clinical observations that children with midline posterior fossa tumours are at greater risk for severe refractory vomiting. The development of clinical practice guidelines and further research to study the effectiveness of novel, multimodal antiemetic therapies are required for this patient population.