The parotids have not been traditionally considered an organ at risk / avoidance structure in whole brain radiation. However, patients receiving whole brain radiation sometimes complain of dry mouth. Investigators hypothesize that standard whole brain radiation fields cause an acute measurable increase in xerostomia at one month post-radiation, and that the severity of xerostomia is related to the dose received by the parotids. In this study, investigators will use the validated University of Michigan Xerostomia Questionnaire to prospectively collect baseline and post-radiation xerostomia scores up to 6 months after treatment. The radiation dose to the parotids will be evaluated to assess whether there is a dose-toxicity relationship. Investigators anticipate a total accrual of 60 patients with a goal of 48 evaluable patients.