Topiramate for the Prophylactic Treatment of Cyclic Vomiting Syndrome in Children

Inclusion Criteria: * Meet the2004 ICHD Criteria for Cyclical Vomiting. * 1 vomiting attack lasting \> 24 hours duration for 3 consecutive months * 4-12 years of age. * If female, subjects must: 1. be premenarchal or otherwise incapable of pregnancy, or 2. have practiced one of the following methods of contraception for at least one month prior to study entry: hormonal contraceptives, spermicide and barrier, intrauterine device, partner sterility, or 3. be practicing abstinence and agree to continue abstinence or to use an acceptable method of contraception (as listed above) should sexual activity commence. * Able to take oral medication in tablet form or sprinkle form * Subjects or their guardians must be willing and able to: a) read and comprehend written instructions, b) complete the assessment forms, c) return for regular visits, and d) adhere to medication regimens. * Subjects (or their legally acceptable representative) must have signed an informed consent document Exclusion Criteria * Have taken topiramate within 14 days prior to the start of the prospective baseline period. * Have taken certain medications for cyclical vomiting prophylaxis * Have progressive neurological disorder or a structural disorder of the brain from birth, trauma or past infection. * Subjects who have taken any medications for migraine prophylaxis, within 2 weeks of the start of the prospective baseline period. * Subjects starting non-pharmacologic prophylactic approaches (e.g., acupuncture, biofeedback, chiropractic methods) within 1 month prior to Visit 1. * Require continuing treatment with anticonvulsant therapy for a non-migraine condition. * Significant major psychiatric disorder (e.g., major depression) or subjects receiving anti-psychotic medication. * History of attempted suicide or suicidal tendencies. * History of substance abuse. * Pregnant or lactating females. * Have clinically unstable neurological, cardiovascular, gastrointestinal, musculoskeletal, pulmonary or other disease. * Have any disease or condition that could compromise the function of those body systems that could result in altered absorption, excess accumulation, or impaired metabolism or excretion of the test medications (e.g., abnormal renal and/or hepatic function). * Have active liver disease. * Have received an investigational drug or used an investigational device within 30 days of study entry. * Employees of the investigator, study center, or sponsor (i.e., principal investigator, sub-investigator(s), study coordinators, other study staff, employees, or contractors of each), with direct involvement in the proposed study or other studies under the direction of that investigator, study center or sponsor, as well as family members of the employees or the investigator.