Cortical Excitability in Cyclic Vomiting Syndrome

This exploratory study will determine if there are differences in cortical excitability between patients suffering from cyclic vomiting syndrome (CVS) and healthy control subjects, as assessed by a non-invasive method of brain stimulation (Transcranial Magnetic Stimulation, TMS).

Inclusion Criteria: * diagnosis of CVS Exclusion Criteria: * history of CVS (for healthy control population only) * psychosis or altered cognitive status * history of head injury, metal in the skull, stroke, or a history of seizures or a history of syncope (fainting or passing out) * implantable devices, such as a pacemaker or nerve stimulator * current use of the following medications or use of substances which are known to lower the seizure threshold: clozapine (Clozaril), chlorpromazine (Thorazine), amphetamines or methamphetamine, Ecstasy, Ketamine, Angel Dust/PCP, cocaine, or 3 or more alcoholic drinks per day * pregnancy