For Parkinson’s patients, deep brain stimulation (DBS) can help control a number of neurological symptoms, like muscle spasms and stiffness. But one weird side effect has surfaced in a string of case studies: Some patients, no matter how good their motor skills, lose their ability to swim after the procedure. Researchers from the University of Zürich in Switzerland published a report today in Neurology identifying nine cases where patients couldn’t stay afloat after DBS. And these people weren’t water-shy, first time doggie paddlers — two of the cases involved former competitive swimmers. And, researchers report, the entire cohort had had...