Sean J. Pittock, M.D., an autoimmune neurologist at Mayo Clinic, discusses a newly discovered autoimmune disease that appears to affect men with testicular cancer. Called testicular cancer-associated paraneoplastic encephalitis, the disease causes severe neurological symptoms in men. They progressively lose control of their limbs, eye movements and, in some cases, speech. The disease begins with a testicular tumor, which appears to cause the immune system to attack the brain. Affected men often find themselves misdiagnosed or undiagnosed and appropriate treatment is delayed.