If the body’s immune system recognizes a cancer, then it may mount an immunological attack against that cancer. However, in so doing, it may mistakenly also attack some of the body’s healthy (noncancerous) cells. This is called a paraneoplastic syndrome. When a paraneoplastic syndrome involves the brain, it often attacks the cerebellum, which can result in unsteadiness, clumsiness, and deficits in coordination. Workup may include imaging studies and serum antibody studies. If a cancer is discovered, then the treatment is removal of the cancer.