The seasonal occurrence of three of the more commonly seen central nervous system diseases is again coming to the forefront. This review will center around the etiology and clinical differentiation of thrombo-embolic memingoencephalitis (TEM), polioencephalomalacia, and listeriosis. There are many conditions which may give similar clinical symptoms; however with a thorough central nervous system examination, each disease has certain peculiarities which may help the practitioner reach a clinical diagnosis.