Neurocysticercosis

Neurocysticercosis is the most common parasitic infection of the central nervous system worldwide. It is caused by larvae of the tapeworm Taenia solium, and the worms form cysts within the body. This tapeworm is usually found in pork, but can be killed by cooking your food to the right temperature, or by freezing it for a prolonged period of time.
Cysticercosis at Wikipedia.