Catatonia is a state of stupor or unresponsiveness in a person who is otherwise awake. Catatonia can occur in association with a psychiatric disorder, like schizophrenia, or in association with a medical condition such as encephalitis. In some patients, catatonia may be present without a known cause. Catatonia is usually episodic, meaning that episodes of catatonia come and go. Symptoms that accompany catatonia can include rigidity, staring, withdrawal, immobility, posturing, and grimacing. Since a person with catatonia cannot give an accurate medical history, it is important in making a diagnosis to determine the specific symptoms from others who have observed the catatonic state. Some causes of catatonic behavior, like nonconvulsive status epilepticus or neuroleptic malignant syndrome, are medical emergencies.

Source: http://www.rxlist.com