Hard to watch, and hard not to keep watching, the HBO documentary "Coma" is not actually about coma but about what comes after. (The more accurate "Traumatic Brain Injury" isn't quite as arresting a title.) A state of profound unconsciousness from which a person cannot wake, a coma provides no information; whatever there is to say about it, there is nothing there to see. It is a dark pool. When the eyes open, the coma ends and the questions begin.
The idea here is simple. Director Liz Garbus (the Oscar-nominated, Emmy-winning "The Farm: Angola, USA") follows four patients at the Center for Head Injuries at the JFK Medical Center in Edison, N.J., over the course of a year, during which time two improve and two do not. When we meet them, all have already emerged into either a vegetative state (awake but unaware) or a state of minimal consciousness (in which a patient fitfully exhibits signs of deliberate response). All are young or relatively young; two fell from great heights, two were injured in car accidents.
Garbus gives a little social-historical context through a medley of clips touching on some of the best-known cases, including Karen Ann Quinlan, Sunny von Bülow, Terry Schiavo and Terry Wallis, who in 2004 began to speak after 19 years in a minimally conscious state. (The subject stays in the news: In March, a Colorado woman awoke from six years in a vegetative state, only to slip away again after three days.
While the camera remains dispassionate, the filmmakers clearly have an agenda. Spurred by the Terri Schiavo media spectacle in Florida, they set out to show that it's difficult and sometimes impossible to determine what's going on in the brain, even when a patient seems conscious. One of those being treated here, for example, refuses to cooperate with therapists. Further testing shows that he can read written words but can no longer hear.