Four kinds of heartache in ‘Coma’

Filmmaker Liz Garbus offers viewers an intimate look at the mysteries of traumatic brain injury with the touching and remarkably informative documentary “Coma” (9 p.m., HBO). “Coma” follows four patients at the Center for Head Injuries in Edison, N.J. Through their stories, we learn the drastic differences between a conscious state, a minimally conscious state and a persistent vegetative state.

Garbus also documents the emotional and financial costs that caring for such patients take on their family and loved ones. A mother gives up her job to be a full-time caretaker for her 19-year-old daughter, whose progress is steady but painfully slow. Lynda, the fiancee of Tom, a victim of a fall, puts her life on hold as he slowly gains mobility and a childlike command of speech. Others are not so lucky and stand vigil as their sons, brothers and friends show flickers of responsiveness only to slip away, probably forever.

Powerful and sad, “Coma” is also a testament to the remarkable strength of the caregivers, both personal and professional.

Tonight’s other highlights

Who needs fireworks? Nothing says “Fourth of July” like spending hour after eye-glazing hour in front of the “Twilight Zone” (8 a.m., Sci Fi) marathon.

A daylong marathon of “Dirty Jobs” (9 a.m., Discovery) kicks off with Mike cleaning sludge. The “Dirty” work continues until 3 a.m., July 4.

It remains to be seen whether “America’s Got Talent” (8 p.m., NBC).

Eleven remain on “On the Lot” (8 p.m., Fox).

A trip to Yale is fraught with meaning on “Gilmore Girls” (8 p.m., CW).

As a firefighter suffers, Gregory faces possible jail time on “House” (9 p.m., Fox).

The big man feels deceived on “Shaq’s Big Challenge” (9 p.m., ABC).

“Critical Situation” (9 p.m., National Geographic) recalls a fatal yacht race.

Treat Williams stars as a novelist accused of killing his wife in the 2007 crime drama “The Staircase Murders” (9 p.m., Lifetime).

A careless journalist sparks a mother’s suicide on “Law & Order: Special Victims Unit” (10 p.m., NBC).

Scheduled on “Primetime” (10 p.m., ABC): family secrets.

“Secret Lives of Women” (10 p.m., WE) looks at women struggling with obsessive-compulsive disorder.