(CNN) -- Stephen Slevin's 22 months in solitary confinement in a county jail left him traumatized and physically weak, but he'll soon be a multimillionaire for his suffering.

The New Mexico county that locked him up on a drunk driving charge, isolated him from other inmates and accused of essentially forgetting about him for nearly two years agreed this week to settle his lawsuit for $15.5 million.

Slevin, now 59, went to jail in August 2005 as "a well nourished, physically healthy adult," but emerged with a long beard, bed sores, bad teeth and weighing just 133 pounds in June 2007, according to the lawsuit.

Jailers separated Slevin from other inmates because of his history of mental illness, according to the lawsuit filed by Albuquerque civil rights attorney Matthew Coyte in December 2008.

The charges of driving while intoxicated and receiving a stolen vehicle were never prosecuted.

"They threw him in solitary and then ignored him," said Coyte a year ago after a federal jury awarded Slevin $22 million. "He disappeared into delirium, and his mental illness was made worse by being isolated from human contact and a lack of medical care."

Slevin suffers from post-traumatic stress from what he called physical and mental mistreatment by corrections officials in Dona Ana County, which shares a border with Mexico in the southern part of the state.

The county's commissioners agreed this week to drop their appeal of the jury's verdict in return for Slevin accepting the lesser amount.

"The Board of County Commissioners deeply regrets the harm Mr. Slevin suffered during this period," the county said in a statement Thursday. "Over the past seven years, Dona Ana County has made significant improvements to detention center staffing, training, facilities and procedures. Dona Ana County is committed to ensuring consistent and appropriate treatment of every detainee in its care."

Slevin's lawsuit alleged he became malnourished, lost significant weight, developed bedsores, fungus and dental problems and was not aware of his situation or surroundings.

He was transferred to another state facility for two weeks, given a psychiatric evaluation and then sent back to the Dona Ana County Detention Center, where he was again placed in solitary confinement. Coyte said Slevin did receive a brief competency hearing a year into his imprisonment, but the case against the man never proceeded.

After 22 months as a pretrial detainee, Slevin was released and the charges dismissed. He then filed suit, claiming his rights of due process were violated since he was not given a hearing before being placed in solitary confinement.

Photos taken before and after his confinement show dramatic appearance changes. The plaintiff said things were so bad he was forced to pull his own tooth while in custody, and that his pleas for help were dismissed.

In pretrial motions, the county denied "that there was lack of medical care. For most of the other allegations, officials either denied them or said they were "without knowledge or information sufficient to form a belief" of the veracity of the claims.

Coyte told CNN he and Slevin hope their victory would "help bring a stop to the use of solitary confinement in America. Other countries recognize it as a form of torture, whereas America uses it as a routine method of incarceration."

"The families and friends of the people who have been subjected to this barbaric treatment know what we are talking about," Coyte wrote in an e-mail. "They see the effects of it every day. Hopefully Stephen's story can make a difference to them and others who are currently sitting in a concrete cell 23 hours a day."

The county said it has taken "bold steps" to improve the 846-bed jail, which it said would make it "the model for detention centers and the care of the mentally ill in the state of New Mexico."

"In the wake of this large settlement, we can say definitively that we have learned from the past," its statement said. "We can also say with confidence that we are leading the way for the future."

Slevin continues to have serious medical issues, and is fighting lung cancer, his lawyer said.

"Stephen is optimistic in his ongoing battle with cancer and is doing as well as can be expected while undergoing some pretty difficult treatments," Coyte wrote. "Mentally, he will always suffer the effects of his inhumane treatment at the hands of Dona Ana County. The money can never replace what they took from him."

CNN's Victor Blackwell and Bill Mears contributed to this report.