A former Dallas neurosurgeon was so neglectful during operations that his actions led to the deaths of two patients and left others with disabling injuries in what’s seen as the worst case of malpractice in Texas, according to state regulators.

Dr. Christopher Duntsch, 44, who lost his medical license in 2013, faces potential prison time after being indicted on multiple assault charges relating to his treatment of patients. He was being held Friday at the Dallas County Jail on bond exceeding $600,000.

"You don't see a doctor charged with this," said Dallas County prosecutor Kevin Brooks, adding that doctors who run afoul of the law usually are accused of insurance or prescription fraud. "It's fairly rare."

Brooks compared the severity of the charges against Duntsch with those levied against a Detroit-area cancer doctor who was sentenced in July to 45 years in prison for collecting millions from insurance companies while poisoning more than 500 patients through needless treatments that harmed their health.

Prosecutors allege Duntsch’s hands amounted to a “deadly weapon” because he used them to improperly insert medical devices and screws into patients meant to alleviate nerve and other pain. He operated on the wrong part of a patient’s spine, damaged nerves and left one woman with chronic pain and dependent on a wheelchair, according to criminal and civil court records. State records show he left a sponge inside a patient following surgery.

A resident of Centennial, Colorado, Duntsch was arrested recently when he returned to the Dallas area to visit his two young children.

His attorney, Mario Herrera, said his client has not yet entered a plea but will defend himself against all charges, which include five counts of aggravated assault causing serious bodily injury and one of injury to an elderly person causing serious bodily injury.

"My client has defended himself throughout this process and has been successful in navigating through these waters," Herrera said.

Duntsch was issued a license to practice medicine in Texas in 2010, according to the Texas Medical Board. But within two years, the board began receiving complaints about him.

In June 2013, the board took an initial step of suspending Duntsch’s license to practice in Texas, finding at the time that he was “unable to practice medicine with reasonable skill and safety due to impairment from drugs or alcohol.” However, in December 2013, the board found that no evidence existed to support claims he was under the influence when performing surgery.

In agreement with the board reached with Duntsch to revoke his license, it was determined that he violated standards of care for six patients. Herrera said the agreement doesn’t mean his client admits to any wrongdoing in the criminal charges.

Duntsch has had at least three lawsuits filed against him in the last few years. One lawsuit filed in Dallas County contends he misdiagnosed the radiating neck pain one woman suffered and botched her 2012 surgery to the point she suffered a stroke and so much blood loss that she died days later. State records show earlier that year another patient he operated on died when she sustained hemorrhaging that he failed to promptly identify.

Medical personnel who assisted Duntsch during a surgery in July 2012 say he appeared distracted and disoriented, according to one lawsuit. At one point he "broke scrub" and left the operating room. When he returned, Duntsch appeared to have lost his focus and his assistants questioned whether he was under the influence of drugs or alcohol, according to the suit.

Criticism that not enough was done to stop Duntsch sooner has focused on the hospitals where he worked and the Texas Medical Board. A reference letter from one hospital that Duntsch used to secure privileges at another made no mention of accusations against him, The Dallas Morning News has reported.

Meanwhile, Jarrett Schneider, spokesman for the medical board, said in a statement that board investigations can be slowed when hospitals fail to notify the agency of improper conduct. Investigations also can take time because state law requires evidence that a physician is a "continuing threat," which is a high threshold of proof, Schneider said.

The Associated Press contributed to this report.