SAN DIEGO -- There are many stories about the injuries members of the military have suffered in Iraq.

However, sometimes those battlefield wounds are not visible.

Marine Cpl. Wilson Otero knows the meaning of danger. His job was to provide security for convoys in Iraq.

"We search for mines, we search for explosives and we search for any kind of weapons hiding on the road like roadside bombs,” said Otero. "We run over a mine and the vehicles keep going, boom and you just keep going and get out of the kill zone.”

Otero escaped many blasts during his time in Iraq, except for the last one.

“April 20, 2005, that’s when I get hit from an improvised explosive device,” said Otero.

The shock waves knocked him unconscious.

"Everything blacked out and I don't remember anything else after that,” said Otero.

When Otero came to he had no injuries, at least none that he could see. He said something did not feel quite right.

"I remember feeling pressure on the right side of my head from an explosion,” said Otero.

Although Otero did not know it at the time, he had suffered a traumatic brain injury. Otero is among as many as 150,000 troops in Iraq and Afghanistan with brain injuries.

Scripps Encinitas neurologist Dr. Michael Lobatz said, “The defining injury in this war in Iraq and Afghanistan is the brain injury."

Since Otero had no visible injuries, he went back to his dangerous job.

"I was still doing my job with migraines and headaches and trouble in the right side of my ear, but I thought it was normal,” said Otero.

He suspected the problems were from spending his sleep-deprived days on the battlefield under the blazing Iraqi sun.

"I said to myself, ‘This is going to go away probably when I get back home,’” said Otero.

However, Otero’s homecoming did not help his condition.

"I couldn't remember their faces or the faces where I meet them,” said Otero.

Things only got worse when Otero returned to loved ones waiting to welcome him home.

10News will continue to follow Otero’s journey to regain his memories and how a local hospital is helping American troops come back, Thursday on 10News Live at 5 p.m.