(CNN) Almost three dozen US service members were diagnosed with traumatic brain injuries after the Iranian missile attack earlier this month, the Pentagon said Friday.
President Donald Trump has said he doesn't consider potential brain injuries to be as serious as physical combat wounds. He downplayed the severity of the symptoms the service members sustained as "headaches."
But traumatic brain injuries are serious. They're also on the rise.
While some people recover relatively quickly, others sustain long-term damage with a range of effects. Traumatic brain injury can range from concussion, which is considered mild, to severe, sustained brain damage.
Plus, it's the brain -- and medicine is only on the forefront of understanding what, exactly, goes on in there.
Here's more about traumatic brain injuries (TBIs) and how devastating they can be.
The CDC defines a TBI as a "disruption in the normal function of the brain" that's typically caused by a bump, a blow, or a jolt to the head. One of the most common forms of TBI is concussion, also known as mild TBI (mTBI).
They're typically seen in car accidents, as when a person's head hits the windshield. They're also frequently seen in sports -- after a football player tackles an opposing player leading with his own helmet, for example.
In 2014 alone, almost 3 million TBI-related emergency department visits, hospitalizations, and deaths were reported in the US, according to the Centers for Disease Control and Prevention. More than 830,000 occurred among children. The total number increased 53% from 2006, the CDC said, indicating brain injuries are on the rise.
They can also be caused by severe shaking, which moves the brain inside the skull and causes injury. That can happen when, using the car accident example, the head jolts from impact but doesn't actually collide with a surface.
Traumatic brain injuries have been linked to sports such as football, soccer, and ice hockey, as well as combat injuries in war zones, and everyday occurrences like falls or fights.
These types of injuries can range from mild to severe. Symptoms of mild injuries include headaches, dizziness and confusion.
For moderate to severe brain injuries, though, symptoms can include severe headaches, a lack of coordination, slurred speech and seizures.
Very severe cases can even result in death.
Repeated trauma or shaking to the brain can be even worse, leading to chronic traumatic encephalopathy, or CTE.
This has been found to be especially common in football.
NFL players Ray Easterling, Junior Seau, Shane Dronett and Dave Duerson were found to have CTE after careers of repeated blows to the head. All died by suicide. Duerson left his family a message before asking they send his brain to be studied.
Hall of Fame quarterback Brett Favre has spoken about his memory loss and changes after his career in the NFL, likely a result of his many concussions while playing.
CTE has been found in war veterans, too, who can suffer from repeated TBIs from events like explosions.
Tommy Shoemaker is one such veteran. He spoke to CNN chief medical correspondent Dr. Sanjay Gupta in 2015 about how his many years in the military -- with more than 30 concussions -- led his own brain to develop CTE.
"I've always been really easygoing," he told Gupta. "But now that's not so ... I yell, I scream, I holler, and that's just never been my manner. I'm sad for my kids and my wife to have to live with that."