The missile strikes Jan. 8 were an apparent retaliation for a U.S. drone strike days earlier that killed one of Tehran's most powerful military figures. Iran attacked Al Assad and Erbil bases that morning around 1:20 a.m. local time.
About 18 hours later, President Donald Trump said in an address to the nation that "no Americans were harmed in last night’s attack by the Iranian regime. We suffered no casualties, all of our soldiers are safe, and only minimal damage was sustained at our military bases."
But since then, 50 service members have been diagnosed with brain injures.
In the days following the attack, the Pentagon first reported that 11 people were taken out of Iraq for medical screening and "several were treated for concussion symptoms," according to a statement from the U.S. Central Command in the region.
A few days later, the number nearly tripled as the Pentagon said 34 service members were diagnosed with injuries.
Then on Nov. 28, Pentagon spokesperson Lt. Col. Thomas Campbell said 16 more service members had been diagnosed with Traumatic Brain Injury, 15 of which had already returned to duty in Iraq.
"As a standard procedure, all personnel in the vicinity of a blast are screened for traumatic brain injury, and if deemed appropriate are transported to a higher level of care," the Pentagon's first statement said. "In the days following the attack, out of an abundance of caution, some service members were transported from Al Asad Air Base, Iraq to Landstuhl Regional Medical Center in Germany, others were sent to Camp Arifjan, Kuwait, for follow-on screening."
Pentagon procedure requires anyone within 50 meters of a blast to undergo medical screening. Those service members are required to get rest and be monitored.
What are concussions and their symptoms?
Concussions are mild forms of traumatic brain injuries. Common symptoms of concussions – headache, memory loss and confusion – may not show up immediately, according to the Mayo Clinic. The symptoms can last for days, weeks or longer.
"Symptoms will evolve over time and usually become apparent within hours to days," said Jennifer Wethe, co-director of the Concussion Program at Mayo Clinic Arizona. "Every concussion tends to be different, and it tends to be different depending on the individual or type of injury."
Concussions are usually caused by a blow to the head. Some but not all concussions can cause victims to lose consciousness.
Daniel Torres, a neurologist at NYU Langone’s Concussion Center, said concussion injuries always cause some form of initial symptoms.
"There needs to be some symptom at the time of the event, but then, over time, the symptoms can change. Even though you need to have something early, you might be dizzy at first and the next day start having headaches. Or you might get a headache and not feel dizzy until a couple days later," he said.
Concussion experts say it's common for patients not to immediately recognize or report their symptoms.
"At the beginning, when you have the injury, most people are in a hyper-alert state. You're not acutely aware, and you're masking some of the things that might be happening. Subtle changes in memory and concentration – you may not feel them until you are challenged to do an activity," said Pablo Celnik, physiatrist-in-chief at the Johns Hopkins Hospital.
"If you're in the field and being attacked, and there are minor symptoms early on, the adrenaline surge that you get is something that could get you to ignore the early symptoms to deal with the emergency that's in front of you. So you might not immediately report what’s going on," Torres said. "Sometimes if people have a minor injury, they might think they’ll shake it off."
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What has the Pentagon said about the troops' injuries?
Pentagon leadership learned of the injuries Jan. 16, a spokeswoman said.
"The Pentagon leadership was notified of the injuries yesterday. The Commander in Iraq met all reporting requirements and took the appropriate steps to ensure the service members received the proper level of care," Press Secretary Alyssa Farah said on Twitter.
The vast majority of service members examined after the missile attack showed no sign of concussive injury and returned to duty, Farah said.
The original 11 service members were taken to facilities in Germany and Kuwait because MRI equipment is available there, Farah said.
The Pentagon leadership was notified of the injuries yesterday. The Commander in Iraq met all reporting requirements and took the appropriate steps to ensure the service members received the proper level of care.
— Alyssa Farah (@PentagonPresSec) January 17, 2020
The 'signature injury' of wars in Iraq, Afghanistan
More than 400,000 service members have been diagnosed with a traumatic brain injury since 2000, according to the Defense and Veterans Brain Injury Center. In 2017, there were nearly 18,000 diagnoses, down from a peak of nearly 33,000 in 2011.
The greatest number of cases occur in the Army, the largest military branch.
Service members can sustain a concussion during day-to-day activities, training and deployment, according to the brain injury center. Most service members who sustain a concussion return to full duty within seven to 10 days.
Brain injuries related to blast exposures from improvised explosive devices (IEDs) have been called the "signature injury" of the wars in Iraq and Afghanistan, according to the Journal of Military and Veterans’ Health.
"Part of the reason we see more of these now is that body armor prevents shrapnel from going into your body and head. So you see more people survive. Unfortunately, all that body armor is not technology that prevents concussions. So you end up with a lot more people coming back with those," Torres said.
Brain injuries caused by blast concussions have been linked to difficulties of returning personnel with reintegrating into civilian society.
"The recovery from concussion is even more complicated than the injury itself. But that’s different from person to person. Someone who has headaches and problems reading and is anxious is going to have a much harder time than someone who is a little off balance," Torres said. "These problems sometimes feed off each other."
This article originally appeared on USA TODAY: Iran missile attack: 50 Americans treated for brain injury, concussion