June 30: This post has been updated.

WASHINGTON, D.C.--The Pentagon has issued a new directive ordering better tracking and treatment of mild traumatic brain injuries in war zones, including a mandatory 24-hour rest period for any soldier exposed to a nearby blast.

The new policy, which has been in development for months, also requires soldiers who have suffered three mild traumatic brain injuries, also known as concussions, to have a complete neurological assessment done before returning to the battlefield.

Military medical experts praised the new policy as an encouraging change in the Pentagon's approach.

The directive places the focus on evaluating all soldiers exposed to a blast or other head trauma, as opposed to relying upon medical staff or soldiers themselves to report symptoms from an injury.

"This relieves the burden of the soldier having to say, 'I'm hurt,'" said Stephen Xenakis, a retired brigadier general who advises the military on medical issues. "When you do that, it's like routine maintenance on a vehicle. It's understood that it's what you need to do responsibly to maintain optimal performance."

Under previous policies, medics were supposed to evaluate soldiers after blasts, but there was no mandatory rest period. Medical guidelines did not specify how many concussions triggered the need for a complete evaluation of a soldier's cognitive functions.

Military officials declined to comment on the memo, which was distributed through secure e-mail channels and was apparently not intended for public release. Issued June 21 by William J. Lynn III, the deputy defense secretary, the policy change was first reported by NextGov.

It was unclear why the memo was released in this manner. Commanders have been testing the new protocols in Afghanistan since late last year and top generals have publicly discussed plans to implement the requirements.

Earlier this month, NPR and ProPublica reported that the military was routinely failing to diagnose soldiers suffering from mild traumatic brain injury, the most common head wound suffered by soldiers in Iraq and Afghanistan. The investigation also found that soldiers had trouble getting adequate treatment at one of America's largest military bases, Fort Bliss in El Paso, Texas.

Official military figures show about 115,000 soldiers have suffered mild traumatic brain injuries since 2002. However, unpublished research and military experts indicate the true toll could be far higher. While most people recover rapidly from concussions, civilian studies suggest that 5 percent to 15 percent of those who suffer mild traumatic brain injuries have lingering problems with memory, concentration and other cognitive functions.

The new policy requires the military to set up a database to track each soldier exposed to a blast and the details of that explosion. The ProPublica and NPR review found that concussions frequently were not documented in soldiers' records.

Gen. Peter Chiarelli, the Army's second in command, told the Senate Armed Services Committee at a hearing earlier this month that the new protocols were an indication that the Army was "serious" about treatment of traumatic brain injury.

"We cannot permit the proud 'warrior spirit' of our soldiers, which leads many of them to ignore their concussions and remain in the fight, to dominate the competing need to protect them against another injury during the vulnerable period of healing," Chiarelli said in a prepared statement.

Some medical officials questioned the science behind the policy's guidelines. For instance, the new rules require the mandatory rest period for soldiers within about 50 yards of a blast. But there is no hard science which establishes that soldiers beyond 50 yards are safe from blast effects. Factors such as the size of the blast and battlefield armor could influence the severity of soldiers' injuries.

Nor is there conclusive evidence that three blasts -- as opposed to two, or four or 10 -- put soldiers at greater risk for long-term damage.

"They are arbitrary numbers, but it's a number," one official said. "It will get us moving in the right direction."

In an interview with NPR and ProPublica before the new directive was issued, Chiarelli acknowledged that the limits were arbitrary. He said that he had argued with medical officials over how to balance the demands of combat, science and medicine in area with many uncertainties.

"I have no biology training, and I'm entering into a world where I’m pitted against some doctors sometimes. And I've got to study harder and look at it harder and come at them from a soldier's standpoint," Chiarelli said. "The doctors say, 'Well, let's make it 100 meters from a blast if you're outside a blast.' I said no. You'll have too many false positives there and soldiers will lose confidence in this."

Some in the military question whether there are resources in place to carry out the new requirements.

One senior medical official said that commanders had expressed worry that a 24- hour rest period might impair short-staffed units from carrying out their missions.

It also may be difficult to carry out the mandated neurological assessments in the field, given limited amounts of specialists and equipment, even though it is estimated that less than 5 percent of soldiers are in three or more blasts per year.

"You don't have the capability to do these complete evaluations yet," the senior official said. "They don't have the equipment in theater that they need."

Update: The Pentagon responded to our questions about their new traumatic brain injury policy late Tuesday. A Defense Department spokeswoman said that the policy was released through secure channels because the "memo was designed for the benefit of the American service member, and knowledge by enemy forces of certain elements of this memo could put troops at risk."