The Washington Post has just published an article on the worrying amount of brain damage suffered by US troops in Iraq because of shockwave injuries from roadside bombs known as improvised explosive devices or IEDs.
These sorts of injuries tend not to damage the skull, but can cause significant injury as the brain rapidly accelerates and decelerates inside the skull, and impacts on the inside of the bone casing.
These types of injury are known as ‘closed head injuries‘ as nothing penetrates the skull.
It’s a common misconception that a skull fracture always leads to a worse brain injury.
In fact, in some cases, if the skull breaks, it can allow some of the force of the impact to be dispersed (this is why bicycle and motorcycle helmets are designed to break).
If the skull doesn’t break, sometimes this can lead to the energy of the impact being more fully absorbed by the brain, often leading to shearing and tearing of the white matter pathways as the brain ‘bounces around’ inside.
The Washington Post article outlines why IEDs are likely to have this effect:
Here’s why IEDS carry such hidden danger. The detonation of any powerful explosive generates a blast wave of high pressure that spreads out at 1,600 feet per second from the point of explosion and travels hundreds of yards. The lethal blast wave is a two-part assault that rattles the brain against the skull. The initial shock wave of very high pressure is followed closely by the “secondary wind”: a huge volume of displaced air flooding back into the area, again under high pressure. No helmet or armor can defend against such a massive wave front.
It is these sudden and extreme differences in pressures — routinely 1,000 times greater than atmospheric pressure — that lead to significant neurological injury. Blast waves cause severe concussions, resulting in loss of consciousness and obvious neurological deficits such as blindness, deafness and mental retardation. Blast waves causing TBIs can leave a 19-year-old private who could easily run a six-minute mile unable to stand or even to think.
The article notes that the military have not had to deal with these sorts of injuries in such large numbers before, as IEDs have rarely been used on this scale.
Apparently, the military are currently poorly equipped to deal with these injuries, which is causing problems both for treatment in the field and for longer-term rehabilitation programmes.
The article also contains an interesting factual error: “Iraq has brought back one of the worst afflictions of World War I trench warfare: shell shock. The brain of a soldier exposed to a roadside bomb is shocked, truly.”
‘Shell shock‘ was given this name during World War I because it was originally thought to be due to the blasts of shells affecting the brain.
It was later discovered that the cause of the condition was combat trauma (i.e. emotional stress) rather than brain injury, so it doesn’t actually describe any type of closed head injury.
Link to Washington Post article ‘A Shock Wave of Brain Injuries’.