How blast waves can damage the brain without a head injury

An explosion does not need to strike the head to injure the brain. When a blast occurs, it generates a sudden pressure wave that can pass through the body and skull in milliseconds, potentially deforming brain tissue and blood vessels along the way.

For soldiers exposed to improvised explosive devices or other blasts, and civilians caught in industrial accidents or explosions in conflict zones, the neurological effects can be long-lasting – even when brain scans appear normal.

Blast injuries can trigger changes in the brain and its blood vessels that standard medical scans do not always detect. When these injuries go unrecognised, people may receive the wrong care or be left without an explanation for symptoms that persist for years.

Most people are familiar with traumatic brain injuries caused by impacts such as falls, road traffic collisions or sports injuries. In these situations, the brain moves suddenly within the skull, leading to bruising or localised damage that can often be seen on scans.

Blast injury works differently. The rapid rise and fall in pressure created by an explosion can travel through the skull and the fluid that surrounds and cushions the brain. This generates complex mechanical forces that stretch and strain brain tissue. As a result, someone can sustain a brain injury even without any direct blow to the head.

Rather than producing one clearly visible injury, blast exposure tends to cause widespread microscopic damage. These tiny injuries can disrupt how brain cells communicate with each other, and can also damage the blood vessels that keep brain tissue healthy.

Although blast injury is often associated with military settings, it is not confined to war zones. Civilians may be exposed through industrial explosions, terrorist attacks or demolition work. In all these situations, the underlying mechanisms of brain injury are similar.

Despite these differences, blast injuries are often managed in the same way as concussions or other head injuries. When damage to blood vessels is overlooked, the severity of the injury and its long-term impact can be underestimated.

More sensitive diagnostic tools, including advanced imaging and specialised blood tests, could improve detection of subtle blood vessel damage. This would allow for more targeted treatment aimed at reducing inflammation, protecting the brain’s circulation, and ensuring patients receive appropriate long-term care.

Blast-related brain injury can also disrupt the brain’s waste-clearance system. This system normally removes harmful proteins and metabolic waste. When it is impaired, vulnerability to long-term post-concussion symptoms and neurodegenerative diseases may increase.

Brain blood vessels are especially vulnerable

One of the most important, and often overlooked, consequences of blast injury is damage to the brain’s blood vessels.

Blood vessels are thin-walled and flexible, allowing them to cope with normal changes in blood flow and pressure. During a blast, however, the rapid pressure shifts can stretch these vessels beyond their limits. This can cause tiny tears and weaken the protective barrier that normally prevents harmful substances in the bloodstream from entering brain tissue.

This protective layer, often called the blood–brain barrier, plays a crucial role in controlling what passes from the blood into the brain. When it is damaged, inflammatory cells and proteins can leak into brain tissue.

The resulting inflammation may persist long after the initial injury, interfering with normal brain function. Over time, this can contribute to symptoms such as headaches, memory problems, difficulty concentrating, slowed thinking, mood changes and fatigue.

Damage to the blood–brain barrier may help explain why some people experience ongoing symptoms months or even years after blast exposure.

Why scans can appear normal

One of the most frustrating experiences for people with blast-related brain injury is being told that their CT or MRI scan is normal, despite persistent symptoms.

Standard imaging techniques are very good at detecting fractures, bleeding or large areas of tissue damage. Blast injuries, however, often involve microscopic changes such as small vessel damage, disruption to communication between brain cells, and ongoing inflammation. These changes are usually too subtle to be seen on routine scans.

This mismatch between symptoms and imaging can delay diagnosis, complicate rehabilitation and, in some cases, affect access to appropriate support or compensation.

Researchers are increasingly using laboratory models and real-world data to understand how blast forces affect the brain and its circulation. Long-term studies are beginning to show how early damage to blood vessels may evolve into lasting neurological problems.

Progress will require close collaboration between neuroscientists, clinicians, emergency services and policymakers. Blast injury is not only a military concern. It offers broader insights into how pressure-related forces damage the brain, and how these injuries might be prevented or treated.

Recognising blast injury as a distinct form of brain trauma, particularly one that affects the brain’s blood vessels, is a crucial step towards improving care for those affected.

Arshad Majid is a NIHR Senior Investigator and his research is funded by the NIHR EME programme and the NIHR Sheffield BRC. His research is also funded by the Stroke Association UK.

Favour Felix-Ilemhenbhio receives funding from the British Heart Foundation (BHF).

Klaudia Kocsy receives funding from Alzheimer's Research UK.