Elsevier

The Lancet Neurology

Volume 12, Issue 9, September 2013, Pages 882-893
The Lancet Neurology

Review
Blast-related traumatic brain injury

https://doi.org/10.1016/S1474-4422(13)70161-3Get rights and content

Summary

A bomb blast may cause the full severity range of traumatic brain injury (TBI), from mild concussion to severe, penetrating injury. The pathophysiology of blast-related TBI is distinctive, with injury magnitude dependent on several factors, including blast energy and distance from the blast epicentre. The prevalence of blast-related mild TBI in modern war zones has varied widely, but detection is optimised by battlefield assessment of concussion and follow-up screening of all personnel with potential concussive events. There is substantial overlap between post-concussive syndrome and post-traumatic stress disorder, and blast-related mild TBI seems to increase the risk of post-traumatic stress disorder. Post-concussive syndrome, post-traumatic stress disorder, and chronic pain are a clinical triad in this patient group. Persistent impairment after blast-related mild TBI might be largely attributable to psychological factors, although a causative link between repeated mild TBIs caused by blasts and chronic traumatic encephalopathy has not been established. The application of advanced neuroimaging and the identification of specific molecular biomarkers in serum for diagnosis and prognosis are rapidly advancing, and might help to further categorise these injuries.

Introduction

Bomb explosions are common in war zones, urban terrorist attacks, and countries where there is sectarian violence, and are mainly caused by improvised explosive devices. Blast-related traumatic brain injury (TBI) comprises four components (panel 1), ranging from isolated and mild to severe TBI with associated polytrauma. These four components are also used to describe blast injury affecting other parts of the body, and suggest to the clinician various mechanisms of injury and resultant pathology caused by the blast.2, 3 Primary blast injury to the brain occurs across the entire range of severity of blast-related TBI, whereas secondary, tertiary, and quaternary blast injuries are associated with moderate and severe TBI. The effects of a bomb blast on the human brain depend on many factors, such as blast energy, distance from the blast, body position, the use of body armour or helmets, the environment (closed environments are usually worse than open spaces), number of blast exposures, and time interval between exposures.3, 4

The US Department of Defense has invested more than US$800 million in research into TBI and psychological health since 2007.5, 6 The escalation of research into blast-related TBI and related mental health disorders has been driven by the return of large numbers of affected military personnel from deployments to Iraq and Afghanistan. However, civilian practitioners are increasingly likely to encounter patients with injuries caused by bomb blasts, including TBI, because many veterans from the Iraq and Afghanistan wars and civilians in affected countries need continuing care after blast exposure. There is also the risk of unexpected terrorist bombings, such as occurred at the Boston Marathon, USA, in April, 2013. Civilian emergency practitioners can be prepared for these events by drawing on the wealth of data available from military studies.7 Blast-related TBI can also be caused by non-bomb blasts, such as chemical or fireworks explosions, or explosions caused by industrial accidents.

In this Review we examine the unique features and effects of blast-related TBI (including pathological changes, diagnosis, and treatment), the links between blast-related TBI, post-traumatic stress disorder (PTSD), depression, and chronic traumatic encephalopathy, and the implications for future care of military personnel and civilians injured by bomb blasts. We focus on blast-related mild TBI, rather than moderate or severe, because it is the most common type and is most likely to be encountered by civilian practitioners, and because of the challenges concerning its diagnosis and its complex relation to PTSD. Blast-related moderate and severe TBI is also discussed briefly, but a comprehensive assessment of the management of blast-related severe TBI is beyond the scope of this Review.

Section snippets

Epidemiology

TBI and PTSD have been called the “signature” and “invisible” wounds of military service in Iraq and Afghanistan,8 although these terms have been criticised because of uncertainty about the diagnosis of blast-related and non-blast-related mild TBI and the negative consequences of these labels on patient outcomes.9 The Rand Corporation7 estimated that 320 000 US military personnel had a TBI, of the 1·64 million deployed to Iraq and Afghanistan in 2001–08. However, this finding is probably an

Experimental pathology

The mechanisms of blast-related TBI are complex and multifactorial, with local and systemic effects of primary, secondary, tertiary, and quaternary blast injury, and different portals for blast wave transmission to the brain (figure 1). Furthermore, the biological basis of neuropsychiatric sequelae continues to be elucidated.21, 22 Animal experiments may provide valuable insights into human pathology and help with the development of new therapies for blast-related TBI. Porcine models of

Definition and diagnosis

The definition of mild TBI is a challenge in both military and civilian settings—a workshop on acute and objective diagnosis was held in the USA in 2010.38 The US Department of Defense defines mild TBI as head trauma associated with loss of consciousness for 30 min or less, alteration of consciousness for a moment up to less than 24 h, or post-traumatic amnesia for 24 h or less.38 Patients with mild TBI have a score on the Glasgow coma scale of 13–15, but this scale is a relatively crude

Blast-related moderate TBI

Patients with blast-related moderate TBI have a score on the Glasgow coma scale of 9–12, and are usually included with blast-related severe TBI in clinical series. These patients have a substantial risk of deterioration due to intracranial haemorrhage and brain oedema, and should be transported to a medical facility that can provide neurosurgery, critical care, and neuroimaging. The management of deterioration in these patients is the same as for severe TBI.116 A prospective study117 of 2443

Blast-related severe TBI

Blast-related severe TBI is characterised by cerebral oedema, intracranial haemorrhage, delayed vasospasm, and pseudoaneurysm formation (figure 2).22, 118, 119 Patients have a score on the Glasgow coma scale of 3–8. Specialists in military trauma in the Iraq and Afghanistan wars have developed a comprehensive system of care from the point of injury through to rehabilitation, which has substantially improved survival and outcome for patients with these severe injuries. Advances in early

Rehabilitation

Health systems for military personnel and veterans have developed extensive rehabilitation programmes for the treatment of injured soldiers with blast injuries. This delivery of care could be adapted for non-military settings. A multidisciplinary team is necessary to provide appropriate rehabilitation care after blast injury. For those referred for rehabilitation, there is an assessment of so-called invisible injuries—such as mild TBI, PTSD, pain, and sensory dysfunction—in addition to other

Conclusions

Injury mechanisms, and the pattern and degree of injury to the brain, differ between blast-related and non-blast-related TBI. The acute clinical aspects of blast-related mild TBI are similar to those of non-blast-related mild TBI, but in military populations the prevalence of post-concussive syndrome, PTSD, depression, and chronic pain are higher after blast-related mild TBI. The prevalence of blast-related mild TBI varies widely because of different diagnostic methods and conditions of

Search strategy and selection criteria

We searched Medline, Evidence-Based Medicine Reviews, the Cochrane Central Register of Controlled Trials, PsycINFO, and Embase with a combination of core terms that included “brain injuries”, “craniocerebral trauma”, “chronic traumatic encephalopathy”, “mild TBI”, and “post concussion syndrome”, and blast or military terms that included “blast injury” and “military medicine”, from 2010 to January, 2013. Searches were limited to the English language. Reference lists of relevant publications were

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