Diffuse Axonal Injury (DAI)
Diffuse axonal injury (DAI) is widespread shearing injury of the nerve-fiber extensions (axons) in the white matter of the brain, caused by high-speed rotational and acceleration-deceleration trauma. It is one of the major causes of severe traumatic brain injury, often runs a course of prolonged loss of consciousness, and may show fewer findings on imaging than expected.
最后更新: 2026-06-07
Definition
Diffuse axonal injury is damage to the axons of the brain's white matter caused by mechanical stretching and shearing forces at the moment of trauma. Because grey and white matter have different densities, they move at different speeds during the injury, and axons are damaged particularly at the grey-white matter boundary, in the corpus callosum and in the brainstem. It is responsible for a significant proportion of severe head injuries and traumatic comas. Because most lesions are microscopic, standard imaging may not show findings proportional to the severity of the clinical picture.
Causes and Mechanism
The most common causes are high-speed road traffic accidents, falls from height and shaking-type injuries in infants. During the trauma the brain undergoes rotational acceleration-deceleration; axons are initially damaged directly (primary injury), and over the following hours to days secondary injury is added through axonal swelling, ionic imbalance and degeneration. This cumulative process disrupts the function of the brain's circuits.
Symptoms
There is typically prolonged loss of consciousness and coma from the moment of trauma; unlike an epidural hematoma, no 'lucid interval' is expected and the patient is in a severe state from the outset. Abnormal posturing, impaired pupil responses and signs pointing to brainstem involvement may accompany this. In surviving patients, long-term problems may emerge such as prolonged coma, a minimally responsive state of consciousness, severe cognitive impairment (memory, attention, executive functions), behavioral changes and movement disorders (spasticity, ataxia).
Diagnosis
In the acute phase brain CT is often close to normal or shows only widespread edema and small punctate hemorrhages; a normal CT does not exclude diffuse axonal injury. The clinical picture (coma from the outset after high-energy trauma, severity out of proportion to imaging) suggests the diagnosis. Magnetic resonance imaging (MRI) is the gold standard; susceptibility-weighted sequences in particular (T2*GRE/SWI) show small hemorrhages in the corpus callosum, the grey-white matter boundary and the brainstem. Diffusion-weighted and diffusion tensor imaging provide information about acute injury and the integrity of white-matter tracts. The level of consciousness is assessed with the Glasgow Coma Scale.
Treatment Approach
There is no surgery specific to diffuse axonal injury, because the lesions are diffuse and microscopic. The basis of treatment is supportive intensive care and management of complications. Respiratory support is provided where needed, intracranial pressure is monitored and, when raised, controlled with methods such as osmotic therapy and sedation. In situations such as accompanying hematomas causing mass effect or refractory raised intracranial pressure, surgery is undertaken only for these complications. Antiepileptic treatment is used if a clinical seizure occurs.
Rehabilitation, Course and Recovery
Once the medical condition is stabilized, early and multidisciplinary rehabilitation (physiotherapy, occupational therapy, speech therapy, cognitive rehabilitation and psychological support) forms the basis of recovery. Recovery is slow, can take months to years, and family support is important. The course varies over a wide range depending on the severity of injury; a high level of consciousness on presentation, a short duration of coma, younger age and early rehabilitation are associated with a more favorable course. Outcomes vary markedly from patient to patient and no result can be guaranteed.
参考文献
- Greenberg MS. Greenberg's Handbook of Neurosurgery. 10th ed. Thieme; 2023:1071-1076.
- Adams JH, Graham DI, Murray LS, Scott G. Diffuse axonal injury due to nonmissile head injury in humans. Ann Neurol. 1982;12(6):557-563.
- Carney N, Totten AM, O'Reilly C, et al. Guidelines for the Management of Severe Traumatic Brain Injury. 4th ed. Neurosurgery. 2017;80(1):6-15.
本文仅供一般参考，不能替代医疗检查。诊断与治疗决策因人而异。