Features of Diffuse Axonal Injury with reference to Posttraumatic Neurocognitive Dysfunction

Masuzawa Hideaki

doi:10.2496/hbfr.35.265

Diffuse axonal injury (DAI) is considered as quantitatively continuous spectrum of traumatic brain injury ranging from prolonged coma state to mild traumatic brain injury. DAI destroys axons and eventually neurons permanently and reduces the bulk of the white matter, thus leaving behind diffuse ventricular enlargement and brain atrophy. In milder DAI such as brain concussion, however, most of the axons temporarily cease functioning only to resume again, thus the victim regains consciousness very soon without obvious neurological deficit nor any noticeable ventriculomegaly. DAI plays the substantial part in the outcome of closed head injury even if associated with local brain injury such as brain contusion. Manifestations of DAI are comprised of mental disorder including neurocognitive dysfunction and emotional or neurobehavioral disorder, and neurological disorder (cerebellar ataxia and spastic hemiparesis) . These disorders are strikingly similar among victims, though varying in severity. One of the characteristic points is lowering or even absence of self-awareness as DAI is more than mild in severity. The victims rarely complain of their own symptoms nor seek medical attentions spontaneously. The outcome of DAI is highly correlated with the duration of the posttraumatic initial unconsciousness and with remaining ventriculomegaly which is compared to the day-of-injury ventricular size as the reference. Another characteristic point is the tendency to clinically improve steadily by months and years. It is faster and more striking in milder DAI and in younger age victims. The neuropsychological scores also improve accordingly. So-called prolonged postconcussive syndrome occasionally observed in selected cases of mild traumatic injury, on the contrary, shows little tendency to improve by time. The neuropsychological test results often decline by time. They visit multiple medical institutions, ardently complain of their subjective symptoms and often create detailed memos of their own symptoms. These are considered as signs of elevated self-awareness or hyperawareness.

Features of Diffuse Axonal Injury with reference to Posttraumatic Neurocognitive Dysfunction

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