Cognitive Sequelae of Diffuse Axonal Injury

Abstract

The results of recent studies on cognitive disability after traumatic brain injury-associated diffuse axonal injury (DAI) are inconsistent. In these studies, the diagnosis of DAI relied on cranial computed tomography. To further clarify the extent and severity of a possibly DAI-associated cognitive impairment by the use of magnetic resonance imaging (MRI) and detailed neuropsychological testing. From a databank of 299 patients with traumatic brain injury, 18 patients (age range, 17-50 years; median initial Glasgow Coma Scale score, 5) who showed an MRI lesion pattern compatible with pure DAI were identified. All of the patients had undergone MRI on a 3-T system. Pure DAI was defined by the findings of traumatic microbleeds on T2*-weighted gradient-echo images in the absence of otherwise traumatic or nontraumatic MRI abnormalities. Neuropsychological performance in the categories of attention and psychomotor speed, executive functions, spans, learning and memory, and intelligence 4 to 55 months (median, 9 months) after traumatic brain injury. All of the patients showed impairments of 1 or more cognitive subfunctions, and no cognitive domain was fundamentally spared. Memory and executive dysfunctions were most frequent, the former reaching a moderate to severe degree in half of the patients. In comparison, deficits of attention, executive functions, and short-term memory were mostly mild. Correlations between the amount of traumatic microbleeds and specific or global cognitive performance were absent. An MRI lesion pattern compatible with isolated DAI is associated with persistent cognitive impairment. The traumatic microbleed load is no sufficient parameter for the assessment of DAI severity or functional outcome.