Monitoring of brain interstitial total tau and beta amyloid proteins by microdialysis in patients with traumatic brain injury

Object Damage to axons contributes to postinjury disabilities and is commonly observed following traumatic brain injury (TBI). Traumatic brain injury is an important environmental risk factor for the development of Alzheimer disease (AD). In the present feasibility study, the aim was to use intracerebral microdialysis catheters with a high molecular cutoff membrane (100 kD) to harvest interstitial total tau (T-tau) and amyloid beta 1–42 (Aβ42) proteins, which are important biomarkers for axonal injury and for AD, following moderate-to-severe TBI. Methods Eight patients (5 men and 3 women) were included in the study; 5 of the patients had a focal/mixed TBI and 3 had a diffuse axonal injury (DAI). Following the bedside analysis of the routinely measured energy metabolic markers (that is, glucose, lactate/pyruvate ratio, glycerol, and glutamate), the remaining dialysate was pooled and two 12-hour samples per day were used to analyze T-tau and Aβ42 by enzyme-linked immunosorbent assay from Day 1 up to 8 days postinjury. Results The results show high levels of interstitial T-tau and Aβ42 postinjury. Patients with a predominantly focal lesion had higher interstitial T-tau levels than in the DAI group from Days 1 to 3 postinjury (p < 0.05). In contrast, patients with DAI had consistently higher Aβ42 levels when compared with patients with focal injury. Conclusions These results suggest that monitoring of interstitial T-tau and Aβ42 by using microdialysis may be an important tool when evaluating the presence and role of axonal injury following TBI.