Impact of Methamphetamine on Regional Metabolism and Cerebral Blood Flow After Traumatic Brain Injury

Substance abuse is a frequent comorbid condition among patients with traumatic brain injury (TBI), but little is known about its potential additive or interactive effects on tissue injury or recovery from TBI. This study aims to evaluate changes in regional metabolism and cerebral perfusion in subjects who used methamphetamine (METH) prior to sustaining a TBI. We hypothesized that METH use would decrease pericontusional cerebral perfusion and markers of neuronal metabolism, in TBI patients compared to those without METH use. This is a single center prospective observational study. Adults with moderate and severe TBI were included. MRI scanning was performed on a 3 Tesla scanner. MP-RAGE and FLAIR sequences as well as Metabolite spectra of NAA and lactate in pericontusional and contralateral voxels identified on the MP-RAGE scans. A spiral-based FAIR sequence was used for the acquisition of cerebral blood flow (CBF) maps. Regional CBF images were analyzed using ImageJ open source software. Pericontusional and contralateral CBF, NAA, and lactate were assessed in the entire cohort and in the METH and non-METH groups. Seventeen subjects completed the MR studies. Analysis of entire cohort: pericontusional NAA concentrations (5.81 +/- A 2.0 mM/kg) were 12 % lower compared to the contralateral NAA (6.98 +/- A 1.2 mM/kg; p = 0.03). Lactate concentrations and CBF were not significantly different between the two regions; however, regional CBF was equally reduced in the two regions. Subgroup analysis: 41 % of subjects tested positive for METH. The mean age, Glasgow Coma Scale, and time to scan did not differ between groups. The two subject groups also had similar regional NAA and lactate. Pericontusional CBF was 60 % lower in the METH users than the non-users, p = 0.04; contralateral CBF did not differ between the groups. This small study demonstrates that tissue metabolism is regionally heterogeneous after TBI and pericontusional perfusion was significantly reduced in the METH subgroup.