Whole-brain magnetic resonance spectroscopy for neuroinflammation

Neuroinflammation, an inflammatory response located within the central nervous system, is observed in a variety of psychiatric and neurodegenerative conditions. Understanding of neuroinflammation is currently limited by the lack of non-invasive techniques. Brain temperature, measured using magnetic resonance spectroscopic imaging (MRSI), may be a useful measure of neuroinflammation. Brain temperature is expected to increase in cases of neuroinflammation as microglial activation increases metabolic demands, leading to production of excess heat. In addition to temperature measurements, MRSI is useful for detecting inflammation-related alterations in the concentrations of metabolites such as choline-containing compounds (CHO), N-acetylaspartate (NAA), and myo-inositol (MI). We conducted a study to investigate the feasibility of MRSI for detection of low-level neuroinflammation using an experimental model of neuroinflammation in humans (intramuscular administration of the typhoid vaccine). Twenty healthy volunteers participated in a double-blind, placebo-controlled crossover study including MRSI scans before and 3 h after vaccine/placebo administration. Results showed that a significant proportion of brain regions (44/47) increased in temperature post-vaccine compared to post-placebo. Changes in metabolite ratios were also observed but did not survive correction for multiple comparisons. Our findings suggest that that regional brain temperature may be a more sensitive measure of low-level neuroinflammation than whole-brain temperature. This technique is also currently being used to investigate neuroinflammation cancer-related cognitive impairment.