1H MR Spectroscopy of inflammation, infection, and ischemia of the brain

Abstract

Different pathologic patterns in multiple sclerosis (MS) are reflected by alterations of metabolites in 1H MR spectroscopy of the brain. Elevated choline (Cho), lactate (Lac), lipids, and macromolecules are reliable markers for acute demyelination regardless of the clinical entity (also in acute disseminated encephalomyelitis). N-Acetyl-aspartate (NAA) is a suitable marker for neuronal integrity. It is reduced in acute MS lesions and in normal-appearing white matter, even distant to acute and chronic lesions. Recovery from reduced NAA levels to subnormal values during remyelination and varying time courses of NAA in normal-appearing white matter during relapsing remitting disease indicate the value of this spectroscopic marker for monitoring activity and recovery. Inositol (Ins) is increased in chronic MS lesions being a marker for astrocytic gliosis. In viral disease, Cho and Ins are always increased, whereas a reduction of NAA mostly reflects an advanced or a deteriorated clinical state. In bacterial brain abscesses, numerous amino acids, lipids, and Lac can be elevated. In ischemia, especially the Lac/NAA, comparison with perfusion and diffusion-weighted imaging seems to be a new measure for areas of metabolic need and may help to better characterise the penumbra of the stroke and the final infarct size.