MRS in cerebral metabolic disorders

Abstract

Key points MR spectroscopy is a valuable tool to direct biochemistry work-up of patients with inborn errors of metabolism. Multivoxel MR spectroscopic imaging is the best method to study the heterogeneous anatomic distribution of metabolic diseases. The interpretation of MR spectra and MR images together increases diagnostic accuracy. Abnormal MR spectral peaks are diagnostic of a few hereditary metabolic disorders. Lactate is elevated in about half of patients with mitochondrial disorders, in most patients with leukoencephalopathies with demyelination or rarefaction of white matter, and in few with organic acidopathies targeting the subcortical gray matter nuclei. In patients with leukoencephalopathy, H-MRSI is a valuable tool for identifying one of the following three underlying tissue pathophysiologies: hypomyelination, demyelination, and rarefaction of white matter. MRS may be useful to monitor response to therapy when available. Introduction The advent of magnetic resonance (MR) imaging has changed the clinical approach to the evaluation of metabolic disorders. MR imaging is highly sensitive and plays a prominent role in the diagnostic evaluation of patients with metabolic disorders of the central nervous system (CNS). However, the structural and signal abnormalities detected on conventional MR imaging are often not specific enough to suggest a definite diagnosis in many of these complex disorders. With advances in MR technology, proton MR spectroscopy ( 1 H-MRS) has become more widely available, and now it can be performed with conventional MR imaging in the same study session. Nowadays, a complete imaging exam lasts no longer than 30 min at 1.5 Tesla or higher magnetic fields.