1H magnetic resonance spectroscopy in human hydrocephalus

Purpose: To evaluate cerebral metabolism in clinical hydrocephalus with H-1 magnetic resonance spectroscopy (MRS). Materials and Methods: In 24 children and adults with progressive, arrested, or normal pressure hydrocephalus, long-echo time H-1 MR spectra were acquired from periventricular white matter and intraventricular cerebrospinal fluid (CSF). Metabolite ratios, and the presence of lactate, were compared with 38 age-matched controls. Results: Metabolite ratios of patients were within the 95% confidence interval (CI) of controls. A small lactate resonance was detected in 20% of control and hydrocephalic subjects. Lactate was consistently visible in CSF spectra, though lactate concentrations were normal. The CSF lactate T-2 was long in comparison with the known intracellular metabolite T-2 relaxation times. In three neonates with hydrocephalus and spina bifida, 3-hydroxybutyrate was detected in CSF in vivo. Conclusion: Within the limits of the present methods, H-1 MRS could not detect cerebral metabolic abnormalities in human hydrocephalus and provided no additional diagnostic information. The long T-2 of lactate in CSF explains its high visibility. Hence, the detection of lactate in spectra acquired from voxels that contain CSF does not necessarily imply cerebral ischemia.