Proton magnetic resonance spectroscopy of late delayed radiation-induced injury of the brain

We prospectively evaluated metabolite changes in late delayed radiation-ind uced injury to the temporal lobes on proton (H-1) magnetic resonance spectr oscopy (MRS) in 34 patients. Morphologically more severe injury on imaging tended to have lower N-acetyl aspartate (NAA)/creatine (Cr) and NAA/choline (Cho) ratios, A significantly higher Cho/Cr ratio was found in the most se vere grade of cerebral necrosis, in which lactate might be present. The pro gressive decrease in NAA with increasing severity reflected neuronal loss a t different stages of fate delayed radiation-induced brain injury, The abse nce of Cho elevation in mild and moderate lesions did not suggest demyelina tion or glial hyperplasia as an etiologic mechanism of late delayed radiati on-induced brain injury. The association of severe morphologic lesions with elevated lactate suggests ischemia as the underlying mechanism for severe lesions,H-1 MRS may provide metabolite information conducive to the underst anding of the pathophysiology of late radiation-induced brain injury. (C) 1 999 Wiley-Liss, Inc.