This study analyses the evolution of metabolite changes in an 8-year-old boy with focal Rasmussen encephalitis. Five MRI examinations, including magnetic resonance spectroscopy (MRS) were performed over 9 months. Following complex partial status, T2-weighted imaging showed transient dramatic signal increase in the left superior temporal gyrus and mesial temporal structures. Subsequent scans showed resolution of the swelling and signal normalization, with development of slight focal atrophy. MRS

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... after status showed a reduction in N-acetylaspartate, total creatine and trimethylamines. Subsequent scans showed complete resolution of these metabolite abnormalities, followed later by development of further abnormal metabolite values. Lactate and glutamine/glutamate were elevated after status. After surgery, ex vivo high-®eld 1 H and 31 P MRS con®rmed metabolite abnormalities (elevated choline and decreased aspartate, N-acetylaspartate, [ 1 H]glutamate together with altered [ 31 P]phospholipid ratios. These ®ndings suggested active disease process in the anterior region of the excised superior temporal gyrus. We conclude that Rasmussen encephalitis is a combination of progressive encephalitic damage and¯uctuating seizure effects, in which neuronal injury and recovery can occur. MRS measurements at a single time point should consider the¯uctuating metabolite pro®le related to seizure activity. Abbreviations: Cho = total choline; CPS = complex partial seizure; Cr = creatine + phosphocreatine; GABA = g aminobutyric acid; gCOSY = gradient correlated spectroscopy; Glx = glutamine + glutamate; Lac = lactate; mI = myoinositol; MRS = magnetic resonance spectroscopy; NA = N-acetylaspartate + N-acetylaspartyl glutamate; NAA = N-acetylaspartate; PRESS = point resolved spectroscopy; ROI = region of interest; SPECT = single photon emission computed tomography; SPS = simple partial seizure.