Frontotemporal dementia and early Alzheimer disease: differentiation with frontal lobe H-1 MR spectroscopy

To evaluate cerebral biochemical abnormalities in patients with frontotemporal dementia and Alzheimer disease and to determine whether proton (hydrogen-1) magnetic resonance (MR) spectroscopy can help differentiate among these two patient groups and healthy (control) subjects.

MR imaging and H-1 MR spectroscopy were performed in 14 patients with frontotemporal dementia, 12 with probable Alzheimer disease (Alzheimer), and 11 healthy (control) elderly subjects. Spectra were acquired from midfrontal and temporoparietal gray matter with a double spin-echo sequence (repetition time, 3,000 msec; echo time, 30 msec). Results were expressed in metabolite concentrations corrected for the presence of cerebrospinal fluid.

In frontotemporal dementia patients, the frontal lobe showed reduced N-acetyl compounds (-28%) and glutamate plus glutamine (-16%), suggestive of neuron loss, and increased myo-inositol (MI) (+19%), suggestive of increased glial content. In three frontotemporal dementia patients, a lactate peak was present in the frontal lobe. In Alzheimer patients, no statistically significant abnormalities were observed in the frontal region, but MI was elevated (+8%) in the temporoparietal region. With use of linear discriminant analysis of MR spectroscopy data alone, 92% of the frontotemporal dementia patients were correctly differentiated from the Alzheimer patients and control subjects. The overall accuracy for discrimination among all three groups was 84%.

H-1 MR spectroscopy demonstrated biochemical abnormalities in patients with frontotemporal dementia and aided differentiation between patients with frontotemporal dementia and Alzheimer disease.