[Magnetic resonance imaging for frontotemporal lobar degeneration].

Frontotemporal lobar degeneration (FTLD) has been clinically categorized into 3 subtypes: frontotemporal dementia, semantic dementia, and progressive nonfluent aphasia. The histological subtypes of FTLD are Pick disease, corticobasal degeneration, dementia with grain, dementia with ubiquitin-positive tau-negative inclusions, and amyotrophic lateral sclerosis with dementia. In this paper, I briefly describe the magnetic resonance imaging (MRI) findings in Pick disease, progressive nonfluent aphasia, semantic dementia, and dementia with grain. In Pick disease, so-called knife-blade atrophy is seen in the frontal and temporal lobes at a relatively early stage of the disease. In progressive nonfluent aphasia atrophy is seen in the upper part of the left frontal lobe. Marked atrophy in the left temporal pole is observed in patients with semantic dementia, and asymmetrical atrophy around the ambient gyri is detected in patients who have dementia with grains. Although such focal atrophy can be observed on routine MRI, it is more easily detected on voxel-based morphometry and voxel-based specific regional analysis system for Alzheimer disease (VSRAD).