Structural magnetic resonance imaging in frontotemporal lobar dementia.

Frontotemporal lobar dementia (FTLD) is a heterogeneous group of neurodegenerative diseases. FTLD encompass: 1) behavioral forms, sometimes associated with amyotrophic lateral sclerosis; 2) linguistic forms (semantic and non-fluent primary progressive aphasia); 3) atypical parkinsonian syndromes (progressive supranuclear palsy and corticobasal syndrome). Standard brain MRI allows for strengthening the clinical suspicion of FTLD, by showing a pattern of atrophy in relation with the patient's clinical symptoms: frontotemporal anterior atrophy in behavioral forms; temporopolar or inferior left frontal atrophy in the linguistic forms; mesencephalic or corticosubcortical hemispheric atrophy in forms with atypical pakinsonism. MRI is now part of the diagnostic criteria of some FTLD (behavioral FTLD, primary progressive aphasia). Genetic forms are common in FTLD, especially in behavioral FTLD. The three main mutations (C9ORF72, GRN and MAPT) are associated with different imaging patterns, which can thus orient the clinician towards a particular mutation in a patient with a familial form of FTLD.