Dementia of frontal lobe type and amyotrophy.

Dementia of frontal lobe type may precede motor signs in a number of adult patients with amyotrophy. Neuropathological studies have shown neuron loss, spongiosis and gliosis mainly in layers II and III of the frontal and temporal lobes, together with myelin pallor of the subcortical white matter. Golgi studies revealed loss of dendritic spines on the apical dendrite of layer III pyramidal neurons, decreased numbers of dendrites, amputation and tortuosities of dendrites, and distal and proximal dendritic swellings and enlargements. Calbindin D-28K immunocytochemistry revealed a marked decrease in the number of cortical immunoreactive neurons and loss of immunoreactivity in dendrites of the remaining cells. These features indicate that pyramidal and non-pyramidal neurons in layers II and III are severely damaged, and suggest that cortical processing is seriously impaired in patients with frontal lobe type dementia.