Medial temporal lobe metabolic impairment in dementia associated with motor neuron disease

In the course of their disease certain patients with frontotemporal dementi a (FTD) develop clinical features compatible with a motor neuron disease (F TD-MND), Previous reports have suggested that the functional pattern is sim ilar in FTD and FTD-MND. However. some neuropathological studies suggest gr eater involvement of medial temporal regions in FTD-MND than in FTD. Using statistical parametric mapping (SPM96), we compared the metabolic patterns obtained at rest with positron emission tomography in 10 FTD patients and t hree FTD-MND patients with those obtained from 46 healthy subjects (HS). Me an age, duration of illness and dementia stage did not differ statistically between the FTD and FTD-MND groups, In comparison with HS, both groups sho wed frontal and anterior temporal hypometabolism at P<0.001, When the FTD-M ND group was compared to the FTD group, significant hypometabolism was only observed in bilateral amygdala, bilateral hippocampus, and bilateral entho rinal and parahippocampal regions (Brodmann's areas, BA 28/36) at P<0.005. We found no significant differences in regional glucose uptake when FTD pat ients were contrasted to FTD-MND patients. Our results suggest statisticall y comparable frontal and lateral temporal hypometabolism in both conditions but greater impairment of medial temporal lobe activity in FTD-MND. Our re sults and a review of the literature support the hypothesis that there is a functional continuum between classical motor neuron disease (cMND), FTD-MN D, and FTD. (C) 1999 Elsevier Science B.V. All rights reserved.