Frontal lobe dementia is not a variant of prion disease

DNA damage and activated caspase-3 expression in neurons and astrocytes: evidence for apoptosis in frontotemporal dementia

Frontotemporal dementia (FTD) is a neurodegenerative disease which affects mainly the frontal and anterior temporal cortex. It is associated with neuronal loss, gliosis, and microvacuolation of lamina I to III in these brain regions. In previous studies we have described neurons with DNA damage in the absence of tangle formation and suggested this may result in tangle-independent mechanisms of neurodegeneration in the AD brain. In the present study, we sought to examine DNA fragmentation and activated caspase-3 expression in FTD brain where tangle formation is largely absent. The results demonstrate that numerous nuclei were TdT positive in all FTD brains examined. Activated caspase-3 immunoreactivity was detected in both neurons and astrocytes and was elevated in FTD cases as compared to control cases. A subset of activated caspase-3-positive cells were also TdT positive. In addition, the cell bodies of a subset of astrocytes showed enlarged, irregular shapes, and vacuolation and their processes appeared fragmented. These degenerating astrocytes were positive for activated caspase-3 and colocalized with robust TdT-labeled nuclei. These findings suggest that a subset of astrocytes exhibit degeneration and that DNA damage and activated caspase-3 may contribute to neuronal cell death and astrocyte degeneration in the FTD brain. Our results suggest that apoptosis may be a mechanism of neuronal cell death in FTD as well as in AD (228).

Familial dementia of frontal lobe type

OBJECTIVE

To describe an unusual case of familial frontal lobe dementia (FLD) with probable spongiform encephalopathy (SE).

METHOD

The patient's clinical presentation, neuropsychological test results, family history, and results on magnetic resonance imaging (MRI) and positron emission tomography (PET) scans, among other routine investigations, are described. His leucocyte deoxyriboneucleic acid (DNA) was isolated, and his Prp (prion protein) gene was amplified with the polymerase chain reaction and sequenced using the Sanger method.

RESULTS

Clinically, the patient had a presenile frontal lobe dementia. Four of the 8 members of the generation preceding the patient had presenile dementia. Autopsies performed on 2 of these cases revealed SE, and a pathological diagnosis of Creutzfeldt-Jakob disease (CJD) was made. One other member of that generation died of a limbic encephalitis, although the neuropathological findings were atypical. Sequencing of the patient's Prp gene did not reveal the abnormalities expected in a familial case of CJD. The results of other investigations were compatible with FLD but were not specific to a particular diagnosis.

CONCLUSIONS

This case is a novel type of SE. The patient presented clinically with FLD, but based on the family history and neuropathology, a diagnosis of prion dementia seems likely. There were no mutations found in the Prp gene, so it is possible that there are SEs caused by genes or other pathological processes unrelated to the Prp gene.

Clinical, neuroimaging, and pathologic features of progressive nonfluent aphasia

We report the clinical, neuroimaging, and neuropathologic features of progressive nonfluent aphasia (PNFA), a rare neurodegenerative syndrome most notable for its distinct language disturbance. Longitudinal observations of 3 patients revealed progressively telegraphic speech and writing, followed by gradual deterioration of sentence comprehension, and finally, preterminal mutism and dementia. Magnetic resonance imaging revealed cortical atrophy most pronounced in anterior regions of the left hemisphere. Functional neuroimaging demonstrated reduced cerebral activity most prominently in left frontal and temporal regions. At necropsy, microscopic pathology of brain was most consistent with the diagnosis of "dementia lacking distinctive histology" (DLDH). A review of published primary progressive aphasia cases with adequate clinical and histopathological descriptions reveals that the most common pathology underlying PNFA is DLDH. PNFA is one example of a family of clinical syndromes with similar underlying histopathology that affects different regions of the frontal lobe.

Canadian guidelines for the development of antidementia therapies: a conceptual summary

The magnitude of the problems faced by Canadian society as a result of an aging population has been identified. Perhaps the most important concern related to this greying of Canada is the increasing incidence of dementia and Alzheimer's disease. Therapeutic options for these disorders have been limited to date. Advances in biotechnology and molecular biology will offer novel approaches to treatment. These and the expansion of more traditional therapeutic avenues require guidelines with the aim of optimizing their development.