The study of neurological disorders using positron emission tomography and single photon emission computed tomography

Regional cerebral distribution of [Tc-99m] hexylmethylpropylene amineoxine in patients with progressive aphasia

Progressive aphasia is a prominent clinical feature of several neurodegenerative disorders. This study used hexylmethylpropylene amineoxine (HMPAO) single photon emission computed tomography (SPECT) to estimate blood flow in areas of the brain that mediate language in patients with progressive aphasia and matched control subjects. The patient population consisted of four men and 12 women with a mean +/- SD age of 69.1 +/- 7.6. Of these, eight were classified as having a nonfluent form of aphasia, whereas the other eight had a fluent form. The patients were compared to 16 healthy volunteers who were studied with an identical protocol. The SPECT images of the brain were acquired with 740 MBq (20 mCi) of Tc-99m-labeled HMPAO on a triple-headed gamma camera equipped with fan beam collimators. The images were analyzed with a set of standardized templates. Mean counts per pixel in 33 regions of interest were compared to the mean counts in the whole supratentorial brain. A laterality index was determined for homotopic regions using the equation 100 x (R - L)/(1/2 x (R - L)). Patients with progressive aphasia had several regions of significantly decreased HMPAO uptake in the left cortex when compared to the homotopic regions on the right. The most prominent deficit in the nonfluent group, as determined by the laterality index, were found in the left dorsolateral prefrontal region (p < 0.05), whereas the most prominent deficits in the group with fluent aphasia were found in the left temporal and parietal language centers (p < 0.05). The left subcortical nuclei were differentially affected, particularly in patients with nonfluent aphasia. The HMPAO SPECT indicates that multiple regions of the left hemisphere are dysfunctional in patients with progressive aphasia. The pattern of perfusion deficits in patients with fluent aphasia appears to be distinct from the pattern in patients with nonfluent aphasia.

Evolution in the conceptualization of dementia and Alzheimer's disease: Greco-Roman period to the 1960s

Most histories of senile dementia commence with Alois Alzheimer's description in 1906 of the first case of Alzheimer's disease, yet the history of senile dementia before 1906 is quite rich, dating back to the ancient Greek and Roman philosophers and physicians. Over the 2500 years since ancient times, the concept of senile dementia has evolved from a rather vague notion that mental decline occurred inevitably in old age, to become defined today by a distinct set of clinical and pathological features with the potential for treatment and prevention within grasp. Throughout history, many elderly individuals with unpredictable behavior were sequestered in institutions, and the line between mental disorders and senile dementia was hazy at best. The identification of Alzheimer's disease at the onset of the 20th century was a turning point for the understanding of senile dementia, and the concepts and histological findings presented by the early researchers of Alzheimer's disease remain relevant still today. Indeed, these early findings are proving to be a continuing source of insight, as many of the issues debated at the turn of the century remain unresolved still today. This paper thus traces the history of the evolution of our current conceptualization of Alzheimer's disease from the amorphous Greco-Roman concept of age-associated dementia.