Spatial, temporal and numeric analysis of Alzheimer changes in the nucleus coeruleus

The distribution of neurofibrillary tangles in the nucleus coeruleus was topographically and quantitatively analyzed. The topographical analysis showed statistically significant differences with regard to the distribution of neurofibrillary tangles in the dorsal-ventral and medial-lateral axes. More neurofibrillary tangles were found to be located in the dorsal and medial regions than in ventral and lateral areas. No significant difference in neurofibrillary tangle content was found between the rostral and the caudal areas of the nucleus coeruleus. Neurofibrillary tangle formation begins in the central parts of the nucleus coeruleus. The total number of neuromelanized neurons in the nucleus coeruleus was determined using a modern, unbiased sampling scheme and related to the cortical stage of Alzheimer's disease-related neurofibrillary changes present. A statistically significant reduction (50%) in nucleus coeruleus neurons was evident only in cases meeting the histopathological criteria for Alzheimer's disease. The extent of reduction in the total number of neurons in the nucleus coeruleus did not correlate with the number of neurofibrillary tangles observed. Our data suggest that despite the relatively early susceptibility of the nucleus coeruleus to neurofibrillary tangle formation, significant neuronal loss appears to occur much later, with an estimated average delay time of at least 25 years. Nonetheless, comparison of the topographical pattern of neurofibrillary tangle formation and cell loss indicates that neuronal loss is tangle-related.