Olfaction in persons with Alzheimer's disease.

The need for low cost, noninvasive procedures for aiding in the diagnosis and understanding of Alzheimer's Disease (AD) has led to theories and procedures examining the role of olfactory disorders because of the finding that the brains of AD patients invariably exhibit neuropathology in the hippocampus and entorhinal cortex. This loss correlates with the increase in the number of plaques and tangles and with the severity of dementia. Considered together, these findings suggest that brain structures closely related to the olfactory system demonstrate significant histopathology in AD. A comprehensive review of the literature pertaining to olfaction in persons with AD revealed that the olfactory identification ability of patients with memory disorders is impaired relative to controls. Consistency is lacking, however, when olfactory detection thresholds are investigated. Also, there is inconsistency in regards to severity of illness and olfactory function. In addition to differentiating AD patients from normals, the olfactory paradigm has shown some limited usefulness in differentiating AD patients from some other demented patients.