Distorted olfactory perception: a systematic review.

The sense of smell provides people with valuable input from the chemical environment around them. The human sense of smell generally fails in three ways; one is an intensity reduction and the other two are the quality of changes. Smell disorders can be classified into central or peripheral depending on their origin. Central causes can be related to an area of hyper-functioning brain cells generating this odor perception, thus olfactory distortions have also been observed with epilepsy and migraine. In this paper, we present a review of the current clinical understanding of olfactory distortions and discuss how they can be evaluated and therapies to treat this debilitating condition.

Host strategies against virus entry via the olfactory system.

In mammals, odorants are inhaled through the nose and inside the nasal cavity they trigger olfactory sensory neurons (OSN)  that are located within the olfactory epithelium. OSN project their axons into glomerular structures of the olfactory bulb. There they synapse with dendrites of second-order neurons that project their axons to the olfactory cortex. Thus, olfaction is based on direct interaction of environmental matters with OSN. This poses the question of how neurotropic viruses are prevented from infecting OSN and entering the central nervous system. Recent evidence indicates that upon instillation of neurotropic virus OSN are readily infected. By axonal transport virus reaches the glomerular  layer of the olfactory bulb where it is efficiently curbed by a type I IFN dependent mechanism. In this review local mechanisms limiting virus entry via the olfactory system and virus spread within the CNS are recapitulated in the context of anatomical properties of the olfactory system.

Olfactory and psychomotor symptoms in HIV and aging: potential precursors to cognitive loss.

In the United States, more than 100,000 adults 50 years old and over are diagnosed with the Human Immunodeficiency Virus (HIV). The number of older adults living with HIV is increasing dramatically due primarily to Highly Active Antiretroviral Therapy (HAART) which is transforming this disease into a chronic condition for many who are responding well to treatment. This population is also growing due to later-life infections and reflects the overall aging of the larger population in general. Yet, despite the novelty of such developing demographic trends, the negative consequences of aging with HIV are largely unknown. Therefore, it is necessary to synthesize the gerontological and HIV/AIDS literatures to hypothesize possible areas that may be of concern to people as they age with this disease. One area of particular concern focuses on tell-tale signs of cognitive problems and the development of dementia. Separately, older adults and adults with HIV are more susceptible of experiencing cognitive declines and dementia. Thus, as people age with HIV, they may be particularly susceptible of such cognitive problems and therefore detecting such problems in the early stages may be vital in preventing further problems. Based on the literature, adults infected with HIV experience impairments in olfaction and psychomotor ability. Similar symptoms are exhibited in older adults with Parkinson's disease and other dementias. Thus, for older adults with HIV, declines in both olfaction and psychomotor skills may be early signs of a developing neurodegenerative disorder. Implications for those aging with HIV are posited.

[Diagnosis of olfactory disorders--clinical standards and research]. / Diagnostik von Riechstörungen--Standards und Forschung.

Olfactory dysfunction has been reported to affect about 79,000 patients who were treated annually in German ORL-hospitals. The incidence of olfactory dysfunctions emphasizes the need for diagnostic strategies. This article features on the dysfunction of human olfaction including neurodegenerative diseases. Standard procedures for the psychophysical and objective assessment of olfactory function are presented. Current diagnostic imaging techniques for routine use and scientific approaches are discussed.

[Analysis of olfactory disorders in aging]. / Analyse des troubles olfactifs liés au vieillissement.

AGING EFFECT: The effect of aging on the olfactory system is generally observed in subjects over the age of 65 and is the number one cause of olfactory disorders. Several studies taking into account the state of the naso-sinus system and possible early stage of developing dementia have examined the precise effects of aging on olfaction. AGE-RELATED CHANGES: Aging affects olfactory thresholds, estimation of the intensity of an olfactory stimulation, and identification and memorization of odors. The elderly subject identifies food and other odors less easily than the young subject although elderly subjects can learn to improve their performance. Changes in the nasal cavity, particularly an alteration of the processes involved in neuron distribution in the olfactory neuroepithelium, may be involved. IMPACT OF OLFACTORY DEFICIENCY: There is much morphological and experimental evidence showing the effect of aging on both peripheral and central olfactory pathways allowing a better understanding of the functional impact of the sensorial deficit. Olfactory deficiency can explain in part the eating problems encountered in elderly patients.