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Chemosensory Disorders and Nutrition
Published in Alan R. Hirsch, Nutrition and Sensation, 2023
Carl M. Wahlstrom, Alan R. Hirsch, Bradley W. Whitman
After serendipitously finding that recurrent daily exposure to androstenone induced an ability to detect this odor in a previously androstenone odor blind lab worker, more formalized attempts to validate and expand this to those with olfactory dysfunction have been entertained (Wysocki, Dorries, and Beauchamp 1989). Over four months, recurrent exposure two times per day per nostril to four high-intensity common odors (lemon, rose, eucalyptus, and clove) has been demonstrated to improve olfaction to not only these specific smells, but odors in general (Hummel, Rissom, Reden, Hahner, Weidenbecher, and Bernd-Huttenbrink 2009). The exact mechanism of such an effect remains unclear, but it does not appear to be through action at the site of olfactory receptors, rather it may be through a top-down process—sniff treatment in normosmics unilaterally led to an increase in ipsilateral olfactory bulb volume by 11.3% and by even more, 13.1%, in the untreated nostril (Pietsch and Hummel 2014; Hummel and Pietsch 2014). While such a treatment approach is appealing, attempts by one author (ARH) to demonstrate clinically significant effects of such treatment have, so far, not been successful.
Abnormalities of Smell
Published in R James A England, Eamon Shamil, Rajeev Mathew, Manohar Bance, Pavol Surda, Jemy Jose, Omar Hilmi, Adam J Donne, Scott-Brown's Essential Otorhinolaryngology, 2022
Richard L. Doty, Steven M. Bromley
In some circumstances, both can be involved. Chronic rhinosinusitis, for example, can produce damage to the olfactory membrane in addition to blocking airflow, and altered membrane function can, over time, lead to degeneration within the olfactory bulb, which is a central structure. Although many causes of olfactory disturbance due to conductive factors or inflammation of the olfactory epithelium can be treated, most olfactory disorders due to sensorineural factors remain untreatable.
Cranial Neuropathies I, V, and VII–XII
Published in Philip B. Gorelick, Fernando D. Testai, Graeme J. Hankey, Joanna M. Wardlaw, Hankey's Clinical Neurology, 2020
Reduced sense of (hyposmia) or complete loss of (anosmia) smell can be congenital (as a result of absence of olfactory epithelium or hypoplasia/aplasia of the olfactory bulb) or more commonly, acquired. Olfactory disorders may be caused by local disease in the nose or by a lesion along the olfactory pathway. A unilateral lesion distal to the decussation of the olfactory fibers is usually asymptomatic due to bilateral cortical representation.3
Representations of the olfactory bulb and tracts in images of the medieval cell doctrine
Published in Journal of the History of the Neurosciences, 2022
In 1501, German physician, philosopher, and theologian Magnus Hundt (Parthenopolitanus; 1449–1519) published Antropologium, in which he sought to explain the body from medical, philosophical, and religious perspectives, believing that humans are created in the image of God and therefore represent a microcosm of the world as God created it. Contained in this work is a complex image summarizing the anatomy of the head and brain, which includes an unusual symbol near the bridge of the nose (Figure 1; see Hundt 1501). According to the original figure legend, the figure symbol “N” indicates Caru[n]cule [i.e., caruncle], derived from the Latin word caruncula (wart). This is a paired bulbous structure from which extend projections toward a meshwork at the base of the brain (the mythical rete mirabili). The projections from the two bulbous structures appear to connect together when they reach the rete mirabili. The entire set of olfactory structures resembles a tiny pair of eyeglasses at the bridge of the nose. These bulbous structures and their projections toward the brain are, in fact, a representation of the olfactory bulbs and the olfactory tracts. This interpretation is supported by a later figure derived from Hundt’s woodcut that has a more detailed and clearer legend (vide infra).
World Trade Center dust induces nasal and neurological tissue injury while propagating reduced olfaction capabilities and increased anxiety behaviors
Published in Inhalation Toxicology, 2022
Michelle Hernandez, Joshua Vaughan, Terry Gordon, Morton Lippmann, Sam Gandy, Lung-Chi Chen
Previously published evidence of both pulmonary and nasal tissue injury in mice intranasally exposed to WTCPM revealed increased inflammatory proteins in both bronchoalveolar- and nasal lavage fluids in mice, as well as WTCPM retention in tissues (Hernandez et al. 2020). Due to their proximity to the nasal passages, olfactory bulbs and their olfactory sensing neurons and receptor cells which line the nasal epithelium may provide a direct link between upper respiratory tissues and CNS tissues, whereby olfaction loss after acute or chronic exposure to several volatile chemicals have been reported. Odor molecules dissolved in the nasal mucus are detected by olfactory neuron and receptor cells within the epithelium, undergoing sensory transduction from the epithelium, through the cribriform plate, thus connecting the epithelia to the limbic system at the olfactory bulbs (Touhara 2014; Doty 2015).
Nose-to-brain drug delivery for the treatment of Alzheimer’s disease: current advancements and challenges
Published in Expert Opinion on Drug Delivery, 2022
Prabakaran A, Mukta Agrawal, Mithun Rajendra Dethe, Hafiz Ahmed, Awesh Yadav, Umesh Gupta, Amit Alexander
As discussed above, the brain is shielded by various protective mechanisms to preserve its integrity and protect it from a harmful stimulus. When a moiety tries to access the brain region via systemic circulation either after oral or IV (intravenous) or any other route of administration it needs to combat the BBB first. Unlike other oral and IV routes, the nasal cavity has a direct connection with the brain through neuronal channels [3,13]. The uppermost region of the nasal cavity, the olfactory region is connected with the frontal cortex of the brain specifically the olfactory bulb. Alongside, the core part (largest region) of the nasal cavity, the respiratory region is equipped with the trigeminal sensory neurons which are connected with the cerebrum, cerebellum, and brain stem [14]. Due to this clear and direct connectivity, the nose-to-brain delivery route could be considered as a “Green Corridor” to reach the brain. By choosing direct nose-to-brain delivery route, a drug could be effectively delivered to the brain without experiencing obstruction by the BBB. It offers various advantages over other conventional routes of brain targeting such as bypassing the GI exposure and GI degradation of drug, sidestepping the first pass or hepatic metabolism, minimizing undesirable adverse effects due to exposure to systemic circulation, faster onset of action, non-invasive and patient friendly. Owing to these perks, nose-to-brain delivery appears as an alternative, promising, and popular approach to target the brain region in the last few years [15].