Chemosensory Disorders and Nutrition
Alan R. Hirsch in Nutrition and Sensation, 2023
In 1985, it was demonstrated that a closed-head injury can impair the ability to identify odors without impairing the ability to detect odors (Levin, High, and Eisenberg 1985). In such cases, the integrity of the olfactory nerve is maintained. In fact, in one study of patients complaining of posttraumatic dysosmia, the peripheral nerves were found intact and free of tears, thus leading to the inference that possibly an abnormality of the frontal lobe or its surrounding structures was responsible for the patients’ inability to identify odors that they were, however, able to detect (Asaka et al. 1988). This same pattern of dysosmia has been identified in patients with nontraumatic brain conditions such as Korsakoff’s syndrome (Jones, Butters, Moskowitz, and Montgomery 1978), thalamic or prefrontal cortical lesions (Potter and Butters 1980), senile dementia of the Alzheimer’s type (Green, Songsanand, Peretz, Hsu, Corkin, and Growdon 1989), and temporal lobectomy (Eichenbaum, Morton, Potter, and Corkin 1983).
Neuroimaging in Sports-Related Brain Injury
Mark R. Lovell, Ruben J. Echemendia, Jeffrey T. Barth, Michael W. Collins in Traumatic Brain Injury in Sports, 2020
Because of the likelihood of frontal injury in head trauma, combined with the location of the first cranial nerve (olfactory nerve), it is common for some disruption in smell to occur acutely, even in mild TBI. When MR imaging demonstrates inferior frontal damage, these changes in olfaction are likely permanent. This is demonstrated in Figure 5.4, a case in which a young adult male was assaulted by being thrown against a wall (back of head striking first; thus, the frontal contusion is likely a result of a contrecoup injury). There was questionable loss of consciousness, but definite confusion and posttraumatic amnesia (PTA) of several hours. The patient’s headache and typical post-concussive symptom’s persisted, yet on standard neurological assessment the patient had only impaired smell but no other major abnormality. Normal olfaction never returned and the follow-up MR imaging demonstrated encephalomalacia in the olfactory groove region and anterior-inferior aspect of the frontal lobes bilaterally (see Fig. 5.4). These types of lesions also indicate a likelihood of more generalized inferior frontal damage that often does not disrupt specific cognitive functions but will produce changes in temperament and emotionality. Such changes were observed in this patient.
Nervous system
David Sturgeon in Introduction to Anatomy and Physiology for Healthcare Students, 2018
The final part of the limbic system (to be discussed here) are the olfactory bulbs that transmit sensory information regarding odours to the amygdala, hippocampus, thalamus and cerebrum via the olfactory tract. The olfactory receptors are embedded in a specialised area of mucous membrane in the roof of the nasal cavity. The olfactory bulbs are situated directly above on either side of the cribiform plate of the ethmoid bone and are innervated by the olfactory nerve (cranial nerve I). The association between smell and memory is particularly strong because of the connection between the olfactory bulb and other parts of the limbic system such as the amygdala and hippocampus. Some smells are closely associated with particular events, people, moods and emotions, and can prompt very different responses from people depending on their experiences. For example, the smell of chlorine might be associated by one person with the swimming pool (good experience) and by another with the hospital (bad experience). I know somebody who still feels nauseous every time they smell a particular soft drink because it was the last thing they drank before surgery some thirty years previously.
Loss of Ocular Surface Sensation in a Covid-19 Patient–a Novel Finding
Published in Ocular Immunology and Inflammation, 2022
Sertaç Argun Kivanç, Berna Akova
Syn-ropanethial-S-oxide, released when the onion is cut, is known as the lacrimator factor and it stimulates the ocular surface and the lacrimal gland without damaging it and allows this substance to move away from the eye surface by irrigating the eye.3 Therefore, it is expected to increase tearing in a normal ocular surface. However, our patient had no response to onion. He had decreased ocular surface sensation, loss of smell and taste. It has been reported that the coronavirus impairs the smell and taste.4 In COVID-19 autopsy cases, presence of high amount of high SARS CoV-2 was detected in the olfactory mucosa underneath the cribriform plate, olfactory bulb, trigeminal ganglion, and medulla oblongata.5 In another study, the virions of SARS CoV-2 were identified in the olfactory nerve, gyrus rectus and brain stem of COVID 19 patients and ultrastructural damage to the axons was shown.6 The anosmia or hyposmia is likely to be associated with the SARS CoV-2 damage to the neurons of olfactory nerve and bulb.
Olfactory perception in patients with a mild traumatic brain injury: a longitudinal study
Published in Brain Injury, 2022
Coline Zigrand, Benoit Jobin, Fanny Lecuyer Giguère, Jean-François Giguère, Benjamin Boller, Johannes Frasnelli
In addition, the typically used clinical tests may not capture changes in intensity and pleasantness of olfactory stimuli. In fact, both dimensions are rarely evaluated in clinical consultations (10). Patients with a history of mTBI rated odors as more intense and less pleasant than controls, suggesting subtle olfactory alterations (24). In line with this, when rating common odors’ pleasantness and intensity, patients with TBI exhibit reduced activation in both primary and secondary areas of the olfactory cortex (25). After a brain injury, OD can be caused by three mechanisms: (1) mechanical damage to the nose, (2) injury/ tear of the olfactory nerve, (3) contusion/ hemorrhage in central olfactory areas (6,26). The most likely olfactory brain region to be injured is the orbitofrontal cortex (6,25), the secondary olfactory cortex (22), which is a key structure to conscious olfactory perception (27–29). However, these proxies have not yet been studied in patients with mTBI during the acute phase.
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
The olfactory nerve pathway is a direct and primary route of drug transport from the nasal cavity to the brain. Based on the nature of drug and cellular structure there are two mechanisms of drug transport including intracellular and extracellular paths. The intracellular path utilizes olfactory neurons usually for lipophilic moieties, while extracellular passage of hydrophilic or polar drugs takes place through olfactory epithelial cells [18,19]. The intracellular passage is a slower mode of drug transport to the brain which takes around 24 h, it is also considered as intraneural path 3. The axonal end of olfactory neurons starts from the mucus layer of olfactory epithelium and ends in cells of the mitral valve at the olfactory bulb by crossing the cribriform plate of lamina propria. This region is filled with CSF, and neurons are surrounded by olfactory ensheathing cells. This olfactory nerve channel is expanded to other different regions of the brain like piriform cortex, anterior olfactory nucleus, olfactory bundle, and hypothalamus [20]. In intracellular transport, the drug is taken up by the neurons via endocytosis from the olfactory epithelial cells and then it passes through the nerve channels and enters the olfactory and other regions of the brain. Besides, transcellular pathway involves drug transfer through passive diffusion, receptor mediated endocytosis, fluid phase endocytosis, etc. This mode is suitable for the passage of highly lipophilic molecules.
Related Knowledge Centers
- Action Potential
- Central Nervous System
- Olfactory Mucosa
- Olfactory Receptor Neuron
- Embryo
- Cranial Nerves
- Sense of Smell
- Afferent Nerve Fiber
- Odor
- Nasal Placode