xRead - Olfactory Disorders (September 2023)

Olfactory distortion

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importantly, whether the sensation persists or not. If it persists, it would be called a phantosmia. If it goes away, it would be called parosmia. Nasal endoscopy is indicated to examine the olfactory pathways in the nose and rule out a sinus infection or fungal myce toma. The olfactory cleft should be examined for signs of edema and purulent discharge. If the distortion is unilateral, application of an anesthetic to the same nostril resulting in resolution of the abnormal odor perception suggests a peripheral cause. Olfactory testing is a useful tool in identifying a peripheral cause for olfactory distortions. The evalu ation should include unilateral olfactory assessment with available standardized identi fi cation and/or threshold tests. Identifying a signi fi cant de fi cit in one side over the other can indicate that the nasal cavity is responsible for triggering the distortion. This not only helps to con fi rm a peripheral cause for the disorder, but also directs the physician to concentrate therapy on one side only, allowing for preservation of function on the contralateral side. According to recent research, the human olfactory bulb is a highly plastic structure that responds to individual changes in olfactory status [21]. Olfactory bulb volume decreases with the duration of the olfac tory loss. Patients with parosmia following infections or head trauma presented with signi fi cantly smaller olfactory bulbs than patients without parosmia [6,7]. In patients with post-traumatic loss of smell, the presence of parosmia was clearly associated with the presence of cerebral damage, especially in the fronto-orbital and anterior temporal cortices [22]. With a clear etiology by history and a negative exami nation such as with URTI, imaging may not be necessary. However, history or physical examination often guides the choice of imaging, which may con fi rm the suspicion. Imaging of the brain and nasal cavity is necessary to rule out tumors, infections, and obstructions. This can be done with contrast enhanced axial and coronal computed tomography (CT) scans or magnetic resonance imaging (MRI) scans. Especially in patients with distortions of no clear cause, the authors recommend MRI to rule out central mass lesions or neurodegenerative disorders. Olfactory testing Imaging

Antecedent events that precede the olfactory distor tion, especially parosmia, have been described in the literature to include URTI, head trauma, allergic rhini tis, and chronic rhinosinusitis [13-16]. According to the analysis of a series of 56 patients with parosmia [7], quantitative and qualitative alterations occurred simul taneously in 32 patients (57.1%). Parosmia onset occurred within 3 months after quantitative olfactory dysfunction in 19 patients (33.9%) and after 3 months in 5 patients (8.9%). In all patients, the sensation of par osmia was unpleasant and was typically described as a ‘ foul, ’ ‘ rotten, ’ ‘ sewage, ’ or ‘ burn ’ smell. Patients reported phantosmia (10 patients, 17.9%) or stimulant-identi fi able parosmia (46 patients, 82.1%). In these patients, the main odorant stimuli eliciting parosmia were gasoline (30.4%), tobacco (28.3%), cof fee (28.3%), perfumes (21.7%), fruits (15.2%, mainly citrus fruits and melon), and chocolate (13%). All the complaints concerned olfactory alterations alone (4 patients, 7.1%) or in combination with fl avor dys function (49 patients, 87.5%). The most common eti ologyofparosmiawasURTI(24patients,42.8%).Other possible etiologies were nasal andparanasal sinus disease (8 patients), toxic chemical exposure (4 patients), neurological abnormalities (3 patients), head trauma (2 patients), nasal surgery (2 patients), aging (1 patient), and idiopathic causes (12 patients) [7]. In contrast to this, most phantosmias present with no history of URTI, head trauma or aging [17]. Parosmias are most often observed as a consequence of infections of the upper respiratory tract, which typically lead also to olfactory loss [18]. Quanti fi cation of parosmias/phantosmias is dif fi cult. One idea relates to a separation of four grades of parosmia/phantosmia (0 – IV): do the distortions appear daily, are they intense, and do they have social/ other subsequences (e.g. weight loss, depression) [19]. Another idea relates to answers to two question 1: Because of my olfactory problem, food tastes different than itshouldtaste, and question 4:The biggest problem is not that I do not or weakly perceive odors, but that they smell different than they should [20]. To evaluate the patients with olfactory distortions, a thorough physical examination is needed. The patient ’ s general demeanor and psychiatric health should be assessed. A standard head and neck exam ination should be performed, paying special attention to the olfactory cleft, nasal mucosa, and airways. A dental examination should be included for the oral diseases that may produce a foul odor, and detailed cranial nerve examination is also important. Unilateral and bilateral nasal occlusion can be done to assess asymmetry in the distorted perception and, Physical examination

Laboratory testing

There is currently no battery of laboratory tests recommended for smell disorders. If a metabolic disorder is suspected, the patient should be referred