xRead - Olfactory Disorders (September 2023)

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INTERNATIONAL CONSENSUS ON OLFACTION

COVID-19 testing is indicated in sudden-onset anosmia, as outlined in numerous studies. 1305–1307 More importantly, COVID-19 represents one of the only causes of PVOL for which antibody testing could become a standard of care as part of the diagnostic workup, taking into account preliminary data obtained so far. 1308,1309 In summary, evidence-based literature on laboratory studies for evaluation and diagnosis of OD is sparse and no firm recommendations can be made at this stage. Further research is required to assess whether a panel of laboratory tests in a large number of patients with hyposmia/anosmia would be useful for routine evaluation and diagnosis of OD. Until then, thorough history-taking, review of sys tems, and knowledge of the various causes of OD are still required to guide the physician on a case-by-case basis. Ordering laboratory testing for patients with OD is better based on specific history as opposed to sending routine tests on all patients. Aggregate grade of evidence : C (Level 3: one study), see sections under Etiology for other specific potential lab oratory investigations suggested based on specific history. H Specific evaluation and workup for phantosmia Phantosmia is a qualitative olfactory disorder in which a person perceives an odor in the absence of an odorant stimulus. 19 As with other olfactory disorders, a thorough history is required to make the diagnosis. Having an under standing of the typical presentation and progression can allow medical providers to elicit specific details from the patient history if phantosmia is suspected. Similar to migraine, phantosmia occurs most frequently in females starting in the second or third decade of life. Initial episodes often begin sporadically without an identifiable inciting event, prompting the person to seek an external source for the unusual odor. Episodes occur more frequently and for longer duration as time goes on, eventually occurring on a daily basis and lasting for most of the day. 1310,19 Patients will often describe phantom smells as smoky, burned, foul, unpleasant, spoiled, or rotten. 1310,1311,19 Phantosmia can occur in one or both nostrils. Occlusion of the affected nostril(s), intranasal instrumentation, Valsalva, head inversion, forced crying, gagging, and sleep are some reported activities that can abort the phantom smell; however, with time, these methods eventually become ineffective. 18,19,1310–1312 In contrast to other qualitative olfactory disorders, most cases of phantosmia are idiopathic and less commonly present after URI, head injury, or with aging. 19,1312,1313 There are several neurologic and psychi

atric disorders that have been shown to be associated with phantom smells including temporal lobe epilepsy, migraine disorder, PD, intracranial neoplasm, depression, schizophrenia, and olfactory reference syndrome. Other reported associations include CRS, iatrogenic causes, and metabolic disorders. 19,23,1311,1312,1314–1320 The exact mechanism is unknown with each of these potential causes, but both peripheral and central triggers have been hypothesized. 18,19,23,1310,1319,1321 Certainly, olfactory pro cessing in the CNS is a major factor. Given the wide range of possible causes, performing a complete history and review of systems can help elucidate a possible etiology and therefore guide treatment more effectively. A standard head and neck examination is indicated for all patients with suspected phantosmia. Examination should include bilateral nasal endoscopy to assess the patency of the OC and rule out the presence of polyps, tumors, or sinonasal mucosal edema, as well as any post operative changes, adhesions, or crusting if applicable. For additional confirmation, each nostril should be blocked individually to note the effect on the phantom smell. If the trigger or cause of the phantom odor is related to the peripheral olfactory neurons, anesthetizing the olfac tory area should abort the phantom smell and can help determine whether it is unilateral or bilateral. 19,246,497,1310 A basic neurologic examination should be performed in addition to assessing the patient’s overall demeanor during history of physical examination given the association with several neurologic and psychiatric disorders. 246,497,1314 Although phantosmia has been shown to be associated with a decrease in quantitative OF in the affected nostril(s), this is not always the case. 23,1312,1314 Nevertheless, uninasal olfactory testing (identification and possibly threshold test ing) should be performed to document the patient’s base line OF at initial evaluation. 19,246,497,1310,1314 Imaging should include a CT scan of the head/sinuses and/or MRI of the brain to rule out intracranial or sinonasal pathology. 19,246,497,1310 Electroencephalography, positron emission tomography, and fMRI are generally reserved for research purposes and not recommended for the initial workup of phantosmia. 246,1310 Laboratory stud ies are not needed in the workup of phantosmia. Appropri ate referrals to neurology, psychiatry, or endocrinology for further evaluation and/or treatment should be considered. IX MANAGEMENT A Prognosis and spontaneous recovery Estimating true spontaneous recovery time after the onset of OD is difficult, as many patients delay reporting smell loss. This makes it difficult to establish a etiology,