Olfactory nerve: from ugly duckling to swan

Abstract

Background: The olfactory nerve has never been the shining star of neurological examination. Quite the contrary, examining the first cranial nerve is often an overlooked step. As cases of anosmia secondary to COVID-19 infection continue to rise, the 2020 pandemic has shed new light on this much-forgotten nerve, its value as an aid to diagnosis of several diseases and its central role in our daily lives. Objective: We aimed to emphasize how essential and simple clinical examination of the olfactory system can be by highlighting practical techniques and clinical tips for its assessment. We also share pearls and pitfalls in localization and differential diagnosis, which may prove valuable to busy clinicians. Methods: A broad review of the literature was conducted by searching PubMed, Cochrane and Google Scholar for articles and books containing topics regarding examination of the olfactory nerve and its anatomy, physiology and pathology. No particular inclusion or exclusion criteria were used. Results: Forty different works were found, between books and articles, from which 20 were selected after careful analysis. Conclusions: Despite the tragedy and adversity that followed the COVID-19 pandemic, its legacy has taught us a crystal-clear lesson: olfaction should no longer be neglected in clinical practice.

Needs assessment of essential anatomy: The perspective of adult primary care resident physicians

“…However, with recognition of olfactory dysfunction as a significant symptom related to coronavirus disease (COVID-19) in many patients, [51][52][53] it is reasonable to expect that a focus on cranial nerve I would be added to the routine neurologic exam. 54,55 Thus, it is perhaps not surprising that this anatomical topic was classified as essential by primary care residents and the data in this study provide evidence to support the conclusion that cranial nerves are essential to the practice of medicine. Furthermore, this presents an opportunity to emphasize the relationship in the UME gross anatomy curriculum between this foundational anatomy (cranial nerves) and the neurologic examination in clinical practice.…”

“…Textbooks of anatomy 40–42,47 and those focused on physical examination 48,49 dedicate chapters or sections to the anatomy of cranial nerves and their functions. Harrison's Principles of Internal Medicine 50 recognizes the neurologic examination as essential for all clinicians, especially generalists, noting “…most clinicians begin with assessment of mental status followed by the cranial nerves, motor system, reflexes, sensory system, coordination, and gait.” Seidel's Physical Examination Handbook 48 notes “Cranial nerves II‐XII are routinely tested; however, taste and smell are not tested unless some aberration is found.” However, with recognition of olfactory dysfunction as a significant symptom related to coronavirus disease (COVID‐19) in many patients, 51–53 it is reasonable to expect that a focus on cranial nerve I would be added to the routine neurologic exam 54,55 . Thus, it is perhaps not surprising that this anatomical topic was classified as essential by primary care residents and the data in this study provide evidence to support the conclusion that cranial nerves are essential to the practice of medicine.…”