The role of surgery in the management of phantosmia.

INTRODUCTION Phantosmia is the qualitative disorder of olfaction characterized by the perception of odor, usually unpleasant, when there are no odorants present. It may be described as cacosmic (rotten, decayed, fecal), torquosmic (burned, metallic, chemical-like), or mixed. Phantosmia is a relatively uncommon disorder of olfaction and represents around 10% to 20% of olfactory disorders among those complaining of olfactory dysfunction. When present, it may lead to a significant reduction in quality of life for patients. Disorders of olfaction can be broadly classified as conductive and sensorineural. Conductive disorders typically involve the presence of a physical barrier, which prevents odorants from reaching olfactory mucosa such as tumors, chronic rhinosinusitis, and nasal polyps. Sensorineural olfactory disorders represent those pathologies for which there is dysfunction of the olfactory sensory receptors, olfactory neurons, or central pathways of olfaction. Hence, phantosmia is considered a sensorineural disorder of olfaction. Phantosmia can be further classified as either peripheral or central in nature. Peripheral phantosmia is thought to be due to the dysfunction of the olfactory receptors or neurons, leading to an inability to form a complete picture of the odor and hence the erroneous interpretation of the odor centrally. It is hypothesized that peripheral phantosmia occurs following an insult to the olfactory mucosa, leading to destruction of the olfactory mucosa innervation and olfactory receptors. As healing occurs, there is the development of spurious or incomplete reinnervation, typically resulting in the erroneous interpretation of presented odors. The pathophysiologic changes may involve a loss of inhibitory neurons or a development of abnormally active olfactory receptors or neurons. Central phantosmia is a condition thought to be unrelated to the olfactory neurons or receptors, and a consequence of errors made at the integrative and interpretive centers of the olfactory pathways. This differentiation between peripheral and central phantosmia is a crucial clinical point because surgery on the olfactory mucosa can only successfully treat peripheral phantosmia and will have no effect on central phantosmia. In this case series, we present the diagnostic features of peripheral and central phantosmia, as well as describe the surgical technique utilized in our institution and the outcomes of the patients after such treatment. Surgical management of phantosmia has been previously described by Leopold, and we elaborate on the author’s original description of the surgical technique.