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Original Investigation
April 2, 2020

Evaluation of the Incidence of Other Cranial Neuropathies in Patients With Postviral Olfactory Loss

Author Affiliations
  • 1Department of Otolaryngology, Navamindradhiraj University, Bangkok, Thailand
  • 2Department of Otolaryngology, Thammasat University, Pathumthani, Thailand
  • 3Department of Otolaryngology–Head and Neck Surgery, Stanford University School of Medicine, Palo Alto, California
JAMA Otolaryngol Head Neck Surg. 2020;146(5):465-470. doi:10.1001/jamaoto.2020.0225
Key Points

Question  Is there increased risk of other cranial neuropathies in patients with postviral olfactory loss compared with a control population?

Findings  In this case-control study of 91 patients with olfactory loss and 100 control patients without olfactory loss, the incidence of other cranial neuropathies in the postviral olfactory loss group was 11%, which was significantly higher than the 2% incidence found in the control group.

Meaning  This finding suggests that there may be an inherent vulnerability to cranial nerve damage or decreased ability for cranial nerve recovery in patients who experience this disease process.

Abstract

Importance  Postviral olfactory loss is a common cause of olfactory impairment, affecting both quality of life as well as overall patient mortality. It is currently unclear why some patients are able to recover fully after a loss while others experience permanent deficit. There is a lack of research on the possible association between postviral olfactory loss and other cranial neuropathies.

Objective  To evaluate the incidence of other cranial nerve deficits in patients with postviral olfactory loss and determine if there is an association with neurologic injury in this group. This study also sought to determine if other known risk factors were associated with postviral olfactory loss.

Design, Setting, and Participants  A case-control study was conducted at a tertiary care rhinology clinic from January 2015 to January 2018 to review the incidence of cranial neuropathies in 2 groups of patients, those with postviral olfactory loss and those with chronic rhinosinusitis without olfactory loss used as a control group.

Exposures  The Stanford Translational Research Integrated Database Environment (STRIDE) system was used for patient identification and data extraction. Patients with a history of olfactory loss or chronic rhinosinusitis as well as incidence of cranial neuropathies were identified by using International Statistical Classification of Diseases and Related Health Problems, Tenth Revision (ICD-10) codes.

Main Outcomes and Measures  This study reviewed incidence of postviral or idiopathic cranial neuropathies in both patient groups, while also evaluating for any difference in demographic characteristics, comorbidities, or other patient-related factors.

Results  There were 91 patients in the postviral olfactory loss group and 100 patients in the control group, which were age and sex matched as closely as possible. Of the 91 patients with postviral olfactory loss, mean (SD) age was 56.8 (15.3), and 58 (64%) were women; for the control group, the mean (SD) age was 57.5 (15.6) years, and 63 (63%) were women. Racial breakdown was similar across cases and controls, with white individuals making up 59% to 65%; Asian individuals, 20% to 24%; black individuals, approximately 3%; Hispanic individuals, approximately 1%; and the remaining patients being of other race/ethnicity. The incidence of other cranial neuropathies in the postviral olfactory loss group was 11% compared with 2% within the control group (odds ratio, 6.1; 95% CI, 1.3-28.4). The study also found 2 cases of multiple cranial neuropathies within a single patient within the olfactory group. Family history of neurologic disease was associated with more than 2-fold greater odds of cranial nerve deficit (odds ratio, 3.05; 95% CI, 0.59-15.68).

Conclusions and Relevance  Postviral olfactory loss appears to be associated with a higher incidence of other cranial neuropathies. It is possible that there is an inherent vulnerability to nerve damage or decreased ability for nerve recovery in patients who experience this disease process.

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