Cerebrospinal fluid from COVID-19 patients with olfactory/gustatory dysfunction: A review.

OBJECTIVE: We reviewed the literature on cerebrospinal fluid (CSF) testing in patients with altered olfactory/gustatory function due to COVID-19 for evidence of viral neuroinvasion. METHODS: We performed a systematic review of Medline and Embase to identify publications that described at least one patient with COVID-19 who had altered olfactory/gustatory function and had CSF testing performed. The search ranged from December 1, 2019 to November 18, 2020. RESULTS: We identified 51 publications that described 70 patients who met inclusion criteria. Of 51 patients who had CSF SARS-CoV-2 PCR testing, 3 (6%) patients had positive results and 1 (2%) patient had indeterminate results. Cycle threshold (Ct; the number of amplification cycles required for the target gene to exceed the threshold, which is inversely related to viral load) was not provided for the patients with a positive PCR. The patient with indeterminate results had a Ct of 37 initially, then no evidence of SARS-CoV-2 RNA on repeat testing. Of 6 patients who had CSF SARS-CoV-2 antibody testing, 3 (50%) were positive. Testing to distinguish intrathecal antibody synthesis from transudation of antibodies to the CSF via breakdown of the blood-brain barrier was performed in 1/3 (33%) patients; this demonstrated antibody transmission to the CSF via transudation. CONCLUSION: Detection of SARS-CoV-2 in CSF via PCR or evaluation for intrathecal antibody synthesis appears to be rare in patients with altered olfactory/gustatory function. While pathology studies are needed, our review suggests it is unlikely that these symptoms are related to viral neuroinvasion.

Prevalence of taste disorders in idiopathic and B. burgdorferi-associated facial palsy.

The frequency of taste disorders in idiopathic facial palsy (IFP) and B. burgdorferi-associated facial palsy (BFP) was retrospectively assessed in a cohort of patients with acute peripheral facial palsy (AFP). A significant (>10/microl) CSF pleocytosis was found in 17% of the patients who underwent lumbar puncture for AFP. In two centres, 26 patients with BFP were identified by CSF and serological criteria. The control group (patients with IFP) consisted of 59 patients from one of the centres in whom BFP was excluded by CSF examination. AFP patients of both centres are routinely questioned about taste disorders according to the hospitals' standards. A taste disorder was found in 46% of the IFP and 31% of the BFP cases (not significant). About one-third of the BFP patients complained of radicular or back pain. We conclude that a history of taste disorder is not helpful in distinguishing clinically between BFP and IFP.