Poorer long-term olfactory performance was noted in patients with Zika virus (ZIKV)-related Guillain-Barre syndrome (GBS) compared with individuals without ZIKV-related GBS, according to study findings published in the European Journal of Neurology.
GBS is a major neurological complication following postnatal ZIKV. It may also be a predictor of ZIKV infection of the peripheral nervous system and olfactory tract. Researchers sought to investigate the significance of GBS-related ZIKV infection on human olfaction.
The researchers conducted a prospective study (ClinicalTrials.gov Identifier: NCT01099852) that included 19 consecutive patients at university hospitals of Guadeloupe and Martinique in the French West Indies with ZIKV-associated GBS. For this group, the time between Zika or neurological onset and olfactory screening was a median 17 months. A total of 9 control individuals with similar GBS severity but without ZIKV were recruited from the same population between January 2018 and October 2019 with the time between Zika or neurological onset and olfactory screening a median of 18 months.
Up to 2 years following the acute phase, patients with GBS-ZIKA+ showed poorer olfactory function compared with individuals in the control group. Patients with GBS-ZIKA+ also had a significantly higher rate of hyposmia (68.4%) vs control individuals (22.2%; P =.042). Lower threshold and identification scores defined these deficits, which were independent of GBS severity.
Additional studies in immunodeficient mice infected with ZIKV found olfaction impairment, with high viral load in downstream brain structures and in the olfactory system.
Study limitations include the broad span in time between GBS onset and olfactory assessment, underpowered sample size, and use of AG129 mice limiting the investigation of long-term infection consequences.
Researchers noted that, “Patients with ZIKV-related GBS had poorer long-term olfactory function than patients with GBS-non-ZIKA, and ZIKV-infected mice are hyposmic.” They believe their observations suggest the list of viruses affecting the olfactory system should be amended to include ZIKV, and they added that, “Clinical evaluation of the olfactory system should be considered for ZIKV-infected patients.”
Lazarini F, Lannuzel A, Cabié A, et al; for the ZikaSmell Working Group. Olfactory outcomes in Zika virus-associated Guillain-Barré syndrome. Eur J Neurol. Published online June 14, 2022. doi:10.1111/ene.15444