Researchers at a major US medical center have explored a novel approach to parosmia, a condition where the sense of smell is distorted. The method targets the stellate ganglion, a bundle of nerves in the neck that modulates automatic bodily functions. The team describes the process as a CT-guided neural block aimed at the regional autonomic nervous system, offering a potential route to reduce abnormal odor perception.
Parosmia has emerged as a notable aftereffect for many individuals recovering from COVID-19. Reports indicate that a sizable portion of patients experience persistent changes in smell, with some studies noting that as many as six in ten people may be affected during the post-illness period. For many, these smell distortions last for months or even years, leading to reduced appetite, altered dining experiences, and a diminished quality of life. This backdrop frames the urgency of exploring effective interventions beyond standard recovery expectations.
The American investigation centers on temporarily inhibiting the stellate ganglion through a precise injection. The stellate ganglia consist of sympathetic nerve fibers that influence involuntary functions such as heart rate, blood pressure, respiration, and digestion. In the described procedure, a local anesthetic is delivered directly into the stellate ganglion on one side of the neck, with corticosteroids co-administered to help lessen nerve inflammation that can accompany infections like COVID-19. The aim is to attenuate abnormal autonomic signaling that may contribute to distorted odor processing.
In their study, 54 participants were enrolled and received the neck injection with a spinal needle placed at the base of the neck to reach the target nerve cluster. The protocol combined anesthesia with anti-inflammatory agents to address nerve irritation that can accompany viral illness. The investigators then monitored changes in smell perception over time, seeking signs of stabilization in the sense of smell and appreciation of odors during daily life.
Longer-term follow-up included 37 participants. Among them, 22 reported a noticeable reduction in parosmia symptoms within one week after the injection, with 18 of those cases continuing to show further improvement a month post-procedure. While a subset of participants—26 in total—opted for a second injection, the later treatment did not yield additional benefits for them. Importantly, there were no reported complications or adverse events linked to the procedure in this cohort.
Researchers note that existing therapies for parosmia have not produced consistent results, underscoring the need for continued exploration of this approach. They emphasize that additional studies with larger populations and longer follow-up are essential to confirm efficacy, determine optimal dosing and timing, and refine patient selection criteria. The findings point to a potential early signal that autonomic modulation may influence smell restoration, but they also stress caution and the requirement for rigorous validation before widespread adoption.
Beyond the immediate procedure, the investigation touches on the broader relationship between neural pathways and smell. The science suggests that altered signaling in the autonomic nervous system could interfere with how the brain interprets olfactory information. By dampening certain neural signals, it may be possible to recalibrate the system enough to reduce distorted odor experiences. This line of inquiry sits at the intersection of neurology, otolaryngology, and perception science, inviting further collaboration across disciplines to map mechanisms, refine techniques, and build safe, repeatable treatments for those affected by parosmia in the wake of COVID-19.
While this work shows promise, it does not yet establish a standard of care. The research community remains focused on confirming results through additional trials, identifying which patients may benefit most, and ensuring procedure-related risks are thoroughly assessed and minimized. In the meantime, clinicians continue to balance symptom management with the goal of restoring a more accurate sense of smell for individuals coping with parosmia after infection.