Introduction

Magnetic resonance spectroscopy (MRS) is a non-invasive quantitative imaging technique with a high impact on diagnosing and managing central nervous system (CNS) disorders. MRS can assess regional levels of metabolites based on chemical alterations. Generally, N-acetyl aspartate (NAA), choline (Cho), creatine (Cr), and their ratios are the most common metabolites of the brain that are detected by MRS 1.
In the last years, COVID-19 infection had been a common cause of olfactory dysfunction. Although most of these anosmic patients will eventually improve within a few months, a considerable number of patients will develop prolonged smell loss more than two years after diagnosis 2,3. Overally, olfactory disorders could be classified as conductive sensory-neural or due to a central nervous system impairment 4. Until now, the basic pathogenesis of these complications remains controversial, and evidence suggests that the main pathogenesis of anosmia can probably depend on CNS dysfunction5. The most important current discussions in COVID-19 related anosmia are the controversies about the biochemical basis of these pathologies, diagnosis, and treatment 6. Therefore, using advanced CNS imaging to fill the lack of knowledge in the context of COVID-19 related anosmia and introduce more sensitive and specific methods for diagnosis is reasonable. Importantly, understanding the basic pathogenesis of the anosmia can potentially shed light on further trials to find a cure 7.
This study seeks to investigate the neurometabolic alterations in the brain structural regions associated with the olfaction process in cases with COVID-19 related anosmia. In this light, single-voxel spectroscopy was performed on five regions of interest (ROI), including anterior cingulate cortex (ACC), dorsolateral prefrontal cortex (DLPFC), insular cortex (IC), orbitofrontal cortex (OFC), and ventromedial prefrontal cortex (VMPFC) in the right hemisphere 8-11.