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.