Volume 29, Issue 12 (3-2023)                   RJMS 2023, 29(12): 130-135 | Back to browse issues page

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Soltanabadi M, Hedayati R, Hekmat S. Role of 99m Tc ECD Brain Perfusion SPECT in Assessment of Chronic Neurologic Complications of COVID-19. RJMS 2023; 29 (12) :130-135
URL: http://rjms.iums.ac.ir/article-1-7740-en.html
MD, Assistant Professor, Hasheminezhad Hospital, Department of Nuclear Medicine, Iran University of Medical Sciences, School of Medicine, Tehran, Iran , dochedayati@gmail.com
Abstract:   (635 Views)
COVID-19, the infectious disease caused by the most recently discovered coronavirus was declared as a pandemic by The World Health Organization (WHO) on March 11, 2020. The widespread spread of infections created an immediate emergency, with the number of affected patients exceeding the capacity of many involved healthcare systems, resulting in significant morbidity and mortality (1). More than 300 million people have been infected as a result of this pandemic disease (2). A significant number of people have also been affected by the acute and chronic complications of the pandemic disease COVID-19. Large-scale studies revealed that many COVID-19 patients experience symptoms for at least six months after recovery. The quality of life of about 10–30% of patients is severely impacted by lingering symptoms. This clinical condition has been acknowledged and labeled as a post-COVID-19 condition by the World Health Organization. Physical, neurocognitive, and psychiatric symptoms of this condition that last longer than two months and cannot be accounted for by another diagnosis are present three months after the onset of COVID-19 (2).
Most clinicians have focused on pulmonary manifestations of this disease since its inception; however, neurologic complications may occur subtly and significantly increase morbidity and mortality in these patients. Although SARS-CoV-2 primarily affects the respiratory system, several studies have found neurological complications in COVID-19 patients. Headache, dizziness, loss of taste and smell, encephalitis, encephalopathy, and cerebrovascular diseases are the most common neurological complications associated with COVID-19. Seizures, neuromuscular junction disorders, and Guillain-Barré syndrome, as well as neurodegenerative and demyelinating disorders, have also been reported as COVID-19 complications (3). PCNS denotes prolonged post-COVID-19 neurological symptoms. Several studies have found that PCNS can manifest as long-term symptoms that last for months, such as muscle pain and weakness, myopathy, sleep impairment, anxiety, depression, severe post-traumatic stress disorder (PTSD), dizziness, headaches, and anosmia. Previous findings suggest that COVID-19 patients should be followed up after recovery for possible long-term post-COVID-19 neurological complications (3). Indeed, SARS-CoV-2 acts on angiotensin-converting enzyme-2 receptors found in lung alveoli type 2 as well as the brain (mainly in the brainstem). In this framework, the neuro-invasion of SARS-CoV2 has even been advocated to explain the development of respiratory failure in some patients (1). Fatigue, muscle weakness, depression, sleep difficulties, headaches, loss of smell and taste, tingling sensations, dizziness, nausea, and severe fatigue are some of the other symptoms. Furthermore, COV-ID-19 has been shown to be a risk factor for acute ischemic stroke (AIS). AIS in SARS-CoV2 patients is associated with more severe neurological deficits and higher in-hospital mortality. The incidence of AIS in COVID-19 patients is estimated to be around 1.5%, though this percentage is higher in critically ill patients (4). Myoclonus and ataxia, with or without opsoclonus, have recently been identified as a central nervous system syndrome associated with coronavirus disease-2019 (COVID-19), one of the other distinct neurological manifestations (5, 6).
The exact mechanism of COVID-19's effects on the brain is unknown: either direct invasion to the brain or indirect invasion through hypoxia of the brain or a severe inflammatory response of the body (3). Many COVID-19 patients with severe hypoxia have disproportionately few symptoms of cerebral hypoxia, a phenomenon known as "happy hypoxia" (7). As a result, the brain's oxygen supply is underestimated, resulting in neurological damage, particularly in brain regions such as the hippocampus, which are particularly vulnerable to hypoxia.
According to studies, a severe inflammatory response involving different immune cells around the vascular system and in brain tissue, as well as microhemorrhages, can develop in the CNS of COVID-19 patients (8).
Because of the neuronal damage, patients may experience ongoing neurological and psychological issues that negatively impact their quality of life. After recovering from COVID-19, many patients, according to researchers, continue to struggle with cognitive issues such as memory loss and impaired concentration for several months.
These COVID-19 neurological manifestations can be diagnosed using imaging, laboratory tests, and CSF analysis, depending on the patient's symptoms. Although CT and MRI are the primary methods used to evaluate these patients, some neurological complications show no abnormal findings in these imaging modalities. Brain SPECT, or single photon emission computed tomography, uses 99m-Tc ECD/HMPAO as a radioactive tracer to measure regional cerebral perfusion and create tomographic images of the three-dimensional distribution of the radiopharmaceutical. As a functional, anatomical, and molecular imaging technique, this method can be utilized for the diagnosis and treatment of neurologic complications in COVID-19 patients.
The imaging algorithm of COVID-19 does not prioritize brain scanning, and for some patients, it may not even be practical. In a small subset of patients, magnetic resonance imaging (MRI) may be useful during the acute phase and may be useful in understanding neuro-COVID mechanisms immediately following recovery. Even though the mid- and long-term effects of SARS-CoV-2 neuro-infection are still unknown, cases of post-COVID-19 likely autoimmune (steroid responsive) but seronegative encephalitis as well as patients with anosemia have been reported in the absence of any change on MRI in COVID-19 patients (1).
There are many uses for brain perfusion scintigraphy in COVID patients that have been demonstrated in the literature, including the assessment of cerebrovascular disease, convulsions, psychiatric issues, etc. By using baseline imaging and follow-up imaging, this imaging modality is useful for the diagnosis and assessment of the severity of cerebrovascular disease, such as CVA, and the assessment of the viability of brain tissue. It is also helpful for choosing the best therapy and evaluating the response to treatment. The evaluation of epileptogenic focus could also be done using this technique.
Pharmaceuticals that improve local cerebral blood flow, like acetazolamide, can be used in conjunction with this modality (carbonic anhydrase). In transient ischemic attack and stroke patients with COVID-19, acetazolamide increases local pCO2 and causes arteriolar dilation, allowing for the assessment of cerebrovascular reserve. It can also be used to differentiate between vascular and neuronal causes of dementia (9).
Additionally, brain SPECT can help with the differential diagnosis and diagnosis of various psychiatric issues, such as mood disorders, depression, anxiety, mild cognitive impairment, and loss of smell, and it can tell a factitious disorder from a real disease (9).
Brain SPECT results can be used to guide the individualized treatment of COVID-19 patients with neurological and psychological complications. Additionally, by comparing baseline and follow-up images, which is done by visually and quantitatively measuring brain perfusion, SPECT brain images could be used to assess treatment response. Brain perfusion scintigraphy may be useful for proper diagnosis, improving patient management, and predicting prognosis. Prompt diagnosis of neurologic and psychiatric manifestations of COVID-19 is essential for appropriate management.
According to an analysis of the literature, brain perfusion scans may be an important imaging tool for the differential diagnosis of neurological sequelae, therapeutic management, and patient follow-up. It is also a helpful research tool because it is widely accessible and allows for non-invasive in vivo evaluation of brain function. Clarification of this method's role in treating COVID patients with neurologic complications requires additional research.

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Type of Study: Letter to the editor | Subject: Neurology Psychiatrics

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