Neurological Symptoms, Comorbidities, and Complications of COVID-19: A Literature Review and Meta-Analysis of Observational Studies.

BACKGROUND: Recently, it has been shown that coronavirus disease 2019 (COVID-19), which has caused a pandemic since December 2019, can be accompanied by some neurological disorders. This study aimed to assess the prevalence of the most common neurological symptoms and comorbidities and systematically review the literature regarding the most prevalent neurological complications of COVID-19 infection. METHODS: All relevant studies had been collected from PubMed, Scopus, Embase, and Web of Science databases. All extracted data were analyzed using Stata version 11.2. The I2 index was applied, and a random-effects model or a fixed-effects model was used for pooled estimation to assess the heterogeneity of studies. Furthermore, Egger and Beeg's tests were used to evaluate the publication bias. RESULTS: Fifty-seven studies (26 observational and 31 case reports) were included (including 6,597 COVID-19 patients). The most prevalent general symptoms were fever, cough, and dyspnea with 84.6% (95% CI: 75.3-92.1; I2 = 98.7%), 61.3% (95% CI: 55.3-67.0; I2 = 94.6%), and 34.2% (95% CI: 25.6-43.4; I2 = 97.7%), respectively. Neurological symptoms observed among COVID-19 patients were fatigue, gustatory dysfunction, anorexia, olfactory dysfunction, headache, dizziness, and nausea with 42.9% (95% CI: 36.7-49.3; I2 = 92.8%), 35.4% (95% CI: 11.2-64.4; I2 = 99.2%), 28.9% (95% CI: 19.9-38.8; I2 = 96.3%), 25.3% (95% CI: 1.6-63.4; I2 = 99.6%), 10.1% (95% CI: 2.7-21.0; I2 = 99.1%), 6.7% (95% CI: 3.7-10.5; I2 = 87.5%), and 5.9% (95% CI: 3.1-9.5; I2 = 94.5%). The most prevalent neurological comorbidity in COVID-19 was cerebrovascular disease with 4.3% (95% CI: 2.7-6.3; I2 = 78.7%). CONCLUSION: The most prevalent neurological manifestations of COVID-19 include fatigue, gustatory dysfunction, anorexia, olfactory dysfunction, headache, dizziness, and nausea. Cerebrovascular disorders can either act as a risk factor for poorer prognosis in COVID-19 patients or occur as a critical complication in these patients. Guillain-Barre syndrome, encephalitis, and meningitis have also been reported as complications of COVID-19.

Importance of Zebrafish as an Efficient Research Model for the Screening of Novel Therapeutics in Neurological Disorders.

Over the previous years, the use of an animal model has become very common for the screening of novel drugs. Animal model represents the complex problems of humans into the simplest forms, so these can be extended further to be included in the experimental procedure. The most successful models in neuroscience, rats and mice, are undoubtedly considered as one of the best models to understand the psychology of the mammalian brain and its associated functions involved in behavioral repertoire. Moreover, recently researchers in behavioral neuroscience are focusing more on the use of aquatic animals, especially fish, as model species due to their simplicity and cost-effectiveness. Zebrafish (Danio rerio) is a tropical fish from the minnow family, a genetic structure surprisingly 84% similar to humans. It is gaining popularity as a model to study the mechanism in behavioral neuropharmacology. Moreover, zebrafish has numerous advantages over other rodent models like the ease in maintenance due to their small size, more breeding power, transparency of embryos, overall reduced cost of experimentation, and many more. Nowadays, it is considered an ideal model to study the neurobehavioral aspects with relevance to humans. It is also used in a variety of scientific studies like genetics, neuroscience, pharmacology, and toxicology. In this manuscript, we have described the feasibility and importance of zebrafish as a model for the screening of novel drugs for different neurological disorders.