The emerge of coronavirus disease 2019 (COVID-19), previously known as novel coronavirus (2019-nCoV), in Wuhan, China, in December 2019, has spread throughout the world. COVID-19 is known to cause respiratory disease. However, several scientific studies have shown nervous system involvement in COVID-19 infection. The potential mechanisms of this infectious disease transmission to the brain are through infected olfactory epithelium, hematogenous spread and immune-related pathway. Nervous system involvement in COVID-19 infection can be classified as central nervous system (CNS) involvement, peripheral nervous system involvement (PNS) and muscle. CNS involvement, including headache, cerebrovascular disease, impaired consciousness, meningitis, encephalitis, dizziness and seizure. PNS manifestations, such as anosmia, ageusia or dysgeusia, oculomotor nerve palsy and Guillain-Barre syndrome (GBS). Myalgia or arthralgia is the most common presentation of muscle involvement in COVID-19 infection. This review concludes that neurological disorders as COVID-19 clinical features must be recognized by medical professionals in order to have appropriate diagnosis and treatment so that COVID-19 patients can have better prognosis.

Aging is the primary risk factor for various neurodegenerative diseases, including Alzheimer’s disease (AD), which is the most frequent form of Dementia. AD is progressive neurodegenerative disease with abnormal protein production, inflammation and memory deterioration. The main clinical manifestations of this illness are cognitive disturbance and memory deficit. Abnormal of beta-amyloid (Aβ), neurofibrillary tangles (NFTs) and tau deposition are the most common findings pathology in this disease. Recent studies indicate that epigenetic modifications strongly correlate in developing these pathology and disease progression. The hallmarks of epigenetic modifications are DNA (deoxyribonucleic acid) methylation, histone modifications, chromatin remodeling and ncRNA (non-coding ribonucleic acid) expressions. This review aims to explain the potential mechanisms of epigenetic modifications associate with this disease. The general conclusion of this review is that epigenetic modifications play an ultimate role in AD and there are potential biomarkers of AD and future novel treatment of AD based on epigenetics.