Peripheral administration of nanomicelle-encapsulated anti-Aß oligomer fragment antibody reduces various toxic Aß species in the brain.

BACKGROUND: Although a large amount of evidence has revealed that amyloid ß (Aß), especially Aß oligomers, protofibrils, and pyroglutamated Aßs, participate primarily in the pathophysiological processes of Alzheimer's disease, most clinical trials of anti-Aß antibody therapy have never acquired successful efficacy in human clinical trials, partly because peripheral administration of antibody medications was unable to deliver sufficient amounts of the molecules to the brain. Recently, we developed polymeric nanomicelles capable of passing through the blood-brain barrier that function as chaperones to deliver larger amounts of heavy molecules to the brain. Herein, we aimed to evaluate the efficacy of newly developed antibody 6H4 fragments specific to Aß oligomers encapsulated in polymeric nanomicelles on the development of Alzheimer's disease pathology in Alzheimer's disease model mice at the age of emergence of early Alzheimer's disease pathology. RESULTS: During the 10-week administration of 6H4 antibody fragments in polymeric nanomicelles, a significant reduction in the amounts of various toxic Aß species, such as Aß oligomers, toxic Aß conformers, and pyroglutamated Aßs in the brain was observed. In addition, immunohistochemistry indicated inhibition of diameters of Aß plaques, Aß-antibody immunoreactive areas, and also plaque core formation. Behavioral analysis of the mice model revealed that the 6H4 fragments-polymeric nanomicelle group was significantly better at maintaining long-term spatial reference memory in the probe and platform tests of the water maze, thereby indicating inhibition of the pathophysiological process of Alzheimer's disease. CONCLUSIONS: The results indicated that the strategy of reducing toxic Aß species in early dementia owing to Alzheimer's disease by providing sufficient antibodies in the brain may modify Alzheimer's disease progression.

Methionine homozygosity for PRNP polymorphism and susceptibility to human prion diseases.

BACKGROUND: No studies have assessed the independent association of methionine homozygosity at codon 129 with the susceptibility to prion diseases, controlling for the effects of the codon 219 polymorphisms and other potential confounders, using a large-scale population-based dataset. METHODS: We conducted a case-control study using a Japanese nationwide surveillance database for prion diseases. The main exposure was methionine homozygosity at codon 129, and the outcome was development of prion diseases. Multivariable logistic regression models were employed for specific disease subtypes (sporadic Creutzfeldt-Jakob disease (CJD), genetic CJD and Gerstmann-Sträussler-Scheinker disease (GSS)). RESULTS: Of 5461 patients registered in the database, 2440 cases and 796 controls remained for the analysis. The cases comprised 1676 patients with sporadic CJD (69%), 649 with genetic CJD (27%) and 115 with GSS (5%). For patients with methionine homozygosity, potential risk for occurring prion diseases: adjusted OR (95% CI) was 2.21 (1.46 to 3.34) in sporadic CJD, 0.47 (0.32 to 0.68) in genetic CJD and 0.3 (0.17 to 0.55) in GSS. Among patients with specific prion protein abnormalities, the potential risk was 0.27 (0.17 to 0.41) in genetic CJD with 180 Val/Ile, 1.66 (0.65 to 5.58) in genetic CJD with 200 Glu/Lys, 3.97 (1.2 to 24.62) in genetic CJD with 232 Met/Arg and 0.71 (0.34 to 1.67) in GSS with 102 Pro/Leu. CONCLUSIONS: Methionine homozygosity at codon 129 was predisposing to sporadic CJD, but protective against genetic CJD and GSS, after adjustment for codon 219 polymorphism effect. However, the impacts differed completely among patients with specific prion protein abnormalities.

Systematic Review of Clinical and Pathophysiological Features of Genetic Creutzfeldt-Jakob Disease Caused by a Val-to-Ile Mutation at Codon 180 in the Prion Protein Gene.

Genetic Creutzfeldt-Jakob disease (gCJD) is a subtype of genetic prion diseases (gPrDs) caused by the accumulation of mutated pathological prion proteins (PrPSc). gCJD has a phenotypic similarity with sporadic CJD (sCJD). In Japan, gCJD with a Val to Ile substitution at codon 180 (V180I-gCJD) is the most frequent gPrD, while the mutation is extremely rare in countries other than Japan and Korea. In this article, we aim to review previously elucidated clinical and biochemical features of V180I-gCJD, expecting to advance the understanding of this unique subtype in gCJD. Compared to classical sCJD, specific clinical features of V180I-gCJD include older age at onset, a relatively slow progression of dementia, and a lower positivity for developing myoclonus, cerebellar, pyramidal signs, and visual disturbance. Diffuse edematous ribboning hyperintensity of the cerebral cortex, without occipital lobes in diffusion-weighted magnetic resonance imaging, is also specific. Laboratory data reveal the low positivity of PrPSc in the cerebrospinal fluid and periodic sharp wave complexes on an electroencephalogram. Most patients with V180I-gCJD have been reported to have no family history, probably due to the older age at onset, and clinical and biochemical features indicate the specific phenotype associated with the prion protein gene mutation.

Characterization of Sporadic Creutzfeldt-Jakob Disease and History of Neurosurgery to Identify Potential Iatrogenic Cases.

We previously reported a phenotype of Creutzfeldt-Jakob disease (CJD), CJD-MMiK, that could help identify iatrogenic CJD. To find cases mimicking CJD-MMiK, we investigated clinical features and pathology of 1,155 patients with diagnosed sporadic CJD or unclassified CJD with and without history of neurosurgery. Patients with history of neurosurgery more frequently had an absence of periodic sharp-wave complexes on electroencephalogram than patients without a history of neurosurgery. Among 27 patients with history of neurosurgery, 5 had no periodic sharp-wave complexes on electroencephalogram. We confirmed 1 case of CJD-MMiK and suspected another. Both had methionine homozygosity at codon 129 of the prion protein gene and hyperintensity lesions in the thalamus on magnetic resonance images of the brain, which might be a clinical marker of CJD-MMiK. A subgroup with a history of neurosurgery and clinical features mimicking dura mater graft-associated CJD might have been infected during neurosurgery and had symptoms develop after many years.

MM2-type sporadic Creutzfeldt-Jakob disease: new diagnostic criteria for MM2-cortical type.

OBJECTIVE: To clinically diagnose MM2-cortical (MM2C) and MM2-thalamic (MM2T)-type sporadic Creutzfeldt-Jakob disease (sCJD) at early stage with high sensitivity and specificity. METHODS: We reviewed the results of Creutzfeldt-Jakob disease Surveillance Study in Japan between April 1999 and September 2019, which included 254 patients with pathologically confirmed prion diseases, including 9 with MM2C-type sCJD (MM2C-sCJD) and 10 with MM2T-type sCJD (MM2T-sCJD), and 607 with non-prion diseases. RESULTS: According to the conventional criteria of sCJD, 4 of 9 patients with MM2C- and 7 of 10 patients with MM2T-sCJD could not be diagnosed with probable sCJD until their death. Compared with other types of sCJD, patients with MM2C-sCJD showed slower progression of the disease and cortical distribution of hyperintensity lesions on diffusion-weighted images of brain MRI. Patients with MM2T-sCJD also showed relatively slow progression and negative results for most of currently established investigations for diagnosis of sCJD. To clinically diagnose MM2C-sCJD, we propose the new criteria; diagnostic sensitivity and specificity to distinguish 'probable' MM2C-sCJD from other subtypes of sCJD, genetic or acquired prion diseases and non-prion disease controls were 77.8% and 98.5%, respectively. As for MM2T-sCJD, clinical and laboratory features are not characterised enough to develop its diagnostic criteria. CONCLUSIONS: MM2C-sCJD can be diagnosed at earlier stage using the new criteria with high sensitivity and specificity, although it is still difficult to diagnose MM2T-sCJD clinically.

Cross-Sectional Area Analysis of the Head of the Caudate Nucleus in Huntington's Disease.

BACKGROUND: Caudate nucleus atrophy is a well-known neuroimaging feature of Huntington's disease (HD). Some researchers have reported a decrease in the volume of the striatum on magnetic resonance images (MRIs) even in the presymptomatic stage of the disease. Despite the many neuroimaging studies on HD, the optimal method for measuring the caudate nucleus area on MRIs and the most effective cutoff values for diagnosing HD remain unclear. OBJECTIVES AND METHODS: To define suitable imaging sequences and cutoff values for HD, we measured the area of the head of the caudate nucleus (HCN) in 11 patients with HD, 22 age- and sex-matched individuals without neurodegenerative disorders in the central nervous system, 22 sex-matched patients with Alzheimer's disease, 22 sex-matched patients with Parkinson's disease, and 7 patients with dentatorubral-pallidoluysian atrophy. RESULTS: On T2-weighted images (T2WIs), we found significantly reduced HCN area at the rostral level in individuals with HD relative to those of the individuals in the other groups. A significant inverse correlation (ρ = -0.61, p = 0.046) was observed between the HD duration and HCN area at the rostral slice level on T2WIs. The cutoff value for distinguishing patients with HD from healthy individuals and those with other neurodegenerative diseases was 85 mm2 at the rostral level on T2WIs (100% sensitivity and specificity). CONCLUSIONS: This cutoff value can be applied clinically to evaluate brain atrophy in HD. Our method is advantageous because it is simple and can be implemented easily in daily clinical practice.

Biochemical features of genetic Creutzfeldt-Jakob disease with valine-to-isoleucine substitution at codon 180 on the prion protein gene.

Valine-to-isoleucine substitution at codon 180 of the prion protein gene is only observed in patients with Creutzfeldt-Jakob disease and accounts for approximately half of all cases of genetic prion disease in Japan. In the present study, we investigated the biochemical characteristics of valine-to-isoleucine substitution at codon 180 in the prion protein gene, using samples obtained from the autopsied brains of seven patients with genetic Creutzfeldt-Jakob disease exhibiting this mutation (diagnoses confirmed via neuropathological examination). Among these patients, we observed an absence of diglycosylated and monoglycosylated forms of PrPres at codon 181. Our findings further indicated that the abnormal prion proteins were composed of at least three components, although smaller carboxyl-terminal fragments were predominant. Western blot analyses revealed large amounts of PrPres in the cerebral neocortices, where neuropathological examination revealed marked spongiosis. Relatively smaller amounts of PrPres were detected in the hippocampus, where milder spongiosis was observed, than in the cerebral neocortex. These findings indicate that abnormal prion proteins in the neocortex are associated with severe toxicity, resulting in severe spongiosis. Our findings further indicate that the valine-to-isoleucine substitution is not a polymorphism, but rather an authentic pathogenic mutation associated with specific biochemical characteristics that differ from those observed in sporadic Creutzfeldt-Jakob disease.

Brain volume loss is present in Japanese multiple sclerosis patients with no evidence of disease activity.

No evidence of disease activity-3 (NEDA-3), defined as absence of clinical relapse, disability progression, and brain magnetic resonance imaging (MRI) activity, has emerged as the therapeutic target of disease-modifying therapy for multiple sclerosis (MS). However, recent studies have revealed that NEDA-3 might not be sufficient to prevent cognitive deterioration and predict long-term disability. In addition to NEDA-3, brain atrophy has recently been recognized as a pivotal biomarker that is closely associated to disability in patients with MS. This retrospective observational study included 22 Japanese MS patients with relatively mild disease (median expanded disability status scale = 1.75). Fifteen patients (68%) received disease-modifying therapy (DMT), including interferon (IFN)-ß (n = 6), IFN-ß, or azathioprine followed by fingolimod (n = 4), fingolimod (n = 4), and IFN-ß followed by natalizumab (n = 1). It revealed that 14 (64.6%) patients achieved NEDA-3 in the 2-year observational period. However, nine (64.3%) of the patients with NEDA-3 were revealed to have a significant BVL, defined as ≥ 0.4% per year. Importantly, these nine patients included all patients receiving IFN-ß therapy (n = 6), whereas patients without BVL included none of these patients. Conversely, patients treated with fingolimod following IFN-ß did not have significant BVL. These results indicate that evaluation of NEDA-4 is encouraged especially in patients with IFN-ß therapy in MS clinical practice in Japan although Japanese MS patients have generally been thought to possess a milder disease including brain atrophy compared to their Western counterparts.

Descriptive epidemiology of prion disease in Japan: 1999-2012.

BACKGROUND: Epidemiologic features of prion diseases in Japan, in particular morbidity and mortality, have not been clarified. METHODS: Since 1999, the Research Committee has been conducting surveillance of prion diseases, and the surveillance data were used to assess incident cases of prion diseases. For the observation of fatal cases, vital statistics were used. RESULTS: Both incidence and mortality rates of prion diseases increased during the 2000s in Japan. However, this increase was observed only in relatively old age groups. CONCLUSIONS: The increased number of patients among old age groups might be due to increased recognition of the diseases. If so, the number of cases should plateau in the near future.

Elevated platelet microparticle levels after acute ischemic stroke with concurrent idiopathic thrombocytopenic purpura.

We report a 60-year-old woman with idiopathic thrombocytopenic purpura who experienced acute infarction of the middle cerebral artery. She was treated with an antiplatelet agent and prednisolone to limit platelet activation and destruction. In parallel with clinical amelioration, levels of plasma platelet microparticles (PMPs), a procoagulant factor in platelet activation, decreased after treatment but increased after reduction of the prednisolone dose, resulting in progression of vascular stenosis. Immunosuppressive therapy with cyclosporine normalized plasma PMP levels, and no additional vascular events occurred during the 3-month follow-up period. Immunosuppressive therapy to decrease plasma PMP levels is warranted after acute ischemic stroke in the context of idiopathic thrombocytopenic purpura.

Specifically Decreased Thalamic Blood Flow Following COVID-19 Infection.

ABSTRACT: Although long COVID refers to numerous COVID-19-related symptoms after infection, including depression, fatigue, anosmia, sleep disturbances, and brain fog, the etiology of long COVID remains largely unknown. A 41-year-old woman presented with a 3-week history of complete insomnia without drowsiness throughout the day after contracting COVID-19. SPECT using N -isopropyl-p-[ 123 I] iodoamphetamine showed a significant regional cerebral blood flow reduction in the bilateral thalamus. We diagnosed her as having insomnia accompanied by thalamic hypoperfusion related to COVID-19 infection. To our knowledge, this is the first case of reduced regional cerebral blood flow specifically confined to the thalamus.

Brain perfusion SPECT in dementia: what radiologists should know.

The findings of brain perfusion single-photon emission computed tomography (SPECT), which detects abnormalities often before changes manifest in morphological imaging, mainly reflect neurodegeneration and contribute to dementia evaluation. A major shift is about to occur in dementia practice to the approach of diagnosing based on biomarkers and treating with disease-modifying drugs. Accordingly, brain perfusion SPECT will be required to serve as a biomarker of neurodegeneration. Hypoperfusion in Alzheimer's disease (AD) is typically seen in the posterior cingulate cortex and precuneus early in the disease, followed by the temporoparietal cortices. On the other hand, atypical presentations of AD such as the posterior variant, logopenic variant, frontal variant, and corticobasal syndrome exhibit hypoperfusion in areas related to symptoms. Additionally, hypoperfusion especially in the precuneus and parietal association cortex can serve as a predictor of progression from mild cognitive impairment to AD. In dementia with Lewy bodies (DLB), the differentiating feature is the presence of hypoperfusion in the occipital lobes in addition to that observed in AD. Hypoperfusion of the occipital lobe is not a remarkable finding, as it is assumed to reflect functional loss due to impairment of the cholinergic and dopaminergic systems rather than degeneration per se. Moreover, the cingulate island sign reflects the degree of AD pathology comorbid in DLB. Frontotemporal dementia is characterized by regional hypoperfusion according to the three clinical types, and the background pathology is diverse. Idiopathic normal pressure hydrocephalus shows apparent hypoperfusion around the Sylvian fissure and corpus callosum and apparent hyperperfusion in high-convexity areas. The cortex or striatum with diffusion restriction on magnetic resonance imaging in prion diseases reflects spongiform degeneration and brain perfusion SPECT reveals hypoperfusion in the same areas. Brain perfusion SPECT findings in dementia should be carefully interpreted considering background pathology.

Substitution of Glu to Lys at Codon 332 on the GFAP Gene Alone Is Causative for Adult-onset Alexander Disease.

A 57-year-old man whose mother had been pathologically diagnosed with Alexander disease (ALXDRD), presented with cerebellar ataxia, pyramidal signs, and mild dysarthria. Brain magnetic resonance imaging revealed typical ALXDRD alterations, such as atrophy of the medulla oblongata (MO) and cervical spinal cord, a reduced sagittal diameter of the MO, and garland-like hyperintensity signals along the lateral ventricular walls. A genetic analysis of GFAP by Sanger sequencing revealed a single heterozygous mutation of Glu to Lys at codon 332 (c.994G>A) in the GFAP gene. Our results newly confirmed that p.E332K alone is the pathogenic causative mutation for adult-onset ALXDRD.

Insight into the frequent occurrence of dura mater graft-associated Creutzfeldt-Jakob disease in Japan.

OBJECTIVE: More than 60% of patients worldwide with Creutzfeldt-Jakob disease (CJD) associated with dura mater graft (dCJD) have been diagnosed in Japan. The remarkable frequency of dura mater grafts in Japan may possibly contribute to the elevated incidence of dCJD, but reasons for the disproportionate use of this procedure in Japan remain unclear. We investigated differences between dCJD patients in Japan and those elsewhere to help explain the more frequent use of cadaveric dura mater and the high incidence of dCJD in Japan. METHODS: We obtained data on dCJD patients in Japan from the Japanese national CJD surveillance programme and on dCJD patients in other countries from the extant literature. We compared the demographic, clinical and pathological features of dCJD patients in Japan with those from other countries. RESULTS: Data were obtained for 142 dCJD patients in Japan and 53 dCJD patients elsewhere. The medical conditions preceding dura mater graft transplantation were significantly different between Japan and other countries (p<0.001); in Japan, there were more cases of cerebrovascular disease and hemifacial spasm or trigeminal neuralgia. Patients with dCJD in Japan received dura mater graft more often for non-life-threatening conditions, such as meningioma, hemifacial spasm and trigeminal neuralgia, than in other countries. CONCLUSIONS: Differences in the medical conditions precipitating dura mater graft may contribute to the frequent use of cadaveric dura mater and the higher incidence of dCJD in Japan.

Visual reproduction on the Wechsler Memory Scale-Revised as a predictor of Alzheimer's disease in Japanese patients with mild cognitive impairments.

BACKGROUND: The Visual Reproduction (VR) test is used to assess mild cognitive impairment (MCI), but the characteristics of visual memory in Japanese MCI patients remain unclear. METHODS: VR scores of 27 MCI patients were evaluated using the Wechsler Memory Scale-Revised. Scores of MCI, no-dementia, and Alzheimer's disease (AD) groups were then compared. RESULTS: The annual conversion rate of MCI to AD was 18.8%. Mean VR-I and VR-II baseline scores for MCI patients were 33.3 ± 5.6 and 20.5 ± 14.0, respectively. Mean VR-II scores for converted and nonconverted MCI patients were 7.2 ± 8.7 and 29.8 ± 9.3, respectively. CONCLUSIONS: It is likely that VR-II and VR-II/I scores are more sensitive for predicting conversion to AD in Japanese than in American MCI patients. Our results indicate that VR is a sensitive and useful measure for predicting the conversion of Japanese MCI patients to AD within 2 years.

Serial changes in regional cerebral blood flow in Gerstmann-Sträussler-Scheinker disease caused by a Pro-to-Leu mutation at codon 105 in the prion protein gene.

Gerstmann-Sträussler-Scheinker disease with a Pro-to-Leu substitution at codon 105 in the prion protein gene (GSS-P105L) is a rare variant of human genetic prion disease. Herein, we report the case of a patient with GSS-P105L, who showed serial changes in regional cerebral blood flow (rCBF) on single-photon emission computed tomography (SPECT). A 42-year-old woman, with an affected father presenting with similar symptoms, had a 1-year history of progressive gait disturbance, lower-limb spasticity, and psychiatric symptoms. Genetic analysis confirmed the diagnosis of GSS-P105L. Eleven months after disease onset, brain magnetic resonance imaging (MRI) showed bilateral frontal lobe-dominant cerebral atrophy without hyperintensity on diffusion-weighted imaging (DWI) sequences; meanwhile, SPECT revealed non-specific mild hypoperfusion. Follow-up MRI at 52 months after onset demonstrated progressive frontal lobe-dominant cerebral atrophy without hyperintensity on DWI, while SPECT revealed a marked decrease in rCBF in the bilateral right-dominant frontal lobe. Patients with GSS with a Pro-to-Leu substitution at codon 102 (GSS-P102L) have been reported to exhibit hyperintensity on DWI-MRI and a diffuse decrease in CBF with a mosaic-like pattern on SPECT, which is absent in patients with GSS-P105L, thereby possibly reflecting the differences in pathophysiology between GSS-P102L and GSS-P105L.

Health-related quality of life in Japanese patients with multiple sclerosis.

OBJECTIVES: Neurological disabilities, especially physical issues, can adversely affect the daily lives of people with multiple sclerosis (MS) and negatively impact their health-related quality of life (HRQOL). On the other hand, physical and psychiatric symptoms are variable in people with MS, and QOL can be influenced by cultural and educational background. This study aimed to evaluate the association of HRQOL with disabilities, fatigue, and depression in Japanese subjects with MS. METHODS: Evaluation of HRQOL, fatigue, and depression was performed in 184 Japanese individuals with MS, using the Functional Assessment of MS (FAMS), Fatigue Severity Scale (FSS), and Beck Depression Inventory-Second Edition (BDI-II), respectively. RESULTS: Multiple linear regression analysis demonstrated negative correlations of the Expanded Disability Status Scale (EDSS) with scores on the FAMS subscales of mobility, symptoms, thinking and fatigue, total FAMS, and additional concerns. The FSS score had negative correlations with mobility, symptoms, emotional well-being, thinking and fatigue, total FAMS, and additional concerns. There were negative correlations between BDI-II scores and all items of FAMS. CONCLUSIONS: HRQOL had relatively close correlations with disabilities and fatigue, and depression had an especially close relationship with HRQOL.

Nationwide Laboratory Surveillance of Progressive Multifocal Leukoencephalopathy in Japan: Fiscal Years 2011-2020.

Progressive multifocal leukoencephalopathy (PML) is a devastating demyelinating disease caused by JC virus (JCV), predominantly affecting patients with impaired cellular immunity. PML is a non-reportable disease with a few exceptions, making national surveillance difficult. In Japan, polymerase chain reaction (PCR) testing for JCV in the cerebrospinal fluid (CSF) is performed at the National Institute of Infectious Diseases to support PML diagnosis. To clarify the overall profile of PML in Japan, patient data provided at the time of CSF-JCV testing over 10 years (FY2011-2020) were analyzed. PCR testing for 1537 new suspected PML cases was conducted, and 288 (18.7%) patients tested positive for CSF-JCV. An analysis of the clinical information on all individuals tested revealed characteristics of PML cases, including the geographic distribution, age and sex patterns, and CSF-JCV-positivity rates among the study subjects for each type of underlying condition. During the last five years of the study period, a surveillance system utilizing ultrasensitive PCR testing and widespread clinical attention to PML led to the detection of CSF-JCV in the earlier stages of the disease. The results of this study will provide valuable information not only for PML diagnosis, but also for the treatment of PML-predisposing conditions.

TMP21 is a presenilin complex component that modulates gamma-secretase but not epsilon-secretase activity.

The presenilin proteins (PS1 and PS2) and their interacting partners nicastrin, aph-1 (refs 4, 5) and pen-2 (ref. 5) form a series of high-molecular-mass, membrane-bound protein complexes that are necessary for gamma-secretase and epsilon-secretase cleavage of selected type 1 transmembrane proteins, including the amyloid precursor protein, Notch and cadherins. Modest cleavage activity can be generated by reconstituting these four proteins in yeast and Spodoptera frugiperda (sf9) cells. However, a critical but unanswered question about the biology of the presenilin complexes is how their activity is modulated in terms of substrate specificity and/or relative activities at the gamma and epsilon sites. A corollary to this question is whether additional proteins in the presenilin complexes might subsume these putative regulatory functions. The hypothesis that additional proteins might exist in the presenilin complexes is supported by the fact that enzymatically active complexes have a mass that is much greater than predicted for a 1:1:1:1 stoichiometric complex (at least 650 kDa observed, compared with about 220 kDa predicted). To address these questions we undertook a search for presenilin-interacting proteins that differentially affected gamma- and epsilon-site cleavage events. Here we report that TMP21, a member of the p24 cargo protein family, is a component of presenilin complexes and differentially regulates gamma-secretase cleavage without affecting epsilon-secretase activity.

[Neurological Manifestations of COVID-19: Meningoencephalitis and Encephalopathy].

Coronavirus disease (COVID-19) causes neurological symptoms in a high percentage of patients and is associated with various types of encephalitides and encephalopathies, which are etiologically classified into (a)direct infection of the central nervous system with severe acute respiratory syndrome coronavirus 2 and resultant meningoencephalitis (this is a rare presentation), (b)COVID-19-induced cytokine storms, which trigger endothelial cell injury, blood-brain barrier disruption, and microangiopathy and consequent encephalopathy and, (c)autoimmune encephalitis secondary to para- or post-infectious mechanisms that play a key role during the acute or post-COVID-19 phase. Notably, some patients present with neurological symptoms as the first manifestation. Radiologically characteristic encephalitides and encephalopathies, such as acute necrotizing encephalopathy, acute disseminated encephalomyelitis, posterior reversible encephalopathy syndrome, and clinically mild encephalitis/encephalopathy with a reversible splenial lesion are also complicated by COVID-19. Further investigations and appropriate treatments are warranted in patients with COVID-19, who develop new neurological symptoms.