Table 2.

Diagnostic features of encephalitis in patients with COVID-19.

No.	Study ID	Neuroimaging		Neurophysiology	Serum Analysis	CSF Analysis					Other Pathogen Investigation
		Brain CT Scan Result	Brain MRI Result	EEG Result		WBC	Total Protein (mg/dL)	Glucose (mg/dL)	SARS-CoV-2	Other Explorations
1	Ahsan 2021	NR	Axial T2 showed left perirolandic cortex and posterior parietal lobe cerebral edema, and axial DWI showed restricted diffusion.	Cerebral slowing with left focal slowing	MOG IgG positive	Elevated	48	46	NR	OCB positive	Bacterial or viral pathogens were negative
2	Allahyari 2021	Generalized brain edema	Generalized brain edema	NR	CRP 2+	Elevated	241	55	Positive	Anti-NMDAR Positive, HSV 1 and HSV 2 DNA negative	NR
3	Andrea 2020	Presented with non-specific diffuse cortical atrophy	NR	Triphasic waves were observed	Normal CRP and LDH, severe hyponatremia	Normal	61	49	Negative	None	HSV negative
4	Ayatollahi 2020	Normal	1st admittance: normal; 2nd admittance: signal hyperintensities on FLAIR and T2-weighted sequences in the claustrum bilaterally	1st admittance: slow wave activity; 2nd admittance: moderate bilateral non-epileptiform abnormalities	Thrombocytopenia, normal RBC, WBC and hemoglobin, CRP. ANA, aPL, aCL, anti-dsDNA, and ANCA were negative	Elevated	30	41	Negative	None	HSV negative
5	Ayuningtyas 2022	NR	No lesion or intracerebral or intracerebellar pathological enhancement was found	NR	Increased CRP level, and increased D-dimer level	Elevated	108	63	Positive	No Bacteria and AFB	Anti-HIV, HbSAg, anti-HCV, HSV, and CMV negative
6	Ayuso 2020	Normal	2nd admittance: hyperintense lesions in the caudal vermis and right flocculus, and contrast enhancement was observed in the floor of the fourth ventricle	Normal	Normal	Normal	41	70	NR	OCB, anti-Hu, anti-Yo, anti-Ri, anti-CV2, anti-Ma2, and anti-amphiphysin abs were negative	Anti-GD1 was positive. HIV, VZV, EBV, CMV, and Mycoplasma Pneumoniae were negative
7	Babar 2020	Normal	Normal	Generalized slowing	Elevated CRP, ferritin, TPO ab, and D-dimer. Negative anti-NMDAR ab, anti-GAD ab, VGKC ab, ANA, ANCA, IgM anti-β2-GPI ab, anti-DNase B ab, anti-streptolysin ab, IL-1 β, IL-6, IL-10, IL-2, C3, and C4	Normal	18	74	Negative	None	Gram bacteria negative
8	Benameur 2020	NR	Cerebral hemispheric restricted diffusion and cerebral edema	NR	Increased levels of anti-S1 IgM; anti-E IgM, IL-6, IL-8, IL-10, IP-10, and TNF-α	Elevated	>200	40	Negative	None	Influenza A virus positive, influenza B virus negative
		NR	Splenium lesion and FLAIR recovery	Diffuse slowing		Normal	37	111	Negative	None	Bacterial or viral pathogens were negative
		NR	Equivocal fluid-attenuated inversion recovery, FLAIR abnormality in the right temporal lobe	NR		Normal	21	88	Negative	None	Bacterial or viral pathogens were negative
9	Bernard-Valnet 2020	NR	Normal	Nonconvulsive, focal status epilepticus, slowed theta background rhythm	NR	Mild elevated	46.6	NR	Negative	None	Bacterial or viral pathogens were negative
		NR	Normal	NR	NR	Mild elevated	46.1	NR	Negative	None
10	Bhavsar 2020	Normal	NR	Slow background without epileptiform discharges or seizures	Normal CBC, CRP and ESR, negative autoimmune encephalopathy antibody panel, hyponatremia	Elevated	173	35	Negative	None	Bacterial or viral pathogens were negative
11	Bodro 2020	Normal	Normal	NR	Elevated D-dimer	Elevated	105.5	80	Negative	Elevated IL-1β, IL-6, ACE	Bacterial or viral pathogens were negative
		Normal	Normal	NR	Elevated CRP, ferritin, LDH, and D-dimer, mild platelet reduction	Elevated	115.5	54	Negative	Elevated IL-6, ACE	NR
12	Burr 2021	NR	Normal	NR	Normal CRP and ESR and positive NMDAR-IgG positivity	NR	25	56	Negative	None	Bacterial or viral pathogens were negative
13	Cao 2020	NR	Bilateral hyperintense lesions in the deep and periventricular supratentorial white matter, either punctiform and slightly diffuse (cases 1–3) or diffuse and confluent (cases 4 and 5), associated with lesions in the pons for two patients (cases 1 and 2)	Unspecific slow-wave activity	Elevated IL-6	normal	32	NR	Negative	Normal IL-6	NR
					Normal IL-6		26		Negative	Normal IL-6
					Elevated IL-6		115		Negative	Elevated IL-6
					Elevated IL-6		18		Negative	None
					Elevated IL-6		18		Negative	Normal IL-6
14	Casez 2021	NR	Hyperintensity of the olfactory tracts on T2 fluid-attenuated inversion recovery, and diffusion-weighted imaging	NR	NR	8 WBC	Normal	NR	Negative	None	NR
15	Chalil 2020	Extensive bilateral parietal and occipital intraparenchymal hemorrhage and extensive edema causing hydrocephalus	Cortical gadolinium enhancement with hyper-intense T2 and FLAIR signal surrounding the hemorrhages	Mild diffuse slowing	Elevated D-dimer, CRP, and ferritin	Elevated	NR	NR	Negative	Elevated CSF IgG ratio	Negative for VZV, HSV, and ENV
16	Cheraghali 2021	NR	Symmetric, cortical, and juxtacortical high T1 and T2 signal abnormality, in bilateral parieto-occipital lobes	NR	Elevated level of blood sugar, AST, ALT, ESR, LDH, and positive CRP test	Normal	15	100	Positive	Negative for bacterial growth	HSV 1 and HSV 2 negative
17	Dahshan 2022	Normal	Normal	NR	NR	Normal	Normal	Normal	NR	HSV 1 and HSV 2 negative	NR
18	Dono 2021	NR	Axial T2 fluid-attenuated inversion recovery (T2-FLAIR) and axial diffusion-weighted imaging showed hyperintense lesions of the bilateral parietal cortex, left temporal cortex, and right cingulate cortex	Epileptiform abnormalities, continuous sharp waves and spike-and-slow-wave complexes	Slight lymphocytopenia, elevated D-dimer, normal CRP	Elevated	47	78	Negative	OCB positive	HSV, EBV, CMV, and VZV were negative
19	Duong 2020 and Huang 2020	Normal	NR	Generalized slowing with no epileptic discharges	Normal	Elevated	100	120	Positive	None	Negative for bacterial culture and HSV 1
20	Durovic 2021	NR	Multiple disseminated pathological T2 and FLAIR hyperintensities	NR	Lyme borreliosis and HIV was negative, MOG antibody positive	Elevated	39.9	64	Negative	HSV 1 and HSV 2 negative	Complete recovery over the follow-up of 2 months
21	Efe 2020	NR	Hyperintense signal in the left temporal lobe in T2 and T2 FLAIR	NR	NR	NR	NR	NR	NR	None	NR
22	El Aoud 2021	Normal	Focal hyperintense signal in the splenium of the corpus callosum on T2 FLAIR and diffusion-weighted images	Slow oscillations without epileptiform features	Lymphophenia, elevated CRP and ferritin, hypoalbuminemia, ANA, and ANCA were negative	normal	49	55	NR	None	Mycoplasma pneumoniae, syphilis, HIV, influenza A and B were negative
23	Elmouhib 2022	Normal	High-signal intensity lesion on DWI, T2 FLAIR in the temporal lobes, without diffusion restriction on apparent diffusion coefficient map	NR	CRP at 200 mg/L with a negative PCT at 0.05 μg/L, ferritin at 2300 μg/L	Normal	100	63	NR	NR	NR
24	Esmaeili 2022	NR	Extensive high signal lesions in T2W and FLAIR sequences on bilateral cerebral hemispheres, para-ventricular and subcortical white matter, middle cerebellar peduncles, centrum semi vale, corpus callosum, basal ganglia, thalami, midbrain, and pons. Post-contrast MRI showed sparse enhancements on midpart of the midbrain and left parietal lobe	NR	Elevated CRP and ESR, prothrombin time and partial thromboplastin time were normal	Normal	Normal	Normal	Negative	EBV, HSV, CMV, VZV negative	NR
25	Etemadifar 2020	Generalized brain edema and signs of brain herniation	Generalized brain edema, downward herniation of cerebellar tonsils and brain stem, and FLAIR hyperintensities in bilateral cerebral cortices and corpus striatum	Normal	Leukocytosis, lymphopenia, elevated D-dimer	NR	NR	NR	NR	None	NR
26	Ferdosian 2021	NR	Diffuse brain edema	NR	CPK: 42, LDH: 554, CRP: weakly +, ESR: 6. COVID-19 PCR was negative	Normal	30	57	Positive	HSV, Enterovirus negative	NR
27	Freire-Álvarez 2020	Normal	Extensive involvement of the brain, including cortical and subcortical right frontal regions, right thalamus, bilateral temporal lobes and cerebral peduncles, with no leptomeningeal enhancement	NR	Elevated ferritin, IL-6, and D-dimer	Elevated	198	48	Negative	None	CMV, HSV 1 and 2, human HHV 6, HPeV, and VZV negative
28	Gaughan 2021	NR	Two tiny punctate T2/FLAIR hyper-intensities in the centrum semiovale bilaterally	Delta slowing	Autoimmune antibody panel negative	NR	43	52.2	Negative	Autoimmune antibody panel negative	HSV and VZV negative
29	Ghosh 2020	NR	Non-enhancing altered intensity lesions in the left high fronto-parietal and right posterior parietal areas with peri-lesional edema; isolated cortical venous thrombosis	NR	All blood parameters normal	Elevated	60	70	Negative	Elevated IgG index, and OCB negative	Bacterial or viral pathogens were negative
30	Grimaldi 2020	NR	Normal	Symmetric diffuse background slowing	Elevated fibrinogen and CRP, IgG autoantibodies extremely high	Normal	49	NR	Negative	OCB negative and IgG autoantibodies	NR
31	Gunawardhana 2021	Bi-frontal white matter oedema	T2 FLAIR hyperintensities in the periventricular white matter, mainly clustered around frontal and occipital horns. FLAIR hyperintensities were also noted in the splenium, basal ganglia, and ventral pons	Low wave discharges consistent with encephalitis	Hemoglobin, liver function tests, creatinine and electrolytes were within normal limits, inflammatory markers (ESR, CRP) were mildly elevated	Elevated	Normal	Normal	SARS-CoV-2 IgM and IgG antibodies are positive SARS-CoV-2 RNA negative	HSV 1 and HSV 2, Japanese encephalitis, VZV were negative	NR
32	Haider 2020	Normal	Small acute/subacute lacunar infarcts and a patchy area of T2 bright signals in the cortical and periventricular regions, consistent with cerebritis	Global cerebral dysfunction and severe toxic metabolic encephalopathy	Autoimmune antibody panel negative	Normal	77	86	Negative	None	Bacterial or viral pathogens were negative
33	Hassan 2021	NR	Mild periventricular ischemic changes	NR	Increased CRP, D-dimer, and serum ferritin	Normal	NR	NR	Positive	HSV, OCBs were negative	NR
34	Hayashi 2020	NR	Abnormal hyperintensity in the splenium of corpus callosum on diffusion-weighted image	NR	Elevated CRP, lymphopenia	NR	NR	NR	NR	None	NR
35	Kahwagi 2021	NR	Normal	Overall slowing of the pattern with the presence of diffuse pseudoperiodic complexes predominating in fronto-temporal area	Elevated CRP	Normal	76	NR	NR	None	NR
36	Kamal 2020	Multiple hypodensities in the external capsules bilaterally, the insular cortex, and the deep periventricular white matter of the frontal lobes bilaterally	Abnormal signal intensity in the temporal lobe cortex bilaterally in a rather symmetrical fashion. In addition, the involvement of the parasagittal frontal lobes bilaterally was evident as well, displaying bright signals on T2-fluid-attenuated inversion recovery and T2-weighted images with corresponding diffusion restriction	Did not display any significant epileptic discharges, possibly due to the masking effect of lorazepam	Elevated D-dimer	Normal	55	67	Positive	Normal LA, RF, ANA and aCL	Mycobacterium Tuberculosis, Gram bacteria, HSV, HHV, and VZV were negative
37	Kasturiarachi 2022	NR	Contrast-enhancing lesion in the left occipital, temporal, and frontal lobes, the vermis folia, and tectal plate colliculi; hyperperfusion on arterial spin labeling in the left hemisphere	Left hemispheric poly spike and waves	Elevated LDH, reticulocyte count and bilirubin, schistocytes, and low haptoglobin. Positive ANA, high anti-SSA (anti-Ro) and anti-SSB (anti-La) antibodies, and significantly elevated COVID-19 antibody	NR	NR	NR	Negative	Meningitis/encephalitis panel negative	NR
38	Khoo 2020	NR	Normal	Normal	Elevated CRP and D-dimer	Normal	Normal	Normal	Negative	Anti-NMDAR ab and A panel of antineuronal abs and OCB were negative	NR
39	Kimura 2021	NR	No significant abnormalities	No evidence of seizure activity nor response to photic and sound stimuli	Seropositive for anti–SARS-CoV-2 antibodies	Normal	20	164	Negative	OCBs positive	Campylobacter jejuni, Haemophilus influenzae, Mycoplasma pneumoniae, cytomegalovirus, and EBV negative
40	Koh 2022	Patchy ground-glass opacities on bilateral lung fields, compatible with COVID-19 pneumonia	Diffuse cortical high signal intensities, especially on bilateral insula with increased arterial spin labeling signals	Repeated high-amplitude polymorphic delta activities from the right frontotemporal area evolving to generalized 1–2 Hz spike-wave discharges, suggesting an impending focal status epilepticus	IL-6 was mildly elevated to 21.7 pg/mL, CRP level normal	Elevated	NR	NR	Negative	Elevated IL-6	HSV, VZV, enterovirus, tuberculosis, EBV, toxoplasmosis, and syphilis negative
41	Kumar 2020	Hypodensities in both thalami and left caudate nucleus; left parasellar-middle cranial fossa mass	Left parasellar-middle cranial fossa mass (MRI was performed about 2 weeks earlier than CT)	NR	Leukocytosis	Normal	Elevated	NR	NR	None	HSV and VZV were negative
42	Kumar 2022	NR	Subcortical volume loss (right occipital and left parieto occipital) with cystic changes, tiny hemorrhages at the caudothalamic groove with loss of myelination at the posterior limb of internal capsule	Normal	COVID Ig G And Ig M antibodies were positive	Normal	Normal	Normal	NR	NR	NR
43	Marques 2022	Normal	Did not show any pathological changes	Moderate encephalopathy	Elevated LDH and d-dimers	Elevated	82	59	Negative	HSV, VZV, cytomegalovirus negative	HSV, HIV, VZV negative
		Normal	Did not show any pathological changes	Mild encephalopathy, without epileptiform activity	HSV 1–2, HIV, and VZV Negative	Normal	16	93	Negative	HSV, VZV, cytomegalovirus negative	NR
44	McAbee 2020	Negative	NR	Frontal intermittent delta activity	NR	Mild elevated	97	92	NR	None	NR
45	Mekheal 2022	Without contrast, an old left cerebellar infarct, with no evidence of acute infarct or hemorrhage	Old infarct, acute infarct involving the left cerebellum, as well as an effacement of the left temporal horn and edema within the left pons, midbrain, left temporal lobe, and surrounding the basal ganglia	Moderate-severe diffuse encephalopathy without epileptiform discharges or seizures	Elevated ESR, CRP, and D-dimer, serum COVID-19 IgG antibody positive	Elevated	145	75	Negative	Meningitis/encephalitis panel by PCR were negative, including all microbial cultures	NR
46	Meshref 2021	Right temporal hypo-dense area	Ill-defined area of faint low signal intensity lesion in T1, hyperintense in T2. FLAIR images showed partial restriction in DWI with no significant enhancement post IV gadolinium contrast injection, involving the right cerebral hemisphere, mainly at the temporal area, suggesting encephalitis	NR	NR	NR	Normal	Normal	NR	No bacterial growth, herpes virus was negative	NR
47	Mierzewska-Schmidt 2022	NR	Diffuse areas of oedema associated with numerous symmetrical changes with punctate hemorrhages in basal ganglia, thalami, brainstem, and cerebral gray matter	NR	Low Hb 9.3 g/dL and Platelet count 183 × 103/μL, CRP 7.4 mg/L, D-dimers 0.97	Elevated	660.00	< 10	Positive	Elevated lactic acid, meningoencephalitis PCR panel was negative	All bacterial cultures were negative
48	Miqdad 2021	Unremarkable	Normal	Different abnormalities suggestive of encephalitis	CRP, D-dimer, and procalcitonin were high	Elevated	832	2.59	NR	HSV PCR and gram stain negative	NR
49	Monti 2020	NR	Normal	Abnormal	Elevated levels of IL-6	Elevated	NR	NR	NR	OCB and anti-NMDAR ab positive, with elevated levels of IL-6 and IL-8	Bacterial or viral pathogens were negative
50	Moriguchi 2020	Normal	Diffusion -weighted images showed hyperintensity along the wall of inferior horn of right lateral ventricle. FLAIR images showed hyperintense signal changes in the right mesial temporal lobe and hippocampus with slight hippocampal atrophy	NR	Elevated levels of WBC and CRP	Mild elevated	NR	NR	Positive	NR	HSV and VZV were negative
51	Morvan 2020	Acute hydrocephalus with diffuse cerebral edema, spontaneous bilateral thalamic hyperdensities, with discrete contrast enhancement and spontaneous hyperdensity in subarachnoidal spaces.	Hypersignal of both thalami brainstem and cerebellum with some hemorrhagic component on T2 sequences	NR	Elevated levels of CRP, fibrinogen, and D-dimer Low Hb, high AST, low factor V, high troponin, high creatinine, very low kaliemia	Normal	79	NR	Negative	None	HIV negative
52	Mullaguri 2021	Axial sections of the brain showed punctate hemorrhages in the right frontal and left frontal and parietal areas	Axial section showed hyperintensities in bilateral centrum semiovale areas. MRI of the brain showing innumerable punctate microhemorrhages in the cerebellar peduncles and subcortical regions of bilateral hemispheres, including bilateral basal ganglia and internal capsules	NR	Hyponatremia (132 mMol/L), significant elevations in D-dimer, LDH, ferritin, CRP, and CK	NR	NR	NR	NR	NR	NR
53	Natarajan 2020	NR	Normal	Normal	NR	Elevated	86	77	Negative	None	HSV, CMV, and VZV were negative
54	Oosthuizen 2021	Central midbrain hypodensity	Features consistent with brainstem encephalitis	Normal	Elevated ESR	Elevated	37	65	Positive	Immunoglobulin G index 0.62, SARS-CoV-2 antibody negative	Tests for infections and malignancy negative
55	Orsini 2021	NR	Normal	Normal	NR	Normal	60	53	Positive	Bacterial culture negative	NR
56	Panariello 2020	Normal	NR	Theta activity at 6 Hz	Elevated CRP and D-dimer with negative ANA, ANCA, anti-ENA, aCL, and anti-β2-GPI abs	NR	65.4	70	Negative	Elevated IL-6 and anti-NMDAR ab	HSV, EBV, CMV, VZV, and enterovirus were negative
57	Picod 2020	Normal	Bilateral lesions (hypersignal or enhancement of meninges, cortical and subcortical regions spread over the insula, the cingula, the medial part of occipital areas, and the internal part of the left-side temporal lobe)	Diffuse intermittent periodic activity	Moderately elevated IL-6	Normal	28	NR	Negative	Elevated IL-6 and OCB negative	HSV negative
58	Pilotto 2020	Normal	Normal	Generalized slowing, with decreased reactivity to acoustic stimuli	Elevated D-dimer, a wide immunological screening of immune-mediated encephalitis was negative	Mild elevated	69.6	NR	Negative	Slightly elevated IL-6, strongly elevated IL-8, TNF-α and β2M	Neurotropic viruses negative
59	Pizzanelli 2021	Normal	Bilateral symmetrical mesial temporal lobes T2/FLAIR/DWI hyperintensities, with mild hippocampal thickening	Autoimmune panel for encephalitis negative	Elevated CRP and fibrinogen	Normal	104	67	Negative	OCB and autoimmune panel for encephalitis negative	Neurotropic viruses negative
60	Poursadeghfard 2021	NR	FLAIR increased signal intensity in the cortical and subcortical regions of both mesial temporal lobe as well as both side hippocampal tails, with relative symmetrical appearance without evidence of significant enhancement or restricted DWI compatible with viral or autoimmune encephalitis	NR	NR	NR	NR	NR	NR	NR	Cat-scratch disease, toxoplasmosis, syphilis, Lyme disease, brucellosis, HIV, VZV, HSV, CMV, EBV, and hepatitis B and C were negative
61	Rebeiz 2020	A questionable subarachnoid hemorrhage within the mesial parietal region and nonspecific hypoattenuation in the splenium of the corpus callosum	1st MRI: DWI and FLAIR hyperintensity of the splenium of corpus callosum; 2nd MRI (after readmission): new abnormal T2/FLAIR hyperintense and restricted diffusion involving the left thalamus, right parasagittal frontal cortex, and bilateral genu of the corpus callosum	Generalized slowing	VES 27; Normal IL-6 and CRP	Elevated	297	56	Negative	None	Neurotropic viruses negative
62	Reddy 2021	4 days after admission: severe diffuse cerebral edema with cerebellar tonsillar herniation	No acute intracranial process	NR	NR	Normal	108	88	NR	None	Bacterial or viral pathogens were negative
63	Sangare 2020	NR	Multiple small hemorrhagic lesions in the pontine tegmentum, bilateral subinsular region	Poorly reactive delta slow waves	NR	Normal	Normal	Normal	NR	None	NR
64	Sarmast 2022	Unremarkable	Hyperintense signals in frontoparietal and parietotemporal lobes on FLAIR/T2 sequence	NR	Mildly elevated CRP, elevated LDH, CPK, ferritin, and D-dimer	Normal	66	81	Negative	VZV PCR, HSV 1–2 PCR, CMV PCR, bacterial antigen negative	Negative for HSV 1–2, HIV, enterovirus, and VZV virus
65	Sattar 2020	Day 20: few scattered foci of white matter hypo-attenuation	Day 25: abnormal medial cortical signals in the bilateral frontal lobe region	NR	Autoimmune antibody panel negative	Mild elevated	39	75	Positive	CSF color pinkish	Bacterial or viral pathogens were negative
66	Sharma 2022	left temporal hypodensity	Intense focal edema within the left hippocampus with mild restricted diffusion, postcontrast enhancement, and hemorrhage seen on susceptibility-weighted imaging	Normal	Creatinine of 1.3 mg/dL, CRP of 42.4 mg/L, ESR of 95 mm/h, CK 858 IU/L, D-Dimer of 1821 FEU, fibrinogen of 644 mg/dL, ferritin of 1352.9 ng/mL, LD of 392 IU/L, prothrombin time (PT/INR) of 1.3/15	Elevated	44	59	NR	Gram stain, bacterial culture, and meningitis/ encephalitis panel were negative. VZV PCR, cryptococcal antigen, culture, AFB smear and culture, and CMV PCR were negative. VZV IgG elevated	NR
		Small right temporal hyperdensity (0.6 cm diameter) suggestive of a hemorrhage with normal vasculature	Right anterior temporal lobe intraparenchymal hemorrhage; additional multiple scattered foci of susceptibility artifact particularly in the gray–white junctions and corpus callosum; and sulcal FLAIR hyperintensity in the right frontal, biparietal, and left temporal lobes	NR	Elevated IL-6, fibrinogen, and thrombocytopenia	Elevated	118	28	NR	Meningitis/encephalitis panel, AFB smear and culture, cryptococcal antigen, and VZV PCR, CMV PCR, CSF cytology were negative	NR
		1st admission: stenosis of the cavernous segment of the right ICA. 2nd admission: unremarkable	1st admission: mild periventricular white matter disease. 2nd admission: multiple punctate foci of restricted diffusion in the bilateral frontal, parietal, occipital, and temporal lobes, mild meningeal enhancement of the anterior and middle cranial fossa, and opacification of multiple ethmoid and mastoid air cells	NR	1st admission; creatinine of 1.4 mg/dL, ESR 111 mm/h, CRP 43.5 mg/L, and HbA1c 12.6%. 2nd admission: fibrinogen of >1000 mg/dL, ferritin of 743 ng/mL, ESR of >130 mm/h, CRP of 313 mg/L, PT/INR of 19/1.6, procalcitonin of 1.24 ng/mL, and antithrombin-3 activity of 62%	Elevated	82	78	NR	Borrelia burgdorferi IgM/IgG titer (0.09 LIV, 0.09 LIV), negative CSF ACE, VDRL, and cryptococcal antigen, EBV PCR positive	AIDP, myasthenia gravis, or vasculitis, secondary infections, mycoplasma IgM, anti-cardiolipin antibodies, B-2 glycoprotein, anti-Xa essay, HIV antibodies, hepatitis panel, serum cryoglobulin PAVAL, autoimmune encephalitis panel were negative
67	Sofijanova 2020	Enlargement of the lateral ventricles, intraventricular masses, pronounced internal hydrocephalus.	NR	NR	Normal	NR	202.7	91.4	NR	None	NR
68	Svedung Wettervik 2020	White matter brain edema with compressed convexity sulci	Increased white matter intensity on flair images, microhemorrhages with involvement of basal ganglia on susceptibility-weighted imaging	Pronounced, generalized slowing over both hemispheres, no electrographic epileptic activity	Mild increased IL-6	Elevated	NR	86.4	Negative	Elevated levels of IL-6	Negative for bacteria and neurotropic viruses
69	Tee 2022	Noncontrast brain CT revealed an old right lenticular infarct	Performed 1 month later, normal findings	Performed 3 weeks later, normal findings	NR	Elevated	116	NR	Positive	NR	NR
70	Urso 2022	NR	CNS involvement, suggestive of encephalitis	A slow base rhythm (theta-delta) together with synchronous bilateral potentials formed by slow waves with predominance on the right side.	NR	Normal	27	Normal	Negative	No bacterial or tuberculous infection	HSV1, varicella-zoster, EBV, and CMV were negative
71	Valadez- Calderon 2022, Mexico	NR	Hyperintensities in the bilateral anterior cingulate cortex and temporal lobes	Subcortical dysfunction in frontal, temporal, and occipital regions	Normal	Normal	Normal	Normal	Negative	NR	NR
72	Vandervorst 2020	Normal	Asymmetric FLAIR hyperintensity of the left medial temporal cortex associated with mild gyral expansion	General excess of beta-rhythm	NR	Normal	Normal	Normal	Negative	None	Negative for enterovirus and HSV
73	Woldie 2020	Non-specific symmetric cerebral enhancement	T2/FLAIR hyper intensity on the medial aspect of each temporal lobe, bilateral basal ganglia, and medial thalami consistent with severe acute necrotizing encephalitis	NR	Elevated LDH	NR	NR	NR	NR	NR	Positive for Cryptococcus neoformans
74	Ye 2020	Normal	NR	NR	Low WBC and lymphocytes	Normal	27	56.5	negative	None	Negative for bacterial or tuberculous infection
75	Zambreanu 2020	Normal	Non-enhancing, symmetrical T2 and FLAIR hyperintensities in mesial temporal lobes and medial thalami and to a lesser extent upper pons, as well as scattered subcortical white matter hyperintensities	NR	Elevated CRP, lymphopenia	Normal	100	63	Negative	Autoimmune antibody panel negative	Negative for streptococci, meningococcus, haemophilus, listeria, Escherichia coli, HSV 1 and 2, HHV6, enteroviruses, parechovirus, CMV, VZV, and Cryptococcus
76	Zandifar 2020	Diffuse brain parenchymal edema and reduced lateral ventricles	NR	NR	Leukocytosis and lymphopenia	Mild elevated	70	30	Negative	None	NR
		NR			Leukocytosis and lymphopenia and LDH elevated	Mild elevated	74	33	Positive
77	Zanin 2021	Increasing vasogenic oedema in the right temporo-fronto-parietal region with extension to the capsular region, to the cerebral peduncle and in the ipsilateral mesencephalic region. Severe compressive effect on the right lateral ventricle	Severe vasogenic oedema of the white matter with 10 mm shift of the midline and compression of the right lateral ventricle; DWI: extensive cortical marked restriction	NR	Increased CRP and WBC with lymphopenia	NR	NR	NR	NR	None	NR
78	Zuhorn 2020	NR	Signal alterations within the claustrum/external capsule region, showed reduced diffusion	NR	LDH, D-dimer, myoglobin, IL-6 and CRP, IgA and IgG positive for SARS-CoV-2	Mild elevated	39.6	57	Negative	None	Negative for HSV, VZV, cytomegaly and Epstein Barr virus

Abbreviation: NR: not reported, AFB: acid-fast bacilli, CT: computed tomography, WBC: white blood cells, RBC: red blood cell, MOG: myelin oligodendrocyte glycoprotein, AST: aspartate aminotransferase, ALT: alanine aminotransferase, HSV: herpes simplex virus, CRP: C-reactive protein, LDH: lactate dehydrogenase, FLAIR: fluid-attenuated inversion recovery, ANA: antinuclear antibody, aCL: anticardiolipin antibody, dsDNA: double-stranded DNA, ANCA: antineutrophil cytoplasmic antibodies, NMDAR: N-methyl-D-aspartate receptor, GAD: glutamic acid decarboxylase, VGKC: voltage gated potassium channel, IL: interleukin, GPI: glycoprotein I, ab: antibody, TPO: thyroid peroxidase, IP: induced protein, CBC: complete blood count, ESR: erythrocyte sedimentation rate, CPK: creatine phosphokinase, CK: creatine kinase, VZV: varicella-zoster virus, ENV: erythrocytic necrosis virus, EBV: Epstein–Barr virus, CMV: cytomegalovirus, OCB: oligoclonal band, DWI: diffusion-weighted imaging, HIV: human immunodeficiency virus, HHV: human herpes virus, HPeV: human parechovirus, LA: lupus anticoagulant, RF: rheumatoid factor, ENA: extractable nuclear antigens, β2M: β2-microglubulin. Normal protein level: 15–45 mg/dL, normal glucose level: 40–70 mg/dL.