Table 1.

List of reviewed studies regarding the neurological disorder of memory and clinical diagnostics in patients after COVID-19 vaccination.

Country	Case	Vaccine	Neurological Disorder of Memory	Clinical Diagnostics	Post-Vaccinal Encephalitis	Ref.
United Kingdom	38-year-old female	First dose of the Pfizer-BioNTech SARS-CoV-2 vaccine	Ongoing difficulties with short-term memory.	The blood pressure, glucose level, and heart rate were found to be normal, as were electrocardiogram and brain CT data.	Functional neurological disorder.	[8]
	36-year-old female	First dose of Moderna SARS-CoV-2 vaccine	Functional weakness, tremor likely due to anxiety, and fatigue symptoms similar to those associated with chronic fatigue syndrome.	MRI of the brain and spine were normal, as were electromyography and nerve conduction velocity studies.	Chronic fatigue syndrome.	[8]
Korea	57-year-old female	Two doses of the AstraZeneca ChAdOx1-S vaccine	Cognitive decline including attention and memory deficits along with gradually worsening dysphasia.	A cerebrospinal fluid (CSF) study was normal. However, magnetic resonance imaging (MRI) of the brain demonstrated restricted diffusion along the left insular and mesial temporal cortices with corresponding hyperintensity on fluid-attenuated inversion recovery (FLAIR) without contrast enhancement.	The follow-up CSF study revealed pleocytosis (22/μL, lymphocytes 91%), glucose of 114 mg/dl, elevated protein as 88.3 mg/dl, a positive oligoclonal IgG band. Autoimmune encephalitis.	[9]
Germany	21-year-old female	First dose of the AstraZeneca ChAdOx1-S vaccine	Subacute onset of working memory impairment, impaired mental status, or psychiatric symptoms.	Emergency brain magnetic resonance imaging (MRI) was performed with normal status of the parenchyma. The extensive diagnostic workup remained negative, including chest X-ray, sonography of the abdomen, and serological examinations of serum and cerebrospinal fluid (CSF).	A lumbar puncture on the day of admission revealed lymphocytic pleocytosis of 46 leukocytes/μL. Autoimmune encephalitis.	[10]
	63-year-old female	First dose of the AstraZeneca ChAdOx1-S vaccine	Subacute onset of working memory impairment, impaired mental status, or psychiatric symptoms.	MRI showed normal status of the parenchyma.	An encephalitis was diagnosed due to the result of lumbar puncture showing a lymphocytic pleocytosis of 115 leukocytes/μL. Autoimmune encephalitis.	[10]
	63-year-old male	AstraZeneca ChAdOx1-S vaccine	Presented with isolated aphasia.	MRI of the brain was normal; in particular, no evidence of ischemia or herpes encephalitis.	A lumbar puncture was performed showing a pleocytosis of 7 leukocytes/μL. Autoimmune encephalitis.	[10]
Taiwan	Age from 42 to 74, 4 females and 6 males	Moderna COVID-19 (mRNA-1273) vaccine	Suspected stroke, transient amnesia, facial nerve palsy, weak hands and feet.	N/A	N/A	[11]
Israel	48-year-old male	Second dose of Pfizer-BioNTech SARS-CoV-2 vaccine	Memory deficits and anterograde amnesia. Severe impairments in short-term memory, temporal orientation, abstraction and language skills.	Electroencephalogram and neurological exam were normal apart from a Montreal Cognitive Assessment (MoCA) score. Cranial magnetic resonance imaging (MRI) showed hyper intense signal on both medial temporal lobes (more on the left) including the parahippocampal gyrus on T2-weighted fluid-attenuated inversion recovery and diffusion-weighted imaging.	CSF cultures were negative and demonstrated normal protein and glucose without pleocytosis.	[12]
Qatar	32-year-old male	Moderna COVID-19 (mRNA-1273) vaccine	Disoriented and amnesic, and onset of forgetfulness and mood disturbance within 24 h of receiving the COVID-19 vaccine dose without remembering what happened after that.	MRI of the brain did not reveal any acute or chronic abnormality.	Lumbar puncture with cerebrospinal fluid (CSF) study was performed, and it showed elevated protein levels (0.76 gm/L, reference range = 0.15–0.45) with average cell counts (white blood cells of 3 u/L) and glucose levels. Acute encephalopathy.	[13]
Indonesia	44-year-old male	Sinovac vaccine	After vaccination, the patient had difficulty communicating verbally. The complaints of difficulty concentrating, and forgetting were getting worse, accompanied by incoherent speech. The patient also had cognitive deficits. The patient’s neurobehavioral status showed short-term memory impairment and impaired concentration.	Brain MRI showed chronic cortical infarct in left temporal lobe and multiple subacute lacunar infarcts in the left corona radiata, left basal ganglia and left frontal lobe. The ENMG results later showed motor and sensory polyradiculoneuropathy on the upper and lower extremities, leading to the diagnosis of chronic inflammatory demyelinating polyradiculoneuropathy (CIDP).	Secondary antiphospholipid syndrome and autoimmune dementia.	[14]
Taiwan	82-year-old female	First dose of the mRNA-1273 SARS-CoV-2 vaccine (Moderna)	Memory impairment, loss of attention and concentration, murmuring, and unsteadiness.	Brain MRI revealed hyperintense signal on fluid-attenuated inversion recovery (FLAIR) sequence imaging and abnormal gyral enhancement on T1-weighted imaging in the right middle and posterior temporal lobe with no evidence of myelitis.	CSF analysis showed no pleocytosis but elevated CSF protein. CSF rapid plasma reagin (RPR), treponema pallidum hemagglutination (TPPA) immunoelectrophoresis, and cytology were negative.	[15]
Taiwan	55-year-old male	First dose of the AstraZeneca ChAdOx1-S vaccine	Impaired verbal expression, progressive disorientation to people and place and slow response.	Magnetic resonance angiography of brain was showed pachymeningeal enhancement without definite abnormal signal intensity over brain parenchyma.	CSF testing showed the white cell count was 16/μL, with a neutrophil/lymphocyte/monocyte count 3/4/7, red cell count was 1/μL, the protein level was 97.3 mg/dL and positive antinuclear antibody. Serum white cell count, platelet count and C-reactive protein were within normal range.	[16]
China	24-year-old female	SARS-CoV-2 vaccine (Vero cells)	Neurological examination showed somnolence, memory decline and poor memory persisted.	Initial brain MRI showed abnormal signals in the bilateral temporal cortex.	The WBC count of CSF was 51 × 106/L. CSF was negative for antibodies to major pathogens and cultures of bacteria and fungi; high-throughput genome sequencing also revealed no pathogens.	[17]
India	65-year-old male	First dose of the AstraZeneca ChAdOx1-S vaccine	Cognitive deficits, memory impairments and sudden memory loss. Unable to describe both short and long-term memory previously acquired.	Non-contrast CT was essentially normal with no evidence of hemorrhage or focal lesion.	All routine blood tests were normal.	[18]