Acute disseminated encephalomyelitis; This literature-non-study case was reported in a literature article and describes the occurrence of ACUTE DISSEMINATED ENCEPHALOMYELITIS (Acute disseminated encephalomyelitis) in an 83-year-old male patient who received mRNA-1273 (Spikevax) for COVID-19 prophylaxis.   Concurrent medical conditions included Hypertension.    On an unknown date, the patient received second dose of mRNA-1273 (Spikevax) (unknown route) 1 dosage form. On an unknown date,  after starting mRNA-1273 (Spikevax), the patient experienced ACUTE DISSEMINATED ENCEPHALOMYELITIS (Acute disseminated encephalomyelitis) (seriousness criterion medically significant). The patient was treated with CEFTRIAXONE (intravenous) at an unspecified dose and frequency and METHYLPREDNISOLONE (intravenous) at a dose of 1000 milligram once a day. At the time of the report, ACUTE DISSEMINATED ENCEPHALOMYELITIS (Acute disseminated encephalomyelitis) had resolved. Related    DIAGNOSTIC RESULTS (normal ranges are provided in parenthesis if available): On an unknown date, Bacterial test: (Negative) Negative. On an unknown date, Blood glucose: 80. On an unknown date, Blood iron: deficiency anemia.. On an unknown date, CSF test: (Negative) Negative. On an unknown date, CSF white blood cell count: 13 with 60%lymphocytes).. On an unknown date, Fungal test: (Negative) Negative. On an unknown date, HIV antibody: (Negative) Negative. On an unknown date, Imaging procedure: showed decreased confluent T2 hyperintensities, but also demonstrated new areas of patchy involvement. and T2-Flair white matter hyperintensities 13 days post Covid- 19 vaccination.. On an unknown date, JC polyomavirus test: (Negative) Negative. On an unknown date, Laboratory test: were unremarkable. On an unknown date, Magnetic resonance imaging head: revealed nonenhancing multifocal and confluent supra/infratentorial T2/FLAIR hyperintensity lesions.. On an unknown date, Mycobacterium test: (Negative) Negative. On an unknown date, Protein total: 54 elevated. On an unknown date, Red blood cell sedimentation rate: 72. On an unknown date, Treponema test: (Negative) Negative. On an unknown date, Vitamin B12: 311 pg/ml. On an unknown date, Vitamin D: 14.9 ng/mL.     For mRNA-1273 (Spikevax) (Unknown), the reporter considered ACUTE DISSEMINATED ENCEPHALOMYELITIS (Acute disseminated encephalomyelitis) to be related.   Company comment: This is a literature non-study case concerning an 83-year-old male patient with no relevant medical history reported, who experienced the unexpected serious (medically significant) adverse event of special interest Acute disseminated encephalomyelitis, reported as acute disseminated encephalomyelitis-like presentation, which occurred 13 days after receiving a dose of mRNA-1273 as the second dose of COVID-19 vaccine (no information disclosed on previous COVID-19 vaccination). Latency cannot be properly assessed since vaccination date nor event onset date were provided. It was reported that the patient had sudden onset of progressive multifocal neurological deficits including blurry vision, upper extremity weakness, numbness and clumsiness with imbalance resulting in multiple falls. A few days later, patient reported dysphagia, intermittent expressive aphasia and confusion. Examination showed mild bilateral upper motor neuron and cerebellar signs. Laboratory tests were unremarkable except for elevated ESR (72), low Vitamins-B12 (311 pg/mL), and D (14.9 ng/mL) levels, and iron deficiency anemia. MRI brain with gadolinium revealed non-enhancing multifocal and confluent supra/infratentorial T2/FLAIR hyperintensity lesions. Cerebrospinal fluid (CSF) analysis showed pleocytosis (white cell count 13 with 60% lymphocytes), elevated protein (54), and glucose (80), suggestive of underlying inflammation. CSF cytology, meningoencephalitis panel, VDRL, JC virus PCR, India ink, acid-fast, bacterial and fungus cultures were negative. HIV antibody was negative. Intravenous Ceftriaxone was initiated until CSF cultures returned negative. Serum anti-MOG and anti-NMO were negative. Repeat imaging within a week showed decreased confluent T2 hyperintensities, but also demonstrated new areas of patchy involvement. The patient received intravenous methylprednisolone 1000 mg daily for 5 days. In the following weeks, his symptoms improved remarkably. The benefit-risk relationship of mRNA-1273 is not affected by this report.   No concomitant medications were reported.; Sender's Comments: This is a literature non-study case concerning an 83-year-old male patient with no relevant medical history reported, who experienced the unexpected serious (medically significant) adverse event of special interest Acute disseminated encephalomyelitis, reported as acute disseminated encephalomyelitis-like presentation, which occurred 13 days after receiving a dose of mRNA-1273 as the second dose of COVID-19 vaccine (no information disclosed on previous COVID-19 vaccination). Latency cannot be properly assessed since vaccination date nor event onset date were provided. It was reported that the patient had sudden onset of progressive multifocal neurological deficits including blurry vision, upper extremity weakness, numbness and clumsiness with imbalance resulting in multiple falls. A few days later, patient reported dysphagia, intermittent expressive aphasia and confusion. Examination showed mild bilateral upper motor neuron and cerebellar signs. Laboratory tests were unremarkable except for elevated ESR (72), low Vitamins-B12 (311 pg/mL), and D (14.9 ng/mL) levels, and iron deficiency anemia. MRI brain with gadolinium revealed non-enhancing multifocal and confluent supra/infratentorial T2/FLAIR hyperintensity lesions. Cerebrospinal fluid (CSF) analysis showed pleocytosis (white cell count 13 with 60% lymphocytes), elevated protein (54), and glucose (80), suggestive of underlying inflammation. CSF cytology, meningoencephalitis panel, VDRL, JC virus PCR, India ink, acid-fast, bacterial and fungus cultures were negative. HIV antibody was negative. Intravenous Ceftriaxone was initiated until CSF cultures returned negative. Serum anti-MOG and anti-NMO were negative. Repeat imaging within a week showed decreased confluent T2 hyperintensities, but also demonstrated new areas of patchy involvement. The patient received intravenous methylprednisolone 1000 mg daily for 5 days. In the following weeks, his symptoms improved remarkably. The benefit-risk relationship of mRNA-1273 is not affected by this report.