TM is a relatively uncommon condition with an estimated incidence between 1.34 and 4.6 cases per million annually , and vaccine-associated myelitis is even rarer. Nine cases of TM were reported in the Centers for Disease Control (CDC)‘s Vaccine Adverse Event Reporting System (VAERS) related to Pfizer-BioNTech, Moderna and Johnson & Johnson’s COVID-19 vaccine . One case has been deemed likely related to the ChAdOx1 nCOV-19 (AstraZeneca™) vaccine during the efficacy and safety trials [2, 3]. Along with previously reported cases, our case suggests a temporal relationship of symptom-onset between 10 to 14 days following ChAdOX1 nCOV-19 vaccine administration, possibly due to delayed immunological reactions [2, 3, 6,7,8]. In addition, possible molecular mimicry by the viral vector may induce autoimmunity by a cascade of inflammatory reactions propagated via dendritic and T-cells . In other vaccines, such as alumuinium-containing vaccines, adjuvants used to amplify the immune response have been associated with autoimmunity . However, the ChAdOX1 nCOV-19 vaccine does not contain adjuvant or preservatives.
LETM is diagnosed when there are contiguous central cord lesions with variable contrast enhancement extending over three or more vertebral segments on spinal MRI . Patients typically have a dramatic presentation of acute or subacute paraparesis or tetraparesis, with sensory disturbances and alteration of gait, bladder, bowel and sexual dysfunction, depending on the location of lesion on the spinal cord . Although our case suggests temporal causality between the ChAdOX1 nCOV-19 vaccine and LETM, other differentials had to be ruled out in particular neuromyelitis optica spectrum disorder (NMOSD), multiple sclerosis (MS), and infectious causes . The absence of both autoantibodies (AQ-4 and MOG) combined with the absence of optic neuritis make the diagnosis of NMOSD unlikely. Furthermore, the absence of CSF pleocytosis, typical lesion of MS in the spine (usually patchy involving one or two vertebrae with peripheral enhancement), negative oligoclonal bands and normal MRI brain are not consistent with MS. However, this patient need to be followed up for the reoccurrence of symptoms in the future as this could be the first isolated lesion (clinically isolated syndrome) in both relapsing-remitting courses of MS. Lastly, sterile CSF with relatively normal inflammatory markers were not suggestive of infectious myelitis. Based on the currently available evidence and the temporal relationship, the occurrence of LETM follwing vaccination, in this case, was probable based on the adverse drug reaction probability scale (point + 6) .
A recent review showed that the prevalence of myelitis in COVID-19 patients is far greater, accounting for approximately 1.2% of all COVID-19 neurological related complications where LETM accounted for 70% of the reported TM in the series . Although unfortunate, patients who have developed LETM following vaccines have responded relatively well to treatment, suggesting what is hopefully a temporary immunogenic reaction.