A 47-year-old Caucasian woman (APS) was admitted by the neurology team with flu, loss of strength bilaterally in the lower limbs and upper limbs, and sudden onset ataxia 7 days after receiving Oxford/AstraZeneca COVID-19 vaccine. After 3 days of hospitalization, she progressed with partial improvement in the upper limbs and worsening loss of strength in the lower limbs, causing her to be bedridden. In addition, she started to present with axial cerebellar ataxia, dysphonia. Clinical examination revealed a woman with regular general health status, no fever, acyanotic, and anicteric. Neurological examination revealed: Glasgow Coma Scale score of 15, no meningeal signs; negative Babinski sign; strength grade 2 in the lower limbs and strength grade 4 in the upper limbs; axial and pendicular cerebellar ataxia; and peripheral facial diparesis predominantly on the right, without conjugate gaze deviation. Cerebral spinal fluid (CSF) was collected upon admission and tested in the laboratory. The results showed albuminocytological dissociation, with protein, 148.9; leukocytes, 1; chlorine, 122; glucose, 65 mg/mL; red blood cells, 2; and non-reactive venereal disease research laboratory test result. The hematological test results were: hemoglobin, 14.8 g/dL; hematocrit, 42.9%; leukocytes, 10.8 mL/mm3 with no left shift; platelets, 274 × 103/mm3; potassium, 4.1 mEq/L; sodium, 138 mEq/L; calcium, 1.118 mEq/L; urea, 38 mg/dL; creatinine, 0.8 mg/dL; and C-reactive protein (CRP), 5.6 mg/L. A number of other tests were also performed following admission, including: lactic dehydrogenase, 290 U/L (normal range: 125–220 U/L); gamma glutamyl transferase (GGT), 56 U/L (normal range: 9–36 U/L); PCR test, 10.8 mg/L. The patient tested negative for the COVID-19 IgG/IgM rapid immunological test. Electroneuromyography (ENMG) revealed a recent and moderate primarily motor and sensory demyelinating polyneuropathy with proximal motor block. The ENMG report was correlated with the patient’s clinical condition to consider acute polyradiculoneuritis, which led to the hypothesis of MFSwhen associated with a cerebellar ataxic component. One week before admission to the hospital, the head computed tomography (CT) showed mineral deposition in the basal ganglia. Head CT was normal on the day of admission. Intravenous immunoglobulin (IVG) was administered, 0.4 g/kg/day for 5 days, associated with motor physiotherapy, which led to improvement of the neurological symptoms during hospitalization. The patient was discharged with follow-up of motor physical therapy and use of gabapentin 300 mg every 12 hours for pain control. She was advised to seek emergency care if neurological condition worsened. At this point, plasmapheresis may be considered.