A 64-year-old female with a complaint of dizziness and gait instability for 1 month was admitted to our hospital. The patient had a history of upper respiratory tract infection 2 days before the onset of these symptoms, which was characterized by nasal congestion and throat dryness, with no significant fever, cough, or expectoration. 2 days later, dizziness and gait instability with visual rotation, nausea, and intermittent vomiting occurred and progressively aggravated within 1 month. There was no headache, limb numbness, unconsciousness, or convulsive episodes during the course of the disease. No previous specific disease history, no drug exposure or alcohol consumption history, and no vaccination history in the last 1 year. On admission, physical examination revealed normal blood pressure of 132/83 mmHg, ataxic dysarthria, gross rotational nystagmus during horizontal and vertical eye movements, normal muscle strength of limbs, no eyelid ptosis, eye movement disorders or pupillary changes, no diminished or absent tendon reflexes, unstable bilateral finger-nose test and heel-knee-shin test, and truncal ataxia. We performed the first assessment of the severity of the patient's cerebellar ataxia using the Scale for the Assessment and Rating of Ataxia (SARA), with a score of 37. Serological examinations including blood routine, C-reactive protein, serum vitamin B1, vitamin B12, folic acid, human immunodeficiency virus (HIV) antibody, as well as other autoimmunity markers including antinuclear antibody (ANA), anti-neutrophil cytoplasmic antibodies (ANCA), and rheumatoid factors were all unremarkable. Imaging examination including cranial magnetic resonance imaging (MRI) (Figure 1) and lung computed tomography (CT) was normal. Transcranial doppler (TCD) revealed there were no cerebrovascular stenosis, atherosclerosis, or other abnormalities. Breast and abdominal ultrasounds were normal. Lumbar puncture revealed clear cerebrospinal fluid (CSF) with an opening pressure of 100 mmH2O. CSF biochemical tests showed slightly increased protein levels (0.47 g/L, reference range (RR): 0.15-0.45 g/L), positive Pan's reaction, while glucose and chlorine levels were normal. CSF cytology showed normal white blood cells (4.00 x 106/L, reference range (RR): 0.00-8.00 x 106 g/L) and visible lymphocytes, no cancer cells were seen. CSF results for infections (rubella virus, cytomegalovirus, and herpes simplex virus antibodies, general bacteria, fungi, and tuberculosis smears) were negative. Antibody analysis of autoimmune encephalitis and paraneoplastic syndrome including anti-NMDAR, anti-AMPA1, anti-AMPA2, anti-LGI1, anti-CASPR2, anti-GABA, anti-Hu, anti-Yo, anti-Ri, anti-MA2, anti-CV2, anti-Amphiphysin, anti-Tr (DNER), anti-Zic4, anti-SOX1, and anti-GAD65, were all negative in both serum and CSF.
Based on the above clinical data, the patient was first considered to have acute cerebellitis that might have been caused by a certain virus infection. The clinical conditions usually improved after 3-5 days of antiviral therapy in acute cerebellitis caused by viruses. Another patient with acute cerebellitis caused by the virus received antiviral and low-dose dexamethasone (10 mg four times daily) treatment for a total of 4 days, with significant improvement of symptoms within 7 days. We referred to previous experience and gave antiviral and medium-dose steroid treatment (methylprednisolone 80 mg/day) for 7 days while cerebellar symptoms did not improve. Considering that the patient's symptoms lasted for more than 1 month with poor antiviral and medium-dose steroid treatment effects, whether there were other factors causing cerebellar ataxia, thyroid color ultrasound, and serum thyroid function were examined. Thyroid color ultrasound (Figure 2) showed that the internal echogenicity was diffuse, rough, and heterogeneous, and lamellar hypoechogenicity was seen, supporting the diagnosis of Hashimoto's thyroiditis. Serum thyroid function showed slightly decreased thyroid stimulating hormone (TSH, 0.3006 uIU/ml, RR: 0.35-4.94 uIU/ml), normal free triiodothyronine (FT3, 4.21 pmol/L, RR: 4.11-6.47 pmol/L), normal free thyroxine (FT4, 13.54 pmol/L, RR: 9.01-19.05 pmol/L), while significantly elevated anti-thyroglobulin autoantibodies (Tg-Ab, 87.72 IU/ml, RR: 0-4.11 IU/ml) and anti-thyroperoxidase autoantibodies (TPO-Ab, 13.18 IU/ml, RR: 0-5.61 IU/ml).
According to the main symptoms of cerebral ataxia, almost normal neuroimaging and CSF tests, by excluding other toxic, metabolic, and infectious causes of encephalopathy, the patient was diagnosed with HE. The patient was given the steroid methylprednisolone (1 g/d) for 3 days and reduced to oral prednisolone 60 mg/d, and then gradually reduced within 2 months to a maintenance dosage of 20 mg/day for 1 month. The patient's symptoms began to show improvement on day 3 of high-dose steroid therapy. 1 month later, her RASA score was 3 and she was discharged from the hospital with a marked improvement in ataxia, showing only slight dysarthria, and less obvious limb ataxia. After follow-up, the patient's symptoms were completely relieved within 3 months. In addition, after being discharged from our hospital, the patient completed a whole-body imaging Positron Emission Tomography Computed Tomography (PET-CT) examination at another hospital with no suspicious positive findings within 1 month.