Table 1.

Diagnostic findings.

Serum analyses	Thyroid-stimulating hormone (TSH) level was suppressed (0.06 mU/mL; reference 0.27–4.20 mU/mL); triiodothyronine (3.57 pmol/l; reference 3.4–6.8 pmol/l), and thyroxine (20.7 pmol/l; reference 10.6–22.7 pmol/l) levels were in normal ranges. Increased autoantibodies against thyroglobulin (832 IU/mL; reference < 115 IU/mL) and thyroid peroxidase (84 IU/mL; reference < 34 IU/mL) were detected. Autoantibodies against TSH receptors were not increased (0.93 IU/mL). No antibodies against intracellular onconeural antigens (Yo, Hu, CV2/CRMP5, Ri, Ma1/2, SOX1) or intracellular synaptic antigens (GAD, amphiphysin) were found. Screening for antinuclear antibodies (ANA), anti-neutrophil cytoplasmic antibodies (ANCA), antiphospholipid antibodies (APA), and rheumatoid factor (RF) was negative. C3, C4, and C3d were normal.
Cerebrospinal fluid analyses	Normal white cell count (2/μL; reference < 5/μL). No blood–brain barrier dysfunction (protein concentration: 401 mg/L; reference < 450 mg/L; albumin quotient: 5.3; age-dependent reference < 8 × 10–3). No CSF specific oligoclonal bands; IgG index not increased (0.44; reference ≤ 0.7). Antibodies against neuronal cell surface antigens (NMDAR, AMPA-R, GABA-B-R, VGKC-complex [LGI1, Caspr2]) were negative. Dementia markers were normal: Tau: 118 pg/mL (reference < 450 pg/mL), phospho-tau: 26 pg/mL (reference < 61 pg/mL), Aß 1–42: 1064 pg/mL (reference > 450 pg/mL, Aß ratio: 1.4 (reference > 0.5)
Cerebral magnetic resonance imaging	Supratentorial deep and peripheral white matter lesions (Fazekas Score 1). No generalized or local atrophy.
Electroencephalography	Intermittent rhythmic slow activity; no epileptic patterns.
Fluorodeoxyglucose positron emission tomography (FDG-PET)	Mild-to-moderate medial and superior dorsolateral frontal hypometabolism. Whole-body FDG-PET/CT for tumor screening was unremarkable.
FP-CIT single-photon emission computed tomography	Normal striatal dopamine transporter availability.