Neurexin-3α-associated autoimmune encephalitis with intracranial diffuse large B lymphoma diagnosed on FDG and TSPO PET/MRI

Excerpt

A 74-year-old female patient presenting with weakness in both lower limbs and cognitive impairment for 3 months was diagnosed with Neurexin-3α-associated autoimmune encephalitis through cerebrospinal fluid (CSF), MRI, and ¹⁸F-FDG PET/CT examinations (blue arrow for prefrontal and parietal hypometabolism, and red arrow for medial-temporal hypermetabolism), according to consensus clinical diagnostic criteria [1, 2] and the literature [3]. Symptom improvement was observed when she was administered methylprednisolone pulse therapy, but the symptoms worsened latterly when dosages were reduced after 3 months. She underwent another CSF, ¹⁸F-FDG, and ¹⁸F-PBR06, which is the translocator protein 18 kDa translocator protein (TSPO) radioligand PET/MRI examination. The antibody titer levels increased, and the PET/MRI demonstrated worsening of the disease with more widespread uptake. There were no associated enhancement lesions on the MRI until 122 days after the initial PET scan. The symptoms worsened again, even after plasma exchange, gamma globulin, and methylprednisolone. She eventually underwent stereotactic needle brain biopsy of the lesion of right frontal lobes (yellow arrow) and was diagnosed with intracranial diffuse large B-cell lymphoma through immunohistochemistry.

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