[A case of neurolymphomatosis that was diagnosed by acoustic nerve biopsy]

A 58-year-old female was admitted to our hospital because of recurrent multiple cranial neuropathy (right facial palsy followed by involvement of the left trigeminal, facial, acoustic, pharyngeal, and vagal nerves and the right abducens nerve). Brain MRI showed gadolinium enhancement of the right abducens, bilateral facial/acoustic, and left pharyngeal/vagal nerves, and ¹⁸F-Fluorodeoxyglucose (FDG)-positron emission tomography revealed abnormal FDG uptake in the right facial, acoustic, pharyngeal, and vagal nerves and the left cervical lymph nodes. Blood and biochemical analyses did not show any abnormalities, including in the patient's lactate dehydrogenase and soluble interleukin-2 receptor (sIL2R) levels. A cerebrospinal fluid (CSF) examination showed gradual increases in the patient's cell counts and protein, β2-microglobulin, and sIL2R levels, but no malignant cells were detected. A thorough investigation involving repeated CSF examinations, whole-body computed tomography, bone marrow aspiration, random skin biopsies, and cervical lymph node aspiration biopsy examinations did not result in any definitive conclusions. Steroid therapy was ineffective, and the patient developed deafness in her left ear. Therefore, we performed a biopsy examination of the left acoustic nerve, which resulted in the patient being diagnosed with diffuse large B-cell lymphoma. High-dose MTX following the intrathecal administration of MTX, cytarabine, and prednisolone partially improved her symptoms, but she died after several episodes of clinical recurrence. Acoustic nerve biopsy may help diagnose neurolymphomatosis in carefully selected cases.