診断に苦慮した視交叉原発悪性リンパ腫の1例

A Case of Primary Central Nervous System Lymphoma Originated from Optic Chiasma and Presenting Difficulty in Diagnosis

Ⅰ．はじめに

　中枢神経原発悪性リンパ腫は近年増加傾向にあるが，視神経交叉原発の報告は少ない．視神経交叉に病変を来し得る疾患には炎症性疾患や膠原病関連疾患などがあるため，病初期には鑑別が困難であることが多い．今回，診断までに苦慮し，開頭下生検にて診断し得た視交叉原発の中枢神経原発悪性リンパ腫を経験したため，文献的考察を加え報告する．

　We report a case of primary central nervous system lymphoma（PCNSL）originating from an optic chiasma, which was difficult to diagnose but was finally diagnosed by biopsy. A 62-year-old immunocompetent man presented with bilateral visual field disturbance, hypopituitarism, and diabetes insipidus;an optic chiasm lesion was detected on MRI. After starting steroid supplementation for adrenal insufficiency, visual field disturbance immediately improved. Since the lesion completely disappeared three months after its onset, it became the follow-up without histological confirmation. Six months after the onset, visual field disturbance progressed, and the lesion recurred. We performed a left optic nerve biopsy to maintain the right visual field, which remained partially. The pathology was PCNSL. We performed postoperative chemoradiotherapy, and the patient showed remission and improvement of the visual field.

　Isolated PCNSLs arising from optic chiasma are very rare. The diagnosis of optic chiasm lesions is difficult due to their similarity with a variety of inflammatory/autoimmune disease and neoplastic lesions. When a lymphoma is considered to be differentiated, early biopsy should be performed before administering a steroid. The approach and sampling site to prevent the function are also important for biopsy.