他山之石007：《神经医学影像联盟》双语病例（001）——原发中枢神经系统淋巴瘤

History: A 34-year-old man with HIV presents with confusion and gait difficulty for the past week.

简要病史：34岁HIV患者，出现意识混乱和步态困难一周。

Findings

• CT: There is a hyperdense mass centered in the periventricular right frontal lobe, exerting mass effect on the frontal horn of the right lateral ventricle and third ventricle and likely obstructing the foramen of Monro. There is surrounding hypoattenuation, likely reflecting, in part, moderate vasogenic edema. There is associated thickening of the septum pellucidum, likely reflecting neoplastic involvement. There is resultant moderate dilation of the lateral ventricles, reflecting hydrocephalus and mild leftward midline shift.
   

• MRI: An ill-defined mass centered in the right periventricular white matter with dominant enhancing component is seen. There is associated hydrocephalus with a ventricular drain in place. The mass is relatively homogeneous in enhancement, with much of the mass demonstrating at least moderate restricted diffusion. Abnormal tissue also involves most of the surrounding brain parenchyma. The tumor bulges into the right frontal horn of the lateral ventricle and extends across midline through the anterior commissure and potentially through the massa intermedia. There is thickening of the septum pellucidum due to tumor infiltration.

影像表现

CT：右额叶脑室周围一高密度肿块，压迫右侧脑室额角和第三脑室，并可能阻塞了孟氏孔。肿块周围可见低密度中等程度的血管源性水肿。透明隔增厚，可能为肿瘤累及所致。侧脑室中度扩张提示有脑积水。中线结构轻度左偏。

MRI：右侧脑室周围白质内可见一个边界不清的肿块，增强后明显强化。因脑积水进行了引流。肿块增强相对均匀，大部分肿块显示中度弥散受限。肿块周围的脑组织大部分也为异常信号的病变：肿瘤突出到右侧脑室额角，并通过前联合延伸至中线，可能累及了丘脑间连合。肿瘤浸润透明隔，导致透明隔增厚。

Diagnosis: Primary CNS lymphom

诊断：原发性中枢神经系统淋巴瘤

Differential diagnosis

• Glioblastoma

• Cerebral abscess

• Toxoplasmosis

• Neurosarcoidosis

• Metastatic disease

鉴别诊断

       胶质母细胞瘤

       脑脓肿

       弓形虫病

       神经结节病

       转移瘤

Primary central nervous system (CNS) lymphoma

原发中枢神经系统淋巴瘤

Pathophysiology

Involvement of the central nervous system by lymphoma can occur in the presence of systemic lymphoma involvement or in isolation as a primary CNS neoplasm. Primary central nervous system lymphoma (PCNSL) originates in the brain, leptomeninges, spinal cord, or eyes and typically remains confined to the CNS. PCNSL is encountered in the immunocompetent and immunocompromised patients, but the cause and behavior of PCNSL differ based on the affected population. Immunocompromised patients are at particular risk for developing PCNSL, which is typically secondary to HIV, organ transplantation, or congenital immunodeficiency syndromes. In this setting, PCNSL arises from Epstein-Barr virus infection of B lymphocytes.

病理生理学

中枢神经系统淋巴瘤可发生在全身性淋巴瘤继发累及或作为原发性中枢神经系统肿瘤孤立存在的情况下。原发性中枢神经系统淋巴瘤（PCNSL）起源于大脑、软脑膜、脊髓或眼球，局限于中枢神经系统。PCNSL可发生在免疫功能正常和免疫功能低下的患者中，PCNSL的表现取决于患者的免疫状态。免疫功能低下的患者尤其容易发生PCNSL，这通常继发于HIV、器官移植或先天性免疫缺陷综合征。在这种情况下，PCNSL起源于B淋巴细胞的EB病毒感染。

Epidemiology

PCNSL accounts for 1% to 5% of all brain tumors. The incidence rates of PCNSL are increasing among immunocompetent patients. Immunocompromised patients have an increased risk of developing PCNSL. Median age at disease presentation is 65 years, with a trend toward an increase of incidence in the oldest population. Approximately 95% of PCNSLs are diffuse, large B-cell lymphomas, while the other 5% include T-cell, Burkitt, lymphoblastic, and marginal zone lymphomas.

流行病学

PCNSL占所有脑肿瘤的1%～5%。在免疫功能正常的患者中，PCNSL的发病率呈上升趋势。免疫功能低下患者发生PCNSL的风险增加。发病年龄中位数为65岁，高龄人群发病率呈上升趋势。大约95%的PCNSL是弥漫性大B细胞淋巴瘤，另外5%包括T细胞性、Burkitt性、淋巴母细胞性和边缘性淋巴瘤。

Clinical presentation

Patients usually present with headache, confusion, focal neurologic symptoms, or nausea and vomiting related to intracranial hypertension. Systemic B symptoms are unusual in patients with PCNSL.

临床表现

患者通常表现为头痛、精神错乱、局灶性神经症状或与颅内高压有关的恶心呕吐。PCNSL患者的全身性B症状（发烧，盗汗和体重减轻）不常见。

maging features

• MRI: PCNSL typically presents as a homogenous mass in the periventricular white matter with T1 and T2 signal intensity that reflects high-cellularity characteristics. The mass typically shows diffuse, homogeneous contrast enhancement. The lesions typically have less mass effect than a comparably sized metastasis or high-grade glioma. There is usually mild to moderate diffusion restriction. The lesions can cross the corpus callosum into the contralateral hemisphere.
   

• CT: PCNSL usually presents as a hyperdense homogeneous mass with contrast enhancement.

影像特征

MRI：PCNSL典型表现为脑室周围脑白质的信号均匀性肿块，T1和T2信号强度反映淋巴瘤高细胞密度特征。肿块通常表现为弥漫、均匀的强化。与同等大小的转移瘤或高级别胶质瘤相比，病灶的占位效应通常较轻。通常有轻度到中度的弥散受限。病变可通过胼胝体进入对侧大脑半球。

CT：PCNSL常表现为高密度、均匀的肿块伴有强化。

Treatment

Corticosteroids may induce a rapid improvement in clinical symptoms and radiographic features. Definitive treatment is usually based on a high-dose methotrexate regimen.

治疗

皮质类固醇可以诱导临床症状和影像表现迅速改善。确定性治疗通常是基于大剂量甲氨蝶呤方案。