Bataduwaarachchi Vipula R, Tissera Nirmali
Department of Pharmacology and Pharmacy, Faculty of Medicine University of Colombo, PO Box 271, Kynsey Road, Colombo 8, Sri Lanka.
Department of Medicine, National Hospital, Ward Place, Colombo, Sri Lanka.
BMC Med Imaging. 2016 Jan 18;16:8. doi: 10.1186/s12880-016-0113-4.
Paraneoplastic limbic encephalitis is an uncommon association of common malignancies such as small cell lung carcinoma, testicular teratoma, and breast carcinoma. The nonspecific nature of the clinical presentation, lack of freely available diagnostic markers, and requirement for advanced imaging techniques pose a great challenge in the diagnosis of this disease in resource-poor settings.
A 64-year-old previously healthy Sri Lankan man was admitted to the general medical unit with subacute memory impairment regarding recent events that had occurred during the previous 3 weeks. Initial noncontrast computed tomography of the brain revealed a hyperdensity in the hypothalamic region surrounded by hypodensities extending toward the bilateral temporal lobes; these findings were consistent with a possible hypothalamic tumor with perilesional edema. The patient later developed cranial diabetes insipidus, which was further suggestive of hypothalamic disease. Interestingly, gadolinium-enhanced magnetic resonance imaging of the brain showed no such lesions; instead, it showed prominent T2-weighted signals in the inner mesial region, characteristic of encephalitis. The possibility of tuberculosis and viral encephalitis was excluded based on cerebrospinal fluid analysis results. Limbic encephalitis with predominant hypothalamitis was suspected based on the radiological pattern. Subsequent screening for underlying malignancy revealed a mass lesion in the right hilum on chest radiographs. Histological examination of the lesion showed small cell lung cancer of the "oat cell" variety.
We suggest that the initial appearance of a hyperdensity in the hypothalamus region on noncontrast computed tomography is probably due to hyperemia caused by hypothalamitis. If hypothalamitis is predominant in a patient with paraneoplastic limbic encephalitis, magnetic resonance imaging will help to differentiate it from a hypothalamic secondary deposit. Limbic encephalitis should be considered in a patient with computed tomographic evidence of a central hyperdensity surrounded by bitemporal hypodensities. This pattern of identification will be useful for early diagnosis in resource-poor settings.
副肿瘤性边缘叶脑炎是小细胞肺癌、睾丸畸胎瘤和乳腺癌等常见恶性肿瘤的一种罕见关联疾病。临床表现的非特异性、缺乏可随时获取的诊断标志物以及对先进成像技术的需求，给资源匮乏地区诊断这种疾病带来了巨大挑战。
一名64岁、既往健康的斯里兰卡男子因近3周内发生的近期事件出现亚急性记忆障碍而入住普通内科病房。最初的脑部非增强计算机断层扫描显示下丘脑区域有高密度影，周围低密度影向双侧颞叶延伸；这些表现符合可能的下丘脑肿瘤伴瘤周水肿。患者后来出现颅性尿崩症，这进一步提示下丘脑疾病。有趣的是，脑部钆增强磁共振成像未显示此类病变；相反，它显示内侧区域有明显的T2加权信号，这是脑炎的特征。根据脑脊液分析结果排除了结核病和病毒性脑炎。基于影像学表现怀疑为以丘脑下部炎为主的边缘叶脑炎。随后对潜在恶性肿瘤的筛查显示胸部X线片上右肺门有肿块病变。病变的组织学检查显示为“燕麦细胞”型小细胞肺癌。
我们认为，非增强计算机断层扫描下丘脑区域最初出现的高密度影可能是由丘脑下部炎引起的充血所致。如果在副肿瘤性边缘叶脑炎患者中丘脑下部炎为主，磁共振成像将有助于将其与下丘脑继发性沉积物区分开来。对于计算机断层扫描显示中央高密度影被双侧颞叶低密度影包围的患者，应考虑边缘叶脑炎。这种识别模式将有助于资源匮乏地区的早期诊断。
