Lee Jae Hee, Na Dong Gyu, Choi Kyu H, Kim Ki Jun, Ryoo Jae Wook, Lee Sung Yong, Suh Yeon-Lim
Department of Radiology, Our Lady of Mercy Hospital, The Catholic University of Korea, Incheon.
AJNR Am J Neuroradiol. 2002 Apr;23(4):535-42.
Subcortical low-intensity lesion on T2-weighted images is an uncommon manifestation of ischemia, multiple sclerosis, and Sturge-Weber disease. This study was performed to determine whether subcortical low signal intensity is an MR feature of meningitis, viral encephalitis, or leptomeningeal metastasis and to investigate a cause of subcortical low intensity.
We retrospectively reviewed MR images of 117 patients with meningitis, encephalitis (viral or unknown), or leptomeningeal metastasis for the presence of subcortical low intensity, meningeal enhancement, signal intensity change of cortex, and change in subcortical low intensity on follow-up images. Diffusion-weighted (DW) images and apparent diffusion coefficient (ADC) maps were obtained in 55 patients. Subcortical low-intensity lesions were also quantitatively analyzed on T2-weighted, fluid-attenuated inversion recovery (FLAIR), and DW images.
Subcortical low intensity was found in nine (23.7%) of 38 patients with encephalitis (viral, 31; unknown origin, 7), five (24%) of 21 with leptomeningeal metastasis, and five (9%) of 58 with meningitis. Leptomeningeal enhancement was observed in 100% and cortical hyperintensity in 14 (74%) of 19 patients with subcortical low intensity. Leptomeningeal enhancement was seen in 46 (47%) and cortical hyperintensity in 33 (34%) of 98 patients without subcortical low intensity. Subcortical low intensity disappeared or decreased in extent on follow-up MR images in all seven patients who underwent follow-up. ADC of subcortical low-intensity lesions was lower than that of the contralateral area and decreased by 9.3 +/- 11.4%.
Subcortical low intensity was uncommonly found in meningitis, viral encephalitis, and leptomeningeal metastasis. It is a nonspecific MR sign of various meningeal and cortical diseases. Although the cause of subcortical low intensity remains uncertain, free radical formation may play a role as a causative factor.
T2加权像上的皮质下低强度病变是缺血、多发性硬化和斯特奇-韦伯病的一种罕见表现。本研究旨在确定皮质下低信号强度是否为脑膜炎、病毒性脑炎或软脑膜转移的磁共振成像（MR）特征，并探究皮质下低强度的原因。
我们回顾性分析了117例患有脑膜炎、脑炎（病毒性或病因不明）或软脑膜转移患者的MR图像，观察是否存在皮质下低强度、脑膜强化、皮质信号强度变化以及随访图像上皮质下低强度的变化。55例患者获取了扩散加权（DW）图像和表观扩散系数（ADC）图。还对T2加权像、液体衰减反转恢复（FLAIR）像和DW图像上的皮质下低强度病变进行了定量分析。
38例脑炎患者（病毒性31例，病因不明7例）中有9例（23.7%）出现皮质下低强度，21例软脑膜转移患者中有5例（24%）出现，58例脑膜炎患者中有5例（9%）出现。19例有皮质下低强度的患者中，100%观察到脑膜强化，14例（74%）出现皮质高信号。98例无皮质下低强度的患者中，46例（47%）观察到脑膜强化，33例（34%）出现皮质高信号。7例接受随访的患者在随访MR图像上，皮质下低强度消失或范围减小。皮质下低强度病变的ADC低于对侧区域，降低了9.3±11.4%。
皮质下低强度在脑膜炎、病毒性脑炎和软脑膜转移中不常见。它是各种脑膜和皮质疾病的非特异性MR征象。虽然皮质下低强度的原因仍不确定，但自由基形成可能是一个致病因素。
