Intracranial arachnoid cysts are collections of cerebrospinal fluid within the arachnoid membrane and subarachnoid space of the cisterns and major cerebral fissures that account for about 1% of all intracranial lesions. Expansion of the cyst and compression on surrounding structures may became symptomatic, which reflects its size and anatomic distribution. Here, we present a very rare case of patient with supratentorial intraparenchymal arachnoid cyst placed in the left frontal lobe without any communication with the subarachnoid space and ventricle and presented with clinical symptoms. The patient underwent fenestration of the lesion and was clinically improved. Although the etiology and the enlargement mechanism of arachnoid cysts remain unclear, both conservative and surgical treatments are optional. According to size, anatomical location, neuroimaging, and clinical symptoms, an arachnoid cyst should be included in the differential diagnosis of primary intracerebral cysts.

中文翻译：

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实质性蛛网膜上腔蛛网膜囊肿1例

颅内蛛网膜囊肿是蛛网膜，水箱和主要脑裂的蛛网膜下腔和蛛网膜下腔内的脑脊液集合，约占所有颅内病变的1％。囊肿的扩张和周围结构的压迫可能成为有症状的，这反映了其大小和解剖分布。在这里，我们介绍了一个非常罕见的病例，即上睑实质性蛛网膜囊肿被放置在左额叶中，而与蛛网膜下腔和心室没有任何联系，并表现出临床症状。患者进行了开窗术，临床上得到了改善。尽管蛛网膜囊肿的病因和扩大机制仍不清楚，但保守治疗和手术治疗都是可选的。根据大小，解剖位置