Meningeal carcinoma has a variety of clinical manifestations and a high mortality and disability rate. Among them, cranial hypertension is one of the important causes of death, which is easy to be missed or misdiagnosed. The purpose of this case report is to describe the clinical features of diffuse leptomeningeal glioneuronal tumor (DNGNT) with the first symptom of headache accompanied by decreased vision misdiagnosed as venous sinus thrombosis. The patient initially suffered from headache and decreased vision, and rapidly developed blindness. According to the clinical manifestations and cerebrospinal fluid (CSF) examination results, the patient was initially misdiagnosed as venous sinus thrombosis, the intracranial pressure was relieved by Ommaya capsule, and the cerebrovascular condition was observed by magnetic resonance venogram (MRV) and digital subtraction angiography (DSA). The degree of meningeal enhancement was observed by enhanced magnetic resonance imaging (MRI), and meningeal cancer cells were found by CSF cytology. The patient was excluded from viral meningitis, tuberculous meningitis, cryptococcal meningitis, optic neuromyelitis, and central nervous system Behcet’s disease by routine examination. Ommaya capsule implantation relieved the intracranial hypertension, and vision was restored after treatment. No venous sinus thrombosis was found in MRV and DSA; brain-enhanced MRI revealed extensive linear enhancement of the meninges, and CSF cytology revealed grotesque, actively dividing tumor cells; she was diagnosed as DLGNT. Meningeal carcinoma cannot be excluded in adolescents without tumor history. When patient has unexplained intracranial hypertension, it is necessary to consider DLGNT; early brain-enhanced MRI and CSF cytology are helpful for early diagnosis. For cranial hypertension, timely placement of Ommaya capsule can improve patient quality of life and save vision in time; molecular targeted therapy as early as possible can prolong survival. J Neurol Res. 2019;9(3):41-47 doi: https://doi.org/10.14740/jnr539