A 64-year-old woman was referred to our hospital because of disturbance of consciousness. She had undergone distal gastrectomy for gastric carcinoma 17 years previously. General physical examination was unremarkable, neurologic examination disclosed hyperactive deep tendon reflexes in the upper limbs. Laboratory abnormalities included elevations of alkaline phosphatase (ALP) and lactate dehydrogenase (LDH), and findings suggesting disseminated intravascular coagulation (DIC). Lumbar cerebrospinal fluid showed a protein concentration of 408 mg/dl and a glucose concentration of 82 mg/dl (blood: 110 mg/dl), as well as a cell count of 16/mm3. Cranial computed tomography indicated brain edema. Magnetic resonance imaging (MRI) of the brain showed diffuse thickening of the dura mater, with contrast enhancement upon gadolinium-DTPA administration. These findings suggested hypertrophic pachymeningitis. Magnetic resonance venography (MRV) showed occlusion of the left transverse sinus and attenuation of the straight sinus. MRI of the spine as well as gallium scintigrams demonstrated multiple areas of increased uptake in areas near the skull and spine. We therefore suspected tumor metastasis. The patient was given heparin as well as pulse therapy with methylprednisolone, but she died 7 weeks after symptom onset. At postmortem examination, the dura was thickened. Histopathologically, numerous tumor cell emboli in the dura were confined to the lumens of veins. The tumor cells were thought to have metastasized to the dura through the vertebral venous plexus (Batson's plexus). Immunostaining demonstrated immunoreactivity of tumor cells to epithelial membrane antigen (EMA) and carcinoembryonic antigen (CEA). The primary origin of the carcinoma was not precisely identified by these findings. Widespread dural vein tumor emboli should be taken into consideration as a cause in cases that develop rapid deterioration of consciousness associated dura mater thickening.