[Brain abscess and ventriculitis associated with entrapment of the lateral ventricle appearing more like remarkable brain edema than ventricular dilatation--a case report].

We present a case with brain abscess associated with entrapment of the lateral ventricle appearing more like remarkable brain edema in the temporo-occipital lobe than ventricular dilatation. A 72-year-old man suffering from headache and vomiting visited our clinic. CT and MRI showed brain abscess in the right parieto-occipital lobe, associated with ventriculitis. Lumbar puncture also revealed purulent meningitis. Both symptoms and CSF findings improved after administration of antibiotics. The improved condition continued for two months after admission, but disturbed consciousness and left hemiparesis than appeared. MRI and CT showed entrapment of the lateral ventricle and brain edema of the right temporo-occipital region without ventricular dilatation. Because brain edema was thought to be caused by transudate of the CSF through the ventricular wall, lobectomy of the right temporal lobe and opening of the temporal horn were carried out. Although left hemiparesis and disturbed consciousness and brain edema disappeared after the operation, subdural effusion appeared. Using a subdural-peritoneal shunt, the subdural effusion was prevented and disappeared. In this case, we thought Hounsfield Unit (HU) of the brain edema caused by transudate of CSF through the ventricular wall (12.6) was markedly lower than that of so-called vasogenic edema (25.1) due to active inflammation. Measurement of the HU seemed to be a useful means to differentiate the types of brain edema in this situation from that of vasogenic edema caused by brain abscess, and thus a means for selection of the appropriate treatment.