[Gas shadow on CT scan following treatment in metastatic brain tumor--an autopsy case]

This is an autopsy case report of a 52-year-old woman with a brain abscess presenting as an intracerebral gas shadow on CT scan. She was admitted to our facility in June 1977, with disorientation and motor weakness of the right upper extremities. CT scan revealed two separate mass lesions in the frontal and occipital lobes on the left side. She was diagnosed as having metastatic carcinoma, and was treated by tumor removal, radiation therapy, and intraneoplastic local chemotherapy. Seventeen months later, she was readmitted with decreased mental activity, hemiconvulsion of the right side and high fever. CT scan revealed a peculiar round gas shadow on the left side of the temporal lobe. Ventricular drainage produced a cloudy cerebrospinal fluid with a protein concentration of more than 400 mg/dl and a leucocyte count of 138,200. An anaerobic culture of the ventricular cerebrospinal fluid revealed Escherichia coli. At that time, the lateral ventricle was irrigated several times with antibiotics. Unfortunately, however, she died one year after readmission. An autopsy was performed shortly after death, at which time serial coronal sectioning of the brain confirmed the CT scan findings presenting as an intracerebral gas shadow, and further demonstrated extension of the brain abscess from the left temporal lobe to the temporal horn of the lateral ventricle. The lesion in the left temporal lobe included yellowish pus with partially brownish capsules. A gas-containing brain abscess confirmed by CT scan and autopsy is rarely seen. The Hounsfield unit obtained from the abscess cavity by utilizing serial CT scan sometimes represents a condition requiring urgent treatment for brain abscess.