Metrizamide computed tomog r aphic cist ernography was used to e xamin e 27 pat ient s (19 males and eight f emales , 14-59 years old) clinicall y suspected o f having ce rebrospinal f luid fist ulae with rhinorrhea. Twenty-one fi stulae were t rau matic and si x w ere spontaneous. Five t o 6 ml of metrizam ide (or lopamidol , t wo cases) were inject ed by lumbar puncture at a concentra t ion of 185-200 mg I/ ml f or direct corona l and ax ial computed tomographic sections o f the skull base. Cerebrospin al fluid rhinorrh ea w as p resent at the time of e xamination in 12 of 27 cases. Results were evalu ated according to three criteria: (1) metrizamide passage th rough t he bony and dural def ect; (2) demonstrable site of t he fracture and / or bony defect; and (3) metrizamide vi sualized within a paranasal sinus, nasal cavity, or cotton p ledget. T he e xam inat ion was considered positive when criterion 1 alone was present and when 2 and 3 we re associated. In 15 o f 27 cases, cisternography was posit ive, wit h t he e xact site of cerebrospinal f luid leakage demonstrated in 10 patients. In si x cases, t he result s were not defi nitive; only one of the criteria (2 or 3) was fulfilled. In si x cases, cisternog raphy w as normal. Seventeen patients underwent surgery. The site of cerebrospinal f ist ulae w as et hmoidal in nine cases, frontoet hmoidal in seven , sphenoidal in t wo, and sphenoethmoidal in one. The relative value of metrizamide computed tomographic cist ernography compared with ot her diagnostic st udies, poly tomography, positive or negative contrast studies, and radionuclides , is discussed. Diagnost ic pitfalls include art ifacts and partia l volume effect.

C.T. scans of 19 patients with histologically proved primary lymphoma of the brain were reviewed and divided into three groups: solitary tumors (58%), multifocal tumors (31,5%), diffuse involvement of the brain (10,5%). The C.T. differential diagnosis are manifold, including meningioma, glioma, metastases, progressive multifocal leukoencephalopathy. Arteriography is not specific, but, correlation with C.T. results may suggest the correct diagnosis and encourage biopsy. The radiosensitivity of primary lymphoma of the brain emphasizes, the importance of an early diagnosis.

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