Differentiation between cerebral abscesses and necrotic or cystic tumours by means of diffusion sequences

Introduction. The diagnosis of a cerebral abscess is a veal challenge since the clinical and radiological findings are often non-specific and undistinguishable from those seen with cystic or necrotic tumours. Recently it has been suggested that diffusion sequences may be useful in the differential diagnosis of a necrotic or cystic mass. Patients and methods. Nine patients with cystic or necrotic intracranial masses were studied. The diagnoses were: three pyogenic abscesses, three metastases and three high grade gliomas. The diffusion images were evaluated visually and by means of maps based on the apparent diffusion coefficient (ADC). Results. All lesions showed fine iso-intense or slightly hyperintense walls in T-1 potentiated sequences, and isointense or slightly hypointense walls in T-2 potentiated sequences. In all cases the wall took up gadolinium intensity with a well-defined smooth edge (ring uptake). In the diffusion sequences the abscesses showed a very strong central signal, as compared with the low signal of other lesions. The ADC were significantly lower in the abscesses than in the tumours. Conclusions. Since cerebral abscesses are potentially curable, early diagnosis should be made. A cerebral abscess should be suspected in all cases of cystic or necrotic masses with hypersignals in diffusion sequences and low ADC.