Annette C. Douglas-Akinwande MD, Presenter: Nothing to Disclose

Amr Mourad MD, Abstract Co-Author: Nothing to Disclose

Eyas M Hattab MD, Abstract Co-Author: Nothing to Disclose

Primary central nervous system germinomas are rare, neoplasms of childhood, in which imaging plays an important role in their diagnosis. A recent report described hyperintense diffusion characteristics in two germinomas which were more conspicuously demonstrated on diffusion weighted images (DWI) than on any other imaging sequence. In this study, we examine the DWI characteristics of central nervous system germinomas.

A retrospective analysis of the diffusion characteristics of biopsy proven germinomas was performed. DWI echo planar images were performed on 1.5 Tesla magnets using b value of at least 1000s/mm2. The apparent diffusion coefficient (ADC) maps and ADC values were calculated. The DWI and ADC, characteristics of the lesions were compared to gray and white matter.

The search resulted in 15 cases in which DWI was performed. Four cases were excluded from the study because apparent diffusion coefficient (ADC) maps and values could not be retrospectively generated. ADC maps and values were available in 11 cases. The lesions were located in the pineal region (27%), and the neurohypophyseal region (73%). The DWI and ADC signals were isointense to gray matter in 7 (64%) cases. The DWI signal was hyperintense with corresponding hypointense ADC signal in 3 (27%) cases. The DWI signal was hypointense with corresponding ADC isointense signal in 1 (9%) case.

While the currently accepted hypothesis for restricted diffusion in neoplasms is the presence of densely packed cells with large nuclei and scant cytoplasm, germinomas are histologically characterized by variable proportions of densely packed cells with large round nuclei, granulomas, microscopic foci of necrosis, septal bands of connective tissue rich in capillaries and lymphocytes. This heterogeneity in their composition might explain the differences in DWI signal. We hypothesize that diffusion characteristics of germinoma are inversely related to the proportion of densely packed cells with large nuclei: those areas with a higher proportion of germinoma cells probably result in restricted diffusions, while those with lower proportions will not.

Douglas-Akinwande, A, Mourad, A, Hattab, E, Primary Central Nervous System Germinoma: Diffusion-weighted Imaging Characteristics.  Radiological Society of North America 2004 Scientific Assembly and Annual Meeting, November 28 - December 3, 2004 ,Chicago IL. http://archive.rsna.org/2004/4410916.html