[X-ray computed tomographic aspects of benign primary cerebral melanomas. Apropos of 4 cases]

Benign primitive melanomas are rare tumours usually involving the leptomeninges. Four cranial localizations are reported: 2 tumours of the foramen magnum, 1 of the cerebellopontine angle and 1 supratentorial. The clinical symptomatology is variable according to the level. Slow medullary compression is frequent. One can emphasize the special and difficult problem of foramen magnum tumours that present with a very variable clinical status frequently simulating a non surgical disease of the central nervous system. The benign and primitive appearance of these tumours is evocated by the slow and favourable evolution and by the absence of extraneurologic melanotic tumour. Our purpose is essentially to emphasize the radiological and particularly the computed tomographic (CT) findings poorly described in the literature. Benign melanomas have resemblance with meningiomas: osseous or meningeal relationship, homogeneity and high density. On the other hand the angiography shows poor vascularization. One can think that a tumor simulating a meningioma by CT but not by angiography is perhaps a benign melanoma. The special problem of the radiological diagnosis of foramen magnum tumours is evocated: Computed myelography, tridimensional imaging by NMR.