Contributory aspects of MRI in the evaluation of basal encephaloceles.

Basal encephaloceles are rare pathologies which belong to the now well-defined complex called median cleft face syndrome. This entity includes median craniofacial dysraphism associated to a varying degree with optic tract pathology, dysfunctioning of the hypothalamus-hypophysis axis, agenesis of the corpus callosum and basal encephalocele. The latter is that virtually constant element for which surgery is frequently requested. Owing to the large number of surgical failures (especially in the transsphenoidal type) medical imaging for the evaluation of malformative damages must be very accurate. Until recently, the techniques available, such as standard radiography, conventional tomography, gas encephalography, carotid arteriography and computerized tomography with or without metrizamide cisternography, were either too invasive or too inaccurate. MRI is the technique which provides the best images of prolapsed meninges, brain regions or ventricles, as well as of the anatomical rapport between the hypophysis, the optic tract and the limbic system.