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Combined metrizamide ventriculogram and basal cisternogram via sub-occipital route.

Although a very useful procedure, lumbar air encephalography is an unpleasant investigation disliked by the patient and neuroradiologist alike. Metrizamide cisternography was first described by Grepe (1975) since when it has been used to demonstrate the suprasellar cistern. The main disadvantage, compared with an air study, is that it does not show the anterior third ventricle. A successful effort has therefore been made to overcome this difficulty. The patient is laid prone on a tilting table with the neck flexed and the forehead on a small pad. Under screen control the needle is inserted just under the posterior rim of the foramen magnum at an angle 30–40° from horizontal.