The Radiological Assessment of the Normal Aqueduct and 4th Ventricle

A study is presented of the normal radiological anatomy of the aqueduct and 4th ventricle based on an analysis of 100 cases. After briefly describing the radiological techniques of investigation, the previous literature on methods of assessing the posterior fossa is reviewed. Measurements are recorded, using the Lysholm skull table, for: (1) The distance between the dorsum sellæ and aqueduct (2·9 to 4·1 cm.). (2) The distance between the dorsum sellæ and the floor of the 4th ventricle (3·1 to 4·3 cm.). (3) The height of the 4th ventricle (1·3 to 2·1 cm.). (4) The distance from the fastigium to the mouth of the aqueduct (3·4 to 5·1 cm.). (5) The ventricular angle (85° to 95°). Personal observations on the radiological anatomy of the 3rd ventricle, aqueduct and 4th ventricle are described. The diagnostic importance of absolute measurements as compared with relative measurements (such as are provided by Twining's line and the Swedish line) is discussed. It is emphasised that in doubtful cases a thorough analysis of all available measurements and dimensions may be required to detect abnormalities.