[Problems in the topographic diagnosis of bilateral abducens pareses]

It is not possible to exactly differentiate bilateral abducent paralysis case topographically into those arising peripherally and those from the brain stem by means of clinical data. The application of electrophysiological methods, especially the acoustically evoked brain stem potentials and the oculo-auricular phenomena, greatly increases the accuracy of topographical diagnosis. If the oculo-auricular reaction can be triggered in the normal way, a lesion of the brain stem may be practically excluded, whereas changed acoustically evoked potentials at an early point may indicate a disturbance of function in the core region of the 6th cranial nerve.