Diagnose und Therapie der Trochlearisparese

Abstract

The diagnosis of unilateral trochlear nerve palsy is based on acute onset vertical deviation which increases in contralateral side gaze, down gaze and ipsilateral head-tilt together with excyclodeviation which also increases in both down gaze and ipsilateral head-tilt. Both vertical deviation and excyclodeviation decrease in contralateral head-tilt. To detect excyclotropia one must ask the patient whether there is a tilted double image in down gaze. Bilateral trochlear nerve palsy causes a change of vertical deviation between right and left gaze and between head-tilt to the right and to the left shoulder. In severely asymmetric bilateral palsy, this change of vertical deviation may be absent. Bilateral symmetric trochlear nerve palsy regularly causes only slight vertical deviation in side gaze and slight head-tilt phenomenon. Major symptoms of symmetric palsy are significant excyclodeviation increasing in down gaze and V-incomitance. Objective assessment of vertical and eventually horizontal deviation is performed by the alternate prism and cover test. Cyclodeviation can be measured by Maddox rods. Differentiated assessment of subjectively localised horizontal, vertical and cyclotorsional deviations in definite gaze directions is preferably being performed at the Harms tangent scale. Treatment of trochlear nerve palsy is nearly exclusively surgical. Prisms are rarely helpful due to incomitance of vertical deviation and since they are not suitable to correct for cyclodeviation. Surgery should be scheduled not earlier than 12 months after onset of the palsy. The preferred surgical strategies include weakening procedures on the inferior oblique, tucking or advancement of the superior oblique tendon, combination of both and, if fitting with the motility pattern rarely as a primary procedure, but usually as a possible second procedure contralateral inferior rectus recession. Surgery will not alter the neurogenic palsy but it modulates the squint angle pattern resulting from the movements of both eyes. Normal binocular vision in all directions of gaze for slight palsy and in large part of the daily used gaze area for severe palsy can be achieved by one or sometimes two operations.