Abstract

DO.18.01

Surgery for acquired trochlear nerve palsy

Gräf M., Weihs J.
Department of Ophthalmology, University of Gießen

Objective: Different surgical procedures are recommended for the treatment of trochlear nerve palsy. Recession of the inferior oblique muscle (IOR), tucking or advancement of the superior oblique tendon, the combination of both procedures (KOP), and the recession of the contralateral inferior rectus muscle are recommended. In this study, the effects of IOR and KOP were compared.
Methods: The patients (18-78 years old; median 51) with acquired unilateral trochlear nerve palsy were examined at the Harms tangent scale before and 3 months after surgery. At a distance of 2.5 m, the squint angles without diagnostic occlusion were measured with a dark red glass in front of the non-paretic eye. The head-tilt phenomenon (HTP) was defined as the difference between the vertical deviations at 45° right and left head-tilt. Squint angles were transformed corresponding to trochlear nerve palsy on the right eye. Vertical and cyclodeviations at primary position (PP), side gaze (25° abduction of the non-paretic eye) and 25° down gaze were evaluated (medians and range).
Results: Vertical and cyclodeviations before IOR (n=13): PP +6° (1;11) ex 5° (2;9), sidegaze +8° (4;14) ex 7° (2;11), downgaze +9° (4;17) ex 7° (4;13), before KOP (n=21) PP +5° (2;14) ex 5° (2;10), sidegaze +9° (3;21) ex 6° (0;10), downgaze +11° (2;21) ex 8° (4;14). Reduction of vertical deviation: PP: IOR 3° (1;9), KOP 6° (0;14), p=0.09, sidegaze IOR 5° (1;11), KOP 9° (3;17), p=0.005, downgaze IOR 3° (-7;11), KOP 8° (2;16), p=0.04. Reduction of excyclodeviation at downgaze IOR 4° (-4/11), KOP 7° (0;14), p=0.05. Reduction of HTP: IOR 1.5° (-5;7), KOP 6° (-8;14), p=0.03.
Conclusions: The HTP and the cyclovertical deviation were more effectively reduced when recession of the inferior oblique muscle was combined with tucking of the superior oblique tendon. The decrease of both the HTP and the vertical deviation, especially at downgaze, seems to be caused by modulation of the cyclovertical innervation on the basis of a change of the fusional vergence tonus. Therefore the dosage should be adequate to achieve incyclotropia during the initial postoperative period.

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