Sherrington innervational surgery in the treatment of chronic sixth nerve paresis.

Introduction and purpose: To describe a new operation to treat unilateral chronic sixth nerve paresis based on Sherrington's innervational law. A recession of the medial rectus (MR) in the good eye, yoke to the paretic lateral rectus (LR), will have the reciprocal innervational effect of relaxing the contracture of the contralateral MR and by doing so will enhance the effect of a weakening procedure performed on this muscle. The goal of this study was to eliminate diplopia in primary position by improving the function of the paretic LR and reducing the contracture of its antagonist MR.

Methods: The records of 14 consecutive patients with unilateral chronic sixth nerve paresis so treated were reviewed. Nine had bilateral medial rectus muscle retroplacement and postop' adjustable sutures. A non-adjustable resection of the paretic lateral rectus muscle was added to the other five. Average time from onset to surgery was 60 months (minimum 9 months). Average post-surgical followup was 22 months.

Results: The function of the paretic LR and the contracture of the ipsilateral MR were improved in all 14 cases. Patients with bilateral medial rectus recessions and postop' adjustable sutures had an average correction of 32 prism diopters in primary position. Patients with the added resection of the paretic LR had an average correction in primary position of 46 prism diopters. Two of the 14 patients failed our goals; one had residual diplopia in primary position and the other one had diplopia within 30 degrees on gaze to one side; for an 86% success rate.

Conclusions: The 86% success rate in this study (ultimately we also achieved a 100% satisfaction rate) indicates that innervational surgery in the form of a recession of the MR in the good eye added to that of the MR in the involved eye in patients with unilateral chronic sixth nerve paresis is a safe and effective surgical procedure.