"Double elevator palsy" eye supraducts during stage II general anesthesia supporting hypothesis of (supra)nuclear etiology.

Background: Double Elevator Palsy (DEP) was originally given its name because the assumption was, that because the affected eye could not elevate in adduction or in abduction, there must be a paresis of both the Superior Rectus (SR) and the Inferior Oblique (IO). Later, it was thought that DEP was due to a paresis of the ipsilateral SR, since the SR is the main elevator of the eye in both adduction and abduction. Gradually, a group of observations accumulated that indicated that the SR was not paretic at all in DEP, leading to the concept that DEP is due to a unilateral deficit in a nucleus that functions to elevate one eye only, a unilateral center for upgaze. The purpose of this paper is to report a clinical case with findings that further support this last hypothesis.

Case Report: A 15 month old girl presenting with classical signs of DEP of the left eye received a 6 mm recession of the left Inferior Rectus (IR). This was insufficient to eliminate a large chin elevation and a 9 prism diopter left hypotropia in the primary position. At the beginning of the second surgery, at which a vertical transposition of the horizontal muscles of the left eye after the technique of Knapp was planned, it was noticed during anesthesia induction that, as the child passed through stage II of the general anesthesia, both eyes briefly elevated, the DEP affected left eye (post 6 mm IR recession) more than the right. A photograph was taken to record this phenomenon.

Discussion And Conclusion: As of this report, there are now at least 4 distinct circumstances under which distinct elevation of eyes diagnosed with DEP have been observed. These 4 include Bell's phenomenon, Dissociated Vertical Deviation of the affected DEP eye, normal upgaze saccades recorded moving from the downgaze position into the primary position, and now elevation during Stage II of a general anesthetic induction. Further, there is no abnormal head posture (head tilt) in patients with DEP, no Bielschowsky phenomenon. All of these pieces of clinical evidence confirm that DEP is not a palsy at all. Instead, they strongly suggest that it is absence of function of a unilateral center for supraduction.