1. Surgery for Supranuclear Monocular Elevation Deficiency
Michael C Struck, M.D.
University of Wisconsin-- Madison
Post-op
Introduction:
What is supranuclear MED?
the inability to elevate one eye equally in abduction, adduction, and primary gaze.
supranuclear MED: originally termed double elevator palsy (DEP)
Intact 3rd Nerve nucleus
Intact orbital anatomy
Deficit in central drive for elevation
Pre-op
Treatment:
For all patients the surgery consisted of treatment of contralateral (sound eye) superior rectus recession, maximum surgery was attempted, not based on preoperative measurements, without interfering with the position of the superior oblique tendon, transection of the superior oblique to superior rectus frenulum and directly suturing the muscle to the sclera 9 to 10.5mm from the original insertion.
Table 1: Characteristics of case study subjects
hypotropia, ptosis or pseudoptosis
when the affected eye fixates, a large secondary vertical deviation of the sound eye. Distinguishing between the different etiologies of MED can be achieved by examining for the presence of Bell’s phenomenon bilaterally.
Secondary
deviation
Comparison to Knapp
Knapp
SR Recession
Force generated
Static/Passive
Active
Average correction
25pd
21 pd
Ptosis
No change or worse
Improved
Overcorrection
Definite concern
Low risk
Technical level
Complex
Less complex
Chin up
posture
Bell’s reflex
Results
Compensatory chin-up head position and alignment in primary position was improved in all patients. Likewise the pseudo-ptosis improved in all patients, but was not eliminated. Table 1 shows the results on an individual basis. Average age at surgery was 5.3 years, range 7 months to 9 years. Average superior rectus recession was 9.7 mm. Mean follow-up was 4.8 years (range 12 months to 11.5 years). Average surgical effect was 21 prism diopters of vertical shift for superior rectus surgery alone. The vertical deviation of the paretic eye in primary position post-operatively was orthotropic for 2 and a small residual hypotropia for 2. One patient (#4), with the smallest preoperative deviation, initially had a small under-correction but over time developed a stable overcorrection. One patient (#1) initially was well corrected, but one year after initial surgery, required a second surgery for recurrence. One patient had had a prior vertical rectus surgery for MED at 16 months of age, with no restriction of the ipsilateral IR muscle noted at the time of either surgery, and at 8 years underwent the procedure described.
Discussion
Methods:
Essentially the innervational principle involves functionally weakening the agonist muscle in the sound eye with surgery, in order to increase the innervation to its paretic yoke muscle via Hering’s Law. The nerve and muscle of the affected eye in supranuclear MED is functional as noted by the intact Bell’s reflex. Applying this principle to SNP MED, the sound eye superior rectus is recessed, therefore stimulating an ipsilateral increased innervation required to maintain primary position, which then results in a contralateral increased innervation transmitted to the yoked SNP superior. This results in increased tonic stimulation of the SNP muscle and elevation of the affected eye. The increased innervation to the SNP superior rectus may also provide additional benefit of stimulation of the levator palpebre and facilitate relaxation of the antagonist inferior rectus via Sherrington’s law, which may further improve outcome and the elevation of the paretic eye.
The surgical results of 5 subjects were reviewed retrospectively for all patients who underwent superior rectus recession for supranuclear MED by the senior author (MCS) between 2003 and The diagnosis of monocular elevation deficiency was made based on the history of paretic eye hypotropia and sound eye hypertropia when the paretic eye fixates, as well as a intact Bell’s phenomenon and negative passive forced duction testing. Patients were excluded if they had restrictions on forced duction testing, and/or absent Bell’s phenomenon.