Comparing Hypertropia (HT) in Upgaze and Downgaze Does Not Distinguish Congenital From Acquired Superior Oblique Palsy (SOP)

Abstract

Purpose : Ivanir & Trobe claimed that HT greater in up than downgaze, or equal to it, is characteristic of decompensated congenital & never present in ischemic, traumatic, or tumorous SOP (J. Neuro-Ophthalmol. 37:2017). This claim was tested in SOP confirmed by MRI demonstration of subnormal superior oblique (SO) size.

Methods : Quasi-coronal, surface coil MRI was performed in target-controlled central gaze to identify patients with unilateral SO hypoplasia indicative of SOP. Nine subjects had unequivocal congenital onset (mean age 38±16 yrs, standard deviation, SD); 7 subjects had unequivocal acquired onset (age 47±14 yrs, symptom duration 5.4±4.8 yrs), including 2 with trochlear Schwannoma and 5 with severe head trauma; and 15 subjects had progressive onset unequivocally not congenital (age 52±19 yrs, symptom duration 13±14 yrs).

Results : Results: Maximum SO cross section averaged 8.6±3.9mm² in congenital & 11.3±3.5mm² in acquired SOP (P=0.08), significantly less than 19mm² identically in both groups contralesionally (P<10^-4). Although mean central gaze HT was greater at 20.6±8.0Δ in 9 cases of congenital than 22 acquired cases at 11.4±6.8Δ (P=0.002), HT was 8.4±16.3Δ less in up than down gaze in congenital SOP, and 3.7±11.2Δ less in acquired SOP. In congenital SOP, 33% of subjects had HT greater in up than downgaze, while in 67% HT was greater in down gaze (by up to 42D). In acquired SOP, HT was greater in up than downgaze, or equal to it in 8 cases (36%, P=0.87, X²); the similar proportions contradict Ivanir & Trobe’s claim. In acquired SOP, HT was greater in up than down gaze in 37%, & greater in down than up gaze in 59% of cases. HT was equal in up & central gazes in 3 acquired and no congenital SOP cases. Trends were similar in unequivocal acquired & progressive acquired (non-congenital) SOP (P>0.4).

Conclusions : HT is not characteristically greater in up than down gaze in congenital SOP proven by SO atrophy on MRI. In fact, average HT is greater in down than up gaze in both acquired & congenital SOP, sometimes strikingly so in the latter. The finding of HT greater in up than downgaze, or equal to it, does not reliably indicate that SOP is congenital.

This is a 2021 ARVO Annual Meeting abstract.

 

T1 contrast MRI of right SO hypoplasia:
Top. 41 yr old man with left head tilt since birth. HT greater down than up, fuses 50D vertically.
Bottom. 27 year old man symptomatic for 14 yrs post trauma. HT greater up than down.