Overelevation In Adduction Research Articles

Inferior oblique muscle fixation to the orbital wall: A profound weakening procedure

Recurrent or persistent inferior oblique overaction may occur after inferior oblique (IO) recession or anterior transposition. IO nasal and temporal myectomy and anterior-nasal transposition may result in undesirable IO palsy, exotropia, incyclotorsion, or limitation of elevation. Previous studies have shown that a rectus extraocular muscle may be profoundly weakened if the muscle insertion is reattached to adjacent orbital periosteum. We describe a reversible profound weakening surgical procedure of the IO muscle. A total of 10 consecutive subjects with V-pattern strabismus and/or IO overaction underwent IO orbital fixation procedure by attaching its insertion to the periosteum of the lateral orbital wall. One subject was not included because short follow-up. Five subjects with persistent IO overaction after IO anterior transposition underwent bilateral IO orbital wall fixation. Four subjects with no previous IO surgery underwent unilateral IO orbital wall fixation; 3 of these 4 subjects had superior oblique palsy with a large vertical deviation in primary position and 1 had a V pattern with asymmetric IO overaction. V pattern significantly improved from 22(Delta) preoperatively to 7(Delta) postoperatively (p = 0.002). IO overaction improved from 2.5 (range, + 1.5 to + 4) to 0.1 (range, -2 to +3) postoperatively (p < 0.001). Six of 9 subjects had no residual overelevation in adduction postoperatively. Unilateral IO orbital fixation corrected 7(Delta) of vertical deviation in the primary position and 23(Delta) in adduction. Mean postoperative follow-up was 5 months. IO orbital fixation has a profound weakening effect on the IO muscle. Advantages of this procedure include reversibility and that it can be converted into another form of weakening procedure, if required.

Ocular Overelevation in Adduction in Craniosynostosis: Is It the Result of Excyclorotation of the Extraocular Muscles?

We sought to determine whether radiological evidence supports excyclorotation of the extraocular muscle cone as a cause of overelevation in adduction in children with craniosynostosis. This was a retrospective case series of 40 patients with craniosynostosis. Ophthalmic findings were assessed for incomitant vertical strabismus in particular excessive elevation in adduction. Computed tomography and magnetic resonance imaging scans were reviewed. Those scans with adequate coronal imaging of their orbits to assess the position and angulation of the horizontal extraocular muscles were identified, and the degree of rotation of the muscles formally measured along with aged matched controls. These groups were analyzed for the association between presence of overelevation in adduction and degree of excyclorotation of the extraocular muscle cone. The identified updrift on adduction that mimics inferior oblique muscle overaction was present in 63% (25/40) of patients. Imaging that permitted accurate measurement of the muscles positions was available in 10 of the 40 patients. Of these 10, 8 had the updrift, and 7 of these 8 (88%) demonstrated more excyclorotation than their aged matched controls. Comparison of scan measurements of patients revealed a significant difference in degree of excyclorotation (mean difference = 16.2, 95% confidence interval 6.2-31.5; P = 0.006) between patients with and without excess elevation in adduction. Overelevation in adduction is significantly associated with excyclorotation of the extraocular muscle cone in children with craniosynostosis. We demonstrate a simple method to assess for the excyclorotation. Our findings support the importance of imaging of the orbits in these children before strabismus surgery.

Abstracts

Abstracts

Magnetic resonance imaging of the functional anatomy of the inferior oblique muscle in superior oblique palsy

Purpose To study size and contractility of the normal inferior oblique (IO) muscle using high-resolution magnetic resonance imaging (MRI) and to evaluate abnormalities of the superior oblique (SO) and IO muscles in chronic SO palsy. Design Prospective, case control study. Participants Thirteen patients with SO palsy and 17 orthotropic subjects. Methods High-resolution, surface coil MRI was used to obtain sets of contiguous, 2-mm thick coronal and sagittal images repeated in multiple gaze directions. Digital image analysis was used to measure IO and SO muscle cross-sectional areas for evaluation of size and contractility. Diagnosis of SO palsy in one bilateral and 12 unilateral cases was based on subnormal contractility and SO size less than the normal 95% confidence limit. Ipsilesional and contralesional oblique muscles were compared with controls and correlated with clinical characteristics. Results In all subjects, anterior movement and contractile thickening of the IO were observed in supraduction, with posterior movement and relaxational thinning in infraduction. The mean (± standard deviation) cross-sectional area of 15 normal control IO muscles was 13.4 ± 3.9 mm 2, with mean contractile increase from infraduction to supraduction of 5.7 ± 2.6 mm 2. Subjects with SO palsy had incomitant hypertropia with a wide range of overelevation and underelevation in adduction (i.e., upshoot, downshoot). SO atrophy correlated with underdepression in adduction ( P < 0.0001). Contralesional SO cross-section was slightly greater than normal ( P = 0.004). The IO cross-section ipsilesional and contralesional to SO palsy did not, however, differ significantly from normal and did not correlate with elevation in adduction ( P > 0.2). Conclusions Quantitative morphometry by MRI can demonstrate IO size and contractility. Even in cases of unequivocal SO palsy associated with ipsilesional SO atrophy and deficient contractility, the degree of elevation in adduction was not correlated with IO size. This finding suggests that the associated overelevation in adduction, commonly termed “inferior oblique overaction,” actually arises from some other mechanism than IO hypertrophy or excess contractility. Revision of clinical terminology seems warranted.