Postoperative results in inferior oblique palsy

Isolated inferior oblique pareses

PURPOSE

To describe etiology, clinical characteristics, radiological features and management of isolated inferior oblique pareses.

METHODS

A diagnosis of inferior oblique paresis was made after a thorough strabismus examination and neuroimaging. The patients were managed surgically with adjustable strabismus surgery, or conservatively. Surgical success was defined as average horizontal deviation within ≤ 10 prism diopters [PD] post-operatively and for vertical deviation, it was ≤ 5 PD, at last follow-up.

RESULTS

Seven cases were congenital, 6 cases were bilateral, with esotropia in 6 cases; 'A' pattern in 7 cases and hypotropia in 3 cases. The mean preoperative horizontal deviation was 52.5 PD, and the mean postoperative horizontal deviation was 2.37 PD (p = 0.028). The pre-operative vertical deviation was 18 PD and post-operative vertical deviation was 5 PD. MRI showed reduced IO muscle size; average area being 11.27 mm² in the affected eyes, with normal sized inferior recti (average: 24.63 mm²) and medial recti muscles (average: 30.08 mm²). Surgical success was seen in all six cases. Average follow-up was 265 days. The Parks' three step test was not valid, except for one acquired unilateral case.

CONCLUSION

Isolated pareses of inferior oblique muscle exhibit defective elevation in adduction of the affected eye, 'A' pattern and fundus intorsion, and is confirmed by neuroimaging. These can be successfully managed surgically to correct the deviation.

Adjustable superior oblique tendon spacer with application of nonabsorbable suture for treatment of isolated inferior oblique paresis

PURPOSE

To evaluate and report the outcomes of a superior oblique tendon spacer procedure using nonabsorbable adjustable sutures in patients with inferior oblique (10) paresis.

METHODS

This interventional case series included 6 eyes of 6 patients with 10 paresis. All met Bielschowsky/Parks Three-step Test criteria to identify an isolated 10 paresis. In all patients, the superior oblique tendon was exposed; 2 nonabsorbable polyester sutures were placed 3 mm apart, and the tendon was cut. With the use of a slipknot, the cut ends of the tendon were separated 5 to 7 mm. Tendon separation was adjusted intraoperatively according to the fundus torsion and exaggerated traction test.

RESULTS

The mean duration of follow-up was 8.1 months (range, 5-12 [corrected] months). Four patients had congenital 10 paresis and 2 had iatrogenic 10 paresis following denervation/myectomy of 10. Mean primary position hypotropia improved from 15.2 prism diopters (PD) before surgery to 2.7 PD in congenital 10 paresis and from 11.5 PD to 2.5 PD in iatrogenic 10 paresis. In congenital 10 paresis, mean preoperative superior oblique overaction and 10 underaction was +2 and -2, which decreased to 0 and -1.25 respectively; fundus incyclotorsion resolved in all patients. Superior oblique overaction and 10 underaction improved in iatrogenic 10 paresis as well. In no patient did an overcorrection develop.

CONCLUSIONS

The adjustable superior oblique tendon suture spacer procedure is an effective and safe option for correcting 10 paresis without developing iatrogenic superior oblique paresis.

High-resolution magnetic resonance imaging demonstrates reduced inferior oblique muscle size in isolated inferior oblique palsy

PURPOSE

The diagnosis of isolated inferior oblique muscle palsy is controversial for 2 reasons: first, clinical findings seem inconsistent with our current understanding of oculomotor neuroanatomy and, second, similar findings can occur with other causes. Because denervated extraocular muscles atrophy, we used high-resolution magnetic resonance imaging (MRI) to assess inferior oblique muscle size in patients with clinically suspected inferior oblique muscle palsy.

METHODS

A diagnosis of inferior oblique muscle palsy in 6 patients (4 unilateral, 2 bilateral) was made clinically. High-resolution coronal and sagittal orbital MRI were obtained in subjects with clinical inferior oblique muscle palsy and in 30 age-matched control subjects. Cross sections of the inferior oblique, inferior rectus (IR), and medial rectus muscles were determined together because each is innervated by the common inferior division of the oculomotor nerve. No subject had pupillary abnormalities or other extraocular muscle weakness or restriction.

RESULTS

Mean cross-sectional area of the affected inferior oblique muscle (n = 8) at the midpoint of the inferior rectus muscle was 10.2 +/- 1.05 mm(2), which was significantly smaller than the value of 18.8 +/- 3.6 mm(2) for control subjects (n = 58, p < 0.00001). Unilaterally affected inferior oblique muscles were significantly smaller than unaffected inferior oblique muscles (p < 0.05). Mean medial rectus muscle cross section (n = 8) ipsilateral to the affected inferior oblique muscle was 36.8 +/- 2.4 mm(2), which was not significantly different from the 35.1 +/- 3.7 mm(2) value for the medial rectus muscles of control subjects (n = 61, p > 0.1). Mean inferior rectus muscle cross section (n = 8) ipsilateral to the affected inferior oblique muscle was 32.5 +/- 2.3 mm(2), which was significantly greater than the 29.9 +/- 3.3 mm(2) measurement for the control subjects (n = 61, p < 0.01).

CONCLUSIONS

We used MRI to demonstrate reduced inferior oblique muscle size in patients with clinically diagnosed inferior oblique muscle palsy, supporting the concept of isolated inferior oblique muscle weakness.

Treatment of inferior oblique paresis with superior oblique silicone tendon expander

INTRODUCTION

Patients with inferior oblique eye muscle paresis may show hypotropia and apparent superior oblique muscle overaction on the side of the presumed weak inferior oblique (IO) muscle. We report 8 such patients successfully treated using unilateral silicone superior oblique (SO) tendon expanders.

METHODS

Eight consecutive cases over the course of 6 years from the authors' private practice are described. None had a history of head trauma or a significant neurologic event. All patients showed IO paresis by 3-step test, with incyclotorsion and SO overacton of the hypotropic (paretic) eye. Forced ductions of the hypotropic eye were normal in all cases, and the vertical strabismus was treated with placement of a 7- mm silicone SO tendon expander in the hypotropic (paretic) eye.

RESULTS

Mean preoperative primary position hypotropia was 6.5 prism diopters (PD); mean postoperative was 0.5 PD. Seven of 8 patients had resolution of primary position hypotropia, whereas the eighth was reduced. Mean preoperative SO overaction was 3+; all patients had postoperative resolution of SO overaction. Of 4 patients with preoperative ocular torticollis, mean preoperative head tilt was 9.3 degrees; mean postoperative tilt was 2.9 degrees. Two patients' head tilts had resolved, the other 2 showed improvement. All patients showed preoperative incylclotorsion of the hypotropic (paretic) eye; inclyclotorsion resolved in all patients after the placement of a SO tendon expander.

CONCLUSION

The silicone SO tendon expander effectively restores ocular alignment in IO paresis with apparent SO overaction. Associated ocular torticollis can also be improved.

Skew deviation and inferior oblique palsy

PURPOSE

To describe ocular motility and neuro-ophthalmologic findings in six patients with an ocular tilt reaction (OTR) that mimicked an inferior oblique palsy (IOP).

DESIGN

Observational Case Series.

METHODS

Series of six patients presenting to tertiary care pediatric or neuro-ophthalmologist.

RESULTS

Five patients had ocular motility and three-step test results suggesting an IOP; one patient had a suspected bilateral IOP. All six patients had excyclotorsion of the hypotropic eye, and four had incyclotorsion of the hypertropic eye. This is contrary to that expected with an IOP (incyclotorsion of the hypotropic eye). In addition, all six patients had other neurologic findings in the history or examination that were associated with neurologic insult rather than an isolated IOP. Two patients had surgery consisting of a superior rectus recession; this was successful in eliminating diplopia in both patients and in eliminating the vertical deviation and head posturing in one patient.

CONCLUSION

While many vertical deviations that appear to be due to an inferior oblique palsy based on the results of the three-step test may be caused by inferior oblique weakness, skew deviation should also be considered in any patient with a history of head trauma, or other neurologic findings. The cyclotorsion observed in IOP is opposite that seen with OTR, and differentiates the two entities clinically. We postulate that these deviations are caused by damage to the otolithic projections that correspond to those from the ipsilateral posterior semicircular canal (on the side of the hypotropic eye).