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Show lounta/ of c/ j1l/ cal Neur( 1-( 1I'hthallllologtt 12( 21: 91- 97, 1992. Thyroid Ophthalmopathy Presenting as Superior Oblique Paresis Mark L. Moster, M. D., Thomas M. Bosley, M. D., Michael L. Slavin, M. D., and Steven E. Rubin, M. D. © 1992 Raven Press, Ltd., New York Six patients with thyroid ophthalmopathy presented with what appeared to be a unilateral superior oblique paresis by the three- step test, which was eventually followed by more typical findings of thyroid disease. This early motility defect in thyroid ophthalmopathy may be caused by a restrictive process due to involvement of the inferior rectus muscle, Clues to the proper diagnosis included an increase in vertical deviation in upgaze, elevation of intraocular tension in upgaze, and the lack of excyclodeviation. These features should be assessed in patients with isolated superior oblique paresis. Key Words: Diplopia- Fourth nerve- Graves' diseaseSuperior oblique- Thyroid. From the Department of Neurology and Ophthalmology ( M. L. M.), Temple Umversity School of Medicine; the NeuroOphthalmology Unit ( T. M. B.). Wills Eye Hospital; and the Divisions of Neuro- Ophthalmology ( M. L. S.) and Pediatric Ophthalmology ( S. E. R.), Long Island Jewish Medical Center, New York, U. S. A. This work was supported in part by a National Institutes of Health Clinical Investigator Development Award # lK08NS01357- 01A1 ( M. L. M.). Address correspondence and reprint requests to Dr. Mark L. Moster, Departmentof Neurology, Temple UniverSity HospitaL Broad and Ontano Streets, Philadelphia, PA 19140, U. S. A. 94 Diplopia from ocular motility defects is a common finding in patients with thyroid ophthalmopathy ( 1). The diagnosis is most often suspected because of associated orbital and lid findings, such as proptosis, chemosis, injection, and lid retraction. Nonetheless, thyroid ophthalmopathy may mimic a variety of ocular motility defects and should be considered in the differential diagnosis of all patients with ophthalmoplegia. Superior oblique paresis is a commonly diagnosed cause of vertical diplopia, presenting with a hyperdeviation that is greatest on gaze contralateral and head tilt ipsilateral to the side of the paretic muscle. Although the differential diagnosis includes skew deviation, myasthenia, and thyroid ophthalmopathy, thyroid ophthalmopathy in patients with isolated superior oblique paresis may be overlooked. To underscore this association, six patients are presented in whom the earliest manifestation of thyroid eye disease simulated a superior oblique paresis. CASE STUDIES Case 1 A 73- year- old healthy man awakened with binocular vertical diplopia. When examined 3 weeks later, he was normotensive and, except for ocular motility, had a normal neurologic and ophthalmologic examination. Ductions and versions were full, but there was a left hyperdeviation measuring 4 prism diopters ( PO) in left gaze, 6 PO in primary position, 8 PO in right gaze, and 10 PO with left head tilt. In addition, he was orthophoric with right head tilt. A 7.5 degree excyclotropia was noted. Sedimentation rate and serum glucose were normal. A diagnosis of presumed vasculopathic left fourth nerve paresis was made, and the patient was followed clinically. THYROID DISEASE WITH FOURTH NERVE PARESIS 95 His symptoms and examination were unchanged 1 and 3 months later. At 6 months followup, examination revealed bilateral chemosis and injection of the conjunctiva, bilateral proptosis ( 23 mm au with Hertel, base 105 mm), right lid retraction, and a bilateral restrictive ocular motility defect with positive forced duction test. His motility in the right eye was limited to 80% normal abduction and adduction and 50% normal elevation. The left eye was limited to 85% normal adduction and abduction and 50% normal depression. Intraocular pressure was 15 mm Hg 00 and 13 mm Hg as with an increase to 20 mm Hg and 26 mm Hg, respectively on upgaze. Visual acuity was 20/ 25 00 and 20/ 30 as and there was a mild dyschromatopsia, tract afferent pupillary defect, and mild visual field constriction as. A diagnosis of thyroid ophthalmopathy was made, and a computed tomography ( CT) scan showed marked enlargement of all extraocular muscles au. Thyroid function tests revealed a high TSH ( 15.3) with normal 13, T4, and RT3U values. Prednisone, 100 mg daily, was prescribed for optic neuropathy. Visual function subsequently deteriorated, but improved following bilateral orbital decompression and irradiation. Case 2 A 37- year- old woman presented with 2 months of vertical binocular diplopia, which was initially associated with mild left periorbital pain. Her diplopia was intermittent and then became constant. Past medical history was negative, and there were no other neurologic or ophthalmologic symptoms. On neuro- ophthalmic examination, visual acuity was 20/ 25 with normal color vision, pupils, and fundi. Visual fields were full. There was no proptosis, and Hertel exophthalmometry measured 18 mm au with base of 100. Intraocular pressure was 18 mm Hg au. The anterior segments were normal. Ocular motility examination revealed full ductions and versions. On alternate cover test there was a right hyperdeviation that measured 3 PO in primary position, right gaze, and left head tilt; 6 PO in left gaze; and 5 PO with right head tilt. Lid examination was normal. Tensilon test was negative, and the neurologic exam was otherwise normal. A CT scan of the brain and serologic evaluation for systemic causes of superior oblique paresis were negative. The diagnosis was an isolated right superior oblique paresis. On re- examination 3 weeks later, ocular motility was unchanged. However, she had marked lid re-traction and lid lag. Thyroid function tests ( 13RIA, T4- RIA, TSH) were normal. Two weeks later, bilateral conjunctival injection over the insertions of the medial and lateral recti was noted. Two years later her examination was unchanged. Case 3 A 41- year- old woman was evaluated for vertical binocular diplopia, which was particularly severe while reading or watching television. She was noted to be orthophoric 2 years earlier when she was evaluated for physiologic anisocoria. Hertel exophthalmometry at that time measured 16 mm 00 and 15 mm as with a base of 100. On examination, she had a spontaneous left head tilt with full ductions and versions. There was a 2 PO right hyperdeviation in primary that increased to 20 PO on left gaze and disappeared on right gaze. There was no deviation with left head tilt and 4 PO of right hyperdeviation with right head tilt. Eyelid examination revealed palpebral fissures of 9 mm au with mild, intermittent lid retraction. The CT scan was negative. The diagnosis was a probable right superior oblique paresis. By the time of the follow- up visit 3 months later, she had developed bilateral proptosis measuring 23 mm 00 and 19 mm as. Orbital retropulsion was diminished, and ductional deficits in upgaze, downgaze, and adduction 00 were noted. Alternate cover test revealed 6 PO of right hyperdeviation in primary gaze, increasing to greater than 25 PO in left gaze and to 12 PO on right head tilt. There was periorbital edema, lid retraction on the right ( with a palpebral fissure 3 mm larger than the left), and bilateral lid lag. Her thyroxin level was elevated, and she underwent treatment for hyperthyroidism. The orbitopathy has remained stable for 1 year. Case 4 A 62- year- old hypertensive woman experienced vertical diplopia for 1 month in December 1985, which spontaneously resolved. One year later, symptoms recurred and persisted, with mild improvement over the ensuing 4 months. Hypothyroidism had been diagnosed 15 years earlier, and the patient was on thyroid hormone replacement. Neuro- ophthalmic examination in March 1987 was completely normal except for ocular motility. A left hypertropia was seen, measuring 4 PO in primary gaze, 8 PO in right gaze, 6 PO in right upgaze, 2 PO in right and downgaze, 4 PO with JClin Neuro- ophtiullmol, Vol. 12. No. 2, 1992 96 M. L. MOSTER ET AL. right head tilt and 10 PO with left head tilt. Double Maddox rod test revealed excyclotropia. Ocular ductions and versions were normal, and there was no ptosis, eyelid retraction, proptosis, retropulsion defects, or conjunctival injection. A CT scan of the brain and orbits was normal. SpeCifically, the extraocular muscles were not enlarged. A diagnosis of left superior oblique palsy was made, and it was decided to observe the patient. Follow- up examination in May 1987 showed subjective resolution of symptoms. Orthophona was noted in primary, left, and right gaze. In August 1987, there was recurrence of diplopia, and a right hyperdeviation of 2 PO was present In pnmary gaze, 3 PO on left gaze, and 8 PO in left upgaze. No relative ocular torsion was seen. The left eye was limited on upgaze in abduction. Intermittent bilateral lid retraction with slight edema was noted. Forced duction was equivocal, and the intravenous edrophonium test was negative. An orbital CT scan showed enlargement of each inferior rectus muscle, with the left greater than the right. Medial and superior recti were also bilaterally enlarged. A diagnosis of Graves' ophthalmopathy was made. The right hyperdeviation worsened to 12 PO in primary gaze in February 1988. A Fresnel prism resulted in relief of diplopia, and subsequent ocular examinations were unchanged. Case 5 A 66- year- old woman developed vertical diplopia in September 1986. On examination there was a right hypertropia measuring 10 PO in primary gaze, 4 PO in right gaze, 12 PO in left gaze, 16 PO in gaze up and left, 6 PO in gaze down and left, 12 PO on right head tilt, and 6 PO on left head tilt. No relative ocular torsion was noted on the double Maddox rod test. There was no proptosis. A tentative diagnosis of a right superior oblique muscle palsy was made. A follow- up examination 2 months later was unchanged. Three months later she was found to be orthophoric in primary gaze, and a left hypertropia was found in left gaze. Slight limitation of elevation of the right eye was noted. An orbital CT scan showed enlargement of multiple extraocular muscles compatible with Graves' ophthalmopathy. In addition, a mildly elevated T3- RIA was noted. Over the next several months the left hypertropia increased and eventually stabilized at 20 PO in primary gaze, and a 7.0 mm recession of the right inferior rectus muscle was performed. JClin Neura- aphtha/ mol, \'(, 1 ! 2. No. 2. 1992 Case 6 A 64- year- old woman presented wi~ h a ~- week history of painless vertical binocular dlplopla. Her past medical history was significant for a mastectomy and chemotherapy for breast cancer 12 years previously and a myocardial in~ arct~ on 10 years earlier. Her medications were DlgoXIn and Card-izem. On examination, ductions and versions were full. Alternate cover test revealed a left hyperdeviation of 4 PO in left gaze, 8 PO in primary, 10 PO in right gaze, S PO with right head tilt: and 12 ~ D with left head tilt. There was bilateral hd retrachon and lid lag, slight conjunctival injection over the medial recti, and mild chemosis au. Intraocular tension was 19 mm Hg au and increased to 23 in upgaze 00. Neurologic and ophthalmologic examination was otherwise normal. In this case the diagnosis of thyroid ophthalmopathy was made on the basis of the associated lid findings, conjunctival injection, and chemosis. A CT scan demonstrated bilateral inferior rectus enlargement. The thyroid function tests were remarkable for an elevated RT3U of 37%, a normal T4 of 7.4 ug/ dl, and a low TSH of < 0.05 miu/ ml. DISCUSSION The first five cases illustrate the diagnostic confusion at initial presentation created by an isolated motility defect that mimicked an isolated superior oblique paresis. In retrospect, the suggestion of mild intermittent lid retraction in the third patient should have been a clue to the etiology of the motility defect. However, the otherwise typical findings of superior oblique paresis were enough to cause diagnostic delay. Although the sixth patient had orbital signs establishing a diagnosis of thyroid ophthalmopathy, she is included because of a motility defect typical for fourth nerve paresis and because the elevated intraocular pressure in upgaze may provide a clue to the mechanism of the hyperdeviation. Four possible explanations for the association between superior oblique paresis and thyroid ophthalmopathy exist. The most likely possibility is that early restrictive ophthalmopathy of the inferior rectus in the hypotropic eye accounted for an apparent superior oblique paresis. This explanation is supported by Case 1, in which the eventual limitation of downgaze as and upgaze aD is a natural progression of the early left hyperdeviation, and by Case 6, in which there was increased intraocular pressure in upgaze 00 ( 2). Cases 4 and THYROID DISEASE WITH FOURTH NERVE PARESIS 97 5 also support an inferior rectus restriction in that the hyperdeviation was greatest on upgaze, rather than downgaze. A second possibility is isolated compression of the trochlear nerve in the orbital apex, particularly in view of optic neuropathy that also developed in two patients. However, we are unaware of any documented cases of neurogenic motility defects caused by orbital apex compression in thyroid disease. A third possibility is that a coincidental idiopathic vasculopathic left fourth nerve paresis preceded the orbitopathy. However, one would have expected spontaneous resolution over months. Additionally, a spontaneous fourth nerve paresis is unusual in a 37- and 41- year- old patient, as in Cases 2 and 3. A fourth possibility is one of coexisting myasthenia gravis. However, the lack of a fluctuating and fatigable deficit and the negative Tensilon test in some patients make this possibility less likely. The time- honored way of diagnosing a fourth nerve paresis is by following the Parks- Bielschowsky three- step test ( 3,4). Step one is to determine the side of hyperdeviation, step two is to determine in which horizontal direction of gaze the deviation is greatest, and step three involves determining which direction of head tilt causes the greatest hyperdeviation. All six patients reported would be diagnosed with a superior oblique paresis using the three- step test. However, in patients in whom the hyperdeviation was measured in upgaze compared to downgaze, the deviation was greatest in upgaze, which would be unusual for an acute superior oblique paresis, although it may occur in a long- standing superior oblique paresis with spread of comitance ( 5). Therefore this " fourth step" should have been performed in all of our patients and is recommended in all patients who have what appears to be a superior oblique paresis. Inferior rectus restriction could cause a contralateral hyperdeviation that is greatest in upgaze. Other disorders that mimic a superior oblique paresis on the three- step test have been described. Kushner ( 6) reported one patient with restriction of upgaze from an orbital floor fracture, one patient with myasthenia gravis, and a third patient with skew deviation, all simulating a superior oblique paresis. Excyclodeviation was noted in two of three patients in whom it was tested. Caygill ( 7) noted excyclodeviation in 43 of 100 consecutive patients with thyroid ophthalmopathy. Trobe ( 8) noted excyclodeviation in 8 of 15 patients with thyroid disease, compared with 30 of 33 patients with fourth nerve paresis and 1 of 13 patients with myasthenia gravis. Therefore, if excyclodeviation is present, one may be dealing either with a fourth nerve paresis or thyroid disease. However, the absence of excyclodeviation is helpful evidence against a diagnosis of fourth nerve paresis and favors an alternative diagnosis, such as skew deviation, ocular myasthenia, or thyroid ophthalmopathy. In summary, six patients had a simulated superior oblique paresis on the three- step test, likely on the basis of early restriction of the inferior rectus from thyroid eye disease. Patients with a typical fourth nerve paresis should therefore be carefully examined for the possibility of thyroid ophthalmopathy. This examination should include increased observation for subtle orbital signs, such as the assessment of intraocular pressure both in primary position and in upgaze. In addition to the three- step test, ocular deviation should be assessed in both upgaze and downgaze. Cyclodeviation should be evaluated, as its absence favors a diagnosis other than superior oblique paresis, such as thyroid disease. If a CT or MRI scan is performed, it is advisable to image the orbits carefully for evidence of muscle enlargement of thyroid ophthalmopathy. REFERENCES 1. Sergott RC, Glaser JS. Graves ophthalmopathy. A clinical and immunologic review. SurF OphthalmoI1981; 26: 1- 21. 2. Gamblin GT, Harper DG, Galentine P. Prevalence of increased intraocular pressure in Graves' disease- Evidence of frequent subclinical ophthalmopathy. N Ellgl J Med 1983; 308: 420- 4. 3. Parks MM. Isolated cyclovertical muscle palsy. Arch OphthalmoI1958; 60: 1027- 35. 4. Bielschowsky A. Lectures on motor anomalies of the eyes II. Paralysis of individual eye muscles. Ophthalmology 1935; 13: 33- 59. 5. Knapp P. Treatment of unilateral fourth nerve paralysis. TrailS Ophthalmol Soc UK 1981; 101: 273- 5. 6. Kushner BJ. Errors in the three step test in the diagnosis of vertical strabismus. Ophthalmology 1989; 96: 127- 32. 7. CaygiIl WM. Excyclotropia in dysthyroid ophthalmopathy. Am JOphthalmol 1972; 73: 437- 41. 8. Trobe JD. Cyclodeviation and acquired vertical strabismus. Arch Ophthalmol 1984; 102: 717- 20. JClin Neuro- ophthalmol, Vol. 12, No. 2, 1992 |
