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MRI of unilateral vertical retraction syndrome with atypical strabismus
Chengyue ZHANG 1, Fengyuan MAN2, Zhenchang WANG2, Gang YU1, Qian WU1,
Yonghong JIAO3 and Kanxing ZHAO4
1
Ophthalmology of Beijing children's hospital affiliated to capital university of
medical science, China
2
Beijing Tongren Medical Imaging Centre, Beijing Tongren Hospital, Capital Medical
University, China
3
Beijing Tongren Eye Centre, Beijing Tongren Hospital, Capital Medical University,
Beijing Ophthalmology and Visual Science Key Lab, China
Correspondence to: DongjiaoMinxiang, Dongcheng, District, Beijing, 100730,
P.R.China.
Tel: 0086 010 58268672
Fax: 0086 010 58269154
E-mail address: [email protected]
4
Tianjin Eye Hospital, Clinical College of ophthalmology, Tianjin Medical University,
China
BACKGROUND
Complicated strabismus cases, especially those accompanied by abnormal eye
movements and anomalous innervations often present diagnostic challenges. With the
development of Magnetic Resonance Imaging (MRI), we can do more detailed study
on the anatomy of ocular motor nerves and their corresponding extraocular muscles
(EOMs) [1-3]. Vertical retraction syndrome is a rare kind of strabismus that consists of
retraction of the globe with narrowing of the lid fissure in attempted elevation or
depression, frequent elevation deficiency with variable retraction of the globe. Two
patients with unilateral vertical retraction syndrome confirmed by images were
discussed in this study.
METHODS
MRI was performed with a General Electric 1.5-T Twinspeed scanner. The study was
performed in accordance with the declaration of Helsinki. Written informed consents
were acquired before MRI. Imaging of the ocular motor nerves in the brainstem was
performed by the 3D-FIESTA sequence. Nerves to EOMs, EOMs and their associated
connective tissues in the orbits were imaged with a T1-weighted and T2-weighted
FSE in triplanar scans by dual-phased coils. Intravenous gadodiamide contrast was
administered.
RESULTS
Case 1
A 7-year-old boy was found to have limitation of elevation of the right eye since 2
years old. His parents denied swelling or bleeding in the orbits at birth. He had no
family history of eye disease. The results of systemic and neurologic examination
were negative. Cycloplegic refraction was +1. 25DS + 0.50 DC× 70 right eye and
+1.25DS + 0.50 DC× 130 left eye. His corrected visual acuities were 12/20 bilaterally.
Enophthalmos of the right eye was revealed in the primary position. Limitation of
elevation of the right eye was seen in both adduction and abduction which was
accompanied by significant narrowing of the palpebral fissure (Figure 1). In the
primary position, when the right eye fixated, 10-diopter exotropia and 60-diopters
hyperdeviation were present in the left eye. When the left eye fixated, a 25-diopters
hypodeviation were present in the right eye. MRI of brainstem showed that CN3 and
CN6 in the cistern were normal. Sagittal reconstruction shows a linear band originated
from the orbital apex and inserted posteriorly to the equator of the globe in the lower
outer quadrant, which appeared slightly lower signal intensity than that of extraocular
muscle on T1-weighted images. Contiguous quasicoronal MRI of the right orbit
showed the orbital structure was separated from the inferior rectus muscle (IR), the
maximum cross-section diameter of the band was about 3mm, and the inferior
division of CN3 sent out an enlarged branch to IR (Figure 2).
Case 2
An 8-year-old girl which had been reported in another paper had a limitation of
elevation of the left eye in both adduction and abduction [4]. She had an intermittent
exotropia of 60 prism diopters in the primary position. MRI of the left orbit showed a
linear band that originated from the orbital apex and insert on the posterior globe in
the inferotemporal quadrant, which appeared slightly lower signal than muscle on
T1-weighted images. The maximum cross-section diameter of the band was about
3mm. The inferior division of CN3 to the inferior oblique muscle was not constantly
revealed. The abnormal band was indicated to originate from the inferior rectus (IR)
at the orbital apex by MRI sagittal reconstruction (Figure 3).
DISCUSSION
The pathogenesis of the vertical retraction syndrome is still not clearly known. Recent
reports including imaging findings revealed that an accessory extraocular muscle or a
fibrous band appeared to cause restriction on elevation and globe retraction in their
cases [5-7]. Detailed clincopathologic evidence of anomalous orbit structures resulting
unusual strabismuses had been reviewed by Gregg T. Lueder [8], and were categorized
into three types: 1. structures arise from the extraocular muscles themselves and insert
in abnormal locations. 2. fibrous bands located beneath the rectus muscles. 3. discrete
anomalous muscles that originate in the posterior orbit and insert in abnormal
locations on the globe. In our study, MRI of the two cases showed similar size and
location of the orbital structure but differed greatly in type of strabismus. The signal
intensity of the linear band was slightly lower than that of extraocular muscle on
T1-weighted images, reflecting the larger percentage of fibrous tissue. Tracing the
EOMs from the orbital apex by contiguous quasicoronal MRI, the precise origin of
the anomalous orbital structure of case 2 could not be ascertained, but the orbital
structure of case 1 arising from the inferior rectus was showed clearly. However, MRI
sagittal reconstruction shows the band arising from the inferior rectus muscle at the
orbital apex in both cases. Normally, the larger inferior division of CN3 and branches
to the target EOMs and CN6 could be well depicted in the orbit [1, 3].However, we
found that inferior division of CN3 to the inferior oblique muscle could not
demonstrated constantly in case 2, an anomalous enlarged branch to IR was revealed
in case 1. These MRI observations implied that the anomalous orbital structure was
anomalous muscle tissue and innervated by the inferior division of CN3 as Fleischer’s
reported [9].
Vertical retraction syndrome caused by abnormal structures may appear as atypical
strabismus. Imaging studies of the ocular motor nerves and their corresponding EOMs
can play an extremely useful role in the diagnosis, and careful communication with
the radiologist may help in their identification. MRI of the orbits of the two cases was
originally interpreted similar size and location of the orbital structure in the
inferotemporal quadrant. Reevaluation of these MRI studies in light of the type of
strabismus differs dramatically showed that the insertions of the band of the two cases
were different which might be related to the strabismus. In case 1 the band was
inserted at the posterior of the equator of the globe. Ocular motility examination
revealed marked enophthalmos in the primary position, large angle hypotropia, and
significant limitation of elevation. Therefore the more anterior insertion of abnormal
orbital band led to more limitation might explain, at least partially, the cause of
hypotripia of this case. The insertion of the band of case 2 was approximately at the
posterior pole of the globe which was near the optic nerve. Ocular motility
examination showed slight enophthalmos and intermittent exotropia in the primary
position. These findings indicated that the terminal of abnormal orbital band ending
near the posterior pole of eyeball would cause slight limitation of elevation.
In conclusion, anomalous orbital structures may partially explain the cause of vertical
retraction syndrome and the anatomical differences of the orbital structures can lead
to atypical strabismus.
References:
1.Demer JL, Ortube MC, Engle EC, et al. High-resolution magnetic resonance
imaging demonstrates abnormalities of motor nerves and extraocular muscles in
patients with neuropathic strabismus. J AAPOS. 2006 Apr; 10(2):135-42.
PMID:16678748
2.Demer JL, Ortube MC, Lim KH, et al. Magnetic resonance imaging evidence for
widespread orbital dysinnervation in dominant Duane's retraction syndrome linked to
the DURS2 locus. Invest Ophthalmol Vis Sci. 2007 Jan; 48(1):194-202. PMID:
17197533
3.Jiao YH, Zhao KX, Wang ZC, et al. Magnetic resonance imaging of the ocular
motor nerves in normal volunteers. 89 Zhonghua Yan Ke Za Zhi. 2009
Mar;45(3):219-24. PMID:19575915
4. Man F, Wang Z, Wang J, et al. Unilateral vertical retraction syndrome with orbital
band. J AAPOS. 2009 Aug; 13(4):419-21. PMID: 19482497
5.Lueder GT, Dunbar JA, Soltau JB, et al. Vertical strabismus resulting from an
anomalous extraocular muscle. J AAPOS. 1998 Apr;2(2):126-8.PMID:10530977
6.Murthy R. Unilateral restrictive ophthalmoplegia and enophthalmos associated with
an intraorbital tissue band. J AAPOS. 2007 Dec; 11(6):626-7.PMID: 17720574
7.Ozkan SB, Ozsunar Dayanir Y, Gökçe Balci Y. Hypoplastic inferior rectus muscle in
association with accessory extraocular muscle and globe retraction. JAAPOS. 2007
Oct; 11(5):488-90.PMID:17933674
8. Lueder GT. Anomalous orbital structures resulting in unusual strabismus. Surv
Ophthalmol. 2002 Jan-Feb; 47(1):27-35.PMID:11801267
9. Fleischer. Musculus retractor bulbi und drittes lid bei einer menschlichen
missbildung. Anat Ant. 1907; 30:465-70.
Figures and legends
Figure1.
Case 1. Ocular versions showed right hypotropia in the primary position. Limitation
of elevation was seen in both adduction and abduction which was accompanied by
significant narrowing of the palpebral fissure.
Figure2.
MRI, Case 1. Contiguous quasicoronal MR Images of the right orbit (A-D). A, The
inferior division of CN3 in the orbital apex. B, An enlarged branch to the inferior
rectus muscle (IR) was revealed. C, The IR is thickened in the orbital apex. D, the
signal intensity of the band is slightly lower than that of the extraocular muscle, and
separated from the IR. E, MRI sagittal reconstruction showed a linear band from the
orbital apex and inserted on the posterior of the equator of the globe in the lower outer
quadrant (black arrows), and the band arising from the inferior rectus muscle at the
orbital apex (open arrow).
Figure3.
MRI, Case 1, 2. A, Quasi-sagittal image through the inferior rectus; B, Quasi-sagittal
image through the optic nerve; C, Quasi-sagittal reconstruction of plane A and B,
showed a linear band from the orbital apex and inserted on the posterior globe in the
lower outer quadrant (arrows).