Dissociated horizontal deviation after traumatic brain injury.

Abstract

A 4-year-old boy visited the hospital with exotropia after brain hemorrhage caused by trauma. He had undergone decompressive craniectomy and cranioplasty 18 months prior to presentation at our hospital. An alternate prism cover test showed more than 50 prism diopters (PD) of left exotropia when he was fixing with the right eye and 30 PD of right exotropia when he was fixing with the left eye at near and far distance. On the Hirschberg test, 60 PD of left exotropia was noted in the primary position. Brain computerized tomography imaging performed 18 months prior showed hypodense changes in the right middle cerebral artery and anterior cerebral artery territories. Subfalcian herniation was also noted secondary to swelling of the right hemisphere. The patient underwent a left lateral rectus muscle recession of 7.0 mm and a left medial rectus muscle resection of 3.5 mm. Three weeks after the surgery, the Hirschberg test showed orthotropia. On alternate prism cover testing, 8 PD of left exotropia and 8 PD of right esotropia were noted at distance. We report a patient who developed dissociated horizontal deviation after right subfalcian subdural hemorrhage caused by trauma.

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Korean J Ophthalmol 2010;24(6):377-379
DOI: 10.3341/kjo.2010.24.6.377
pISSN: 1011-8942 eISSN: 2092-9382
Case Report
Dissociated Horizontal Deviation after
Traumatic Brain Injury
Tae-Eun Lee1, Deok-Sun Cha1, Seong-Beom Koh2, Seung-Hyun Kim1
1Department of Ophthalmology, Korea University College of Medicine, Ansan, Korea
2Department of Neurology, Korea University College of Medicine, Seoul, Korea
A 4-year-old boy visited the hospital with exotropia after brain hemorrhage caused by trauma. He had undergone
decompressive craniectomy and cranioplasty 18 months prior to presentation at our hospital. An alternate prism
cover test showed more than 50 prism diopters (PD) of left exotropia when he was fixing with the right eye and 30
PD of right exotropia when he was fixing with the left eye at near and far distance. On the Hirschberg test, 60 PD of
left exotropia was noted in the primary position. Brain computerized tomography imaging performed 18 months prior
showed hypodense changes in the right middle cerebral artery and anterior cerebral artery territories. Subfalcian
herniation was also noted secondary to swelling of the right hemisphere. The patient underwent a left lateral rectus
muscle recession of 7.0 mm and a left medial rectus muscle resection of 3.5 mm. Three weeks after the surgery, the
Hirschberg test showed orthotropia. On alternate prism cover testing, 8 PD of left exotropia and 8 PD of right eso-
tropia were noted at distance. We report a patient who developed dissociated horizontal deviation after right sub-
falcian subdural hemorrhage caused by trauma.
Key Words: Brain injuries, Dissociated horizontal deviation, Wounds and injuries
ⓒ2010 The Korean Ophthalmological Society
This is an Open Access article distributed under the terms of the Creative Commons Attribution Non-Commercial License (http://creativecommons.org/licenses
/by-nc/3.0/) which permits unrestricted non-commercial use, distribution, and reproduction in any medium, provided the original work is properly cited.
Received: November 16, 2009 Accepted: February 3, 2010
Reprint requests to Seung-Hyun Kim. Department of Ophthalmology,
Korea University Ansan Hospital, #516 Gojan-dong, Danwon-gu, Ansan
425-707, Korea. Tel: 82-31-412-5160, Fax: 82-31-414-8930, E-mail:
ansaneye@hanmail.net
Dissociated horizontal deviation (DHD) is defined as a
change in horizontal ocular alignment, unrelated to accom-
modation that is brought about solely by a change in the bal-
ance of visual input from the two eyes [1]. DHD usually
presents in patients who have undergone surgery for in-
fantile esotropia. Binocular decorrelation is a sufficient
cause of DHD when imposed during a critical period of
stereopsis development [2]. We present an unusual case of
DHD developing after brain hemorrhage caused by trauma.
Case Report
A 4-year-old boy developed exotropia after undergoing a
decompressive craniectomy for brain hemorrhage because
he fell over and bumped his head against the desk, 18 months
prior to presentation at our hospital. Brain computed tomog-
raphy and magnetic resonance imaging performed at that
time showed hypodense changes in the right middle cerebral
artery territory and both anterior cerebral artery territories, as
well as subfalcian herniation due to swelling of the right
hemisphere (Fig. 1).
When he was fixing with the right eye, alternate prism
cover test showed more than 50 prism diopters (PD) of the
left exotropia was noted. 30 PD exotropia of the right eye
was noted when he was fixing with the left eye (Fig. 2, top
and middle). Unfortunately, we could not determine if the pa-
tient had stereopsis, due to his lack of cooperation. Abnormal
head posture and limitation of extraocular motility was not
noted. On the forced duction test under general anesthesia,
muscle tightening or loosening was not noted.
We treated the patient with left lateral rectus muscle re-
cession of 7.0 mm and left medial rectus muscle resection of
3.5 mm. Three weeks after surgery, the Hirschberg test
showed orthotropia (Fig. 2, bottom). Alternate prism cover
testing showed 8 PD of left exotropia and 8 PD of right eso-
tropia at distance. Six months after surgery, alternate prism
cover testing showed 4 PD of exotropia in the left eye and 2
PD of esotropia in the right eye at distance.

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Korean J Ophthalmol Vol.24, No.6, 2010
378
AB
Fig. 1. (A) Computerized tomo-
graphy showed hypodense change at
right middle cerebral artery, both ante-
rior cerebral artery territory (black ar-
row) and subfalcian herniation due
to swelling of right hemisphere
(white arrow). (B) Diffuse magnetic
resonance imaging showed high sig-
nal at the right frontoparietooccipital
lobe which means decreased dif-
fusion and acute infarction.
Fig. 2. Note large temporal deviation of left eyeball about 60 prism diopters (PD) fixing with the right eye (top) and right exotropia of 30 PD
fixing with the left eye (middle) preoperatively. A small amount of esodeviation in the right eye and 8 PD of exodeviation in the left eye were
noted postoperatively (bottom).
Discussion
Dissociated strabismus is regarded as a marker of early
disruption of normal binocular function [2,3], and DHD usu-
ally manifests as spontaneous unilateral exodeviation of
greater magnitude in one eye. In some instances, fixation
with one eye evokes an esodeviation of the other eye during
prism and alternate cover testing [1]. DHD is usually present
in patients who experienced binocular disruption in early in-
fancy, such as infantile esotropes. Brodsky [4] reviewed 28
patients with consecutive exotropia and found that 50% of
patients had DHD. Tychsen [5] studied infant monkeys ex-
posed to binocular decorrelation and found that those ex-
posed at 12 weeks and at 24 weeks had dissociated deviation
(dissociated vertical deviation or DHD).
The visual cortex and visual association cortex lie in the
occipital lobe of the brain. The visual cortex (V1, striated
cortex) processes visual information from the eyes, while the
visual association cortex (V2-V8, extrastriated cortex) proc-
esses the more complex data, such as color and movement,
and stereopsis. Among all the parts of the cortex, stereo-
scopic vision depends on the magnocellular pathway in the
V4 extrastriate cortex which is located in the right parie-
to-occipital lobe [6].
The presented patient might have injured the extrastriate
cortex, which controls stereoscopic vision. Hence, this case
might suggest that dissociated strabismus can develop in pa-
tients who have sustained a brain injury. We were not able to
test our patient’s stereopsis because of poor cooperation. We
also question why the patient presented with DHD instead of
dissociated vertical deviation (DVD). This may be explained
by the difference in brain lesions associated with DHD and
DVD, but this possibility needs to be investigated in future
studies.

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TE Lee, et al. Dissociated Horizontal Deviation after Traumatic Brain Injury
379
Conflict of Interest
No potential conflict of interest relevant to this article was
reported.
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