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Resident’s Day Abstract
Zachary Roth O.D.
Ocular Disease Resident
Northern Indiana VA HCS
Abstract:
Optic tract syndrome is an uncommon clinical entity with a pathognomonic triad of
homonymous hemianopia, contralateral relative afferent pupillary defect, and
characteristic optic atrophy. We present an iatrogenic case secondary to a rare
arteriovenous malformation.
I. Case History
Patient demographics:
-63 year old white male
Chief complaint:
-Patient presents with complaint of glasses causing headaches, but also
notes of a brain surgery in 1994 and 2006 which affected right side vision.
Ocular history:
-Right, congruous hemianopsia; longstanding since microsurgical resection
of AV malformation
-Longstanding diplopia
Medical history:
-Hyperlipidemia
-Post-traumatic stress disorder
-Depression
-History of opium abuse
-Tobacco use
-Left-sided arteriovenous malformation with bleed requiring multiple
microsurgical resections and single episode of stereotactic radiotherapy
-Sequelae of headaches, vertigo, and personality changes
II. Pertinent findings
Pupil testing:
-2+ left relative afferent pupillary defect
Visual fields:
-HVF 30-2 revealed congruent complete right homonymous hemianopsia
Spectralis OCT:
-Retinal nerve fiber layer thinning superior and inferior OS
Dilated examination:
-Moderate optic nerve cupping OD>OS with 1+ sectoral pallor OD and
question of pallor OS
Physical:
-Full neurology workup including CN testing
-Neurologist reports
Radiology studies:
-CT scan
-MRI
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Zachary Roth O.D.
Ocular Disease Resident
Northern Indiana VA HCS
III. Differential diagnosis
-Postoperative ischemic optic neuropathy
-Toxic/Metabolic optic neuropathy
-Compressive optic neuropathy
-Optic neuritis
-Pseudotumor Cerebri
-Cerebrovascular accident
-Trauma
IV. Diagnosis and discussion
A diagnosis of optic tract syndrome was made based upon the pathognomonic
triad of findings consistent with history and imaging modalities.
The optic tract contains ipsilateral retinal temporal fibers and contralateral retinal
nasal fibers which have decussated in the optic chiasm. The majority of these fibers
project to the lateral geniculate body with a minority to the prectectal nuclei. As such,
the optic tracts carry visual information from the contralateral visual field bound for the
lateral geniculate nucleus as well as sparse fibers destined for sole inclusion into the
oculomotor pathways. Damage to these fibers results in retrograde axonal degeneration
which is observed as optic disc pallor in a classic bowtie pattern; a relative afferent
pupillary defect (RAPD); and a hemianopsia.
In incomplete lesions, the RAPD is expected to be present in the eye with more
extensive field loss, while a complete lesion results in an RAPD present in the eye with
temporal field loss. This is due to the fact that the nasal retinas is more extensive than the
temporal retina and there are more crossed than uncrossed fibers with the proportion of
decussating and non-decussating fibers estimated to be 53:47. As a result, each optic
tract contains more pupillomotor input from the contralateral eye and lesions will result
in a contralateral RAPD.
The classic bowtie pattern of atrophy is the result of the orientation of the axonal
cell bodies affected by the lesion and their orientation at the optic nerve. The uncrossed
fibers subserve temporal retina while the crossed subserve the nasal retina with both
representing contralateral visual field. Axons subtending vision nasal to the fovea are
overrepresented on the horizontal meridian of the optic nerve while those subtending
vision temporal to the fovea are oriented along the vertical meridian of the optic nerve.
As such, post-chiasmal/pre-geniculate lesions will result in horizontal pallor of the optic
nerve ipsilateral to the lesion and vertical pallor of the contralateral optic nerve.
Hemianopsia is common in optic tract, optic radiation, and generalized occipital
lobe lesions. While the degree of congruity is useful in localizing a potential lesion, a
complete hemianopsia has no localizing value.
We present a case of a rare AV malformation resulting in an iatrogenic optic tract
syndrome with classic findings which are further elucidated by newer imaging modalities
including OCT.
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Zachary Roth O.D.
Ocular Disease Resident
Northern Indiana VA HCS
V. Treatment, management
Treatment:
-occupational therapy
-physical therapy
-driver rehabilitation training
-binocular vision evaluation
Bibliography:
Hsu, Chen Yu, Yu Hung Lai, Sheng Yao Hsu, Yih Chun Lin, and Rong Kung Tsai. "Optical
Coherence Tomography (OCT) Findings in Patients with Optic Tract Syndrome." Taiwan
Journal of Ophthalmology (2011): 16-20.
Ishikawa, Hiroshi, Hanako Matsunaga, Keiko Asayama, and Noriko Saito. "Optic Tract
Syndrome, Horner's Syndrome, and Trochlear Nerve Palsy Due to Suprasellar
Germinoma." Neuro-Ophthalmology 29 (2005): 129-32.
Remington, Lee Ann., and Eileen C. McGill. Clinical Anatomy of the Visual System. Boston:
Butterworth-Heinemann, 1998.
Rodriguez, Amadeo R., and Kesava Reddy. "Pearls and & Oy-sters: Optic Tract Syndrome."
Neurology 75.e86 (2010)
Savino, Peter J., MD, Mark Paris, MD, Norman J. Schatz, MD, Linda S. Orr, MD, and James J.
Corbett, MD. "Optic Tract Syndrome - A Review of 21 Patients." Archives
Ophthalmology 96 (1978): 656-63.
VI. Conclusions
Optic tract syndrome is a relatively uncommon manifestation of a central nervous
system lesion or defect that manifests in a contralateral hemianopsia, contralateral RAPD,
and bowtie atrophy of the ipsilateral optic disc. Both visual acuity and color acuity are
typically unaffected. If pallor of the nerve is not obvious on clinical examination, an
OCT may be useful in highlighting the atrophy.
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