Radiologic-Clinical CorrelationJunctional Visual Field Loss

Andrew G. Lee, Karl J. Siebert, and Ajay Sanan

From the Departments of Ophthalmology (A.G.L., K.J.S., A.S.), Neurology (A.G.L.), andNeurosurgery (A.G.L.), Baylor College of Medicine, Houston, Tex

Nerve fibers originating in the retina followa specific topographical arrangement in theoptic nerve and chiasm. Compressive lesionsat the junction of the intracranial optic nerveand optic chiasm can produce characteristicvisual field defects. Optic nerve involvementat the junction of the optic chiasm results inunilateral visual field loss. If fibers from theinferonasal retina of the contralateral eye(Wilbrand’s knee) are involved, there will alsobe a superotemporal visual field defect in thecontralateral eye. These defects can be pro-duced by pituitary tumors, suprasellar men-ingiomas, supraclinoid aneurysms, cranio-pharyngiomas, gliomas, and other entities(1–4). We describe two patients with intra-cranial lesions and junctional visual field de-fects.

Clinical Histories

Case 1

A 46-year-old morbidly obese woman pre-sented with painless, progressive loss of vi-sion in the right eye over 1 year. Her symp-toms began as mild, gradually progressivevisual loss in the right eye 1 year before,which worsened over the next several monthsto complete blindness. She felt that her left

Supported in part by a grant from Research to Prevent BlindnessInc.

Address reprint requests to Andrew G. Lee, MD, Department ofOphthalmology, Baylor College of Medicine, Houston, TX 77030.

Index terms: Optic chiasm; Vision; Radiologic-clinical correlations.

AJNR 18:1171–1174, Jun 1997 0195-6108/97/1806–1171

© American Society of Neuroradiology

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eye was normal. She had no other neurologicor ophthalmologic symptoms. Her medicalhistory was unremarkable, and she was tak-ing no medications. Neuroophthalmologicexam revealed a visual acuity of no light per-ception in the right eye and 20/20 in the lefteye. She correctly identified 14 of 14 Ishiharacolor plates in the left eye. The pupils wereisocoric, and the left pupil reacted normallyto light. The right pupil was nonreactive. Mo-tility examination showed full ductions andversions, but there was a 20-prism dioptersensory exotropia present. Findings of slitlamp biomicroscopy, intraocular pressuremeasurements, and external examinationwere normal. Ophthalmoscopic examinationrevealed diffuse pallor of the optic disk on theright with a normal optic disk on the left. Theremainder of the retinal examination in botheyes was normal. Static visual field testing ofthe left eye revealed a superior temporal ar-cuate defect extending from the blind spot tothe vertical midline (Fig 1A).

Magnetic resonance (MR) imaging couldnot be performed because of the morbid obe-sity of the patient. Computed tomography(CT) revealed a 2.5 3 2.1 3 2.0-cm well-circumscribed parasellar mass on the right,consistent with a giant aneurysm of the inter-nal carotid artery (Fig 1B). The lesion showedhomogenous enhancement after the admin-istration of contrast material. Before cerebralarteriography could be performed, the patientbecame acutely obtunded at home and died.No postmortem study was obtained, but itwas presumed that there had been a fatalrupture of the giant carotid artery aneurysm.

1

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Fig 1. Case 1. A, Static visualfield testing (Humphrey 30-2 pro-gram) of the left eye reveals a su-perotemporal arcuate defect ex-tending from the blind spot to thevertical midline. There was no lightperception in the right eye.

B, Postcontrast CT reveals a2.5 3 2.1 3 2.0-cm mass (arrow)arising from the right internal ca-rotid artery.

Case 2

A 61-year-old woman presented with pain-less, progressive visual loss in the left eyeover the previous year. The patient deniedany other neurologic or ophthalmologicsymptoms. Medical history was significant forhypertension, hypothyroidism, and degener-ative joint disease. Her medications includedpropranolol and levothyroxine. Neurooph-thalmologic examination revealed visual acu-ity of 20/20 in the right eye and 20/200 in theleft eye. The pupils were isocoric, and theright pupil reacted normally to light. The leftpupil reacted sluggishly to light, and therewas a left afferent pupillary defect. She cor-rectly identified 14 of 14 Ishihara color plateswith the right eye, but could see only grosscolors with the left eye. Findings of slit lampbiomicroscopy, intraocular pressure mea-surements, and external and motility exami-nations were all normal. Ophthalmoscopicexamination revealed diffuse optic atrophyon the left. The remainder of the retinal ex-amination was within normal limits. Static vi-sual field testing of the left eye revealed atemporal visual field defect involving centralfixation (Fig 2A). Static visual field testing ofthe right eye was normal.

MR of the head revealed a 3.0 3 2.0 32.0-cm suprasellar mass extending from theleft anterior clinoid region and the tuberculumsellae with compression of the left optic nerveand chiasm anteriorly. The lesion was isoin-tense to brain on T1-weighted images (Fig2B) and showed homogenous contrast en-hancement (Fig 2C and D). On the T2-weighted images, the lesion was homog-

enously slightly hyperintense to gray matter.The MR findings were consistent with menin-gioma.

Discussion

The intracranial optic nerves extend poste-riorly from the optic foramen and join at theoptic chiasm. Within the chiasm, fibers fromthe nasal retina of each eye cross into thecontralateral optic tract, and fibers from thetemporal retina pass uncrossed into the ipsi-lateral optic tract (5). Within the intracranialoptic nerve, the crossed (nasal retinal) anduncrossed (temporal retinal) fibers are ana-tomically separated at the junction of the op-tic nerve and chiasm. In addition, inferior na-sal crossing fibers can loop anteriorly for ashort distance into the contralateral opticnerve. These fibers are often referred to as theanterior knee or Wilbrand’s knee (5) (Fig 3).

Lesions at the junction of the optic nerveand chiasm can produce specific types ofvisual field defects that allow topographicallocalization (6–8). Selective compression ofthe crossed or uncrossed visual fibers at thejunction can result in a unilateral temporal (4)or nasal (2) hemianopic field defect, respec-tively. In addition, involvement of the infero-nasal fibers of the anterior knee results in asuperotemporal visual field defect contralat-eral to the lesion (5).

In 1927, H. M. Traquair (6) used the termjunction scotoma to refer to a unilateral tem-poral hemicentral field defect caused bycompression of the nasal fibers crossing inthe intracranial optic nerve at the junction ofthe optic nerve and chiasm (Fig 3). Miller (7)

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Fig 2. Case 2. A, Static visualfield testing (Humphrey 30-2 pro-gram) of the left eye reveals a tem-poral hemifield defect with involve-ment of central fixation. Findings ofvisual field testing in the right eyewere normal.

B, Coronal T1-weighted MR im-ages (450/15/1 [repetition time/echo time/excitations]) reveals anisointense lesion (arrow) arising atthe level of the anterior clinoid andcompressing the left optic nerve andanterior optic chiasm (arrowhead).

C, Axial and D, coronal T1-weighted postcontrast MR images(450/15/1) show homogeneous en-hancement of the mass (arrow).

emphasized that the junctional scotoma de-scribed by Traquair refers to a strictly unilat-eral temporal scotoma, which is assumed toarise from the junction of the optic nerve andchiasm. Unfortunately, some confusion hasarisen regarding the use of the term junc-tional scotoma. Unlike Traquair (6), some au-thors have used the term to refer to an ipsi-lateral optic neuropathy with a contralateralsuperotemporal visual field defect. This su-perotemporal defect is caused by compres-sion of the inferonasal fibers from the contra-lateral eye travelling in Wilbrand’s knee (5).

To clarify this distinction, Miller (7), citingJ. Lawton Smith, recommended that the uni-lateral temporal visual field defect describedby Traquair should be referred to as the junc-tional scotoma of Traquair in order to differ-entiate it from the contralateral superotempo-ral defect more commonly referred to as thejunctional scotoma.

Recently, the existence of Wilbrand’s kneehas come into question. Wilbrand was re-stricted to examining human subjects who

had undergone enucleation. In the enucleatedeye, the nerve fibers atrophied and becamedistinct from the nerve fibers of the normaleye on myelin staining. J. C. Horton (“Wil-brand’s Knee of the Optic Chiasm Is an Arti-fact of Long-Term Monocular Enucleation,”presented at the annual meeting of the NorthAmerican Neuro-Ophthalmology Society,Snowbird, Utah, February 1995) used axonlabeling techniques in nonenucleated mon-keys but was unable to demonstrate crossingfibers looping into the contralateral opticnerve (Wilbrand’s knee). In one monkey thathad undergone enucleation 4 years previ-ously, however, nerve fiber topography simi-lar to that described by Wilbrand was found.Horton hypothesized that Wilbrand’s kneecould be an artifact of enucleation caused byatrophy of the optic nerve, not a normal an-atomic finding. Nevertheless, whether theWilbrand’s knee exists anatomically, the lo-calizing value of junctional visual field loss tothe junction of the optic nerve and chiasmremains undiminished since chiasmal com-

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pression alone can result in the contralateralsuperotemporal visual field defect (junctionalscotoma).

Trobe and Glaser (8) felt that junctionalvisual field loss would be caused by a masslesion in 98 of 100 cases. The differentialdiagnosis of a junctional syndrome includespituitary tumors, suprasellar meningiomas,supraclinoid aneurysms, craniopharyngio-mas, and gliomas (1–4). Chiasmal neuritisand trauma are rare causes of the junctionalsyndrome.

Patients with the junctional scotoma of Tra-quair or the junctional scotoma should beconsidered to have a compressive lesion atthe junction of the optic nerve and chiasmuntil proved otherwise. Neuroimaging studiesshould be directed to this location. Patientswith the junctional scotoma can be unaware

Fig 3. Schematic diagram illustrates the nasal fiberscrossing from the ipsilateral retina to the contralateral optictract via the optic chiasm (solid and dotted lines). The de-cussating inferonasal fibers, representing superotemporal vi-sual field, pass for a short distance into the contralateral opticnerve as Wilbrand’s knee (solid line, not drawn to scale). Thehatched area represents the visual field deficit and the corre-sponding retinal areas as described in case 1. ST indicatessuperotemporal; SN, superonasal; IT, inferotemporal; and IN,inferonasal.

of a small superotemporal visual field defect,and patients with strictly unilateral visualsymptoms can be misdiagnosed as having anoptic neuritis or other unilateral neuropathy.Therefore, in any patient with presumed uni-lateral visual loss, careful visual field testingshould be performed in the contralateralasymptomatic eye.

Both of our patients presented with pain-less progressive loss of vision and clinicalevidence of optic neuropathy. These findingsare very suggestive of a compressive lesionof the anterior visual pathway. Junctional vi-sual field defects in these patients were oflocalizing significance. Case 1 presented withan ipsilateral optic neuropathy and a con-tralateral superotemporal defect consistentwith the junctional scotoma. Case 2 pre-sented with temporal visual field loss consis-tent with the junctional scotoma of Traquair.Loss of visual acuity in this case was probablythe result of further compression of the mac-ular fibers in the intracranial optic nerve. Bothcases illustrate the localizing value of visualfield defects at the level of the junction.

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