Junctional Scotoma and Junctional Scotoma of Traquair
Junctional scotoma and the junctional scotoma of Traquair are visual field defects that arise from damage to the junction of the optic nerve and the optic chiasm. Sellar masses including pituitary tumors are the most common cause of these visual field defects. Ophthalmologic findings include ipsilateral central scotoma and typically a contralateral superior temporal visual field defect (junctional scotoma, JS) or temporal hemianopia or rarely nasal hemianopia (junctional scotoma of Traquair JST).
Optic Chiasm Anatomy
The optic chiasm is formed by the union of the two optic nerves. At the junction of the optic nerve with the chiasm, 53% of the fibers from the nasal hemiretina of each eye will cross over while the fibers from the temporal hemiretina (47%) of each eye remain uncrossed. The optic chiasm has a transverse length of 12 - 18 mm, an anteroposterior width of 8 mm, and a height of 4 mm. It lies over the sella turcica and the pituitary gland. The optic chiasm is in direct contact with cerebrospinal fluid in the subarachnoid space anteriorly and forms the floor of the third ventricle posteriorly.
Lesions that produce a junctional scotoma or the junctional scotoma of Traquair are typically extrinsic compressive mass lesions at the junction of the optic nerve and the chiasm. The most common causes include: 
- Pituitary adenoma ( most common cause)
- Sphenoid wing meningioma
- Aneurysms of the internal carotid or the anterior communicating artery
Other demyelinating, infectious, inflammatory, infiltrative, traumatic, and other etiologies can occur in this location however.
Pathology of Junctional Scotoma
The junctional scotoma classically presents as a central scotoma (or other optic nerve type of visual field defect) in one eye as well as a superior temporal visual field defect respecting the vertical meridian in the other eye. The lesion involves the ipsilateral optic nerve at the junction and also the contralateral crossing inferior nasal retinal fibers (producing the superotemporal visual field loss in the fellow eye). In the junctional scotoma of Traquir, the lesion , also at the junction of the optic nerve and chiasm, will cause a temporal or rarely a nasal visual field defect respecting the vertical midline ipsilateral to the lesion depending on which fibers get involved.
Patients with either the junctional scotoma or junctional scotoma of Traquair complain of ipsilesional visual loss. Despite a superior temporal visual field defect in the contralesional eye in the typical junctional scotoma, the patient may be asymptomatic in that eye. Often these patients also present with endocrine abnormalities and headaches due to either mechanical compression of nervous structures or hormonal dysregulation from a pituitary macroadenoma for instance.
Patients may present with varying levels of decreased visual acuity (in addition to the visual field defects above). There will be an ipsilesional relative afferent pupillary defect (RAPD). Band type optic atrophy may be seen on fundus exam in cases which involve nasal fibers. In the junctional scotoma the band atrophy is in the contralesional eye (superotemporal visual field loss) and in the junctional scotoma of Traquair will be in the ipsilesional eye if the defect is monocular and a temporal hemianopsia is present. In the nasal hemianopic variety (rare) of the junctional scotoma of Traquair the optic atrophy will be more likely in the hour glass (temporal fiber atrophy) and not the band configuration (nasal fiber atrophy). Figure 1 shows the junctional scotoma of Traquair and Figure 2 shows the junctional scotoma
Formal visual field imaging is necessary to accurately diagnose patients with junctional visual field loss Automated (e.g., Humphrey visual field testing) perimetry has been shown to be sensitive and specific in patients with visual field defects including junctional loss. Optical Coherence Tomography (OCT) can also aid in identifying band atrophy when the damage involves nasal fibers, or the hour glass pattern of atrophy in cases affecting the temporal fibers. OCT of the macular ganglion cell layer can also document the findings and may predict final visual recovery following surgical correction of the underlying compressive cause.
Laboratory studies may be considered in cases suspected to be from pituitary adenoma. Infectious (e.g., syphilis, tuberculosis), inflammatory (e.g., sarcoid, granulomatous disease, vasculitis), infiltrative (e.g., lymphoproliferative), and demyelinating (e.g., multiple sclerosis, neuromyelitis optica, myelin oligodendrocytic glycoprotein) disorders should also be considered in the differential diagnosis especially if the neuroimaging does not disclose a compressive etiology or shows optic nerve/chiasmal enhancement after contrast administration.
The treatment should be aimed at the underlying etiology but in general compressive lesions require surgical decompression. Corticosteroids may be used for inflammatory etiologies and antimicrobial therapy for infectious etiologies.
Computed tomography (CT) Scan can be used in traumatic cases to identify skull fractures in the frontal and anterior skull base, the orbital roof, the sphenoid bone. Damage to the sella turcica can also be visualized through this method. CT scan is also a more rapid initial neuroimaging for acute cases but in general MRI is superior for imaging the junctional visual field loss. Magnetic resonance imaging (MRI) with contrast may show the chiasmal compressive lesion. High resolution MRI with contrast provides excellent imaging of the soft tissues and can be used to identify other causes such as enhancement, edema or herniation around the optic chiasm. MRI can also identify chiasmal contusion, hemorrhage, or tumor infiltration.. Cerebral Angiography is usually not necessary in junctional visual field loss but if initial neuroimaging suggests a vascular etiology then cerebral angiography may be helpful. The optic chiasm is surrounded by the anterior cerebral artery, the anterior communicating artery, the internal carotid artery, the middle cerebral artery, and the cavernous sinus. An aneurysm in these vascular structures can compress the adjacent nervous structures and a junctional visual field change can develop.
Treatment differs according to the cause of the junctional visual field defect.
Visual prognosis depends on the cause and duration of symptoms. Analysis of the macular ganglion cell layer using OCT can help predict visual recovery in these cases.
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