- Clinical science
Disorders of the visual pathway
Overview
The visual pathways transmit signals from the retina to the visual cortex (striate cortex, brodmann area 17).
Structure | Characteristics | Lesions | Causes |
---|---|---|---|
Retina |
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Optic nerve |
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Optic chiasm |
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Optic tract |
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| |
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Optic radiations |
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|
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Visual cortex |
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Unilateral visual field loss → pathology mainly in front of the optic chiasm. Bilateral visual field loss → pathology mainly in or behind the optic chiasm
References:[1][2]
Prechiasmal visual pathway damage
Prechiasmal damage to the visual pathway mainly involves the optic nerve.For retinal diseases see table above.
Optic nerve
Optic neuritis
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Definition: inflammation of the optic nerve
- Retrobulbar neuritis: inflammation of the retrobulbar part of the optic nerve
- Papillitis: inflammation of the intrabulbar part of the optic nerve
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Etiology
- Most common cause: multiple sclerosis
- Infections
- Toxic
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Clinical features
- Vision impairment: blurry vision, sudden vision loss, color blindness, visual field defects (e.g., central scotoma)
- Retrobulbar pain (increased pain caused by eye movements)
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Diagnostics
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Ophthalmoscopy
- Retrobulbar neuritis: normal ophthalmoscopic finding
- Papillitis: poorly defined papilla, hyperemia, hemorrhage at the border of the papilla
- Visual evoked potential (VEP)
- Neurological examination
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Ophthalmoscopy
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Treatment
- High-dose treatment with glucocorticoids
- Corresponding treatment in the case of multiple sclerosis
Multiple sclerosis is the most common cause of optic neuritis!
Optic atrophy
- Definition: irreversible loss of axons in the optic nerve
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Etiology
- Most common causes: optic neuritis, glaucoma
- Vascular
- Hydrocephalus, orbital/intracranial lesion
- Hereditary: Leber optic atrophy, Krabbe disease, autosomal-dominant optic atrophy
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Clinical features:
- Vision impairment: blurry vision, color blindness, visual field defects (e.g., central scotoma)
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Diagnostics
- Fundoscopy
- Perimetry
Anterior ischemic optic neuropathy (AION)
- Definition: segmental or generalized infarction of the anterior part of the optic nerve
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Etiology
- Nonarteritic form due to atherosclerosis (NAION)
- Arteritic form due to giant cell arteritis (AAION)
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Clinical features
- Sudden unilateral loss of vision
- Wedge-shaped and altitudinal visual field defects
- AAION: other symptoms of giant cell arteritis
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Diagnostics
- Fundoscopy
- Laboratory findings
- AAION: temporal artery biopsy
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Treatment
- AAION: immediate high-dose systemic glucocorticoids
- NAION: trial of hemodilution and systemic glucocorticoid therapy
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Prognosis
- Typically poor: permanent loss of vision
- Involvement of the other eye is common during the course of the disease.
Immediate high-dose glucocorticoid treatment is essential in AAION!
Papilledema
- Definition: swelling of optic disc due to elevated intracranial pressure
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Etiology:
- Hypertensive emergency
- Idiopathic intracranial hypertension (pseduotumor cerebri)
- Intracranial tumors (e.g., medulloblastoma)
- Hydrocephalus
- Cerebral abscess
- Hypervitaminosis A
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Clinical features
- Acute: usually asymptomatic, can present with loss of visual acuity due to enlargement of blind spot
- Chronic (rare): impaired vision, can cause visual field defects and blindness
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Diagnostics
- Fundoscopy
- Acute: edematous, poorly defined, prominent optic disc; radial hemorrhage around the disc margin
- Later stages of disease: optic atrophy possible
- Cranial CT or MRI to detect cause of increased intracranial pressure
- Fundoscopy
Damage in the region of the optic chiasm
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Etiology
- Most commonly: compression by pituitary adenoma (prolactinoma), craniopharyngioma, meningioma, aneurysms of the internal carotid artery
- Demyelination, multiple sclerosis
- Trauma
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Pathophysiology
- Medial lesion (e.g., pituitary adenoma) → temporal visual field defects
- Lateral lesion (e.g., aneurysm of the internal carotid artery) → nasal visual field defects
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Clinical features
- Visual field defects/impaired vision: most commonly bitemporal heteronymous hemianopsia
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Treatment
- Depending on the cause
- Neurosurgical
- Pharmacological
- Depending on the cause
Retrochiasmal visual pathway damage
- Definition: damage in the region of the optic tract, lateral geniculate nucleus, optic radiation, or visual cortex
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Etiology
- Cerebral ischemia/hemorrhage
- Tumors
- Trauma
- Other causes
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Clinical features
- Visual field defects/impaired vision: most commonly homonymous hemianopsia and homonymous quadrantanopsia
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Diagnostics
- Perimetry
- Imaging: CT, MRI