Causes of Right Homonymous Quadrantanopsia
Right homonymous quadrantanopsia results from lesions in the left retrochiasmatic visual pathway, most commonly caused by ischemic stroke, followed by hemorrhage, trauma, brain tumors, and less frequently demyelinating disease or neurosurgical complications 1.
Primary Vascular Causes
Ischemic Stroke (Most Common)
- Posterior cerebral artery (PCA) territory infarction affecting the left occipital lobe is the leading cause 1
- Superior quadrantanopia: involves inferior calcarine cortex and cuneus
- Inferior quadrantanopia: involves superior calcarine cortex
- Middle cerebral artery (MCA) territory infarction affecting the left optic radiations 1
- Superior quadrantanopia (pie-in-the-sky): damage to Meyer's loop in the temporal lobe 2
- Inferior quadrantanopia (pie-on-the-floor): damage to superior optic radiations in the parietal lobe
Hemorrhagic Stroke
- Parenchymal hematoma in the left occipital lobe or optic radiations 1
- Venous infarction (often hemorrhagic) from dural venous sinus or cerebral vein thrombosis 1
- Posterior superior sagittal sinus thrombosis can cause occipital cortex venous infarction
Structural/Mass Lesions
Brain Tumors
- Primary or metastatic tumors affecting the left optic radiations or occipital cortex 1
Trauma
- Traumatic brain injury affecting the left retrochiasmatic pathway 1
Inflammatory/Demyelinating Causes
Multiple Sclerosis
- White matter lesions in the left posterior optic radiations or visual cortex 3
- Typically produces congruous quadrantanopic defects from small trigone area lesions
Iatrogenic Causes
Neurosurgical Complications
- Temporal lobe resection (e.g., for epilepsy) disrupting Meyer's loop produces superior quadrantanopia 2
- Other neurosurgical procedures affecting the visual pathway 1
Rare/Unusual Causes
Metabolic
- Hyperosmolar hyperglycemic syndrome can rarely present with quadrantanopia 4
Anatomical Variants
- Giant Virchow-Robin spaces compressing the left optic tract or lateral geniculate body 5, 6
- These perivascular spaces can enlarge sufficiently to cause visual field defects
- May improve with surgical fenestration
Extrastriate Cortical Lesions
- Infarction of V2/V3 extrastriate cortex can produce quadrantanopia with associated visual perceptual abnormalities 7
Key Anatomical Localizations
For right homonymous quadrantanopsia, the lesion is in the LEFT hemisphere:
- Superior quadrantanopia: Left inferior calcarine cortex, cuneus, or Meyer's loop (temporal optic radiations)
- Inferior quadrantanopsia: Left superior calcarine cortex or superior parietal optic radiations
Clinical Pitfalls
- Patients may not immediately recognize hemianopic or quadrantanopic defects, so acute onset doesn't always correlate with symptom awareness 1
- Visual acuity typically remains relatively intact with retrochiasmatic lesions, distinguishing these from anterior pathway lesions 1
- Smaller infarct volumes and less geniculocalcarine tract involvement differentiate quadrantanopia from complete hemianopia 8
- Congruity of the field defect increases as lesions occur more posteriorly along the visual pathway