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Section II: Sensory Systems
15. Visual Processing: Cortical Pathways
Part 6 of 7

Valentin Draogoi, Ph.D.
(Content adapted from material by Chiyeko Tsuchitani, Ph.D.).
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Clinical Examples

example 4


Figure 15.19

The perimetry test results indicate a right homonymous hemianopia (i.e., a binocular visual defect involving the right hemifields of both eyes) with macular sparing (i.e., central field vision was not affected). 

Symptoms:  A patient is brought to the emergency room complaining of a severe headache and nausea.  He is conscious and coherent when examined in the ER. Ophthalmoscope examination does not reveal abnormalities in either eye. Confrontation field testing indicates a visual loss in the right hemifield of both eyes. 

The patient is referred for neuroradiographic tests and perimetry testing.

Perimetry Test Results:   The results indicate a right homonymous hemianopia with macular sparing (Figure 15.19).

Side & Retinotopicity of damage:  The visual loss

  • is not related to changes in the retina of either eye
  • involves field losses for both eyes
  • involves the right hemifields
  • is homonymous or congruent
  • spares the central visual field

You conclude that the visual field defect is related to damage that

  • is retrobulbar (beyond the retina)
  • is retrochiasmatic or postchiasmatic (beyond the optic chiasm)
  • involves the left calcarine cortex  
  • may involve hemorrhage from a branch of the left posterior cerebral artery 
  • spared the more caudal and lateral parts of the striate cortex, which receives collateral blood flow from branches of the middle cerebral artery

Neural imaging results indicate injury to the rostral half of the left calcarine cortex, which receives blood from the left posterior cerebral artery (Figure 15.20).  Recall that the rostral calcarine cortex processes information from the visual field periphery, whereas the caudal and lateral striate cortex process information derived from the visual field center. 


Figure 15.20

The perimetry test results indicate a right homonymous hemianopia with macular sparing.  The medial and inferior portions of the occipital lobe receives blood from branches of the posterior cerebral artery.

Calcarine Cortex Damage. An infarct created by obstruction of, or a hemorrhage in, branches of the posterior cerebral artery may result in damage to the rostral calcarine cortex.  Damage to the calcarine cortex on one side may produce a binocular, contralateral homonymous hemianopia with macular sparing (Figure 15.20).  A collateral blood supply from branches of the middle cerebral artery is believed to spare the cortical neurons in the caudal and lateral regions of the striate cortex, which receive information from the macular area. 

Clinical Examples: Example 1, the periperal nervous system Clinical Examples: Example 2, the periperal nervous system Clinical Examples: Example 3, the spinal cord Clinical Examples: Example 4, the spinal cord Clinical Examples: Example 5, the spinal cord

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