Sectoranopia: a stroke in the lateral geniculate nucleus or optic radiations?
BACKGROUND
The lateral geniculate nucleus (LGN) is the site at which ganglion cell axons of the optic tract synapse with neurons that form the optic radiations. Lesions of the perigeniculate visual pathway are characterized by distinct pupillary, visual field, and ophthalmoscopic findings. Such findings, combined with results from neuroimaging, enable one to precisely locate the area of the visual pathway that is involved.


METHODS
A patient who presented to our clinic with a complaint of narrowly missing several motor vehicle accidents recently was found to have a left horizontal sectoranopia on a screening visual field. Magnetic resonance imaging confirmed the presence of an old infarct involving the optic radiations. The patient's medical history was significant for high homocysteine levels that likely contributed to his having had several cerebral vascular accidents in the past, one of which affected the optic radiations.


CONCLUSIONS
Damage to the LGN and optic radiations can produce sectoranopic visual field defects. Although it may not be possible to specify the exact location of a lesion, understanding the blood supply of the visual pathway and retinotopic organization of the LGN aids in the localization of infarcts that cause characteristic visual field defects.
Huang
Minna
M
San Diego VA Healthcare Center, San Diego, California 92161, USA. minnahuang@yahoo.com
Ilsen
Pauline F
PF
D020520:Brain Infarction / Q000150:complications* / Q000175:diagnosis; D003937:Diagnosis, Differential; D005829:Geniculate Bodies / Q000098:blood supply*; D006423:Hemianopsia / Q000175:diagnosis / Q000209:etiology* / Q000503:physiopathology; D006801:Humans; D008279:Magnetic Resonance Imaging; D008297:Male; D008875:Middle Aged; D020521:Stroke / Q000150:complications* / Q000175:diagnosis; D058609:Visual Field Tests; D014794:Visual Fields / Q000502:physiology