optic chiasm


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chiasm

 [ki´azm]
a decussation or X-shaped crossing.
optic chiasm a structure in the forebrain formed by the decussation of fibers of the optic nerve from each half of each retina.

op·tic chi·asm

[TA]
a flattened quadrangular body in front of the tuber cinereum and infundibulum, the point of crossing or decussation of the axons of the optic nerves. Axons from the nasal retina cross to the opposite side, whereas axons from the temporal retina run directly caudal without crossing; some pass transversely on the posterior surface between the two optic tracts, and others pass transversely on the anterior surface between the two optic nerves.

optic chiasm

Etymology: Gk, optikos, sight, chiasma, crossed lines
a point near the thalamus and hypothalamus where parts of each optic nerve cross over.

op·tic chi·asm

(op'tik kī'azm) [TA]
A flattened quadrangular body in front of the tuber cinereum and infundibulum, the point of crossing or decussation of the fibers of the optic nerves; most of the fibers cross to the opposite side, some run directly forward on each side without crossing, some pass transversely on the posterior surface between the two optic tracts and others pass transversely on the anterior surface between the two optic nerves.
Synonym(s): optic decussation.

op·tic chi·asm

(op'tik kī'azm) [TA]
A flattened quadrangular body in front of the tuber cinereum and infundibulum, the point of crossing or decussation of the fibers of the optic nerves.
Synonym(s): optic decussation

optic chiasm (op´tik kī´azm),

n a point near the thalamus and hypothalamus at which portions of each optic nerve cross over.

chiasm

a decussation or Y-shaped crossing.

optic chiasm
a structure in the forebrain formed by the decussation of fibers of the optic nerve from each half of each retina.
References in periodicals archive ?
Ast=astrocyte, MCN= magnocell neuron, OC= optic chiasm, SO= supraoptic nucleus, VGL= ventral glial limitans.
Optic chiasm compression can result in bitemporal hemianopia.
Patients may have symptoms due to compression of adjacent structures, particularly the optic chiasm and optic nerves.
The tumor's location between the carotid artery, optic chiasm, pituitary gland, and cavernous sinus made en bloc resection impossible.
Magnetic resonance imaging of the pituitary revealed a pituitary macroadenoma with suprasellar extension to the optic chiasm.
The mass extended into the suprasellar cistern, causing slight mass effect on the optic chiasm.
A high-speed suction and irrigation diamond bur was used to thin the bone overlying the optic nerve from the posterior ethmoid cavity to the area of the optic chiasm.
Review of the MRI obtained in May 1999 revealed a nearly empty sella that contained a cystic mass with suprasellar extension, The mas s did not enhance with contrast medium and was isointense with CSF on all image sequences; there was obvious distortion and elevation of the optic chiasm (Fig 2).
And for the patient with recurrent glioblastoma, we saw a definite advantage to the RapidArc plan, in terms of protecting the optic nerve and optic chiasm.
One patient (patient 4) exhibited sphenoid sinus involvement with extension into the sellar area, cavernous sinuses, and optic chiasm.
T1 MRI image of the head showed a gadolinium contrast-enhancing tuberculum sella mass lesion compressing the left optic nerve (Figure) just anterior to the optic chiasm.
Swinging flashlight test: This is one of the most important objective tests for the detection and quantification of abnormalities of the retina, optic nerve, optic chiasm or optic tract.