optic chiasm


Also found in: Dictionary, Thesaurus, Encyclopedia, Wikipedia.

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.
A craniopharyngioma can develop in the pituitary stalk in the suprasellar region, next to the optic chiasm (Recht, 2005), and invade the sella turcica, shifting important neurologic structures around it.
Brain MRI revealed a lesion involving the left temporal lobe, basal ganglia, and invasion of the hypothalamus, optic chiasm, canalicular optic nerves, and sella.
Organs at Risk (OAR) constraints were achieved for brainstem, spinal cord, optic chiasm, pituitary and right and left orbits, optic nerve, lens and cochlea.
IVa: Tumor is an intracranial intradural mass that does not infiltrate the cavernous sinus, pituitary fossa, or optic chiasm.
Acute compression of the hypothalamus and optic chiasm may cause hyperintensity along the optic tracts on T2W MR images.
Most common among these is glioma of the optic pathway, which may be isolated to a single optic nerve, the optic chiasm or the entire optic pathway (Figure 1).
12 Similar to the previous scan Similar to the previous scan (at 9th month of therapy) (at 9th month of therapy) 15 Normal cranial MRI findings, The lesion on the level of except for a 2-3 mm optic chiasm disappeared.
For instance, retinal ganglion cells from the nasal retina must cross the midline of the cortex, through the optic chiasm (Fig 2), to the contralateral hemisphere.
A MRI detected a tumor that had grown within the optic chiasm, impairing her vision and pressing on the hypothalamus gland.
Right cerebellum 26 75/M/B Right frontal lobe 27 35/M/B Right frontal lobe 28 23/M/W Cerebellum 29 35/M/B Left CP angle 30 48/M/B Falx 31 41/F/B Left sphenoid ridge 32 27/M/B Optic chiasm 33 .
Lesions of the optic chiasm can produce a variety of visual field defects including bitemporal hemianopia, junctional scotoma (anterior chiasmal defect), quadrantanopia and bitemporal, or unilateral temporal scotoma depending on the site and extent of the lesion.