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 (kī-ăz′mə) also chi·asm (kī′ăz′əm)
n. pl. chi·as·ma·ta (-mə-tə) or chi·as·mas also chi·asms
1. Anatomy A crossing or intersection of two tracts, as of nerves or ligaments.
2. Genetics The point of contact between paired chromatids during meiosis, resulting in a cross-shaped configuration and representing the cytological manifestation of crossing over.

[Greek khīasma, cross-piece, from khīazein, to mark with an X, from khei, khī, chi (from the letter's shape).]

chi·as′mal, chi·as′mic, chi′as·mat′ic (-măt′ĭk) adj.
ThesaurusAntonymsRelated WordsSynonymsLegend:
Adj.1.chiasmal - of or relating to a chiasm
anatomy, general anatomy - the branch of morphology that deals with the structure of animals
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References in periodicals archive ?
Therefore, every case with a mild and transient VA improvement, or with a lack of response to systemic corticosteroid therapy, must be regarded as a warning sign of compressive lesion of optic nerve or chiasmal region, and it should warrant a proper and prompt neuroimaging diagnostics (MRI or CT head scans).
Chiasmal glioma in neurofibromatosis tipe I with severe visual loss regained with radiation.
Pituitary tumors which were only more than 10mm in height could only cause chiasmal compression.
5-8) Neurologic causes include injury to the optic nerve itself (normally monocular) or defects in the chiasmal or retrochiasmal regions (causing partial loss in both eyes).
Repeat MRI revealed enlargement of the sellar mass with extension into the cavernous sinus bilaterally and significant chiasmal compression.
In patients with symptomatic chiasmal compression, urgent shrinkage of the tumour is important, whereas in patient with a microadenoma, a less rapid escalation of dopamine agonists may be required.