Optic chiasm
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At the time the article was created Craig Hacking had no recorded disclosures.
View Craig Hacking's current disclosuresAt the time the article was last revised Elmira Hassanzadeh had no financial relationships to ineligible companies to disclose.
View Elmira Hassanzadeh's current disclosures- optic chiasma
- chiasm
The optic chiasm or chiasma is the midline structure where the nasal (medial) fibres of the optic nerves decussate to continue posteriorly as the optic tracts. It lies in the chiasmatic cistern and along with the pituitary stalk, is completely encircled by the circle of Willis.
On this page:
Gross anatomy
Relations
The circle of Willis encircles the pituitary stalk and optic chiasma.
lateral: anterior perforated substance
anterior: optic nerves
posterior: optic tracts, tuber cinereum, pituitary stalk, mammillary bodies, posterior perforated substance
superior: supraoptic recess of the third ventricle, anterior commissure
superoposterior: hypothalamus
inferior: suprasellar cistern
The anterior-to-posterior location of the chiasm relative to the pituitary fossa is variable 4:
prefixed: tuberculum sellae (15%)
normal: diaphragma sellae (70%)
postfixed: dorsum sellae (15%)
Historically, it has been believed that the crossing fibres made an anterior bend into the prechiasmatic optic nerve; this is known as Wilbrand knee. However, this has been suggested to possibly be artifactual ref.
Blood supply
Small branches of the anterior cerebral artery and the superior hypophyseal artery supply the chiasm and intracranial portion of the optic nerves whereas the optic tracts are supplied by small branches of the anterior choroidal and posterior communicating arteries.
Related pathology
Lesions compressing the chiasm classically produce the visual field defect of bitemporal hemianopia, where there is loss of the temporal fields.
References
- 1. Keith L. Moore, Arthur F. Dalley, A. M. R. Agur. Clinically Oriented Anatomy. (2013) ISBN: 9781451119459 - Google Books
- 2. Last, R. J., McMinn, R. M. H.. Last's Anatomy, Regional and Applied. (1994) ISBN: 044304662X - Google Books
- 3. Paul Butler, Adam Mitchell, Jeremiah C. Healy. Applied Radiological Anatomy. (2012) ISBN: 9780521766661 - Google Books
- 4. Gulsen S, Dinc A, Unal M, Cantürk N, Altinors N. Characterization of the Anatomic Location of the Pituitary Stalk and Its Relationship to the Dorsum Sellae, Tuberculum Sellae and Chiasmatic Cistern. J Korean Neurosurg Soc. 2010;47(3):169-73. doi:10.3340/jkns.2010.47.3.169 - Pubmed
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- Adamantinomatous craniopharyngioma
- Diaphragma sellae
- Wilbrand knee (optic radiation)
- Medical abbreviations and acronyms (O)
- Lymphocytic hypophysitis
- Pituitary fossa
- Pituitary lymphoma
- Pituitary apoplexy
- Non-decussating retinal-fugal fibre syndrome
- Hypothalamus
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- Pituitary MRI (an approach)
- Pituitary metastasis
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- Rathke cleft cyst
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- Tuberculum sellae meningioma
- Optic nerve glioma (pilocytic astrocytoma) - neurofibromatosis type 1
- Intracranial epidermoid cyst
- Bilateral cavernous segments internal carotid artery aneurysms
- Pituitary macroadenoma with apoplexy
- Normal MRI orbits
- Tuberculum sellae meningioma
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- Anterior clinoid process meningioma
- Trigeminal schwannoma
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- Optic nerve and chiasm (Gray's illustration)
- Anophthalmia
- Pituitary xanthogranuloma
- Planum sphenoidale meningioma
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- Hypothalamitis regression after steroid administration
- Neurofibromatosis type 1 - with optic pathway gliomas
- Optic pathway glioma
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