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Several important structures are located adjacent to the optic chiasm. The supraclinoid branches of the internal carotid artery flank the chiasm. The cavernous sinuses are lateral and inferior to the chiasm. The frontal lobe of the brain lies above. The pituitary gland sits below in the sella turcica.
Bitemporal hemianopsia most commonly occurs as a result of tumors located at the mid-optic chiasm. Since the adjacent structure is the pituitary gland, some common tumors causing compression are pituitary adenomas and craniopharyngiomas. Also, another relatively common neoplastic cause is meningiomas.
The optic chiasm, or optic chiasma is the part of the brain where both optic nerves cross. It is located at the bottom of the brain immediately inferior to the hypothalamus. [7] Signs and symptoms associated with optic chiasm lesions are also known as chiasmal syndrome.
The initial symptoms of pituitary apoplexy are related to the increased pressure in and around the pituitary gland. The most common symptom, in over 95% of cases, is a sudden-onset headache located behind the eyes or around the temples. It is often associated with nausea and vomiting.
Septo-optic dysplasia (SOD), known also as de Morsier syndrome, is a rare congenital malformation syndrome that features a combination of the underdevelopment of the optic nerve, pituitary gland dysfunction, and absence of the septum pellucidum (a midline part of the brain).
The optic chiasm is found in all vertebrates, although in cyclostomes (lampreys and hagfishes), it is located within the brain. [2] [3] This article is about the optic chiasm of vertebrates, which is the best known nerve chiasm, but not every chiasm denotes a crossing of the body midline (e.g., in some invertebrates, see Chiasm (anatomy)).
Damage to the pituitary stalk blocks the release of antidiuretic hormone, resulting in polydipsia (excessive water intake) and polyuria (excessive urination, central diabetes insipidus). The diameter of the pituitary stalk at the level of optic chiasm is 3.3 mm, and at the pituitary gland insertion site is measured at 1.9 mm. [3]
A craniopharyngioma is a rare type of brain tumor derived from pituitary gland embryonic tissue [1] that occurs most commonly in children, but also affects adults. It may present at any age, even in the prenatal and neonatal periods, but peak incidence rates are childhood-onset at 5–14 years and adult-onset at 50–74 years. [2]