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 etiology is Meningiomas.
What is meant by bitemporal hemianopia?
Bitemporal hemianopsia (or bitemporal hemianopia) describes the ocular defect that leads to impaired peripheral vision in the outer temporal halves of the visual field of each eye.
What is the most common cause of Bitemporal Hemianopsia?
Lesions of the chiasm lead to bitemporal hemianopsia; the most common causes are pituitary adenoma, craniopharyngioma, meningioma, hypothalamic glioma, ectopic pinealoma or dysgerminoma, and metastases. Homonymous hemianopsia is the result of a tumor in the contralateral occipital cortex or optic tract.
What is bilateral bitemporal hemianopia?
Bitemporal hemianopia (bi-: both eyes, temporal: temporal/peripheral, hemi-: half, anopsia: blindness) is defect in visual pathway causing loss of sight in the outer half of the visual field. A lesion compressing or disrupting optic chiasm would result in bitemporal hemianopia.
Why does pituitary tumors cause bitemporal hemianopia?
A pituitary tumor frequently causes bitemporal hemianopia by compressing the optic chiasm initially. Visual field defects are thought to be due to the direct compression or the effect on the blood supply of the optic chiasm.
Is bitemporal hemianopia tunnel vision?
Bitemporal hemianopsia (tunnel vision) is a type partial blindness affecting the lateral halves of vision in both eyes (see attached diagram), and is usually associated with lesions or compression of the optic chiasm.
What does Bitemporal mean?
Medical Definition of bitemporal : relating to, involving, or joining the two temporal bones or the areas that they occupy.
What does Bitemporal hemianopia look like?
Why is macular sparing?
Causes. The favored explanation for why the center visual field is preserved after large hemispheric lesions is that the macular regions of the cortex have a double vascular supply from the middle cerebral artery (MCA) and the posterior cerebral artery (PCA).
What causes Bitemporal upper Quadrantanopia?
Homonymous superior quadrantanopia is caused by damage to the contralateral inferior parts of the posterior visual pathway: the inferior optic radiation (temporal Meyer loop), or the inferior part of the occipital visual cortex below the calcarine fissure.
What is the optic chiasm?
The place in the brain where some of the optic nerve fibers coming from one eye cross optic nerve fibers from the other eye. Also called optic chiasm.
How do you access the pituitary gland?
To reach the pituitary, the surgeon opens the boney walls of the sphenoid sinus with small surgical chisels, drills, or other instruments depending on the thickness of the bone and sinus. Small tools and a microscope are used to remove the tumor.
Why does optic chiasm lesion caused Bitemporal hemianopia?
When there is compression at optic chiasm, the visual impulse from both nasal retina are affected, leading to inability to view the temporal, or peripheral, vision. This phenomenon is known as bitemporal hemianopsia.
What is the difference between pituitary adenoma and craniopharyngioma?
However, pituitary adenomas and craniopharyngiomas differ from each other, as follows: 1) pituitary adenomas are the third most common type of intracranial tumor and represent a significant proportion of brain tumors affecting humans and approximately 80% of sellar lesions, whereas craniopharyngiomas represent only 1 …
What is a Heteronymous Hemianopsia?
Heteronymous hemianopia. This is the area in your brain where the optic nerves cross and form an X. The two types of heteronymous hemianopia are bitemporal and binasal. Bitemporal hemianopia is when you lose vision in the outer half of each eye.
What is Nelson syndrome?
Nelson syndrome is a disorder characterized by abnormal hormone secretion, enlargement of the pituitary gland (hypophysis), and the development of large and invasive growths known as adenomas. It occurs in an estimated 15 to 25 percent of people who undergo surgical removal of the adrenal glands for Cushing disease.
What are the symptoms of pituitary Microadenoma?
Symptoms of a pituitary microadenoma may include the following:
- Vision problems.
- Menstrual or breast changes.
- Unexplained hair growth or loss.
What is Macroadenoma?
A macroadenoma is a tumor that typically develops in the pituitary gland, a pea-sized organ behind the eyes. They are almost always noncancerous.
What is the optic tract?
The optic tract is a bundle of nerve fibers that serves to carry visual information from the optic chiasm to the left and right lateral geniculate bodies as a part of the visual pathway.
What can compress optic chiasm?
Lesions that may compress the visual chiasm include pituitary adenoma, craniopharyngioma, and meningioma. Of these, pituitary adenoma is the third most common intracranial tumour in Japanese national statistics, and it is also common in other countries, accounting for 12%15% of all intracranial tumors6 8.
What is automated perimetry?
Automated perimetry is one product of the computer revolution that has had a dramatic impact on the practice of ophthalmology, affecting the quality of both the perimetric test (perimetric technique) and the interpretation of the test results.
What is temporal and Bitemporal relation?
In this definition, bi refers to the capture of exactly two temporal aspects. An alternative definition states that a bitemporal relation captures one or more valid times and one or more transaction times. In this definition, bi refers to the existence of exactly two types of times.
What is Bitemporal narrowing?
A ridge on the top of the head can usually be felt through the scalp. When this suture closes early, the baby begins to have an elongation of the head from front to back (scaphocephaly) with narrowing of the temple region (bitemporal narrowing).
What is Bitemporal epilepsy?
Bitemporal epilepsy is a difficult problem, especially when the epilepsy originates in the hippocampus. The diagnosis of bitemporal epilepsy is mostly reached after some form of invasive monitoring. There are now four standard surgical epilepsy treatments available to patients.
Where are the optic nerves?
The optic nerve begins at the optic disk, a structure that is 1.5 mm (0.06 inch) in diameter and is located at the back of the eye. The optic disk forms from the convergence of ganglion cell output axons as they pass out of the eye.
What is right temporal hemianopia?
Right homonymous hemianopia is a loss of vision in the temporal half of the visual field of the right eye and the nasal half of the visual field of the left eye. Common causes are occlusion of the posterior cerebral artery (stroke), trauma and tumours. See macular sparing.
What causes left homonymous hemianopia with macular sparing?
A right occipital lobe infarction causes a left homonymous hemianopsia with macular sparing.
What is macula in retina?
The macula is part of the retina at the back of the eye. It is only about 5mm across but is responsible for our central vision, most of our colour vision and the fine detail of what we see. The macula has a very high concentration of photoreceptor cells the cells that detect light.
What is the blood supply to the macula?
In about 1 out of 5 people, the inner layer of the macula is dually supplied by cilioretinal arteries branching from the posterior ciliary arteries. Retinal blood vessels maintain the blood-retinal barrier due to nonfenestration of the vascular endothelium. Choroidal endothelial vascular cells are fenestrated.
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