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https://doi.org/10.29013/ESR-19-11.12-35-39
Nabiev Akmal Adkhamjonovich, Assistant of Neurosurgery Department of Samarkand State Medical Institute Aliev Mansur Abdukholikovich, PhD, Assistant of Neurosurgery Department of Samarkand State Medical Institute E-mail: dr.mansoor1982@mail.ru
CHARACTERISTIC FEATURES OF CHANGES IN THE FIELD OF VISION IN PATIENTS WITH BRAIN TUMORS
Abstract. It is known that optic recess is located in that part of the optic chiasm where the pap-illomacular bundle passes with its ceased fibers. The carried out research allows to consider that changes in the central field of vision in posterior cranial fossa tumors with the development of internal hydrocephalus is caused by the direct action of the enlarged optic recess of the third ventricle on the chiasm of the optic nerves.
Keywords: brain tumors, hydrocephalus, intracranial pressure.
Due to a number of negative factors, both in na- earliest signs of the brain tumors is the loss of visual
fields [13; 14; 15].
Aim of the study. Identification of changes in visual fields depending on the location of brain tumors.
Material and methods of the research. We
studied the state of central and peripheral visual fields in 136 patients with brain tumors between 4 to 76 years old, 72 men and 54 women, who received treatment at the Neurosurgery Department of the Samarkand State Medical Institute. From 136 patients, 89(65.4%) had supratentorial and 47(34.6%) of patients had infratentorial localization of the brain tumor. All patients with the diagnosis of a brain tumor were verified by histological examination.
During the examination were excluded patients with tumor which could directly affect the optic pathway. Study of the peripheral field of vision conducted on projection perimeter. The central field of vision was studied using the LambD-100 device.
ture and in our life, the number of people who suffer from tumors of the central nervous system (CNS) is growing [1; 2; 8; 9]. These circumstances require constant attention to the development of a system for providing medical care to neurosurgical patients, as well as improving the methods of neurosurgical research in the examined patients [1; 2; 6; 7; 10; 16].
Brain tumors are manifested by different signs and present severe form of neurosurgical pathology, which requires early and specific surgical treatment [1; 2; 5; 8; 10]. A clinical progression of brain tumors leads to a significant impairment of brain function [6; 7; 10; 18].
Intracranial pressure rises due to an increase of brain mass caused by brain tumor and perifocal edema or stasis of cerebrospinal liquid because of decreased outflow from the ventricular system, this difficulty in cerebrospinal fluid outflow which underlies the formation of internal obstructive hydrocephalus [3; 4; 6; 9; 11; 12; 17]. One of the
Diagram 1. Distribution of patients by location of brain tumor
The results of the study. The peripheral field of striction or irregular constriction along the entire me-
vision was studied in 136 patients with brain tumors. ridian with the presence ofblind spot (scotoma) were
The constriction of vision field - a concentric or bi- observed in 22(16.2%) patients with the development
temporal bias - was observed in 46(33.8%) patients of secondary optic nerves atrophy with absence of
out of 83 with congestive optic nerve discs. Various congestion of ocular fundus, bitemporal visual field
visual field damages in the form of a concentric con- constriction was observed in 8 patients (5.9%).
Picture 2. Distribution of patients by neurophtalmic alteration
Under the examination of the central field of of bitemporal hemianoptic scotoma - 49(36%) pa-
vision, changes were found in 71(52.2%) patients tients: central homonymous hemianoptic scotoma
with congestion in the ocular fundus. The pattern - 12(8.8%) patients: central binasal hemianoptic
of changes were following: alteration on the type scotoma - 2(1.5%) patients: asymmetry of disorders
when there was an alteration in one eye, and were absent in the other 8(59%) patients: among 32 patients without congestion in the ocular fundus, alterations were found in 9(6.6%) patients.
From 47(34.6%) patients with tumors of the posterior cranial fossa, alteration in the central field ofvi-sion occurred in 38(27.9%). Among 37 patients with tumors of supratentorial localization without (accompanied) internal hydrocephalus, the peripheral visual field was changed in 6 patients (4.4%). The central field ofvision was changed in 8 patients (5.9%).
Thus, in patients with brain tumors which is not accompanied by internal hydrocephalus, alteration in peripheral and central fields of vision were less common.
The studies suggest that changes in the central field of vision in tumors of the posterior cranial fossa with the development of internal hydrocephalus are caused by the direct effect of the expanded ophthalmic bundle of the third ventricle on the chiasm of the optic nerves. It is known that optic recess is located in that part of the optic chiasm where the papillomacular bundle passes with its ceased fibers. Therefore, development of obstructive hydrocephalus is purely mechanical pressure of the fibers protruding optic recess, leading to a violation of their conductivity and then, as a result of compression - violation of microcirculation and ischemia of this area. As our studies have shown, with internal hydrocephalus, the expansion of the optic recess is variable, often asymmetrically. This explains the variability and the asymmetry that occurs in alteration of central vision.
Alteration of the central field of vision in patients with hypertension syndrome due to tumors of the cerebral hemispheres are less common, because in these cases there is an increase of intracranial pressure without occlusion of the ventricular system and the direct effect of the extended optic recess onto chiasm. In case of when these alterations occur, the dislocation of the brain or the direct effect of the tumor to the optic pathways are more important.
Our studies allow us to express certain considerations about the dependence of visual function impairment on the level of pressure of the extended optic recess of the optic chiasm:
- in the initial degree of compression appears depression in the low-temporal parts of the central field of vision:
- in the second degree, a further increase in compression leads to a construction of the peripheral field of vision and the appearance of absolute paracentral scotoma.
- in the third degree ofcompression visual acuity begins to fall, the field ofvision will change even more in the absence of atrophy on the disc of optic nerve:
- in the fourth degree of compression - severe impairment of visual function with the appearance of signs of atrophy on the optic fundus:
- in fifth degree - atrophy of the optic nerves.
In the pathogenesis of the above mentioned disorders factor of compression expanded optic recess of the optic chiasm plays an important role simultaneously with microcirculatory disorder and ischemia of chiasm. At the initial degree of compression, the mechanical factor is crucial and with an increase of internal hydrocephalus - circulatory disturbance and ischemia in the compression zone. Further, altered nerve fibers begins to join, which gradually leads to atrophy of the optic nerves.
Conclusion:
1. The alteration ofvisual fields in brain tumors is determined not by the increase in intracranial pressure, but by the development of obstructive hydrocephalus accompanied by the expansion of the optic recess of the third ventricle by the direct effect of the latter on chiasm.
2. Alterations in the central field of vision in tumors of the posterior cranial fossa are more often observed, having the character of bitemporal hemianopsia. Changes in the peripheral boundaries of the visual fields are observed in more than 55% of patients and have bitemporal or concentric constriction.
3. The impairment of the central field of vision is caused by the extension of the optic recess which effect on the papillomacular bundle conducting in
the dorsocaudal parts of the chiasm, causes both a purely mechanical compression of these structures and the distribution of microcirculation.
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