ANALYSIS OF CHANGES IN THE FIELD OF VISION IN PATIENTS WITH BRAIN
TUMORS Aliev M.A.
Aliev Mansur Abdukholikovich - PhD, DEPARTMENT OF NEUROSURGERY, SAMARKAND STATE MEDICAL UNIVERSITY, SAMARKAND, REPUBLIC OF UZBEKISTAN
Abstract: it is known that optic recess is located in that part of the optic chiasm where the papillomacular 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. Key words: brain tumors, hydrocephalus, intracranial pressure.
Due to a number of negative factors, both in nature 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, 18].
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 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.
The results of the study. The peripheral field of vision was studied in 136 patients with brain tumors. The constriction of vision field — a concentric or bitemporal bias - was observed in 46 (33,8%) patients out of 83 with congestive optic nerve discs. Various visual field damages in the form of a concentric constriction or irregular constriction along the entire meridian with the presence of blind spot (scotoma) were observed in 22 (16,2%) patients with the development of secondary optic nerves atrophy with absence of congestion of ocular fundus, bitemporal visual field constriction was observed in 8 patients (5,9%).
Under the examination of the central field of vision, changes were found in 71 (52,2%) patients with congestion in the ocular fundus. The pattern of changes were following: alteration on the type of bitemporal hemianoptic scotoma - 49 (36%) patients: central homonymous hemianoptic scotoma - 12 (8,8%) patients: central binasal hemianoptic scotoma - 2 (1,5%) patients: asymmetry of disorders when there was an alteration in one eye, and were absent in the other 8 (5,9%) 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 of vision 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 of vision was changed in 8 patients (5,9%).
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.
Conclusion:
1. The alteration of visual 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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