Optic nerve glioma is a tumor arising from the glial elements of the optic nerve. Disease may have intraorbital or intracranial localization. It is characterized by a low-symptom onset and gradual development, leading to a progressive decrease in vision and exophthalmos, primary or secondary atrophy of the optic nerve. Pathology is diagnosed by ophthalmological examination (perimetry, visiometry, ophthalmoscopy), X-ray of the skull and CT of the brain. Treatment is carried out mainly by a combination of radiation therapy and surgical removal of the affected area of the optic nerve.
C72.3 Malignant neoplasm of the optic nerve
According to various data, disease accounts for up to 35% of all eye socket tumors. It can be localized at any site along the entire length of the optic nerve. The optic nerve glioma localized within the orbit is called intraorbital and belongs to clinical ophthalmology. Glioma located in the cranial part of the optic nerve is called intracranial. Specialists in the field of neurology and neurosurgery are engaged in its diagnosis and treatment. When the tumor is located in the area of the visual intersection, it is said about the glioma of the chiasm, when it germinates in the brain tissue — about an intracerebral tumor.
Disease occurs mainly in childhood, most often in the first years of a child’s life. However, recently, cases of its occurrence in persons over 20 years of age have become increasingly described. In some cases, optic nerve glioma occurs in conjunction with Recklinghausen’s neurofibromatosis.
The optic nerve consists of axons surrounded by glial tissue, the cells of which synthesize myelin, provide metabolism and carry a supporting function. It is from glial cells that the optic nerve glioma originates. Most often it develops from astrocytes (astrocytoma), less often from oligodendrogliocytes (oligodendroglioma). In addition to true gliomas, characterized by the proliferation of glial tissue and infiltrative growth, there is a so—called gliomatosis – hyperplasia (increase in size) of glial cells. Some authors believe that gliomatosis is the initial stage of disease.
Starting from glial cells, the pathology sprouts the intervaginal spaces and the surrounding nerve membranes. Its spread occurs mainly along the nerve trunk. As the optic nerve glioma grows, it can reach the size of a chicken egg and lead to complete destruction of the nerve. Cysts with mucous or liquid contents may form inside the tumor.
In the initial stage of its development, optic nerve glioma has practically no clinical manifestations. The earliest sign of its occurrence is a progressive decrease in visual acuity, resulting from compression, and later destruction of nerve fibers by an increasing tumor. However, often in young children, visual impairment remains unnoticed, and in older children they require differentiation from developing myopia. As the optic nerve glioma grows, areas of prolapse (scotomas) appear in the field of vision, there is a progressive extinction of visual function up to complete blindness.
The later clinical manifestations include exophthalmos. It is usually characterized by a gradual increase in the degree of retention of the eyeball and the absence of its lateral displacement. The appearance of a displacement of the eye to the side, as a rule, occurs in the presence of a tumor cyst or an eccentric growth of glioma. It is exophthalmos that is often the reason for going to the doctor in children with optic nerve glioma. With pronounced exophthalmos, there is a restriction of the mobility of the eyeball and incomplete closure of the eye slit, leading to drying of the cornea with the development of keratitis and corneal ulcers. Further development of pathological processes in the cornea can lead to its thinning and perforation, resulting in the loss of the eye.
Intracranial optic nerve glioma is not accompanied by exophthalmos. If it spreads to brain tissue, there is a clinic characteristic of brain glioma (symptoms of hydrocephalus, vestibular ataxia, motor and sensory disorders, etc.). Exophthalmos can be observed in the late stages of intracranial optic nerve glioma, when it grows into the eye socket.
The diagnosis of an optic nerve tumor is established on the basis of clinical data, the results of a study of visual function and fundus, X-ray examination and computed tomography.
Often, the first doctor to whom patients with optic nerve glioma turn is an ophthalmologist. By checking visual acuity, he reveals its decrease, during perimetry and computer perimetry, individual scotomas may be detected in the field of vision. Examination of the fundus (ophthalmoscopy) in the early stages of the development may not reveal the presence of any changes. Later, the stagnant disc of the optic nerve and the pattern characteristic of secondary optic nerve atrophy are determined. There may be thrombosis of the central retinal vein. In cases where the optic nerve glioma sprouts the optic nerve disc, an oval or rounded formation of yellowish-pink or white color is determined during ophthalmoscopy, which can have both a bumpy and smooth surface. With intracranial glioma, primary atrophy of the optic nerve is observed.
Most reliably, optic nerve glioma is diagnosed using CT of the brain, which allows you to visualize a thickened optic nerve, determine the boundaries of tumor growth and its germination into the cranial cavity. If CT is not possible, targeted X-ray of the skull and orbit X-ray are used, which, with intraorbital localization of glioma, reveal unilateral expansion of the orbital cavity and the optic nerve channel, their darkening, thinning of the walls of the orbit.
Optic nerve glioma must be differentiated from optic nerve meningioma, which, unlike glioma, is more common in older people. In the presence of exophthalmos, hyperthyroidism should be excluded. Differential diagnosis is also performed with angioma, neurinoma, retinoblastoma, hemorrhage in the eye socket.
Given the high radiosensitivity of gliomas, treatment can be carried out by irradiating it. Often, radiation therapy leads to a stop in tumor growth and even to an improvement in visual function. In the case of rapidly progressive deterioration of vision, surgical treatment is indicated.
Ophthalmologists and ophthalmologists are engaged in the removal of intraorbital optic nerve glioma. The volume of the operation depends on the degree of tumor growth. Removal of small gliomas is possible by orbitotomy and resection of the affected area of the optic nerve. The germination of glioma to the scleral ring is an indication for enucleation of the eyeball. The most acceptable technique in this case is enucleation with the formation of a supporting stump for subsequent prosthetics of the eye. If the optic nerve glioma grows into the cranial cavity, then the question of the possibility of surgical treatment is decided by a neurosurgeon. The operation is performed in accordance with the general principles of removal of glial brain tumors.
Unfortunately, disease in 100% of cases leads to complete loss of vision. In intraorbital gliomas, the preservation of the eye is an important issue, and in the case of adequate treatment, the prognosis for life is usually favorable. In intracranial gliomas, the prognosis for life depends on the prevalence of the tumor process and the timeliness of the treatment. According to some data, up to 50% of patients die in situations when the optic nerve glioma spreads to the area of the optic intersection.