Optic neuritis is an inflammatory lesion of the optic nerve. Also, this disease includes nerve lesions in demyelinating diseases. Intra- and retrobulbar neuritis are distinguished within the framework of optical neuritis, which differ significantly in the ophthalmoscopic picture. Common symptoms are: decreased vision and the appearance of cattle; in some forms, pain in the eye is possible. Ophthalmoscopy plays a primary role in the diagnosis. Treatment is based on a combination of methods of decongestant, anti-inflammatory, desensitizing, antibacterial or antiviral, immunocorregulating, detoxification and metabolic therapy.
ICD 10
H46 Optic neuritis
General information
The optic nerve (n. opticus) consists of processes (axons) of retinal neurons. The latter perceive the image and transmit information about it in the form of nerve impulses traveling along the axons to the cerebral visual centers. Each optic nerve consists of more than 1 million axons. It begins with the disc of the optic nerve located on the retina and accessible to ophthalmological examination. The part of the n. opticus located inside the eye socket is called intrabulbar (intraocular). After leaving the orbit, the optic nerve passes into the cranial cavity, this part of it is called retrobulbar. In the area of the Turkish saddle, there is an intersection of the optic nerves (chiasm), where they partially exchange their fibers. The optic nerves end in the visual centers of the middle and intermediate brain.
Throughout, the optic nerve is enveloped in membranes that are closely connected to the nearby structures of the orbit and brain, as well as with the cerebral membranes. This causes the frequent occurrence of optic neuritis in inflammatory diseases of the eye socket, brain and its membranes.
Causes
Among the factors provoking optic neuritis, the most common are inflammatory processes of the orbit (periostitis, phlegmon), eyeball (iridocyclitis, retinitis, keratitis, panophthalmitis) and brain (arachnoiditis, meningitis, encephalitis); infectious processes in the nasopharynx (ethmoiditis, sinusitis, frontitis, chronic tonsillitis, angina, pharyngitis). Common infections can lead to the development of optic neuritis: tuberculosis, malaria, typhus, brucellosis, ARVI, diphtheria, gonorrhea, etc. Other causes include alcoholism, TBI, complicated pregnancy, systemic diseases (gout, collagenosis), blood diseases, diabetes mellitus, autoimmune disorders. Optic neuritis often manifests in multiple sclerosis.
Pathogenesis
Inflammatory process (neuritis) it can develop both in the membranes of the optic nerve and in its trunk. At the same time, inflammatory edema and infiltration lead to compression of the visual fibers with their subsequent degeneration, which is the reason for the decrease in visual acuity. After the acute inflammation subsides, some fibers can restore their function, which is clinically manifested by improved vision. Severe course of optic neuritis often leads to the breakdown of nerve fibers and the proliferation of glial tissue in their place. Optic nerve atrophy develops with an irreversible drop in visual acuity.
In multiple sclerosis, neuritis is based on the process of demyelination of nerve fibers — the destruction of their myelin sheath. Although demyelination is not an inflammatory process, in the medical literature and in practice, the demyelinating lesion of N. opticus is attributed to retrobulbar neuritis, since their clinical symptoms are identical.
Classification
Optic neuritis can be classified depending on its etiology and localization of the lesion. In connection with the etiological factor, infectious, parainfectious, demyelinating, ischemic, toxic and autoimmune neuritis are distinguished. Parainfective include optic neuritis, which are the result of vaccination or a viral infection. Ischemic neuritis can occur as a result of ACVA. The classic type of toxic neuritis of the optic nerve is its defeat by poisoning with methyl alcohol.
Intrabulbar and retrobulbar optic neuritis are distinguished by the site of the lesion of N. opticus. Intrabulbar neuritis (papillitis) occurs with changes in the optic disc and is the most common form of optic neuritis in children. The combination of papillitis with damage to the retinal nerve fiber layer is classified as neuroretinitis. The latter is quite rare and may be a consequence of viral diseases, cat scratch disease, Lyme disease and syphilis. Retrobulbar neuritis is spoken of when the optic nerve is affected after its exit from orbit. It is most often associated with multiple sclerosis. With retrobulbar neuritis, ophthalmoscopy does not reveal changes on the part of the optic disc, they can appear only in the later stages of the disease when the process spreads to the intraocular part of the nerve. Due to the spread of inflammatory and degenerative changes of N. opticus in the course of the disease, the division of neuritis into intra- and retrobulbar is very conditional.
Symptoms of intrabulbar neuritis
Typically acute occurrence of visual disturbances. Their severity and nature depend on the degree of damage to the diameter of the optic nerve. With a total process, visual acuity drops down to complete blindness (amaurosis). With partial — visual acuity can be maintained even at the level of 1.0. However, spots appear in the field of vision — paracentral or central scotomas having an arc-like or rounded shape; there is a decrease in color perception and dark adaptation, a low level of lability of the optic nerve and the critical frequency of fusion of flickers.
From the first days of the existence of neuritis, a pathognomonic picture of changes in the optic nerve disc is revealed: hyperemia, blurred borders, exudative swelling, moderate vasodilation, the presence of dashed hemorrhages in the tissue of the disc and near-disc area. If the exudate fills the vascular funnel and inhibits the adjacent layers of the vitreous body, then the fundus is not clearly visualized. Unlike stagnant discs associated with intracranial hypertension and hydrocephalus, with optic neuritis there is no pronounced protrusion (prominence) of the disc, the changes are usually unilateral.
The acute period lasts from 3 to 5 weeks. Then the hyperemia and swelling of the disc gradually pass, the hemorrhages resolve, the boundaries of the disc again acquire clear outlines. In more rare cases, with severe course of optic neuritis, atrophy of the n. opticus occurs. In this case, ophthalmoscopy reveals a pale disc with filiformly narrowed vessels and clear boundaries.
Symptoms of retrobulbar neuritis
In the clinic of the retrobulbar form of optic neuritis, there are 3 types of inflammatory changes: axial, peripheral and transversal.
Axial inflammation mainly affects the bundle of axons passing through the optic nerve. It is characterized by a disorder of central vision with the formation of central cattle in the field of vision and a significant decrease in functional tests.
The peripheral type of retrobulbar neuritis is associated with the occurrence of an inflammatory process in the nerve membranes and its subsequent spread deep into the nerve trunk. At the same time, there is a significant accumulation of exudate under the membranes of the optic nerve, causing the appearance in patients of so-called “shell” pain in the eye, increasing with the movement of the eyeball. Typically, a concentric narrowing of the visual fields with the preservation of central vision. The results of functional testing may be within normal limits.
The most severe is the transversal type of retrobulbar neuritis, in which inflammation covers all the tissues of the optic nerve. Visual acuity decreases to blindness. Functional tests show extremely low results.
All types of retrobulbar neuritis are characterized by the absence of changes in the optic disc. Only a month after the manifestation of the disease during ophthalmoscopy, disc decoloration, signs of total or partial atrophy of the optic nerve can be determined.
Diagnostics
Since optic neuritis is an interdisciplinary pathology, its diagnosis often requires the joint participation of specialists in the field of neurology and ophthalmology. In typical cases, an ophthalmologist’s consultation is sufficient to verify the diagnosis, during which the patient’s complaints, visual acuity test data, results of perimetry and ophthalmoscopy are compared.
The most important task is to differentiate disc changes in optical neuritis from a stagnant disc. This is especially true with a mild course of neuritis with minimal disorders of visual function and with a combination of neuritis with swelling of the disc. In such cases, the detection of foci of exudation and small hemorrhages in the disc tissue indicates in favor of neuritis. Fluorescent angiography of the fundus helps to distinguish these conditions. To exclude a stagnant disk in difficult cases, a neurologist’s consultation, echo-encephalography, lumbar puncture may be required.
In order to determine the etiology of optical neuritis, it is possible to conduct MRI of the brain, blood culture for sterility, PCR studies, ELISA, RPR test, consultation of an infectious disease specialist, rheumatologist, immunologist, etc.
Treatment and prognosis
Etiotropic therapy is determined by the cause of the development of neuritis. Treatment is carried out urgently in a hospital setting. Before the etiology of the disease is established, anti-inflammatory, dehydration, antibacterial, metabolic, desensitizing and immunocorrective treatment is usually used. Prescribe broad-spectrum antibiotics (except for the aminoglycoside group), corticosteroids, acetazolamide with potassium preparations, intravenous glucose infusions, intramuscular administration of magnesium sulfate, piracetam, vitamins of group B. After establishing the nature of the lesion of the optic nerve, they proceed to specific etiotropic therapy (for example, anti-tuberculosis treatment, surgical treatment of tonsillitis and sinusitis).
Emergency therapy in the event of optical neuritis against the background of methyl alcohol poisoning consists in urgent gastric lavage and giving the patient 30% ethyl alcohol (vodka) inside. The latter acts as an antidote, displacing methyl alcohol from the body. A single dose is 100g and is administered every 2-3 hours.
If signs of optic nerve atrophy are detected, antispasmodics and drugs to improve microcirculation (nicergoline, pentoxifylline, nicotinamide, nicotinic acid) are additionally recommended. The outcome of both intra- and retrobulbar forms of optic neuritis depends on the type and severity of the lesion. It varies from complete restoration of visual function to the development of atrophy and amaurosis.