Opticochiasmal arachnoiditis: causes, symptoms, diagnosis, treatment

Opticochiasmal arachnoiditis is essentially an intracranial complication of an infection that penetrates the basal membranes of the brain that surround the optic chiasm. The most common cause of opticochiasmal arachnoiditis is a sluggish inflammatory process in the sphenoid sinus.

Contributing factors are abnormalities in the relationship between these sinuses and the optic canals. Optico-chiasmatic arachnoiditis, according to A.S. Kiseleva et al. (1994), is the most common form of arachnoiditis of the base of the brain, the clinical picture of which is dominated by visual impairment. Optico-chiasmatic arachnoiditis is characterized by a diffuse productive process in the basal membranes of the brain and adjacent areas of the brain tissue with a predominant lesion of the basal cisterns of the brain, the membranes of the optic nerves and the optic chiasm. Thus, the concept of optico-chiasmatic arachnoiditis combines two nosological forms - retrobulbar neuritis and optic neuritis proper in the area of their chiasm, and in this variant, the primary pathological process is arachnoiditis, and the secondary is optic neuritis.

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What causes optochiasmal arachnoiditis?

According to many authors, optic-chiasmatic arachnoiditis is a polyetiological disease, among which are such diseases as general infections, diseases of the paranasal sinuses, traumatic brain injury, family predisposition, etc. According to O.N. Sokolova et al. (1990), from 58 to 78% of all cases of optic-chiasmatic arachnoiditis are caused by infectious-allergic processes with predominant involvement of the paranasal sinuses.

The polyetiology of optic-chiasmatic arachnoiditis determines the diversity of pathological forms in which this disease manifests itself, as well as the pathological processes underlying it. Great importance in this regard is given to allergies, autoimmune processes, traumatic brain injury, the presence of a focal infection, for one reason or another having access to the meninges of the base of the skull. The result of the action of these factors is the occurrence of inflammatory proliferative-productive processes in the membranes of the brain and cerebrospinal fluid, which are both a nutrient medium and a protective barrier for the brain. Changes in metabolism in these environments contribute to the occurrence of sensitization to the resulting catabolites (autoantigens), disrupting intracellular metabolism and leading to the disintegration of nerve cells. The products of the disintegration of the substance and membranes of the brain close the vicious circle, intensifying the general pathological process, sometimes bringing it to a state of irreversibility. Since the main allergic processes develop in the arachnoid membrane, it can be considered the main substrate on which the pathogenetic mechanisms of optic-chiasmatic arachnoiditis arise and develop.

The occurrence of cerebral arachnoiditis is closely related to the state of the body's immune system. Thus, N.S. Blagoveshchenskaya et al. (1988) established that rhinogenic cerebral arachnoiditis is accompanied by significant changes in the immunological indices of cellular and humoral immunity, accompanied by secondary immune depression or immunodeficiency. Viral infection plays a major role in this. Thus, it was established that damage to the nervous system can occur not only in acute influenza, but also as a result of its subclinical forms, expressed in the prolonged presence of the virus in the cerebrospinal fluid. According to V.S. Lobzin (1983), it is the latter fact that causes the occurrence of so-called fibrosing arachnoiditis, which can play a decisive role in the occurrence of optic-chiasmatic arachnoiditis of "unclear etiology".

According to many authors, a certain significance in the development of optic-chiasmatic arachnoiditis may be a hereditary predisposition to this disease, or its specific form in the form of Leber's syndrome - bilateral decrease in visual acuity, central scotoma, swelling of the optic disc with subsequent complete atrophy of the optic nerves.

Symptoms of Optico-chiasmatic Arachnoiditis

The main symptom of optic-chiasmatic arachnoiditis is a sharp, often rapidly occurring visual impairment in both eyes, caused by bitemporal hemianopsia, characteristic of damage to the central part of the optic chiasm. Along with decreased visual acuity and changes in its fields, with optic-chiasmatic arachnoiditis, color perception is also impaired, especially for red and green colors. With optic-chiasmatic arachnoiditis, there are almost always some signs of inflammation in the fundus.

Optico-chiasmatic arachnoiditis is often accompanied by unexpressed neurological and endocrine symptoms. Periodically, there is a weak or moderate headache, some diencephalic, hypothalamic and pituitary symptoms, such as increased thirst, sweating, subfebrile temperature, carbohydrate metabolism disorder, rhythmicity in alternating sleep and wakefulness, etc. Increased headaches indicate further spread of the inflammatory productive-proliferative process to the membranes of the brain with the formation of adhesions and cysts in them, disrupting cerebrospinal fluid dynamics. In this case, an increase in intracranial pressure may also occur.

Diagnosis of optic-chiasmatic arachnoiditis

Diagnostics, as a rule, is difficult at the initial stage of optic-chiasmatic arachnoiditis. However, suspicion of the presence of optic-chiasmatic arachnoiditis should be raised by a complaint of a patient suffering from any form of inflammatory process in the paranasal sinuses about decreased visual acuity and "volume". Such a patient should urgently undergo a thorough comprehensive otolaryngological, ophthalmological and neurological examination. During general X-ray craniography, signs of increased intracranial pressure can be detected, and during X-ray, CT, MRI of the paranasal sinuses - the presence of pathological changes in them, among which even a small parietal edema of the mucous membrane of the sphenoid sinus or a slight veil of the posterior cells of the ethmoid labyrinth are significant for establishing the diagnosis of optic-chiasmatic arachnoiditis. The most valuable diagnostic method is pneumocisternography, which can detect cystic-adhesive process in the area of basal cisterns of the brain, including the optic chiasm cistern, when damaged it is either not completely filled with air or is excessively expanded. The CT method allows to detect deformations of various parts of the subarachnoid space, arising due to the formation of cysts and adhesions in the chiasm cistern, as well as the presence of hydrocephalus, and MRI - structural changes in brain tissue.

Differential diagnostics of optic-chiasmal arachnoiditis is performed with tumors of the pituitary gland and chiasmal-sellar region, in which the most common symptom, as in optic-chiasmal arachnoiditis, is bitemporal hemianopsia. For hemiapsias of tumor origin, in contrast to optic-chiasmal arachnoiditis, their contours are clear and the appearance of a central scotoma is not typical. Optic-chiasmal arachnoiditis is also differentiated from aneurysms of the vessels of the arterial circle of the brain located above the sphenoid sinus, in which paracentral hemianopsia may be observed. These changes in the visual fields can be difficult to distinguish from paracentral scotomas, which occur in 80-87% of cases of optic-chiasmal arachnoiditis. Optico-chiasmatic arachnoiditis in the acute stage should also be differentiated from thromboembolism of the cavernous sinus and other space-occupying processes in the area of the optic chiasm and the base of the skull.

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Treatment of optic-chiasmatic arachnoiditis

Treatment methods for patients with optic-chiasmatic arachnoiditis are determined by its etiology, localization of the primary infection site, stage of the disease, depth of pathomorphological changes both in the structure of the optic nerves themselves and in the tissues surrounding the optic chiasm, general condition of the body, its specific (immune) and non-specific resistance. As a rule, non-surgical treatment is used in the debut stage of the disease; if there is no effect or if the primary infection site is determined, non-surgical treatment is combined with surgical treatment, for example, in chronic ethmoiditis or sphenoiditis - opening of the indicated sinuses and elimination of pathological contents.

Non-surgical treatment in the acute stage: antibiotics, sulfonamides, desensitizing drugs, immunocorrectors and immunomodulators, dehydration methods, angion protectors, antigynoxants, B vitamins, neurotropic agents. The use of biostimulants, steroid drugs and proteolytics in the acute stage is not recommended due to the risk of generalization of the process. These agents are used in the chronic stage or in the postoperative period, when effective outflow from the sinus is established. Their use is indicated to prevent intensive scarring of tissues in the area of surgical intervention. To achieve a greater effect, some authors recommend intracarotid administration of appropriate antibiotics.

When positive dynamics are achieved, along with continuation of complex anti-inflammatory treatment, it is advisable to prescribe neuroprotectors and drugs that improve nerve conduction. Positive results were obtained from the use of the method of transcutaneous electrical stimulation of the optic nerves. Promising methods of non-surgical treatment of optic-chiasmal arachnoiditis are HBO and methods of extracorporeal therapy, in particular plasmapheresis, UFO-autohemotherapy.

In chronic optic-chiasmatic arachnoiditis, it is advisable to use complex-action proteolytic enzymes to dissolve adhesions in the optic-chiasmatic region. These include lekozyme, which contains active proteolytic substances of papaya, chymopapain, lysozyme, and a set of proteinases.

If drug treatment is ineffective, some authors recommend using X-ray therapy focused on the optic-chiasmal region, and introducing air into the subarachnoid region. In general, with non-surgical treatment of patients with optic-chiasmal arachnoiditis, vision improves in 45% of cases; the remaining patients face the question of surgical treatment, otherwise they are doomed to progressive deterioration of visual acuity, even to blindness. According to various authors, as a result of surgical treatment for various forms of optic-chiasmal arachnoiditis, on average 25% of patients with visual impairment experience improvement of vision, of which 50% have partial labor rehabilitation. The optimal period for surgical treatment is the first 3-6 months after the onset of visual acuity decline, since during this period it already becomes clear whether non-surgical treatment is effective or not. Neurosurgical treatment is usually performed on patients with visual acuity below 0.1. The goal of the operation is to free the optic nerves and optic chiasm from arachnoid adhesions and cysts.

Surgical treatment of optic-chiasmatic arachnoiditis. In the complex treatment of patients with optic-chiasmatic arachnoiditis, it is important to sanitize chronic foci of infection. There are two points of view regarding the sanitization of the paranasal sinuses. According to the first, all paranasal sinuses in which even the slightest indication of a pathological process is suspected should be opened. In such cases, L.S. Kiselev et al. (1994) recommend performing polysinusotomy by endonasal opening of the ethmoid labyrinth, the maxillary sinus through the middle nasal passage, and the sphenoid sinus transseptally. According to the second point of view, only those paranasal sinuses in which signs of purulent inflammation are detected should be opened. The experience of recent years shows that preference should be given to preventive opening of all paranasal sinuses even in the absence of signs of any form of inflammation. The benefits of this method are evidenced by the fact that even opening of the obviously normal sphenoid sinus and other paranasal sinuses leads to an improvement in vision. Probably, this is due not only to an accidental "hit" in a latent focus of infection, but also to the unloading humoral effect resulting from the occurrence of inevitable bleeding during the operation, interruption of the hemato- and lymphogenous routes of infection circulation, destruction of barriers that cause congestion in the optic-chiasmal region.

In the postoperative period, patients are prescribed antibacterial, dehydration and desensitizing therapy, proteolytic enzymes and complex antineuritic treatment. After careful hemostasis, the sinuses are loosely tamponed using tampons soaked in a suspension of the appropriate antibiotic and sulfanilamide in sterile vaseline oil. The next day, some of the most easily extracted tampons are removed, the rest are removed after 2 days. Subsequently, the sinuses are washed with various antiseptics followed by the introduction of various agents that accelerate the epithelialization of the sinus and minimize scarring of its inner surface. The main non-surgical treatment for optic-chiasmatic arachnoiditis, carried out by ophthalmologists, begins 3-4 weeks after surgery on the paranasal sinuses. However, in our opinion, it should begin 2-3 days after the removal of the last tampons from the operated sinuses.