Demyelination

Demyelination is a pathological process in which myelinated nerve fibers lose their insulating myelinated layer. Myelin, phagocytosed with microglia and macrophages, and later astrocytes, is replaced by a fibrous tissue (plaques). Demyelination disrupts the conduct of the impulse along the conducting paths of the white matter of the brain and spinal cord; peripheral nerves are not affected.

[1], [2], [3], [4], [5], [6], [7], [8], [9]

Demyelinating diseases, which are the cause of eye pathology:

• isolated optic neuritis with the absence of clinical manifestations of generalized demyelination, often developing later;
• Multiple sclerosis is most frequent;
• Devic disease (neuromyelitis optica) is a rare disease that occurs at any age. Characterized by bilateral optical neuritis and the subsequent development of transverse myelitis (demyelination of the spinal cord) within days or weeks;
• Schilder's disease is a very rare, steadily progressing, generalized disease beginning at the age of 10 and leading to death within 1-2 years. Bilateral neuritis of the optic nerve can develop without a prospect of improvement.

[10], [11], [12], [13], [14], [15]

Eye manifestations

• lesions of the visual pathway most often touch the optic nerves and lead to optic neuritis. Demyelination can sometimes occur in the region of the chiasma and very rarely in the visual tracts;
• lesions of the brainstem can lead to internuclear ophthalmoplegia and paralysis of the eye, lesions of the oculomotor, trigeminal and facial nerves and nystagmus.

Communication of optic neuritis with multiple sclerosis. Despite the fact that some patients with optic neuritis do not have a clinically demonstrable associated systemic disease, there is a close relationship between neuritis and multiple sclerosis.

• Patients with optic neuritis and normal brain MRI results have a 16% chance of developing multiple sclerosis within 5 years.
• At the first episode of optical neuritis, approximately 50% of patients with no other symptoms of multiple sclerosis have signs of demyelination according to MRI. These patients have a high risk of developing the symptoms of multiple sclerosis within 5-10 years.
• Signs of optical neuritis can be detected in 70% of cases of established multiple sclerosis.
• In a patient with optic neuritis, the risk of developing multiple sclerosis increases in the winter season, with HLA-OK2-positivity and the phenomenon of UhlolT (increased symptoms with increased body temperature, physical activity or after a hot bath).

[16], [17], [18], [19], [20], [21], [22]

Demyelinating optic neuritis

Appears subacute monocular vision impairment; simultaneous defeat of both eyes is rare. Discomfort in the eye or around it - a common phenomenon, which often increases with movement of the eyeball. Discomfort can precede or accompany visual impairment and usually lasts a few days. Some patients have pain in the frontal region and tenderness of the eyeballs.

Symptoms

• Visual acuity usually between 6/18 and 6/60, occasionally can be reduced to the absence of light perception.
• The disc of the optic nerve is normal in most cases (retrobulbar neuritis); much less often - a picture of papillitis.
• On the paired eye, the pallor of the temporal part of the disc may be noted, indicating the preceding optical neuritis.
• Dyshromatopsia is often more pronounced than could be expected at a given level of visual impairment.
• Other manifestations of optic nerve dysfunction, as described previously.

Defects of the field of view

• Most often there is a diffuse decrease in sensitivity and the limits of the central 30, the next in frequency are altituminal and / or arquate defects and central scotoma.
• Scots are often accompanied by general depression.
• Changes can also be in the field of view of the paired eye, which does not have obvious clinical signs of the disease.

Flow. The restoration of vision usually begins with 2-3 weeks and lasts for 6 months.

Forecast. Approximately 75% of patients have visual acuity restored to 6/9 or more; in 85% of cases recovery to 6/12 or more, even with a decrease in visual acuity during the acute stage before the absence of light perception. Despite the restoration of visual acuity, other visual functions (color vision, contrast and light sensitivity) often remain disturbed. An afferent pupillary defect can persist and atrophy of the optic nerve develop, especially if the disease recurs.

Treatment

Indications

• With a moderate loss of vision, treatment is probably unnecessary.
• With a decrease in visual acuity during 1 mild disease> 6/12 treatment may accelerate the recovery period by several weeks. This is important in the case of acute bilateral injuries, which is rare, or with poor eyesight of the pair eye.

Mode

Intravenous administration of sodium succinate methylprednisolone 1 g per day for 3 days, then - prednisolone inside 1 mg / kg per
day 11 days.

Efficiency

• The delay in the development of further neurological manifestations, characteristic of multiple sclerosis, for 2 years.
• Acceleration of vision recovery with optical neuritis, but not up to the original level.

Oral monotherapy with steroids is contraindicated. Since does not bring benefits and doubles the frequency of relapses of optic neuritis. Intramuscular injection of interferon beta-la during the first episode of optic neuritis is useful for weakening clinical manifestations of demyelination in patients at high risk of developing multiple sclerosis, determined by the presence of subclinical brain changes no MPT.

[23], [24], [25], [26], [27], [28], [29], [30]