Cortical blindness is a complete lack of vision caused by damage to the occipital lobes of the brain. It is manifested by a violation of visual perception with a preserved reaction of the pupils to light. With the congenital variant of the disease, there are difficulties in the development of speech and motor activity in the child. Visometry, perimetry, ophthalmoscopy, CT of the head, electroencephalography, echoencephalography are used for diagnostics. Etiotropic therapy is reduced to the elimination of the underlying disease. Drug treatment is indicated for malignant hypertension, encephalopathy. Surgical intervention is used for arteriovenous malformations.
Cortical blindness was first described by the Spanish ophthalmologist Marquis in 1934. The prevalence of pathology in the general structure of blindness is 5-7%. In 48% of patients, the etiology of the disease is associated with prenatal damage to the central nervous system. In children under 3 years of age, postgenicular visual lesions are most often the cause. In encephalopathy, damage to the organ of vision is observed in 15-20% of cases. Paroxysmal type occurs in 63% of patients, while permanent type occurs in 37%. Pathology can develop at any age. Men and women get sick with the same frequency. Geographical features of distribution are not described.
The disease often occurs sporadically. The development of the congenital form is potentiated by intrauterine hypoxia, toxemia of pregnant women, brain damage by viral agents during infection of the fetus during pregnancy. The etiology of the acquired form is due to:
- Hypoxic-ischemic encephalopathy. Insufficient number of anastomoses between the cortical branches of the middle and posterior cerebral arteries in the occipital cortex leads to ischemia of this area. Hypoxic changes lead to a violation of central (macular) vision.
- Malignant arterial hypertension . With an increase in blood pressure above 220/130 mmHg, edema of the optic nerve disc occurs with the formation of multiple zones of hemorrhage and exudation on the fundus, however, blindness of central genesis can occur only with an increase in the clinic of hypertensive encephalopathy.
- Progressive multifocal leukoencephalopathy (PML). PML is a rapidly progressive demyelinating pathology of the central nervous system, in which there is an asymmetric lesion of the cortex. This disease more often causes the development of hemianopia, less often – complete cortical blindness.
- Arteriovenous malformations (AVM). Against the background of pathological changes in blood vessels, hemorrhages occur in the brain tissue. The organization of a blood clot entails irreversible changes in the lesion area. When the bleeding zone spreads to the occipital lobe, vision loss occurs.
- Pathological neoplasms. When the volume formations are localized in the occipital lobe, the destruction of the neural network with irreversible visual dysfunction occurs.
- Head injury. Cortical blindness develops with traumatic injuries in the visual cortex.
- A sharp increase in intracranial pressure. Intracranial hypertension leads to compression of brain structures and temporary visual dysfunction.
Cortical blindness occurs only in the case of a total lesion of the occipital region of the cerebral cortex. Additionally, the visual radiance of Graziole may be involved in the pathological process. With unilateral damage to the occipital lobe, a congruent central scotoma appears. Color agnosia is characteristic of an isolated pathology with localization in the zone of the occipital lobe of the left hemisphere. The function of the macular divisions is not impaired. Bilateral lesion leads to complete blindness, which is often accompanied by achromatopsia, apraxia of friendly eye movements. With concomitant damage to the speech centers, dysphasia develops.
In most cases, cerebral blindness is an acquired pathology. Congenital cases are extremely rare. The clinical classification includes the following forms of the disease:
- Permanent. The most common option. It develops with irreversible lesions of brain structures due to hemorrhagic stroke.
- Paroxysmal. This is reversible blindness, which is more often observed at a young age. Occurs against the background of metabolic disorders, hypertensive crisis, hydrocephalus.
The first manifestations of pathology are the loss of individual areas from the field of view. Patients complain about the appearance of opacities, “shrouds” in front of their eyes, disorientation in space. Patients cannot direct their gaze towards an object that is located in the peripheral departments. The progression of the pathological process leads to a total violation of visual perception. The pupillary response to light is preserved because the neural pathways from the retina to the brain stem function normally. Patients note that when looking at the light source, there is no reflex closing of the eyelids. Patients respond to a loud sound by turning their heads and moving their eyes towards the source of irritation. In children with a congenital form of cortical blindness, a common concomitant manifestation is dysphasia (speech formation disorder).
If visual dysfunction is combined with an inability to distinguish colors and shades, this indicates a unilateral lesion. With the development of the disease against the background of functional lesions of the cortex, the symptoms regress independently. Visual acuity is restored after 3-4 days. First, light perception occurs, then object vision, then patients note the regeneration of the color perception function. The disease is isolated in nature. In rare cases, concomitant cortical disorders are observed in the form of alexia (inability to understand written text), hemichromatopsia (loss of color sensitivity in one half of the visual field). Also, patients complain of memory disorders, unilateral muscle weakness (hemiparesis). With extensive damage to the brain tissue, concomitant neurological symptoms are revealed.
The congenital variant of the disease is complicated by a delay in the formation of motor skills and conversational speech. When pathology occurs in adulthood, adaptation of the patient in the social environment is sharply difficult. Patients with cortical blindness have a high risk of developing vestibulopathy. Complications of cerebral blindness are largely determined by the nature of the background disease. With the hypertensive etiology of the disease, there is a high probability of hemorrhages in the anterior chamber of the eye or vitreous. With multifocal leukoencephalopathy, the spread of infection to nearby areas leads to memory loss, speech disorders, and motor disorders.
The diagnosis is based on anamnesis data and the results of specific examination methods. Cortical blindness is supported by such anamnestic information as the connection of the first manifestations of the disease with traumatic injuries, brain infections, and increased blood pressure. Instrumental diagnostics is based on the following:
- Ophthalmoscopy. When examining the fundus, pathological changes are detected only with the hypertensive nature of the disease. Edema of the optic nerve disc, local hemorrhage zones on the inner shell are visually determined.
- Visometry. In the initial stages, visual acuity is slightly reduced. The progression of pathology leads to amaurosis.
- Perimetry. It allows to identify defects of the visual field in the form of concentric narrowing or loss of individual halves at the initial stages of pathogenesis. At the terminal stage, peripheral vision is absent.
- CT of the head. Computed tomography is used to visualize organic damage to cortical brain centers and pathological neoplasms.
- Electrophysiological examination (EEG). In hypoxic encephalopathy or multifocal leukoencephalopathy, diffuse disorganization of bioelectric activity is detected on the EEG. Epiactivity is uncharacteristic.
- Echoencephalography (Echo-EG). With the development of visual dysfunction in persons with intracranial hypertension or hypertensive encephalopathy, it is possible to diagnose signs of increased intracranial pressure.
Etiotropic therapy is based on the elimination of the underlying disease. Symptomatic treatment has an effect only in the early stages. All patients with a history of hypertension need to monitor their blood pressure. With the malignant nature of the disease, hypotensive therapy is indicated. In ischemic encephalopathy, it is advisable to use pentoxifylline, vinpocetine, nicergoline. Planned surgical intervention is performed for AVM of the brain, as well as for epidural hematoma in patients with traumatic brain injury. The tactics of treatment of cortical blindness in patients with multifocal leukoencephalopathy and congenital forms have not been developed.
Prognosis and prevention
The prognosis for life and work capacity is determined by the nature of damage to brain structures. Visual dysfunction is often irreversible, but in some cases spontaneous remission is observed. There are no specific methods of prevention. Non-specific preventive measures are reduced to the prevention of perinatal pathology, intrauterine hypoxia. Patients suffering from malignant hypertension should be monitored daily blood pressure levels. The development of visual dysfunction in the absence of objective signs of eye damage requires a detailed examination of brain structures.