Cerebral edema is a rapidly developing accumulation of fluid in the cerebral tissues, leading to death without adequate medical care. The basis of the clinical picture is a gradually or rapidly increasing deterioration of the patient’s condition and deepening of disorders of consciousness, accompanied by meningeal signs and muscular atony. The diagnosis is confirmed by MRI or CT of the brain. Additional examination is carried out to find the cause of edema. Therapy begins with dehydration and maintenance of the metabolism of cerebral tissues, combined with the treatment of causal disease and the appointment of symptomatic drugs. According to the indications, urgent (decompression trepanation, ventriculostomy) or delayed (removal of a volume formation, bypass surgery) surgical treatment is possible.
General information
To date, it has become clear that cerebral edema is not an independent nosological unit, but is a secondary developing pathological process that occurs as a complication of a number of diseases. It should be noted that edema of any other tissues of the body is a fairly common phenomenon that does not relate to urgent conditions at all. In the case of the brain, edema is a life-threatening condition, because, being in a closed space of the skull, cerebral tissues do not have the opportunity to increase in volume and are squeezed. Due to the polyetiological nature of brain edema, both specialists in the field of neurology and neurosurgery, as well as traumatologists, neonatologists, oncologists, and toxicologists face it in their practice.
Causes
Most often, cerebral edema develops with injury or organic damage to its tissues. Such conditions include: severe TBI (brain injury, skull base fracture, intracerebral hematoma, subdural hematoma, diffuse axonal injury, brain surgery), extensive ischemic stroke, hemorrhagic stroke, subarachnoid hemorrhage and ventricular hemorrhage, primary brain tumors (medulloblastoma, hemangioblastoma, astrocytoma, glioma, etc.) and its metastatic lesion. Cerebral tissue edema is possible as a complication of infectious diseases (encephalitis, meningitis) and purulent processes of the brain (subdural empyema).
Along with intracranial factors, anasarca resulting from heart failure, allergic reactions (Quincke’s edema, anaphylactic shock), acute infections (toxoplasmosis, scarlet fever, swine flu, measles, mumps), endogenous intoxication (with severe diabetes mellitus, acute kidney failure, liver failure), poisoning with various poisons and some medications.
In some cases, cerebral edema is observed in alcoholism, which is associated with sharply increased vascular permeability. In newborns, brain edema can be caused by severe toxicosis of a pregnant woman, intracranial birth trauma, umbilical cord entanglement, prolonged labor. Among fans of alpine sports, there is a so-called “mountain” swelling of the brain, which is the result of too sharp a climb without the necessary acclimatization.
Pathogenesis
The main link in the development of cerebral edema are microcirculatory disorders. Initially, they usually occur in the area of the lesion of the brain tissue (the site of ischemia, inflammation, trauma, hemorrhage, tumor). Local perifocal edema of the brain develops. In cases of severe brain damage, failure to carry out timely treatment or lack of proper effect of the latter, a disorder of vascular regulation occurs, leading to total expansion of cerebral vessels and an increase in intravascular hydrostatic pressure. As a result, the liquid part of the blood sweats through the vessel walls and permeates the cerebral tissue. Generalized edema of the brain and its swelling develops.
In the process described above, the key components are vascular, circulatory and tissue. The vascular component is the increased permeability of the walls of the cerebral vessels, the circulatory component is arterial hypertension and vasodilation, which lead to a multiple increase in pressure in the cerebral capillaries. The tissue factor is the tendency of brain tissues to accumulate fluid in case of insufficient blood supply.
In the limited space of the cranial box, 80-85% of the volume falls on cerebral tissues, from 5 to 15% — on cerebrospinal fluid (CSF), about 6% is occupied by blood. In an adult, normal intracranial pressure in a horizontal position varies between 3-15 mm Hg. During sneezing or coughing, it briefly rises to 50 mm Hg., which does not cause disorders of the functioning of the central nervous system. Cerebral edema is accompanied by a rapidly increasing increase in intracranial pressure due to an increase in the volume of cerebral tissues. Vascular compression occurs, which exacerbates microcirculatory disorders and ischemia of brain cells. Due to metabolic disorders, primarily hypoxia, there is a mass death of neurons.
In addition, severe intracranial hypertension can lead to dislocation of underlying cerebral structures and infringement of the brain stem in the large occipital foramen. Violation of the function of the respiratory, cardiovascular and thermoregulatory centers located in the trunk is the cause of many deaths.
Classification
Due to the peculiarities of pathogenesis, cerebral edema is divided into 4 types: vasogenic, cytotoxic, osmotic and interstitial. The most common type is vasogenic cerebral edema, which is based on an increase in the permeability of the blood-brain barrier. In pathogenesis, the main role is played by the transition of fluid from the vessels to the white medulla. Vasogenic edema occurs perifocally in the area of a tumor, abscess, ischemia, surgery, etc.
Cytotoxic edema of the brain is the result of glial cell dysfunction and disturbances in the osmoregulation of neuronal membranes. It develops mainly in the gray brain matter. Its causes may be: intoxication (including cyanide and carbon monoxide poisoning), ischemic stroke, hypoxia, viral infections.
Osmotic edema of the brain occurs when the osmolarity of cerebral tissues increases without disruption of the blood-brain barrier. Occurs with hypervolemia, polydipsia, drowning, metabolic encephalopathies, inadequate hemodialysis. Interstitial edema appears around the cerebral ventricles when the liquid part of the cerebrospinal fluid sweats through their walls.
Symptoms
The leading sign of brain edema is a disorder of consciousness, which can vary from mild sopor to coma. The increase in the depth of the disturbance of consciousness indicates the progression of edema. It is possible that the debut of clinical manifestations will be loss of consciousness, which differs from the usual fainting by its duration. Often, the progression of edema is accompanied by convulsions, which after a short period of time are replaced by muscular atony. On examination, shell symptoms characteristic of meningitis are revealed.
In cases where cerebral edema occurs against the background of chronic or gradually developing acute cerebral pathology, the consciousness of patients in the initial period can be preserved. Then the main complaint is an intense headache with nausea and vomiting, possible motor disorders, visual disorders, discoordination of movements, dysarthria, hallucinatory syndrome.
Menacing signs indicating compression of the brain stem are: paradoxical breathing (deep breaths along with shallow ones, variability of time intervals between breaths), sharp arterial hypotension, pulse instability, hyperthermia over 40 °C. The presence of divergent strabismus and “floating” eyeballs indicates the separation of subcortical structures from the cerebral cortex.
Diagnostics
The neurologist can suspect brain edema due to the progressive deterioration of the patient’s condition and the increase in impaired consciousness, accompanied by meningeal symptoms. Confirmation of the diagnosis is possible with the help of CT or MRI of the brain. Performing a diagnostic lumbar puncture is dangerous by dislocation of cerebral structures with compression of the brainstem in the large occipital foramen. Collection of anamnestic data, assessment of neurological status, clinical and biochemical blood test, analysis of the results of neuroimaging studies — allow us to make a conclusion about the cause of brain edema.
Since brain edema is an acute condition requiring urgent medical care, its primary diagnosis should take a minimum of time and be carried out in stationary conditions against the background of therapeutic measures. Depending on the situation, it is carried out in the conditions of the intensive care unit or intensive care unit.
Treatment
The priority areas in the treatment of brain edema are: dehydration, improvement of cerebral metabolism, elimination of the root cause of edema and treatment of concomitant symptoms. Dehydration therapy is aimed at removing excess fluid from the cerebral tissues. It is carried out by intravenous infusions of mannitol or other osmotic diuretics, followed by the appointment of loop diuretics (torasemide, furosemide). Additional administration of 25% magnesium sulfate and 40% glucose potentiates the action of diuretics and supplies cerebral neurons with nutrients. It is possible to use L-lysine escinate, which has the ability to remove fluid, although it is not a diuretic.
In order to improve cerebral metabolism, oxygen therapy is performed (if necessary, ventilator), local hypothermia of the head, the introduction of metabolites (mexidol, cortexin, citicoline). Glucocorticosteroids (prednisone, hydrocortisone) are used to strengthen the vascular wall and stabilize cell membranes.
Depending on the etiology of brain edema, its complex treatment includes detoxification measures, antibiotic therapy, removal of tumors, elimination of hematomas and areas of traumatic brain injury, shunting operations (ventriculoperitoneal drainage, ventriculocysternostomy, etc.). Etiotropic surgical treatment, as a rule, is carried out only against the background of stabilization of the patient’s condition.
Symptomatic therapy is aimed at relieving individual manifestations of the disease, is carried out by prescribing antiemetics, anticonvulsants, painkillers, etc. According to indications, decompressive trepanation of the skull, external ventricular drainage, endoscopic removal of a hematoma can be performed urgently in order to reduce intracranial pressure by a neurosurgeon.
Forecast
In the initial stage, brain edema is a reversible process, as it progresses, it leads to irreversible changes in brain structures — the death of neurons and the destruction of myelin fibers. The rapid development of these disorders causes the fact that it is possible to completely eliminate edema with 100% restoration of brain functions only with its toxic genesis in young and healthy patients who were delivered to a specialized department on time. Independent regression of symptoms is observed only with mountain edema of the brain, if timely transportation of the patient from the height at which he developed was successful.
However, in the vast majority of cases, the surviving patients have residual effects of the transferred cerebral edema. They can vary significantly from symptoms that are hardly noticeable to others (headache, increased intracranial pressure, absent-mindedness, forgetfulness, sleep disorders, depression) to pronounced disabling disorders of cognitive and motor functions, mental sphere.