Cerebral syndrome

Main nosological forms of encephalopathies

The concept of cerebral syndrome includes a whole spectrum of pathologies. Among them, several key forms caused by metabolic disorders or toxic effects are distinguished:

• Alcoholic encephalopathy. A direct consequence of alcohol abuse. The acute form develops as a result of a sharp disruption of metabolic processes. The chronic form is the result of gradual neurodegeneration of tissues against the background of constant intoxication. The disease is often accompanied by concurrent polyneuropathies and myelopathies.
• Wernicke's encephalopathy. A life-threatening condition triggered by an acute or chronic vitamin B1 (thiamine) deficiency. It is important to remember that the genesis can be either alcoholic or non-alcoholic. The pathogenesis is based on brainstem edema, which produces pronounced generalized and focal symptoms.
• Toxic encephalopathy. A collective term for structural and functional brain disorders caused by exposure to various poisons (toxicants). It manifests as a complex of neuropsychiatric disorders.
• Reversible syndromes. This group includes posterior reversible encephalopathy syndrome and reversible cerebral vasoconstriction syndrome.

Brain edema and swelling

This is a severe complication of neuroinfections (meningitis, meningoencephalitis) or global ischemia and hypoxia, for instance, in severe meningococcemia with the development of infectious-toxic shock. The essence of the process lies in the excessive accumulation of fluid inside cells or in the intercellular space.

The increase in fluid volume inevitably leads to an increase in the volume of the brain itself. In the confined space of the cranium, this causes a sharp increase in intracranial pressure (ICP) and the progression of cerebral insufficiency.

Four pathogenetic forms of brain edema and swelling are distinguished, which in practice usually combine:

1. Vasogenic — the permeability of the blood-brain barrier (BBB) and capillary walls is disrupted.
2. Cytotoxic — toxins have a direct destructive effect on brain cells.
3. Osmotic — the osmolarity of the brain tissue itself increases.
4. Hydrostatic — cerebrospinal fluid pathways are blocked, and pressure in the ventricular system rises.

The most formidable consequence of edema is herniation syndrome (brain herniation). Due to high ICP, parts of the brain herniate into natural openings (e.g., the foramen magnum) or under the folds of the dura mater. Clinically, this is manifested by impaired consciousness, seizures, severe hemodynamic disorders, and focal symptoms.

Metabolic defect: Lesch-Nyhan syndrome

This is a severe X-linked hereditary disorder. The molecular primary cause is the complete absence of activity of the enzyme hypoxanthine-guanine phosphoribosyltransferase (HGPRT). This defect disrupts the "salvage" pathway of purine nucleotide synthesis.

As a result, a cascade of pathological reactions occurs:

• Purine bases (guanine and hypoxanthine) are no longer reused. They are irreversibly transformed into uric acid, causing severe hyperuricemia.
• Due to poor utilization, phosphoribosyl pyrophosphate (PRPP) accumulates in cells. Its excess potently activates the key enzyme PRPP amidotransferase, which avalanche-like enhances purine synthesis de novo.

The clinical picture is very specific. Already in early childhood, patients develop urate kidney stones (nephrolithiasis), tophi, and gouty arthritis. In parallel, profound neurological abnormalities develop: cerebral palsy, intellectual disability, speech defects. A pathognomonic symptom is the tendency to self-mutilation (self-aggression) — patients constantly bite their lips, tongue, and phalanges of the fingers, which leads to ulceration and deformation.

Neurological lesions in neuroborreliosis

Tick-borne borreliosis can seriously affect the nervous system, manifesting as encephalopathy, cerebral vasculitis, and encephalomyelitis.

• Peripheral nervous system involvement. It proceeds in the form of radiculopathies and radiculoneuritis. It begins acutely, with a pronounced infectious syndrome. Flaccid paresis of the neck and arm muscles develops (atonia, hyporeflexia). Inflammatory shifts are detected in the cerebrospinal fluid (changes in cytology, protein, and glucose levels). This symptom complex requires careful differential diagnosis with tick-borne encephalitis.
• Progressive encephalomyelitis. Spinal cord and brain involvement manifests as spastic paraparesis, ataxia, sleep inversion, dizziness, and reflex asymmetry. Morphologically, this is multifocal demyelination, which is easily confused with multiple sclerosis. A crucial clue for the physician is the combination of encephalomyelitis with joint involvement (arthropathies).
• Hemodynamic disorders. The tone of small and medium arteries increases, vascular resistance grows, and venous outflow is hindered. This leads to pronounced ischemia and suppression of the blood supply to the cerebral cortex.

There is also evidence that borreliosis in rare cases can provoke the development of Guillain-Barré syndrome.

Class and exam questions

What else to study on this topic

• Mechanisms of formation and clinical criteria for posterior reversible encephalopathy syndrome.
• Reversible cerebral vasoconstriction syndrome: differential diagnosis.
• Topographic anatomy of herniation syndromes (types of brain herniation).
• Specific cerebrospinal fluid changes (cytology, glucose, protein) in various neuroinfections.
• Criteria for the differential diagnosis of the encephalopolyomielitic form of tick-borne encephalitis.

Prepared by WhiteCoat Pro faculty in accordance with the medical school curriculum. For educational purposes only.