Chapter 23. Infectious Diseases of the Nervous System
8 topics with a brief review: definitions, key facts, and classroom questions.
The nervous system is reliably protected by the blood-brain barrier, but if an infection breaches it, the consequences are severe and time is measured in hours. In this chapter, we analyze inflammatory lesions of the meninges, brain parenchyma, and spinal cord caused by bacteria, viruses, fungi, and specific agents.
The section covers acute inflammatory processes: meningitis, encephalitis (including seasonal tick-borne encephalitis), and myelitis. A separate block is dedicated to viral lesions (poliomyelitis) and specific infections: you will study the neurological manifestations of syphilis (neurosyphilis), complications of HIV infection (neuroAIDS), and rare but fatal prion diseases that destroy the brain at the molecular level.
In clinical classes and exams, you will most frequently be asked about the differential diagnosis of meningitis based on cerebrospinal fluid analysis, focal symptoms of tick-borne encephalitis, and the classic syndromes of tabes dorsalis. Learn to quickly distinguish a purulent process from a serous one — in emergency neurology, this exact skill saves patients' lives.
What is the difference between primary and secondary meningitis?
Primary meningitis develops without an infectious focus in other organs (e.g., meningococcal). Secondary is always a consequence of another infection, such as pneumococcal meningitis secondary to otitis media or sinusitis.
What is the difference between primary and secondary encephalitis?
Primary encephalitis is caused by a virus that directly invades the brain (e.g., herpes, tick-borne encephalitis virus). Secondary develops as an autoimmune or vascular complication following other infections (measles, influenza) or after vaccination.
What is the difference between routine and emergency prophylaxis for tick-borne encephalitis?
Routine prophylaxis is carried out in advance using a tissue-inactivated vaccine. Emergency prophylaxis is used after a tick bite and consists of administering preformed antibodies — tick-borne immunoglobulin.
How does the cerebrospinal fluid change in borrelial myelitis?
Cerebrospinal fluid analysis reveals lymphocytic pleocytosis (up to 3,000 cells per 1 mm³), elevated protein levels, while glucose concentration remains normal.
Does antiretroviral therapy affect neurological complications in AIDS?
In most cases, therapy does not affect already developed neurological disorders. The only exception is progressive multifocal leukoencephalopathy, in which cART has a positive effect.
What is the difference between subdural empyema and epidural abscess?
Subdural empyema is located between the dura mater and the pia mater of the brain, while epidural abscess is located between the dura mater and the cranial bones.
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