Digant D Shastri
Chairman, Pediatric Infectious Diseases Fellowship Council
Infections of the central nervous system (CNS) are a serious threat to the developing brain and are a major cause of neurologic handicap in the young children. The laboratory diagnosis of CNS infection is essential for optimal therapy in order to improve the outcome of the diseases with rapid and accurate detection of the pathogens. The prognosis mainly depends on rapid identification of the site of inflammation and pathogen to install effective antimicrobial treatment as early as possible.
Since microbial agents infecting CNS are numerous and have different features, conventional laboratory tests may not be sensitive enough to identify and characterise viruses and bacteria in human biological specimens. Many laboratory issues addressing the diagnosis of CNS infection are changing or evolving. These evolvement represent significant improvements over previous testing. Availability of array of tests needs judicious selection of tests due to their high cost and needs for the new skills for performance and interpretation. The responsibility for proper use of laboratory testing lies both with the clinician and laboratory technician. Aanalysis of CSF remain the gold standard for the differential diagnosis,neuroimaging plays a crucial role both in the diagnosis and therapeutic decision making in infectious diseases of the nervous system. Recent technological advancements in imaging technology for central nervous system imaging has not only improved the clinical outcome but has also opened new vista of case management.
Key words: CNS infections, Laboratory diagnosis, Neuroimaging
Points to remember:
• CSF cell analysis( WBC count) should be done immediately after it’s collection.
• CSF glucose : blood glucose is important in diagnosing bacterial meningitis.
• 50 % of patients with clinically cured bacterial meningitis, the CSF glucose, protein & WBC count may remain abnormal.
• Gram stain is the single best test for rapid diagnosis of bacterial meningitis.
• For culture CSF should be inoculated as soon as possible, preferably at bedside only.
• Neuroimaging has a crucial role in diagnosis &therapeutic decision making.
Table-1 Common viral infections of nervous system and their confirmatory laboratory tests
Virus Disease Laboratory confirmation
Encephalitis ELISA for IgM or IgG in serum or CSF
Herpes Simplex Encephalitis
Elevated CSF globulin
Coxsackie and Echovirus Meningitis
Peripheralneuritis Culture of Stool , CSF
Culture of CSF
Neuroradiology: Neuroimaging plays a crucial role in the diagnosis and therapeutic decision making in infectious diseases of the nervous system. Following are the conditions where it is indicated:
1. When there are focal signs/seizures
2. Seriously raised ICT
3. failure to display clinical improvement -No significant response to medical treatment
4. Persistence of fever or coma
5. Suspected complication
Table -2 Preferred Imaging Procedures in Infectious CNS Diseases
Meningitis or encephalitis
Intially CT without and with injection of contrast material
MRI after initial assessment and treatment
Cerebral or cerebellar abscess
CT without and with contrast injection for initial diagnosis or, if stable, MRI instead of CT;
MRI without and with injection of contrast material subsequently
MRI without and with injection of contrast material
Disclaimer: The Views and opinions expressed in the articles are of the authors and not of the journal.
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