CNS Infections: Bacterial Meningitis Symptoms

Study Notes

Classic Triad of Symptoms for Bacterial Meningitis

Fever, stiff neck (nuchal rigidity), and headache are the classic symptoms.
Major sign in infants includes bulging fontanelle and petechiae.
Nuchal rigidity prevents neck flexion, causing pain and spasms when attempting to flex.
Spinal rigidity may present as hyperextension of the spine, also known as opisthotonus.
Other symptoms include vomiting, seizures, and impaired consciousness.

Kernig's Sign

Push on the knee while it is flexed at 90 degrees, then passively extend the lower extremity.
Resistance or pain during this maneuver indicates possible meningitis.

Brudzinski's Sign

Patient lies supine; immobilize the trunk against the bed.
Flex the neck to bring the chin to the chest; involuntary hip flexion suggests meningeal irritation.

Papilledema

Characterized by increased intracranial pressure.
Possible causes include brain tumors, cerebral trauma, meningitis, and idiopathic intracranial hypertension.

Non-Specific Rashes for Meningococcal Meningitis

Petechiae and purpura are common non-specific rashes that do not blanch under pressure.

Symptoms Comparison: Viral vs. Bacterial Meningitis

Bacterial meningitis typically presents with high fever, altered mental status, and rapid onset.
Viral meningitis may have a several-day onset with fever not always present and mental status may not be altered.

Lumbar Puncture Use & Contraindications

Lumbar puncture differentiates between viral and bacterial infections.
Contraindicated in cases of increased intracranial pressure or suspected cerebral mass lesions.
Common complications include headache and back pain, with rare events such as infection or hematoma.

CSF CBC Findings

Bacterial meningitis: increased neutrophils, increased protein, decreased glucose.
Viral meningitis: increased lymphocytes, normal protein and glucose.
Low glucose and high protein suggest bacterial activity consuming glucose.

Imaging for CNS Infections

Imaging is indicated with significant suspicion of CNS abnormality (papilledema, altered mental status).
CT scan is preferred in emergent situations; MRI is better for non-emergent evaluations.

Common Routes of CNS Infection

Bloodborne route is the most common method for CNS infection.
Other routes include local invasion (e.g., from the ears or sinuses) or through the olfactory tract.

Common Pathogens by Age Group

Newborns: Group B Streptococcus, followed by E. coli.
Children: Streptococcus pneumoniae, Neisseria meningitidis, Haemophilus influenzae type B.
Adolescents and Young Adults: Neisseria meningitidis, followed by Streptococcus pneumoniae.
Older Adults: Streptococcus pneumoniae, followed by Neisseria meningitidis.

Characteristics of Streptococcus pneumoniae

Gram-positive cocci in chains or diplococci; lancet-shaped.
Alpha-hemolytic, optochin sensitive, and bacitracin resistant.
Bile soluble with a positive Quellung reaction.
Key virulence factors include polysaccharide capsule and pneumolysins, aiding in colonization of the nasopharynx alongside pili and IgA protease.

Description

This quiz focuses on the classic triad of symptoms for bacterial meningitis and other CNS infections. It explores key signs to observe in infants, as well as the explanations for nuchal and spinal rigidity. Test your knowledge on these critical aspects of CNS infections.