Meningitis

Question 1

Define Meningitis.

Answer 1

Meningitis is an inflammation of the leptomeninges (the pia mater and arachnoid mater) and the cerebrospinal fluid (CSF) within the subarachnoid space surrounding the brain and spinal cord.

Question 2

What are the main categories of causative agents for Meningitis?

Answer 2

1. Infectious: Bacteria (most critical), Viruses, Fungi, Protozoa, Parasites. 2. Non-Infectious: Drugs (e.g., NSAIDs, IVIG), Malignancy, Autoimmune diseases (e.g., SLE).

Question 3

List the most common bacterial causes of Meningitis in a NEONATE (0-3 months).

Answer 3

• Group B Streptococcus (S. agalactiae) • Escherichia coli (especially with K1 antigen) • Listeria monocytogenes

Question 4

List the most common bacterial causes of Meningitis in a CHILD (6 months - 5 years).

Answer 4

• Streptococcus pneumoniae (Pneumococcus) • Neisseria meningitidis (Meningococcus) • Haemophilus influenzae type b (Hib) - Note: Hib incidence has drastically reduced due to vaccination.

Question 5

List the most common bacterial causes of Meningitis in an ADULT.

Answer 5

• Streptococcus pneumoniae (most common overall in adults) • Neisseria meningitidis • Listeria monocytogenes (risk increases in adults >50 years and the immunocompromised)

Question 6

What are the classic clinical features of acute bacterial meningitis?

Answer 6

The classic triad is: 1. Fever 2. Headache 3. Neck Stiffness (Nuchal Rigidity). Other key features: Altered mental status, photophobia, phonophobia, nausea/vomiting, and seizures.

Question 7

What are the two main clinical signs of meningeal irritation and how are they performed?

Answer 7

• Kernig’s Sign: Pain/resistance in the hamstrings when attempting to extend the knee with the hip flexed. • Brudzinski’s Sign: Involuntary flexion of the hips and knees when flexing the patient’s neck.

Question 8

What are the typical CSF findings in ACUTE BACTERIAL MENINGITIS?

Answer 8

• Appearance: Cloudy • Opening Pressure: Elevated • WBC Count: Markedly elevated (>1000 cells/μL) • Predominant Cell Type: Neutrophils (PMNs) • Protein: High (>150 mg/dL) • Glucose: Low (<40 mg/dL or <40% of serum glucose)

Question 9

What are the typical CSF findings in ACUTE VIRAL (ASEPTIC) MENINGITIS?

Answer 9

• Appearance: Clear • Opening Pressure: Normal or slightly elevated • WBC Count: Moderately elevated (50-1000 cells/μL) • Predominant Cell Type: Lymphocytes • Protein: Normal or slightly elevated • Glucose: Normal

Question 10

What are the typical CSF findings in TUBERCULOUS or FUNGAL MENINGITIS?

Answer 10

• Appearance: Clear or slightly cloudy • Opening Pressure: Elevated • WBC Count: Elevated (50-500 cells/μL) • Predominant Cell Type: Lymphocytes (can be mixed early on) • Protein: Very High • Glucose: Very Low

Question 11

What is the most critical initial diagnostic test for suspected meningitis, and what is a key contraindication?

Answer 11

Lumbar Puncture (LP) for CSF analysis. A key contraindication is suspected elevated intracranial pressure (ICP) due to a mass lesion (e.g., tumor, abscess) or signs of brain herniation. A CT head scan is often required before LP in these cases.

Question 12

What is the ‘Meningitis Belt’?

Answer 12

A region in sub-Saharan Africa, including Nigeria, that experiences frequent, large-scale epidemics of meningococcal meningitis, primarily during the dry season (December-June). Serogroup A was historically dominant.

Question 13

What are the main risk factors for developing meningitis?

Answer 13

• Extremes of Age (very young, elderly) • Immunosuppression (HIV, chemotherapy) • Crowded Living Conditions (dorms, military barracks) • Anatomical Defects (skull fracture, cochlear implants) • Splenectomy • Complement Deficiency

Question 14

What are the two primary routes of pathogenesis for microbes to reach the meninges?

Answer 14

1. Hematogenous Spread (most common): Organisms enter the bloodstream from a mucosal site (e.g., nasopharynx) and seed the meninges. 2. Direct Spread: From a contiguous focus of infection (e.g., sinusitis, otitis media, skull fracture).

Question 15

Why is meningitis considered a medical emergency?

Answer 15

Because it can lead to death or severe permanent neurological disability within hours. Rapid diagnosis and immediate administration of antibiotics are critical to improve outcomes.

Question 16

What is the principle of EMPIRICAL antibiotic therapy for suspected bacterial meningitis in an ADULT?

Answer 16

Cover the most likely pathogens: • A 3rd generation Cephalosporin (e.g., Ceftriaxone or Cefotaxime) for S. pneumoniae and N. meningitidis. • PLUS Ampicillin or Amoxicillin to cover Listeria monocytogenes in patients >50 years or immunocompromised.

Question 17

What is the principle of EMPIRICAL antibiotic therapy for a NEONATE (0-3 months)?

Answer 17

Cover pathogens common in this age group: • Ampicillin (covers Listeria and Group B Strep) • PLUS an Aminoglycoside (e.g., Gentamicin) or a 3rd generation Cephalosporin (e.g., Cefotaxime) to cover Gram-negative rods like E. coli.

Question 18

What is Waterhouse-Friderichsen Syndrome?

Answer 18

A severe complication of fulminant meningococcemia (N. meningitidis infection). It is characterized by hemorrhagic adrenal gland necrosis leading to adrenal insufficiency, profound shock, disseminated intravascular coagulation (DIC), and widespread purpura.

Question 19

What are some common long-term complications of bacterial meningitis?

Answer 19

• Hearing Loss (most common) • Cognitive Deficits / Learning Disabilities • Seizures / Epilepsy • Hydrocephalus • Focal Neurological Deficits (e.g., paresis) • Behavioral Problems

Question 20

How can meningitis be prevented?

Answer 20

• Vaccination (Most Effective): Hib vaccine, Pneumococcal Conjugate Vaccine (PCV), Meningococcal Conjugate Vaccine (MenACWY), Meningococcal B vaccine (MenB). • Chemoprophylaxis: For close contacts of meningococcal disease (e.g., Rifampicin, Ciprofloxacin). • General Measures: Avoiding overcrowding, good hygiene.

Question 21

What is the role of Dexamethasone in the management of bacterial meningitis?

Answer 21

Dexamethasone (a corticosteroid) is recommended to be given before or with the first dose of antibiotics in specific cases (e.g., suspected or proven pneumococcal meningitis in adults). It reduces the inflammatory response and can decrease the risk of neurological sequelae, particularly hearing loss.

Question 22

Which virus is classically associated with Mollaret’s Meningitis?

Answer 22

Herpes Simplex Virus type 2 (HSV-2). Mollaret’s meningitis is a rare condition characterized by recurrent, self-limiting episodes of aseptic meningitis.

Question 23

What is a key difference in the presentation of meningitis in infants compared to adults?

Answer 23

Infants may not show the classic signs of neck stiffness. Instead, look for: • Bulging Anterior Fontanelle • High-pitched cry • Irritability or Lethargy • Poor Feeding • Hypothermia or Fever

Question 24

What CSF test is crucial for diagnosing Tuberculous Meningitis?

Answer 24

• CSF Acid-Fast Bacilli (AFB) Smear and Culture (definitive but slow). • CSF PCR for M. tuberculosis (faster and more sensitive). • CSF Adenosine Deaminase (ADA) levels can be a supportive marker.

Question 25

What is the significance of a positive CSF Gram stain?

Answer 25

It provides a rapid (within 30 minutes) presumptive identification of the causative bacterium, allowing for targeted antibiotic therapy before culture results are available (which take 24-48 hours).

Question 26

Which fungal pathogen is most commonly associated with meningitis in HIV/AIDS patients?

Answer 26

Cryptococcus neoformans (and C. gattii). It is a major cause of morbidity and mortality in immunocompromised individuals.

Question 27

Name a protozoan and a parasite that can cause meningitis.

Answer 27

• Protozoan: Naegleria fowleri (causes Primary Amoebic Meningoencephalitis - PAM). • Parasite: Angiostrongylus cantonensis (the rat lungworm, causes eosinophilic meningitis).

Question 28

What is the significance of a low CSF glucose (hypoglycorrhachia)?

Answer 28

It indicates increased glucose utilization by pathogens (bacteria, mycobacteria, fungi) and/or by the host's inflammatory cells (WBCs). It is a hallmark of bacterial, tuberculous, and fungal meningitis.