Preparatory Mindset
This chapter covers acute bacterial meningitis (the emergency), the CSF differential, and Kawasaki disease (with the paediatric rash illnesses touched from the rashes lecture). The mindset:
- Meningitis: fever + headache + neck stiffness + altered consciousness (infants — non-specific: poor feeding, lethargy, bulging fontanelle, high-pitched cry, seizures) → think sepsis + meningitis, start empiric antibiotics WITHOUT delay (after LP if safe, but NEVER delay antibiotics for imaging/transfer). CSF analysis is the key diagnostic — bacterial = purulent (↑WBC neutrophils, ↓glucose, ↑protein, gram stain +); viral = lymphocytic, normal glucose; TB = lymphocytic, very low glucose, ↑protein. Purpura in a febrile child = meningococcaemia until proven otherwise (do not wait) — IV ceftriaxone + dexamethasone (Hib/pneumococcal).
- Kawasaki disease: fever ≥5 days + 4 of 5 criteria (conjunctivitis, mucositis, rash, cervical lymphadenopathy, extremity changes) → IVIG + aspirin within 10 days to prevent coronary artery aneurysms (the serious complication; ECHO surveillance).
- The OSCE stations: "febrile child with rash — meningococcaemia?" and "the child who won't move his neck."
Core Concepts
1. Acute bacterial meningitis — the emergency
Aetiology by age:
| Age | Organisms |
|---|---|
| Neonate (<3 mo) | Group B strep (GBS), E. coli, Listeria monocytogenes |
| Infant/child (3 mo-5 yr) | S. pneumoniae, N. meningitidis, H. influenzae type b (Hib — now vaccine-preventable) |
| Older child/adolescent | N. meningitidis, S. pneumoniae |
Risk factors (neonate): LBW, prolonged rupture of membranes, chorioamnionitis → septicaemia + meningitis.
Clinical:
| Age | Signs |
|---|---|
| Neonate/infant | Non-specific — poor feeding, lethargy/irritability, vomiting, fever or hypothermia, bulging fontanelle, high-pitched cry, seizures, apnoea |
| Older child | Fever, headache, vomiting, neck stiffness, photophobia, altered consciousness, seizures; Kernig sign, Brudzinski sign |
Meningococcal sepsis clue: purpura/petechiae in a febrile child = meningococcaemia until proven otherwise — even if not acutely ill. Shock signs (tachycardia, poor capillary refill, oliguria, hypotension) — treat as sepsis.
Investigations:
| Test | Finding |
|---|---|
| CSF analysis (the key) | See table below |
| Blood culture | Positive in many (septicaemia) |
| CRP/WBC | ↑ (non-specific) |
| Imaging (CT) | Before LP only if: focal neuro signs, papilloedema, reduced consciousness, seizures, immunocompromised, recent head trauma (LP contraindication — raised ICP) |
| LP contraindications | Focal signs, papilloedema, GCS drop, shock, coagulopathy, skin infection over LP site, suspected space-occupying lesion |
CSF differential (must memorise):
| Parameter | Normal | Bacterial (purulent) | Viral (aseptic) | TB |
|---|---|---|---|---|
| Appearance | Clear | Cloudy/purulent | Clear | Clear/opalescent |
| WBC | <5 (lymphocytes) | ↑↑ (100-1000+, neutrophils) | ↑ (lymphocytes) | ↑ (lymphocytes) |
| Glucose | ~2/3 blood | ↓↓ (<50% blood) | Normal | ↓↓ (very low) |
| Protein | 0.2-0.4 g/L | ↑↑ | Normal/↑ | ↑↑ (very high) |
| Gram stain/culture | Negative | Positive | Negative | AFB stain/culture |
| Other | — | Latex antigen (pneumo/meningo/Hib) | PCR (enterovirus, HSV) | TB PCR/IGRA; ↑ lymphocytes |
Management (the emergency drill):
- Neonate: ampicillin + cefotaxime (or gentamicin) — covers GBS, Listeria, Gram-negatives. - Child: IV ceftriaxone (or cefotaxime) ± vancomycin (if resistant pneumococcus risk).
- ABC + sepsis management (fluid, inotropes if shock — meningococcaemia).
- Empiric IV antibiotics IMMEDIATELY (don't wait for LP/CT/transfer):
- Dexamethasone (0.15 mg/kg q6h × 2-4 days) — given with/just before first antibiotic in Hib and pneumococcal meningitis — reduces hearing loss and neurological sequelae.
- LP — after stabilisation if initially deferred; notify lab (urgent gram stain).
- Isolation — droplet precautions (meningococcal/Hib) for 24 h after antibiotics; chemoprophylaxis for contacts (meningococcal — rifampicin/ciprofloxacin; Hib — rifampicin for unvaccinated young contacts).
- Complications: hearing loss (most common — audiology follow-up), seizures, subdural effusion/empyema, hydrocephalus, cerebral oedema, SIADH, septicaemic shock, DIC, death.
- Prevention: Hib, pneumococcal (PCV13), meningococcal vaccines; chemoprophylaxis of contacts.
2. Kawasaki disease (mucocutaneous lymph node syndrome)
Definition: acute self-limiting systemic vasculitis of small/medium arteries — affects infants/young children (peak 6 months-5 years); the leading cause of acquired heart disease in children in developed countries.
Diagnosis — fever ≥5 days + ≥4 of 5 criteria:
- Bilateral non-exudative conjunctivitis
- Oral mucosal changes — strawberry tongue, cracked lips, pharyngeal erythema
- Polymorphous rash (truncal)
- Cervical lymphadenopathy (>1.5 cm, usually unilateral)
- Extremity changes — erythema/oedema of hands/feet → periungual desquamation (2-3 weeks)
(Incomplete Kawasaki — fewer criteria but ECHO changes — more common in infants <6 months.)
Complication — coronary artery aneurysm (25% untreated): coronary vasculitis → aneurysm, thrombosis, MI, sudden death; the reason for early treatment.
Investigations: CRP/ESR ↑↑, WBC ↑, platelets ↑ (2nd week), anaemia, hypoalbuminaemia, ↑ALT, sterile pyuria; ECHO (baseline + follow-up) for coronary arteries.
Management:
| Treatment | Detail |
|---|---|
| IVIG (2 g/kg single dose) | Within 10 days of fever onset — reduces coronary aneurysm risk from ~25% to <5% |
| Aspirin (high dose, anti-inflammatory) | 30-50 mg/kg/day in acute phase (fever) → then low dose (3-5 mg/kg/day) antiplatelet × 6-8 weeks (until platelets/ECHO normal) |
| Resistant disease | Second IVIG dose, steroids, infliximab |
| Coronary aneurysm | Long-term aspirin, anticoagulation (warfarin) if giant aneurysm, ECHO surveillance, cardiology follow-up; restrict strenuous activity |
| Live vaccines | Defer for 11 months after IVIG (neutralising antibodies) |
Prognosis: excellent with early IVIG (<5% aneurysm); untreated — significant coronary morbidity.
3. Febrile rash illnesses in children (from 15 Infections (Rashes).ppt — key differentials)
| Disease | Rash | Key features |
|---|---|---|
| Measles (rubeola) | Maculopapular, starts face → spreads; Koplik spots (buccal) | Fever, cough, coryza, conjunctivitis (3 Cs); vaccine-preventable |
| Rubella | Pink maculopapular, face→body; lymphadenopathy (post-auricular) | Mild; congenital rubella syndrome in pregnancy |
| Chickenpox (varicella) | Vesicular "dew drops on rose petals", all stages together | Itchy; vaccine; neonatal/immunocompromised — severe |
| Scarlet fever (strep) | Fine sandpaper rash + strawberry tongue + circumoral pallour; desquamation | Group A strep — penicillin; treat to prevent rheumatic fever |
| Meningococcaemia | Petechiae/purpura (non-blanching) | Emergency — antibiotics immediately |
| Hand-foot-mouth (enterovirus) | Vesicles on palms/soles/mouth | Coxsackie A16, EV71 (severe — encephalitis) |
| Kawasaki | Polymorphous + conjunctivitis + strawberry tongue | As above — IVIG |
The febrile child + non-blanching rash = meningococcaemia → IV antibiotics immediately (do not wait for LP or observation).
High-Yield Points
| Topic | Must-remember |
|---|---|
| Bacterial meningitis commonest | S. pneumoniae, N. meningitidis (child); GBS, E. coli, Listeria (neonate) |
| CSF bacterial | Neutrophils ↑↑, glucose ↓↓, protein ↑↑, gram stain + |
| CSF viral | Lymphocytes, normal glucose |
| CSF TB | Lymphocytes, very low glucose, very high protein |
| Purpura + fever | Meningococcaemia — antibiotics immediately, no waiting |
| Empiric child | Ceftriaxone ± vancomycin |
| Empiric neonate | Ampicillin + cefotaxime (Listeria/GBS cover) |
| Dexamethasone | With/just before antibiotics (Hib/pneumo) — ↓ hearing loss |
| LP contraindications | Focal signs, papilloedema, shock, GCS ↓, coagulopathy |
| Meningitis complication | Hearing loss (most common) |
| Kawasaki criteria | Fever ≥5 d + 4 of 5 (conjunctivitis, mucositis, rash, lymphadenopathy, extremities) |
| Kawasaki complication | Coronary artery aneurysm (25% untreated) |
| Kawasaki treatment | IVIG 2 g/kg within 10 days + aspirin (high then low dose) |
| IVIG + vaccines | Defer live vaccines 11 months |
| Measles 3 Cs | Cough, coryza, conjunctivitis |
| Chickenpox rash | Vesicles "dew drop on rose petal" |
| Scarlet fever | Sandpaper rash + strawberry tongue; treat GAS |
Topic Summary
Bacterial meningitis is an emergency: fever + neck stiffness + altered consciousness (infants — non-specific), CSF analysis differentiates bacterial (neutrophils, ↓glucose, ↑protein) vs viral (lymphocytes) vs TB (lymphocytes, very low glucose); empiric IV ceftriaxone (neonate: ampicillin + cefotaxime) immediately + dexamethasone; purpura = meningococcaemia — antibiotics without delay; contacts need chemoprophylaxis; complications — hearing loss, hydrocephalus. Kawasaki disease — fever ≥5 days + 4 of 5 criteria → IVIG + aspirin within 10 days to prevent coronary aneurysm; ECHO follow-up. Febrile rashes (measles, chickenpox, scarlet fever, HMFD) complete the picture — non-blanching rash + fever = emergency.
LMCHK OSCE Practice — The Febrile Child with a Rash
Station setup: A 2-year-old boy presents with 2 days of high fever, now lethargic, with widespread non-blanching purpuric rash on his trunk and legs. He has poor capillary refill (3 s), HR 160, BP 85/50, and neck stiffness. A petechial rash is spreading.
Candidate tasks (8 min):
- Recognise meningococcaemia with sepsis/meningitis — febrile child + non-blanching rash = emergency.
- Resuscitate immediately: ABC, high-flow O₂, IV access × 2, IV fluid bolus (20 mL/kg) for shock, monitor.
- Give IV antibiotics NOW — ceftriaxone (empiric) — do NOT wait for LP, CT, or transfer.
- State the LP plan (after stabilisation, if no contraindications — for CSF analysis) and contraindications.
- Isolation (droplet) + notification + chemoprophylaxis for close contacts (rifampicin/ciprofloxacin); explain to parents (prognosis, sequelae — hearing, limb ischaemia, DIC).
Key marking cues:
- Antibiotics without delay — the exam-critical point.
- Recognises septic shock (poor perfusion, tachycardia, hypotension) and resuscitates.
- Meningococcaemia → droplet isolation + contact prophylaxis.
- Knows LP contraindications and when CSF analysis is safe.
- Counsels parents on sequelae (hearing loss, amputations, DIC).