Paediatrics chapters
Brain abscess in children
A localised collection of pus in the brain: the conditions that predispose children to it, the organisms, how it presents as an infection plus a mass, why lumbar puncture is dangerous, and how it is treated.
- A brain abscess is a focal collection of pus in the brain, commonest at 4-8 years; key causes are cyanotic congenital heart disease with right-to-left shunt (tetralogy of Fallot), chronic otitis media or mastoiditis (temporal lobe, cerebellum), sinusitis (frontal lobe), penetrating injury and immune deficiency.
- It behaves like an infected space-occupying lesion: headache, vomiting, low fever, then seizures, focal signs, papilloedema and coma; fever may be mild or absent.
- Contrast CT or MRI shows a ring-enhancing lesion; lumbar puncture is contraindicated (herniation); treat with IV antibiotics for weeks (vancomycin, a third-generation cephalosporin and metronidazole) plus aspiration or excision when needed.
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Overview
A brain abscess is a localised collection of pus within the brain tissue, surrounded by a capsule and severe oedema. In children it behaves as an infected space-occupying lesion: signs of raised intracranial pressure and focal deficits matter more than fever, which may be mild or absent. A child with cyanotic heart disease who develops headache, vomiting or seizures must be assumed to have an abscess until scanned.
Epidemiology
- Commonest between 4 and 8 years.
- About 10-15% have no cause found.
- Most abscesses are single; about 30% are multiple, sometimes in more than one lobe.
Predisposing conditions
| Source | Typical site |
|---|---|
| Cyanotic congenital heart disease with right-to-left shunt (for example tetralogy of Fallot): infected material bypasses the lung filter | Often multiple; anywhere |
| Infective endocarditis | Embolic, often multiple |
| Chronic otitis media, mastoiditis | Temporal lobe or cerebellum |
| Sinusitis, orbital cellulitis | Frontal lobe |
| Dental infection, face or scalp infection | Adjacent lobe |
| Chronic lung infection (bronchiectasis, empyema) | Embolic |
| Penetrating head injury | Single; Staph. aureus |
| Immune deficiency | Fungi, unusual organisms |
| Infected ventriculoperitoneal shunt | Near the shunt |
In a child with tetralogy of Fallot, a new headache, seizure or focal sign points to brain abscess; the other main concern is stroke, for which cyanotic heart disease is also the leading risk.
Organisms
- Streptococci: viridans, microaerophilic, pneumococci.
- Staphylococcus aureus (trauma, surgery).
- Anaerobes: Bacteroides, Fusobacterium, anaerobic cocci, Actinomyces.
- Gram-negative bacilli: enteric rods, Proteus, Pseudomonas, Haemophilus.
- Fungi in immunocompromised children.
- Often mixed aerobic and anaerobic flora, especially from ear, sinus and dental sources.
Clinical features
Early
Non-specific: low-grade fever, headache, lethargy. Nelson stresses that fever, malaise, anorexia and neck stiffness may be subtle or absent.
Progressive
- Vomiting, worsening headache.
- Seizures (often focal).
- Papilloedema and other signs of raised ICP.
- Focal neurological signs: hemiparesis, aphasia, visual field loss, depending on the site.
- Drowsiness progressing to coma.
Cerebellar abscess
Nystagmus, ataxia and dysmetria on the same side, headache and vomiting.
Rupture
Rupture into the ventricles causes sudden ventriculitis, shock and death.
Papilloedema is uncommon in plain bacterial meningitis; when a febrile child has papilloedema, think of abscess, subdural empyema or venous sinus thrombosis.
"Fever may fade, but the mass remains": a brain abscess presents more like a tumour than like meningitis.
Investigations
| Test | Finding |
|---|---|
| Contrast CT | Ring-enhancing lesion with a low-density centre and surrounding oedema; the key test |
| MRI | Shows the capsule and surrounding oedema; better for early cerebritis and the posterior fossa |
| Blood count | White count normal or raised |
| Blood culture | Positive in only about 10% |
| CSF (if already taken) | Pressure normal or raised; cells normal or slightly raised (up to about 100, neutrophils) unless it ruptures; protein slightly raised; glucose normal or slightly low |
| EEG | Focal slowing |
| Search for the source | Ear, sinus and dental examination and imaging; echocardiography; chest X-ray |
| Pus from aspiration | Gram stain, aerobic and anaerobic culture, guides antibiotics |
Lumbar puncture is contraindicated when a brain abscess is suspected, because removing CSF can cause tentorial or cerebellar tonsillar herniation, and the CSF rarely gives the organism.
Remember the sites: ear → temporal lobe or cerebellum, sinus or orbit → frontal lobe, penetrating wound → single Staph. aureus abscess.
A normal white count and negative blood culture do not exclude an abscess; blood cultures are positive in only about a tenth.
Differential diagnosis
Brain tumour, tuberculoma, subdural empyema, meningitis, encephalitis (especially herpes simplex with a temporal lesion), stroke and venous sinus thrombosis.
Management
Antibiotics
| Situation | Empirical regimen (Akbar) |
|---|---|
| Most cases | Vancomycin + a third-generation cephalosporin + metronidazole |
| Cyanotic congenital heart disease | Ampicillin-sulbactam alone, or a third-generation cephalosporin + metronidazole |
| Infected VP shunt | Vancomycin + ceftazidime |
| Immunocompromised | Add amphotericin B to broad-spectrum antibiotics |
- Adjust to culture and sensitivity results.
- Duration is usually several weeks of IV treatment (Akbar about 3-4 weeks), guided by clinical and scan response.
Surgery
- Aspiration (needle drainage) with antibiotics for an encapsulated abscess causing mass effect or raised ICP.
- Excision or open drainage if the abscess contains gas, is multiloculated, lies in the posterior fossa, or is fungal.
Supportive care
Control seizures with anticonvulsants, reduce raised ICP (head up, mannitol), and treat the source (ear, sinus or dental surgery; heart disease).
Complications and sequelae
- Rupture into the ventricles (ventriculitis), herniation.
- Long term: seizures (epilepsy), hemiparesis, hydrocephalus, cranial nerve palsies, behaviour and learning problems.
Prognosis
Akbar links a higher mortality with:
- Multiple abscesses.
- Coma at presentation.
- Lack of CT scanning (late diagnosis).
Rupture into the ventricles is often fatal.
Expect: cyanotic congenital heart disease (tetralogy of Fallot) as the classic predisposing condition; otitis media leading to temporal lobe or cerebellar abscess and sinusitis to frontal abscess; presentation as a mass lesion with headache, vomiting, seizures and focal signs, fever often mild; ring-enhancing lesion on contrast CT; lumbar puncture contraindicated; mixed organisms with anaerobes; vancomycin, cephalosporin and metronidazole; aspiration or excision; seizures and hemiparesis as sequelae.
Quick revision
- Pus in brain tissue; peak 4-8 years; 30% multiple.
- Cyanotic CHD (Fallot), endocarditis, otitis (temporal, cerebellar), sinusitis (frontal), trauma (Staph. aureus).
- Mixed streptococci, anaerobes, staphylococci, Gram-negatives.
- Headache, vomiting, seizures, focal signs, papilloedema; fever may be absent.
- Cerebellar: nystagmus, ipsilateral ataxia.
- Contrast CT ring-enhancing lesion; no lumbar puncture.
- Vancomycin + third-generation cephalosporin + metronidazole for weeks; aspirate or excise.
- Sequelae: epilepsy, hemiparesis, hydrocephalus, learning problems.
Written by The House Job from standard references (Basis of Paediatrics by Pervez Akbar; Nelson Essentials of Paediatrics).
FAQ
Why do children with cyanotic heart disease get brain abscesses?
Blood bypasses the lungs through the right-to-left shunt, so bacteria that the lung capillaries would normally filter out reach the brain directly.
Why is a lumbar puncture avoided in suspected brain abscess?
The abscess acts as a mass with raised pressure, so removing CSF from below can cause brain herniation. The CSF also rarely identifies the organism.
Is fever always present?
No. Fever may be low-grade or absent, and the child may present only with headache, vomiting, seizures or a focal deficit.
When is surgery needed?
An encapsulated abscess causing mass effect is usually aspirated. Excision is considered for abscesses containing gas, multiloculated or posterior fossa abscesses, and fungal abscesses.