Otogenic Brain Abscess

🧠 Otogenic Brain Abscess

📌 Definition of Otogenic Brain Abscess

Otogenic Brain Abscess is a localized collection of pus in the brain parenchyma, usually occurring as a complication of chronic suppurative otitis media (CSOM) or acute otitis media.

Incidence:

• Accounts for 50% of brain abscesses in adults
• 25% of brain abscesses in children are otogenic

Common Sites:

• Temporal lobe
• Cerebellum

What is the most common site of otogenic brain abscess?

Age Distribution:

• Bimodal peaks: Pediatric age group and 4th decade

Sex Distribution:

• Male : Female = 3 : 1

🧠 Causes of Otogenic Brain Abscess

• Children: Most commonly due to acute otitis media
• Adults: Most commonly due to cholesteatoma

🧬 Routes of Infection of Otogenic Brain Abscess

• Cerebral abscess:

  • Direct spread via tegmen
  • Retrograde thrombophlebitis

• Cerebellar abscess:

  • Spread through Trautmann’s triangle
  • Sometimes retrograde thrombophlebitis

What are the boundaries of Trautmann's Triangle?

🦠 Microbiology of Otogenic Brain Abscess

• Aerobes: Staphylococcus, Streptococcus pneumoniae, Streptococcus haemolyticus, Proteus, E. coli, Klebsiella, Pseudomonas

• Anaerobes: Peptostreptococcus, Bacteroides fragilis

Which is the most common microorganism seen in Otogenic Brain Abscess?

🔬 Pathological Stages of Otogenic Brain Abscess

1. Early Cerebritis (Day 1–3):

   • Perivascular inflammation
   • Mild symptoms (headache, fever, malaise)

2. Late Cerebritis (Day 4–9):

   • Pus formation
   • Enlarged necrotic center
   • Cerebral edema

3. Early Capsule Formation (Day 10–13):

   • Capsule forms on cortical side
   • Ring enhancement on CT/MRI
   • Symptoms: Raised intracranial pressure, focal neurological signs

4. Late Capsule Formation (Day 14+):

   • Dense collagenous capsule, necrotic core
   • Reduced edema, gliosis outside capsule
   • Risk of rupture → ventricles/subarachnoid space → fatal meningitis

🩺 Clinical Features of Otogenic Brain Abscess

Due to Raised Intracranial Pressure

• Severe generalized headache
• Nausea & projectile vomiting
• Lethargy → drowsiness → coma
• Papilledema
• Bradycardia, subnormal temperature

Localizing Features

• Temporal Lobe Abscess:

  • Nominal aphasia
  • Contralateral homonymous hemianopia
  • Contralateral motor paralysis
  • Epileptic fits
  • Oculomotor palsy, pupillary changes

• Cerebellar Abscess:

  • Suboccipital headache, neck rigidity
  • Spontaneous nystagmus
  • Ipsilateral hypotonia, ataxia
  • Past pointing, intention tremor
  • Dysdiadochokinesia

🧪 Investigations of Otogenic Brain Abscess

• Imaging:

  • CT Brain: Ring-enhancing lesion (temporal lobe/cerebellum)

  • MRI Brain: More sensitive, detects early spread/ventricular rupture

  • CT Temporal Bone: To evaluate ear disease

• Lumbar puncture:

  • Usually avoided (risk of coning)

What is the Investigation of choice (IOC) of Otogenic Brain Abscess?

What are the findings on performing lumbar puncture in Otogenic Brain Abscess?

💊 Treatment of Otogenic Brain Abscess

1- Medical

• Antibiotics:

  • 3rd gen cephalosporins, chloramphenicol, metronidazole
  • Aminoglycosides if pseudomonas suspected
  • Guided by culture sensitivity of ear discharge

• Intracranial pressure control:

  • Dexamethasone
  • Mannitol 20%

What is the dose of Dexamethasone and Mannitol for reducing intracranial pressure in Otogenic brain abscess?

• Ear discharge management: Suction clearance, topical ear drops

2- Surgical

Neurosurgery:

• Repeated aspiration via burr hole
• Excision
• Open drainage & evacuation

Otologic Surgery:

• Performed after neurological stabilization
• Acute OM cases: Often resolve with antibiotics
• CSOM cases: Require radical mastoidectomy

⚠️ Complications of Otogenic Brain Abscess

• Ventriculitis
• Status epilepticus
• Respiratory failure
• Motor/speech/visual deficits
• Encephalitis
• Septicemia

🩻 Differential Diagnosis of Otogenic Brain Abscess

• Subdural empyema
• Bacterial meningitis
• Viral meningoencephalitis
• Superior sagittal sinus thrombosis
• Acute disseminated encephalomyelitis