Correct Answer: D. Temporal lobe abscess
Chronic suppurative ear infection (CSOM) is a well-established risk factor for intracranial complications, particularly brain abscess. The temporal bone's anatomical proximity to the temporal lobe, combined with osteitis and thrombophlebitis of cortical veins, creates a direct pathway for infection to spread. The clinical triad of fever, headache, and altered mental status (confusion, irritability) with vomiting strongly suggests a space-occupying lesion with raised intracranial pressure. The CT imaging showing a focal lesion in the temporal lobe region adjacent to the infected mastoid confirms localized parenchymal infection rather than diffuse meningeal involvement. Temporal lobe abscess is the most common site of brain abscess secondary to otogenic infection in Indian clinical practice, accounting for approximately 40–50% of otogenic intracranial complications. The mechanism involves direct extension through cortical erosion, retrograde thrombophlebitis of cortical veins draining the infected mastoid, or rarely, hematogenous spread. The focal neurological signs and imaging findings distinguish this from meningitis (which presents with diffuse meningeal enhancement) and subdural collections (which are typically epidural or subdural in location, not parenchymal).
Why the other options are wrong
A. Cerebellar abscess — While cerebellar abscess is a recognized otogenic complication, it accounts for only 5–10% of otogenic brain abscesses in Indian series. The clinical presentation and CT imaging localization to the temporal lobe region (not the posterior fossa) rule this out. Cerebellar abscess typically presents with ataxia, nystagmus, and signs of hydrocephalus due to fourth ventricle compression—not the focal temporal lobe findings described here. B. Meningitis — Meningitis presents with diffuse meningeal inflammation and would show diffuse meningeal enhancement on contrast CT/MRI, not a focal parenchymal lesion. While fever, headache, and confusion occur in both conditions, meningitis lacks the focal neurological deficits and localized space-occupying lesion seen on imaging. The CT finding of a discrete temporal lobe lesion is pathognomonic for abscess, not meningitis. C. Subdural abscess — Subdural abscess is a collection between dura and arachnoid, typically appearing as a crescent-shaped or lens-shaped lesion on CT/MRI, not a focal intraparenchymal lesion. While otogenic infection can cause subdural empyema, the imaging description and clinical context point to a parenchymal (temporal lobe) location. Subdural collections are less common than parenchymal abscess in otogenic disease.
High-Yield Facts
- Temporal lobe abscess is the most common site (40–50%) of otogenic brain abscess in Indian patients with chronic suppurative ear infection.
- Otogenic brain abscess typically presents with fever, headache, vomiting, and altered mental status (confusion/irritability) due to raised intracranial pressure.
- Mechanism of spread: direct cortical erosion, retrograde thrombophlebitis of cortical veins, or rarely hematogenous dissemination from infected mastoid bone.
- CT imaging shows a focal intraparenchymal lesion with ring enhancement (after contrast), distinguishing it from meningitis (diffuse enhancement) and subdural collections (extra-axial location).
- Mortality of untreated otogenic brain abscess exceeds 80%; early neurosurgical drainage combined with prolonged IV antibiotics (4–6 weeks) is the standard of care in Indian practice.
Mnemonics
OTOGENIC BRAIN ABSCESS SITES (OTO-BRAIN) Temporal lobe (40–50%) > Cerebellar (5–10%) > Subdural (rare). Remember: Temporal is Top in otogenic disease. SPREAD PATHWAYS (3 Vs) Veins (retrograde thrombophlebitis) > Vascular (hematogenous) > Vertebral (direct cortical erosion). Veins are the primary culprit in otogenic spread.
NBE Trap
NBE may pair "meningitis" with fever + headache + confusion to trap students who forget that meningitis shows diffuse meningeal enhancement (not focal parenchymal lesion) on imaging. The focal CT finding is the discriminator.
Clinical Pearl
In Indian ENT practice, any patient with CSOM presenting with neurological symptoms (headache, confusion, vomiting) must undergo urgent CT/MRI brain to rule out intracranial extension. Temporal lobe abscess is the most common finding and requires immediate neurosurgical consultation for drainage alongside prolonged IV antibiotics—delay significantly increases mortality.
_Reference: Bailey & Love Ch. 63 (Otology); Robbins Ch. 28 (CNS Infections)_