A 9 year old boy with Fallot's tetralogy, had high grade fever followed by focal seizure 2 days prior to hospital admission. His blood counts were increased and predominantly polymorphs. CT scan of the head showed a focal lesion suggestive of an abscess. Where would be the commonest location of brain abscess in this patient?

Cyanotic congenital hea diseases like TOF are a significant risk factor for brain abscess. The moality associated with the condition is very high. Focal ischemia in the brain, paicularly the parietal lobe is the cause. Otogenic : Temporal lobe and cerebellum ; Paranasal sinuses : Frontal Lobe. Intracranial abscesses can originate from infection of contiguous structures (eg, otitis media, dental infection, mastoiditis, sinusitis) secondary to hematogenous spread from a remote site (especially in patients with cyanotic congenital hea disease), after skull trauma or surgery, and, rarely, following meningitis. In at least 15% of cases, no source can be identified.