AKT · Neurology/Infection & structurallow yield

Brain abscess

Focal suppurative intracranial infection (contiguous/haematogenous spread)

Overview

A focal collection of pus within the brain parenchyma, from contiguous spread (sinusitis, otitis, dental) or haematogenous seeding (endocarditis, right-to-left shunt). Presents with the combination of raised ICP, focal deficit and infection. Imaging shows a RING-ENHANCING lesion.

Recognise

Headache (raised ICP), fever, focal neurological deficit, seizures; the classic triad is present in a minority
Source: sinusitis/otitis/dental infection, endocarditis, cyanotic heart disease, immunocompromise
Ring-enhancing lesion on contrast CT/MRI

Red flags

Raised ICP, rapid deterioration, rupture into the ventricles; immunocompromise

Differentials & how to tell them apart

Brain tumour (primary/metastasis)also ring-enhancing — but less acute, no infective source/fever; imaging characteristics + biopsy

Toxoplasmosismultiple ring-enhancing lesions in HIV/immunocompromise

TuberculomaTB context

Encephalitisdiffuse parenchymal, no discrete pus collection

Investigations

Contrast CT/MRI (ring-enhancing lesion + oedema), blood cultures, raised CRP/ESR; aspiration for microbiology; find the source.

Management

IV antibiotics (ceftriaxone + metronidazole) + neurosurgical drainage; treat the source

1Contrast imaging; IV empirical antibiotics (ceftriaxone + metronidazole) and neurosurgical aspiration/drainage; identify and treat the source (sinus/ear/dental/cardiac).Gate: A ring-enhancing lesion is not automatically a tumour — fever + an infective source + raised inflammatory markers point to abscess (aspiration is both diagnostic and therapeutic)
2Culture-directed prolonged antibiotics, anticonvulsants for seizures, manage raised ICP; treat the primary source.

IV antibiotics (e.g. ceftriaxone + metronidazole) — empirical, then culture-directed

Surgical drainage — aspiration/excision if accessible/large

Key points

Ring-enhancing lesion + fever + a source (sinus/ear/dental/endocarditis) = abscess, not tumour. Multiple ring-enhancing lesions in HIV → toxoplasmosis. Aspiration gives the organism.

Monitor & prognosis

Neuro status, repeat imaging, inflammatory markers, antibiotic course.

Good with drainage + antibiotics; worse with delay or ventricular rupture.

Source: StatPearls; neurosurgical guidance