Clinical Features

Sudden, severe, progressive symptoms. Severe throbbing headache, fever, vomiting, rapid deterioration points to subdural abscess. Due to meningeal irritation, cortical vein thrombophlebitis, raised CSF pressure.

Meningeal irritation: Headache, high-grade fever, malaise, progressive drowsiness, neck rigidity, Kernig's sign. May be masked by prior antibiotics.
Thrombophlebitis of cortical veins: Aphasia, contralateral hemiplegia, hemianopia, seizures.
Raised CSF pressure: Papilledema, ptosis, dilated pupils (third cranial nerve involvement). Other cranial nerves may be involved.

Diagnosis

MRI superior to CT scan. Distinguishes epidural/subdural abscess. CT scan shows loculated subdural abscess. Lumbar puncture contraindicated (cerebellar tonsil herniation risk).

Treatment

Surgical emergency. Burr holes to drain abscess. High-dose broad-spectrum IV antibiotics. Mastoidectomy after abscess resolves, patient condition improves.

Otogenic Brain Abscess

Focal suppurative infection of brain parenchyma. ~50% in adults, 25% in children are otogenic. In adults, follows CSOM with cholesteatoma. In children, AOM. Cerebral abscesses (temporal lobe) commoner than cerebellar. Bimodal age distribution (pediatric, fourth decade).

Route of Infection

Direct extension of middle ear infection or retrograde thrombophlebitis of dural vessels.
Often associated with extradural abscess.
Cerebellar abscess: Direct extension through retrograde thrombophlebitis from sigmoid sinus (posterior mastoid wall).

Bacteriology

Both aerobic and anaerobic organisms. Polymicrobial cultures influenced by immune status.

Aerobic: Pyogenic staphylococci, S. pneumoniae, S. haemolyticus, P. mirabilis, E. coli, P. aeruginosa.
Anaerobic: Peptostreptococcus, B. fragilis.
H. influenza rarely found.

Pathogenesis

Brain abscess develops in four stages:

Invasion (initial encephalitis): Mild symptoms (headache, low-grade fever, malaise, drowsiness). Often unnoticed. Lasts 1-3 days.
Localization (latent abscess): Pus localizes, capsule forms. Patients asymptomatic for days/weeks. Lasts 4-10 days.
Enlargement (manifest abscess): Abscess enlarges, edema creates symptoms. Due to raised intracranial tension, cerebrum/cerebellum dysfunction. Lasts 10-13 days.
Termination (rupture of abscess): Expanding abscess ruptures into ventricle/subarachnoid space, resulting in fatal meningitis.

Clinical Features

Often associated with extradural abscess, perisinus abscess, meningitis, sigmoid sinus thrombosis, labyrinthitis. Clinical picture can overlap.

Toxic, drowsy.
Dizziness, nystagmus, vomiting, ataxia (cerebellar abscess). Temporal abscess (seizures).
Due to raised intracranial tension or affected brain area.

Symptoms and Signs of Raised Intracranial Tension

Headache: Severe, generalized, worse in morning.
Nausea, projectile vomiting (more in cerebellar lesions).
Altered consciousness: Lethargy to drowsiness, confusion, stupor, coma.
Papilledema: Absent early, appears late (>2-3 weeks). Appears early in cerebellar abscess.
Slow pulse, subnormal temperature.

Localizing Features of a Temporal Lobe Abscess

Nominal aphasia: (Dominant cerebral hemisphere, left in right-handed). Inability to name objects.
Contralateral homonymous hemianopia: Pressure on optic radiations. Visual field defect (upper quadrant). Confronta