Brain Abscess In Children

Brain abscesses can occur in children of any age but are most common in children between 4 and 8 yr and neonates.

CAUSES.
The causes of brain abscess include embolization due to congenital heart disease with right-to-left shunts (especially tetralogy of Fallot), meningitis, chronic otitis media and mastoiditis, sinusitis, soft tissue infection of the face or scalp, orbital cellulitis, dental infections, penetrating head injuries, immunodeficiency states, and infection of ventriculoperitoneal shunts.

PATHOLOGY.
Cerebral abscesses are evenly distributed between the two hemispheres, and aapx. 80% of cases are divided equally between the frontal, parietal, and temporal lobes.. An abscess in the frontal lobe is often caused by extension from sinusitis or orbital cellulitis, whereas abscesses located in the temporal lobe or cerebellum are frequently associated with chronic otitis media and mastoiditis.

ETIOLOGY.
The responsible bacteria include streptococci (S. milleri, S. pyogenes group A or B, S. pneumoniae, S. faecalis), anaerobic organisms (gram-positive cocci, Bacteroides spp., Fusobacterium spp., Prevotella spp., Actinomyces spp.), and gram-negative aerobic bacilli (Haemophilus aphrophilus, H. parainfluenzae, H. influenzae, Enterobacter, E. coli, Proteus spp.). Citrobacter is most common in neonates. One organism is cultured in the majority of abscesses (70%), two in 20%, and three or more in 10% of cases. Abscesses associated with mucosal infections (sinusitis) frequently have anaerobic bacteria.

CLINICAL MANIFESTATIONS.
The early stages of cerebritis and abscess formation are associated with nonspecific symptoms, including low-grade fever, headache, and lethargy. The significance of these symptoms is generally not recognized, and an oral antibiotic is often prescribed with resultant transient relief. As the inflammatory process proceeds, vomiting, severe headache, seizures, papilledema, focal neurologic signs (hemiparesis), and coma may develop. A cerebellar abscess is characterized by nystagmus, ipsilateral ataxia and dysmetria, vomiting, and headache. If the abscess ruptures into the ventricular cavity, overwhelming shock and death usually ensue.

DIAGNOSIS.
The peripheral white blood cell count can be normal or elevated, and the blood culture is positive in about 10% of cases. Examination of the cerebrospinal fluid (CSF) shows variable results; the white blood cells and protein may be minimally elevated or normal, and the glucose level may be low. CSF cultures are rarely positive.

The electroencephalogram (EEG) shows corresponding focal slowing, and the radionuclide brain scan indicates an area of enhancement due to disruption of the blood-brain barrier in >80% of cases. CT with contrast and MRI are the most reliable methods of demonstrating cerebritis and abscess formation. MRI is the diagnostic test of choice.

TREATMENT.
The initial management of a brain abscess includes prompt diagnosis and institution of an antibiotic regimen that is based on the probable pathogenesis and the most likely organism. When the cause is unknown, the combination of vancomycin, a 3rd-generation cephalosporin, and metronidazole is commonly used.

A brain abscess can be treated with antibiotics without surgery if the abscess is <2 cm in diameter, the illness is of short duration (<2 wk), there are no signs of increased intracranial pressure, and the child is neurologically intact. If the decision is made to treat with antibiotics alone, the child should have weekly neuroimaging studies to ensure the abscess is decreasing in size.

Surgery is indicated when the abscess is >2.5 cm in diameter, gas is present in the abscess, the lesion is multiloculated, the lesion is located in the posterior fossa, or a fungus is identified. Associated infectious processes, such as mastoiditis, sinusitis, or a periorbital abscess, may require surgical drainage.

The duration of antibiotic therapy depends on the organism and response to treatment, but is usually 4–6 wk.

PROGNOSIS.
Mortality rate associated with brain abscess has decreased significantly to appx. 15–20 % with the use of CT or MRI and prompt antibiotic and surgical management.

Long-term sequel occur in at least 50% of survivors and include hemiparesis, seizures, hydrocephalus, cranial nerve abnormalities, and behavior and learning problems.