Giant gram-negative brain abscesses. Report of two cases

Giant brain abscesses have become a rarity in North American pediatric neurosurgery practice. A high index of suspicion and readily available noninvasive brain imaging have made the diagnosis of brain abscess easier and more prompt than in past decades. There are complicating factors, however, that may delay a timely diagnosis and allow the disease to progress to extremes before becoming evident. Children with hydrocephalus and ventricular shunts can harbor large abscesses. As the volume of purulent material expands, cerebrospinal fluid can be forced down the shunt system, reducing the intracranial pressure (ICP), at least for a time. Infants are typically more tolerant of an expanding mass lesion, allowing considerable time to pass before symptoms of increased ICP manifest. The authors report two cases of brain abscess, which achieved giant dimensions before the children became symptomatic. The pathogens were found to be Gram negative and of several species. The properties of these Gram-negative pathogens to create abscess and the clinical circumstances, including the presence of meningitis and ventricular shunts, which contributed to the process, are explored.