Cerebral abscesses produced by bacterial implantation and septic embolisation in primates

Case report on successful treatment for brain abscess in a Japanese monkey (Macaca fuscata)

BACKGROUND

A brain abscess in human beings is a focal infection of the central nervous system frequently characterized by areas of localized cerebritis and central necrosis surrounded by a well vascularized capsule. A brain abscess, although sporadically reported, is relatively rare disease in domestic animals (horses, cattle, goats and alpacas), companion animals (dogs and cats) and laboratory nonhuman primates. Brain abscesses are life threatening disease that needs early and aggressive veterinary therapy.

CASE PRESENTATION

The purpose of this study on a brain abscess in a Japanese monkey was to report the investigational and therapeutic processes including clinical observations, hematological and serum biochemical profiles, and magnetic resonance imaging (MRI) features, probiotic and antibiotic therapy. In clinical observation, the monkey presented with slowly progressive gentle and depressed behavioral change. Hematological findings showed that slightly declined platelet counts gradually increased in the course of the treatment. Serum biochemical profiles revealed initial markedly elevated. A series of chemotherapy provide prominent relief from the influence of the brain abscess. MRI images illustrated that a brain abscess was located in the right frontal lobe and the mass was delineated by a thick rim, indicating the capsule formation stage. The lesion chronologically decreased in size over the course of treatment. Until 11 weeks after treatment of the brain abscess, the size of brain abscess continued to reduce, leaving an organized lesion trace. To the best of my knowledge, this is the first report on successful treatment for a brain abscess in a Japanese monkey (Macaca fuscata).

CONCLUSIONS

Medical management of simian brain abscesses is possible based on the controlled and resolving nature of the lesions as determined by MRI and completion of a of chemical antibiotic treatment presented in this study.

Intratumoral abscess: an unusual complication of ventriculoperitoneal shunt infection

INTRODUCTION

Ventriculoperitoneal shunts were routinely used in the past in children with posterior fossa tumors and hydrocephalus. They can, however, cause a multitude of problems.

CASE REPORT

This report highlights a previously unencountered phenomenon of a pyogenic abscess forming within a posterior fossa ependymoma as a result of shunt infection. The shunt was exteriorized and the child treated with antibiotics before surgery was done. Only a partial excision of the tumor was possible, as the inflammatory response caused by the abscess had obliterated tissue planes.

Multiloculated Pyogenic Brain Abscess: Experience in 25 Patients

OBJECTIVE

To report our experience in treating multiloculated pyogenic brain abscess and determine whether there are differences in the bacteriology, predisposing factors, treatment choices, and outcomes between multiloculated and uniloculated brain abscesses.

METHODS

We studied clinical data collected during a 16-year period from 124 patients with pyogenic brain abscess, including 25 cases of multiloculated abscess.

RESULTS

The incidence of multiloculated brain abscess was 20%. In these 25 patients, hematogenous spread from a remote infectious focus was the most common cause of infection, as it was for the cases of uniloculated abscess. Headache and hemiparesis were the most common symptoms in patients with multiloculated abscess. In patients with uniloculated abscess, fever was the most common symptom. Viridans streptococci were the most commonly isolated pathogens. Bacteroides fragiliswas the most common anaerobe in multiloculated abscess, and aerobic gram-negative bacilli were the most common pathogens in patients with uniloculated abscess. Of the patients with multiloculated abscess, 21 were treated surgically and 4 were treated with antibiotics only. Overall, eight patients (38%) needed another operation because of abscess recurrence after the initial operation. In uniloculated abscess, the rate of abscess recurrence after initial surgery was 13.1%. Mortality was 16% in multiloculated abscess and 17.1% in uniloculated abscess.

CONCLUSION

Multiloculated abscesses accounted for 20% of our patients with pyogenic brain abscess. Excision seems to be the more appropriate surgical choice in multiloculated abscess. Prognosis for patients with multiloculated abscess can be as good as that for patients with uniloculated abscess. However, clinicians must carefully monitor these patients because the possibility of recurrence after surgery is significantly higher in patients with multiloculated abscess than in those with uniloculated abscess.

Diagnosis and management of abscesses in the basal ganglia and thalamus: a survey

A review is made of the current management strategies of abscesses in basal ganglia and thalamus, based on a review of the literature and three of our own cases. Clinical picture, aetiology, diagnostic, surgical treatment and outcome are discussed. Stereotactic abscess puncture in combination with temporary drainage and rinsing of the abscess cavity in combination with systemic medication of antibiotics has become the management of choice with satisfactory results.

Reevaluation of an experimental streptococcal canine brain abscess model

An experimental cerebral abscess model in which alpha-hemolytic Streptococci were inoculated into the brain parenchyma of dogs was evaluated for assessment of antimicrobial therapy. Intracerebral ring-enhancing lesions were visualized by computerized tomography, but they resolved after time without therapeutic intervention. Histopathological study demonstrated evolution of the lesions into sterile granulomas. Quantitative cultures were performed and uniformly became sterile in the early cerebritis stage, approximately 3 days after bacterial inoculation. Therefore, this brain abscess model should not be utilized for the evaluation of new antimicrobial treatment regimens. Rather, other models which document persistent viable organisms within cerebral abscesses need to be developed.

Multiple brain abscesses associated with a mycotic aneurysm of the left common carotid artery. Case report

A case is reported of multiple microabscesses confined to the left cerebral hemisphere and an aneurysm of the left common carotid artery. The aneurysm was presumed to be mycotic, secondary to extension of a tonsillar and pharyngeal infection. Infected microemboli dislodged from the aneurysmal sac were presumed to be the cause of the multiple microabscesses.

A model of brain abscess: septic homologous blood clot emboli in rats

Brain abscesses in rats were produced by intra-arterial injection of septic homologous blood clot emboli. The production rate was 100% and the histopathological features closely resembled those seen in other animal models and in spontaneously occurring brain abscesses in humans. This small-animal model may be useful for systematic study of the development of brain abscesses as well as for evaluation of various therapeutic procedures.

Experimental anaerobic brain abscess. Computerized tomographic and neuropathological correlations

The neuropathological progression of brain abscess formation induced by a mixed anaerobic culture of Bacteroides fragilis and Staphylococcus epidermidis was studied experimentally in dogs. Histological findings were correlated with computerized tomographic (CT) brain scans. The evolution of brain abscess formation could be divided into three stages based on histological criteria: early cerebritis (Days 1 to 3); late cerebritis (Days 4 to 9); and capsule formation (Day 10 and later). Capsule formation could not be divided into early and late stages because encapsulation was delayed compared with a previously reported model of alpha-Streptococcus brain abscess. Histologically, there was evidence for a very virulent infection. Leptomeningitis was significant even in the late stages. Early ventricular rupture occurred in 25% of the animals. A pattern of extensive purulent encephalitis was seen in 25% of the animals. In the early cerebritis stage, blood vessels near the necrotic center were engorged and were surrounded by hemorrhage and/or protein-rich fluid. Cerebral edema was extensive. Although fibroblasts appeared in late cerebritis, there was marked delay of capsule formation. Three-week-old lesions still had areas of incomplete capsule formation and foci of uncontrolled infection. In the cerebritis stages, CT scans showed an area of ring enhancement which was incomplete on early scans (at 5 minutes after injection of contrast material) but partially filled in and thickened on delayed scans (at 20 to 45 minutes). On even later delayed scans there was no decrease in intensity of ring enhancement. Lesions in which capsule formation occurred also showed ring enhancement, but delayed scans showed a decrease in the intensity of enhancement. The lesions that ruptured into the ventricular system showed atypical CT findings, with either lack of contrast enhancement (histologically there was minimal cerebritis adjacent to the abscess cavity) or a marked delay in contrast enhancement (cerebritis was more extensive and corresponded to the width of ring of enhancement). This study suggests that Bacteroides fragilis is a virulent organism in the brain. The developing abscesses enlarged quickly, were prone to early ventricular rupture, and showed incomplete and delayed encapsulation.

Clinical stages of human brain abscesses on serial CT scans after contrast infusion. Computerized tomographic, neuropathological, and clinical correlations

The authors describe a classification of human brain abscesses into stages of development as demonstrated on computerized tomography (CT) scans. The results of CT staging of 14 human brain abscesses are compared with the previously published findings in an experimental brain abscess model developed by the same authors. The CT criteria for categorizing brain abscesses into cerebritis and capsule stages were based on the pattern of contrast enhancement and the time-density curve of enhancement obtained from sequential CT scans after contrast infusion. Using these CT criteria, it was possible to accurately categorize all 14 brain abscesses into cerebritis and capsule stages. Histological examination of surgical and autopsy specimens provided immediate confirmation of the abscess stage in six patients. Indirect staging, based on surgical findings and/or subsequent autopsy findings, was possible in eight patients. Corticosteroid administration greatly reduced contrast enhancement in the cerebritis stage, but had little effect in the capsule stage. A systematic approach utilizing CT for establishing the diagnosis, staging, and treatment planning of brain abscess is proposed.

Brain abscess in congenital cyanotic heart disease

Sixty-two cases of brain abscess with congenital cyanotic heart disease are reviewed. A sharp peak in the age distribution was seen at 4 to 7 years of age. Of 62 cases, 38 (61.2%) had a tetralogy of Fallot, and six had a transposition of the great vessels. The majority of these abscesses were supratentorial and 76% of abscesses were found in the frontal, temporal, and parietal lobes. Multiple abscesses were present in 19.4% of cases. Sterile cultures were obtained in 61% of the abscesses, and the increasing percentage of sterile cultures seems to be the result of broad-spectrum antibiotic therapy. The overall mortality rate was 37% but there were no deaths after surgical excision secondary to aspiration. Since the introduction of computerized tomography, aspiration without total excision has produced good results, and therefore it is believed that the number of cases which are cured with aspiration therapy alone will gradually increase in the future.

Neuropathological and computerized tomographic findings in experimental brain abscess

The neuropathological progression of brain abscess formation was studied experimentally at sequential stages in dogs, and the findings correlated with the appearance on computerized tomographic (CT) brain scans. The evolution of brain-abscess formation was divided into four stages based on histological criteria: early cerebritis (Days 1 to 3); late cerebritis (Days 4 to 9); early capsule (Days 10 to 13); and late capsule (Days 14 and later). The cerebritis stage was characterized by prominent perivascular cuffing by inflammatory cells in the area adjacent to the developing necrotic center. However, the early elements of capsule formation appeared with the presence of fibroblasts by Day 5. The CT scans showed ring-shaped contrast enhancement by Day 3. Delayed scans at 30 minutes revealed diffusion of the contrast material into the developing necrotic center, forming a solid lesion. In lesions that were well encapsulated (14 days and older), five distinct histological zones were apparent: 1) a well formed necrotic center; 2) a peripheral zone of inflammatory cells, macrophages, and fibroblasts; 3) the dense collagenous capsule; 4) a layer of neovascularity associated with continuing cerebritis; and 5) reactive astrocytes, gliosis, and cerebral edema external to the capsule. The CT appearance of well encapsulated abscesses showed a typical ring-shaped contrast-enhancing lesion. On the delayed scans, the "ring" did not fill in with contrast enhancement. The diameter of the ring correlated best with the presence of cerebritis (perivascular infiltrates in the adventitial sheaths of vessels surrounding the abscess). The discussion focuses on the relevance of this study to the current management of patients with brain abscess.