Difficulties in the diagnosis of brain abscesses

The diagnosis of brain abscesses has been improved during the last 10 years because to introduction of computerized tomography (CCT) and improved methods for the analysis of cerebrospinal fluid (CSF). Typical ring-like enhancement in the CT and an elevated CSF cell count combined with disturbances of the blood-brain barrier and elevated CSF lactate are common and confirm preliminary diagnoses. However, in spite of these procedures, brain abscess is still sometimes misdiagnosed because of the lack of pathological CT findings or a misleading case history sometimes causing cerebral affections. We present the case histories of two young patients in whom diagnosis of brain abscess was delayed. We recommend the immediate performance of contrast-enhanced CT and CSF analysis. If these procedures do not exclude a brain abscess, antibiotic treatment should be begun immediately.     

Nocardia farcinica brain abscess: clinical and specific radiological findings and management. Report of two cases in immunononcompromised patients

Nocardia spp. cerebral abscesses are rare and usually occur in immunocompromised patients. We report two recent cases of cerebral abscesses due to Nocardia farcinica in immunocompetent patients and review the literature about diagnosis and therapeutic issues. Outcome was good for the two patients following an early identification of the bacteria. Stereotactic biopsy was performed in one case and craniotomy with excision of the abscess in the other case. In both cases, complete identification of the bacteria could be achieved, followed by prolonged antibiotic therapy. Exposure to the germ (mainly telluric) is often difficult to suspect from the past medical history of the patient. Diagnosis is also unexpected. Despite the typically and characteristic aspect on CT and MRI, specific identification and anti-microbial sensitivity profiles are necessary to optimize treatment. In some rare cases, unusual species like Nocardia farcinica, can be resistant to numerous antibiotics requiring adjustments of medical management. Early identification of the bacteria is necessary to achieve good outcome in immunocompetents patients.     

Brain stem abscess managed with computed tomography-guided stereotactic aspiration

The importance of stereotactic aspiration to the successful management of three cases of brain stem abscess is discussed with special reference to the advantages offered over medical treatment alone. Stereotactic aspiration allows evacuation of pus, accurate bacteriological diagnosis, selection of an optimal antibiotic regimen, and instillation of antibiotics directly into the abscess cavity. In two of the three cases described here, the abscess reaccumulated after initial aspiration despite appropriate maximal medical therapy. A repeat aspiration was required before resolution occurred. We conclude that medical management alone is not adequate for some cases of brain stem abscess. There was no morbidity that could be attributed to the procedure, suggesting that the risk of stereotactic aspiration is probably quite low and is likely to be less than the risk of incorrect diagnosis, suboptimal choice of antibiotics, or progression of the lesion despite appropriate maximal medical therapy.     

Current concepts of bacterial infections of the central nervous system. Bacterial meningitis and bacterial brain abscess

Investigative work continues to provide guidance toward more rational management of bacterial meningitis and bacterial brain abscess. An increased understanding of the host's response in cases of bacterial meningitis has established that diffusibility of an antibiotic into the cerebrospinal fluid (CSF) is necessary, but is not sufficient for microbial cure. The antibiotic must also have a bactericidal effect on the pathogen. Meningitis after neurosurgery may be caused by Gram-negative aerobic bacilli. In some of these cases the newer cephalosporin antibiotics may be a useful advance. Meningitis complicating ventricular CSF shunts presents a paradigm for the problem of eradicating foreign body-related infections. Studies of the interaction of the host, the organism, and the shunt material offer some explanation for the limited efficacy of antibiotics observed in this setting. There have been advances in microbial definition of bacterial brain abscess. The identification of Bacteroides fragilis as a pathogen in certain brain abscesses has established a role for a newly available antibiotic, metronidazole. The study of the pathological distinction between cerebritis and frank abscess is clarifying two clinical characteristics of brain abscess: the limited success of antibiotic treatment and the increase in intracranial pressure. Computerized tomography has offered a valuable clinical "look" at brain abscesses; however, there are still problems in correlating the scan images with the evolving pathological process.     

Infections of the central nervous system

Bacterial meningitis is a medical emergency. Presentation commonly includes headache, fever and neck stiffness. Prompt treatment with high-dose parenteral antibiotics is essential. Prior or concurrent dexamethasone administration improves neurological outcome. Diagnosis is confirmed by analysis of cerebrospinal fluid. Lumbar puncture should be preceded by a computed tomography (CT) head scan when raised intracranial pressure is likely. Brain abscesses usually result from spread from a local infection such as otitis media or sinusitis. Patients present with a 2–3-week history of fever, convulsions and signs of an intracranial mass lesion and can be very ill. CT scan classically demonstrates a ring-enhancing lesion. Treatment includes surgical drainage and high-dose parenteral antibiotics for 6–8 weeks. Subdural empyema is a collection of pus between the dura and arachnoid mater. Presentation is more acute than for brain abscesses. The mortality rate is ～34%. Epidural abscesses are commonly caused by Staphylococcus aureus and are associated with intravenous drug abuse and compromised immunity. Fever and backache are common signs. The diagnosis is confirmed by magnetic resonance imaging. Urgent surgical drainage is vital to preserve neurological function. Epidural abscesses following neuroaxial procedures occur in ～1:1000 patients. Strict adherence to infection guidelines is essential to limit this risk.     

The management of brain abscess in a developing country: are the results any different?

A retrospective study of 57 surgically-managed brain abscesses at the Neurosurgical Unit, Bir Hospital during a 6-year period from October 1990 is presented. Detailed hospital case notes could be traced in only 37 cases, consisting of 25 males and 12 females with age range from 5 months to 60 years. Cryptogenic abscess was the commonest category followed by abscess caused by chronic ear infection. The diagnosis was made with enhanced computed tomography (CT) in all the cases. Positive bacteriology was found in only nine cases. The treatment consisted of 6 weeks of intensive intravenous antibiotics and emergency surgical drainage of the abscess. Five out of the total cases died (13.5%). These patients were all in an extremely poor condition at the time of presentation. All the survivors made a good recovery. With timely CT diagnosis, surgical drainage and antibiotics, good results can be achieved even in a developing country.     

CT-guided stereotactic surgery of brain abscess

Seven patients with brain abscess underwent CT-guided stereotactic aspiration using Iseki's stereotactic apparatus. Three of them were under the age of fifteen and four were older than thirty. The lesions were single and round in four cases, multilobular in two and multiple in one patient. Operations were performed after systemic administration of antibiotics for more than two weeks and after capsule formation was confirmed on CTs. Preoperative volume of the abscesses was estimated from CTs. The target point chosen was the center of the ring of the largest diameter in the enhanced lesion. Abscess was aspirated under monitoring with intraoperative CT scan. No continuous drainage was performed and no antibiotics were given directly into the abscess cavity. In all cases the center of the abscess was punctured with a single trial. Average volume of the preoperative brain abscesses was 18.8ml. Aspirated volume at the time of the operation averaged 16.9ml and all the abscesses decreased to unmeasurable size on CTs. In five of seven patients abscesses were cured after a single aspiration, and in one case after the second operation. One case required extirpation of the lesion. During the follow-up period of four months to five and a half years six patients showed no recurrence. One patient died of unrelated cause four and a half years after the operation. No operative complication was noted. There was no operative morbidity or mortality. Using a CT guided stereotactic method, brain abscess is punctured so accurately, regardless of its location and size, that damage to the surrounding brain during operation can be minimized. Therefore it is highly possible to aspirate abscesses completely.(ABSTRACT TRUNCATED AT 250 WORDS)     

Liver abscesses

Clinical suspicion of a liver abscess mandates an investigation of the liver for evidence of a liver abscess by radionuclide, ultrasound, or CT scan. Amebic abscesses have a lower mortality rate than pyogenic abscesses. Amebic and pyogenic abscesses can be distinguished on the basis of epidemiologic, clinical, and laboratory studies. The definitive studies for identifying amebic liver abscesses are hemagglutinin or gel diffusion studies. Amebic abscess of the liver may be complicated by extension to the lung, with pulmonary complications. Patients suspected to have amebic abscesses require metronidazole. Emetine or chloroquine may be added if there is no response or if the abscess recurs. Unless there is a failure of the amebic abscess to resolve or secondary infection occurs, there is seldom a need to aspirate or drain these abscesses. Pyogenic abscesses should be treated with broad-spectrum antibiotics to cover gram-negative aerobes and anaerobic organisms. All pyogenic abscesses larger than 1.5 cm in diameter should be aspirated, and the aspirate should be Gram stained and cultured. Percutaneous or surgical drainage should then be performed. Operative intervention is required in those patients with intra-abdominal pyogenic infections that are seeding the liver abscess. The marked reduction in the mortality rate of pyogenic liver abscess witnessed in this decade is multifaceted and attributable in part to earlier diagnosis, permitting definitive treatment in a timely fashion, as well as to improved intensive unit care, antibiotic management, and operative technique.     

CT-guided stereotactic aspiration and treatment of brain abscesses

Summary The present study reports our experience with stereotactic puncture, aspiration and drainage of brain abscesses in 24 patients from a series of 34 consecutive cases. In all patients an intracavitary catheter was left in place for external drainage and daily irrigation with antibiotics. The patients received pre- and postoperatively triple broad spectrum antibiotic treatment, associated with low dose steroids and anti-epileptic drugs. Follow-up CT scans showed immediate reduction of the abscess size and gradual diameter diminution of the enhancing ring structure until its disappearance. The clinical presentation, risk factors, aetiology, outcome, bacteriological and CT findings were analysed. Mortality in this series was 4%. The majority of patients (96%) had no or minimal disability according to the Glasgow Outcome Scale. Our results confirm the value of this treatment policy and suggest that the stereotactic technique is a simple and safe method with minimal mortality and morbidity in the treatment of the majority of chronic brain abscesses.     

Stereotactic aspiration of brain abscesses: Is this the treatment of choice?

Summary Despite a reduction in the mortality of patients with brain abscess since the introduction of the computed tomography (CT) scanner, controversy persists as to the prefered method of treatment for this condition. Eleven patients were treated by CT guided stereotactic aspiration of pus and appropriate antibiotic therapy. A total of 14 aspirations were performed. Ten abscesses were supratentorial and one was in the posterior fossa.In 9 patients a bacterial cause was identified while in 2 a fungus was identified. A good outcome was achieved in 7 patients but 3 patients died. Another elderly patient remains disabled at home. The deaths occured in severely systemically ill patients with poor conscious levels on admission. Only one patient has epilepsy, controlled with anticonvulsants while another has not had further seizures since abscess treatment a year ago.Stereotactic aspiration should be considered the treatment of choice in all but the most superficial and largest cerebral abscesses, although the mortality of this condition in the severely ill remains high.     

Brain abscess following cerebral infarction: a case report

The authors report a case of brain abscess following cerebral infarction. A 73-year-old man was admitted to our clinic with symptoms of right hemiparesis and total aphasia. CT scan revealed abnormal low density area in the left fronto-temporo-parietal region. Cerebral angiography demonstrated occlusion of the left middle cerebral artery at the M1 portion. On the 16th hospital day, an episode of generalized seizure with high fever appeared, and intermittent high fever persisted thereafter. Two months after admission, CT scan revealed several cystic lesions with marked ring enhancement at the site of cerebral infarction, suggesting multiple abscesses. Aspirations of left frontal and parietal abscesses were accomplished and the cultures of the pus disclosed Proteus vulgaris. Due to progressive hydrocephalus, a ventriculoperitoneal shunt was constructed one month later. Repeated CT scans showed a gradual diminution of the abscesses. It is considered that the blood-brain barrier is broken and the local immunological system against bacteria may be weakened when the brain is damaged by ischemia. Brain abscess seems to be developed in such circumstances even under the influence of transient bacteremia which originates in other parts of the body. Therefore the possibility of cerebral abscess should be suspected if patients with cerebral infarction suffer from the symptoms such as fever, neck stiffness or disturbance of consciousness.     

Relevance of antibiotics in the treatment of brain abscesses

Summary A case of eight simultaneous brain abscesses in the right cerebral hemisphere, treated medically after puncture of two of them, is reported. Antibiotics and hypertonic mannitol and, after seven days, dexamethasone were sufficient to cure these lesions. CT scan was of primary importance to follow the evolution under treatment. To get the best efficiency from antibiotics, identification of the microorganism and assessment of its resistance to antibiotics are necessary. It is suggested that in certain conditions medical therapy might be sufficient to treat cerebral abscess, after simple puncture to isolate the infecting agent. Corticosteroids should be avoided in the acute phase because they prevent antibiotics from penetrating the abscesses.     

Cerebrovascular permeability and delivery of gentamicin to normal brain and experimental brain abscess in rats

Antibiotics vary widely in their ability to penetrate the blood-brain barrier. In studies of 70 rats, the permeability of the normal blood-brain barrier to gentamicin was shown to be poor. In experimental brain abscesses, during the cerebritic stage of development, the penetration of intravenous antibiotics was increased compared to normal brain but was very inconsistent. Antibiotic delivery to brain abscess was not significantly altered with the administration of high-dose steroids, but the macrophage and glial response was markedly decreased with high-dose steroid therapy. Reversible osmotic blood-brain barrier modification with mannitol increased the delivery of gentamicin both to brain abscess and to the surrounding brain. It also resulted in more consistent tissue drug levels. The clinical implications of these studies suggest that, because of the inconsistent delivery of gentamicin to brain abscess, the therapeutic efficacy of medical management alone may be quite variable. This mode of therapy could possibly increase the efficacy of medical management of brain abscesses, especially in patients with multiple or surgically inaccessible brain abscesses.     

Subtentorial cerebral nocardiosis in immunocompetent patients: CT and MR imaging findings

PurposeTo describe the clinical presentation and computed tomography (CT) and magnetic resonance imaging (MRI) appearances of subtentorial nocardia cerebral abscesses developing in immunocompetent patients.Patients and methodsThe clinical findings and the results of CT and MRI examinations of three immunocompetent patients with nocardiosis located initially only in the subtentorial region were studied. Three patients underwent CT examination and two patients had MRI.ResultsClinically, two patients had cerebellar syndrome and the third had meningism with fever. The diagnosis of nocardiosis was bacteriologically confirmed by demonstrating the organism in lumbar puncture fluid in one patient and by an aspiration biopsy of the abscess in the other two. Two of the patients improved under targeted antibiotic therapy whereas the third patient died. The main imaging features of the lesions were a multiloculated appearance with peripheral enhancement after intravenous administration of iodinated contrast material on CT and a multicystic appearance on MRI, with a peripheral hypointense rim on T2-weighted images, a relatively minor mass effect and a multiloculated appearance on gadolinium-chelate enhanced T1-weighted images.ConclusionThe clinical presentation of cerebral nocardiosis is relatively non-specific. A microcystic lesion surrounded by hypointensity on T2-weighted MR images with a multiloculated pattern after gadolinium chelate administration on T1-weighted MR images in association with a relatively minor mass effect should suggest this diagnosis even if the lesion is single and in the absence of immunosuppression.     

Treatment of bacterial brain abscess by repeated aspiration--follow up by serial computed tomography

Bacterial brain abscess often requires repeated aspiration before the abscess finally resolves. However, there are no guidelines for treatment by aspiration; for example, when should the abscess be tapped again, or when can an abscess be treated by antibiotics alone without further aspiration. Eleven patients with bacterial brain abscess treated by aspiration were evaluated to establish treatment guidelines for brain abscess, in particular the abscess size on serial computed tomography (CT) after aspiration. CT was performed about 24 hours after aspiration to evaluate the size of the abscess, and almost weekly during follow up. The diameter of the brain abscess before and after the initial and last aspirations were reviewed. In eight of the 11 patients, abscesses were aspirated repeatedly: two to three times in most patients. The diameter of the abscesses was 2.5-4.5 cm (mean 3.5 cm) before the last aspiration, and 1.4-3.4 cm (mean 2.3 cm) after the last aspiration, or when continuous drainage was discontinued. Perifocal edema was moderately decreased within 3 weeks after the last aspiration by medical treatment alone, with a concomitant decrease in the volume of the abscess. There were no deaths, and most patients had a favorable outcome. These results suggest that after the diameter of the abscess becomes less than 2 to 3 cm and does not increase anymore on serial CT, medical treatment alone can be anticipated to give satisfactory results without further aspiration.     

Brain abscess in 142 patients: factors influencing outcome and mortality

BACKGROUND: With the introduction of CT, stereotactic techniques, and broad-spectrum antibiotics, the outcome for brain abscess has dramatically improved. The purpose of this study was to identify prognostic factors by reviewing data on 142 patients with brain abscess. METHODS: Clinical data, including age, sex, medical history, duration of symptoms, initial neurological status, associated predisposing factors, laboratory data, treatment, and abscess characteristics, were considered as potential prognostic factors. A comparison was made between patients with favorable (GOS: moderate disability or good recovery) and those with unfavorable (GOS: death, persistent vegetative status, or severe disability) outcomes at discharge. Univariate (chi(2) analysis or Fisher's exact test) and multivariate logistic regression analyses were used to identify prognostic factors. Data were considered significant when the 2-tailed P value was lower than .05. RESULTS: There were 98 male and 44 female patients (male/female ratio, 2.2). Their average age at diagnosis was 41.5 years (range, 2-84 years). There were 105 patients with a favorable outcome and 37 with an unfavorable outcome. Both univariate and multivariate analyses indicated that patients who were male, had an initial GCS score >12, had no other septic complication, or had Gram-positive cocci grown in abscess cultures had better outcomes. No association was found between outcome and other factors, including age, focal neurological deficits, seizures, laboratory findings, characteristics of the abscesses, associated factors, and treatment modalities. CONCLUSIONS: With the advancement of imaging studies and broad-spectrum antibiotic therapies, the outcome of brain abscess depends on prompt awareness of the diagnosis and effective infection control.     

Supratentorial neurenteric cyst with spontaneous repetitive intracystic hemorrhage mimicking brain abscess: a case report

Neurenteric cyst (NC) is a benign epithelial cyst (BEC) of endodermal origin that mostly occurs in the spinal subdural space or posterior cranial fossa. A 28-year-old male presented with a left frontal lobe NC associated with spontaneous repetitive intracystic hemorrhage, which was initially diagnosed and treated as a brain abscess. He presented with headache and disorientation, without underlying diseases. A cystic tumor was suspected because of a hypointense signal on diffusion-weighted magnetic resonance imaging (MRI). One day after admission, his condition deteriorated rapidly and emergency cyst aspiration was performed. A brown viscous liquid like bloody pus comprising many neutrophils and macrophages was obtained. Although culture was negative, we initially started antibiotic treatment because of cyst content characteristics and rapid clinical course compatible with brain abscess. He was discharged without neurological deficits, but occasionally complained of intense headache. Computed tomography/MRI showed repetitive intracystic hemorrhage and gradual re-enlargement of the lesion. He underwent radical cyst excision by frontal craniotomy 34 months after aspiration. The pathological diagnosis was NC. We believe this is the first report of a supratentorial NC with spontaneous repetitive intracystic hemorrhage. BECs, especially with intracystic hemorrhage, are difficult to be distinguished from brain abscesses. In cases of cystic lesions or presumed brain abscesses refractory to treatment with aspiration and/or antibiotics, BECs should be considered, and radical cyst wall removal should be considered a treatment option.     

Surgical treatment of cerebral abscess with the use of a mobile ultralow-field MRI

Surgical intervention in cerebral abscess is indicated to confirm diagnosis, to identify pathogens for specific antibiotic therapy, or to reduce mass effect. Regarding long-term outcome, freehand or stereotactic aspiration are equally efficient compared to surgical resection. However, direct observation of relief of mass effect is not possible by either method. Six patients presenting with neurological symptoms and laboratory signs of infection and diagnosed with an intra-axial cystic lesion underwent frameless stereotactic aspiration of a cerebral abscess in our institution with the use of a mobile intraoperative magnetic resonance imaging (MRI) with a field strength of 0.15 T. Images were acquired before and during the procedure and used for neuronavigation. In all six cases, complete evacuation of the abscess with collapse of the cyst could be achieved and documented intraoperatively. No complications were observed. All patients showed clinical improvement postoperatively. We highlight the advantages of using a mobile intraoperative MRI unit with an illustrative case of a patient who had already undergone abscess evacuation without alleviation of symptoms before using intraoperative MRI. Finally, we discuss surgical treatment options of cerebral abscesses.     

Retroperitoneal abscesses--analysis of a series of 66 cases

OBJECTIVE: To analyze our experience with the management of retroperitoneal abscesses. PATIENTS AND METHODS: A retrospective study was made of 66 patients with retroperitoneal abscesses treated at our hospital from January 1975 to July 2001 for the purpose of analyzing the diagnosis and treatment of these rare infections. In each case, we analyzed patient characteristics, abscess location and origin, predisposing factors, clinical presentation, microbiology, radiographic findings, treatment, and outcome. RESULTS: In our series, the most frequent type of abscess was perinephric (45.4%), and the most frequent origin was the kidney (72.7%), generally renal lithiasis or previous urological surgery. Gram-negative bacilli were the microorganisms most often involved as causal agents of abscesses. CT had the best diagnostic performance (95%). Percutaneous drainage resolved the abscess in 86.3% of the patients in which it was used, compared with 87.5% for traditional surgical drainage. In 4 cases, the only treatment was administration of antibiotics. In all these cases the abscesses were smaller than 3 cm and patients were in good general condition. The mortality rate was excellent (1.5%), probably due to the low rate of comorbidity in our patients. CONCLUSIONS: Gram-negative bacilli were the most frequent microorganisms in our retroperitoneal abscesses. CT was the imaging technique that produced the most reliable and rapid diagnosis. Radiographically-guided percutaneous drainage was a safe and effective therapeutic alternative when used as definitive treatment or preoperatively.     

Prodromal signs and clinical factors influencing outcome in patients with intraventricular rupture of purulent brain abscess

OBJECTIVE: To elucidate prodromal signs and clinical factors influencing the prognosis in patients with intraventricular rupture of brain abscess (IVROBA) to prevent and manage this catastrophic condition. METHODS: In this study, 33 consecutive patients with IVROBA diagnosed by computed tomography (CT) were treated. Basic and therapeutic parameters were evaluated as independent predictive factors of a poor prognosis by using univariate analysis. The factors were statistically analyzed based on the interval between initial symptoms and IVROBA. RESULTS: Patients with a good outcome were younger (<21 yr old) (P < 0.003) and had fewer complications after IVROBA (P < 0.03). For the most part, these patients had undergone aspiration for brain abscess with ventricular drainage combined with the immediate administration of appropriate intravenous and intrathecal antibiotics (P < 0.02). In just a short time, abscesses located in the parieto-occipital region ruptured into the ventricle (P < 0.004), and those with nonsterile cultures (P < 0.01) developed into IVROBA. Just before IVROBA, patients had severe headaches, signs of meningeal irritation, and a rapidly deteriorating clinical condition within 10 days after the signs of meningeal irritation developed. A CT scan obtained before IVROBA ascertained localized enhancement of the ventricular wall adjacent to the abscess. CONCLUSION: Our findings suggest that signs of meningeal irritation and localized enhancement of the ventricular wall adjacent to the abscess, as observed on CT scans, preceded IVROBA. To decrease the mortality rate associated with purulent brain abscesses, signs forewarning of IVROBA should be recognized, and aggressive management of IVROBA should be initiated. Aggressive CT-guided aspiration of deep-seated abscesses, particularly in the parieto-occipital region, at the time forewarning signs of IVROBA are observed lead to the prevention of IVROBA and an improvement in outcome.