European Journal of Cardiovascular Medicine

Brain abscess may result from a traumatic brain injury, neurosurgical procedures, contiguous spread from a local source, or hematogenous spread of a systemic infection.  Immunosuppressed patients, especially those patients who have received an organ transplant, are susceptible to the development of cerebral infections. ^[1]

Brain imaging is critical to diagnosis and management and is critical to improving outlook for brain abscess. Typical characteristics of imaging studies are illustrated. The early stages of cerebritis are characterized on non-contrast computed tomography (CT) by localized hypoattenuation. Contrast enhancement is variable in this stage and when present may demonstrate a nodular or ring-like pattern. This pattern remains unchanged or progresses on delayed images performed 30 to 60 minutes after contrast bolus administration. In the late cerebritis phase, non-contrast CT again demonstrates an area of hypoattenuation but contrasted images demonstrate a thick ring-like or nodular enhancement that persists on delayed images. ^[2] As a capsule begins to form, a round or ovoid area of hypoattenuation will present with ring enhancement that dissipates on delayed scans. En bloc abscess excision had historically been the approach of choice, but in the preceding several decades, CT-guided aspiration has become the more commonly practiced initial intervention. The improved outcome and prognosis of brain abscess in the CT era is largely credited to the feasibility and availability of stereotactic drainage. ^[3]

Computed tomography-guided aspiration is simpler than open excision and spares the patient the morbidity associated with the complications of extensive surgical trauma. It is favored in abscess in eloquent locations or in deep-seated abscess. It is preferred also in patients with multiple abscesses necessitating drainage. In cases where there is significant uncertainty in diagnosis, abscess wall biopsy is possible through a limited approach and may yield important information

The prospective study was done. Patients coming in to the authors’ department of Radiology with suspected space taking lesions in the brain and requested for computed tomography (CT) brain were included in the present study. Informed consents were obtained from the patients or their relatives before the present study. The present study was approved by the institute ethical committee. CTP scan was performed only in patients whose non-enhanced scans showed abnormal low density or mass effect. The pathological results were obtained in who patients underwent surgery. For patients treated by medical treatment, clinical outcomes and follow up were concluded to separate between brain abscess and tumor. CT perfusion study the locations of CTP were selected from levels that showed abnormality on non-enhanced scan. With the 64-multidetector CT scanner (Lightspeed; GE Medical Systems, Milwaukee, Wisconsin), 4 cm coverage was achieved with 5 mm slice thickness and interval. The 40-ml non-ionic contrast media was injected during the scan with a rate of injection 4 ml/ second. Post processing measurement was done using commercial work station (Advantage Windows; GE Medical System). With the deconvolution algorithm, cerebral blood volume, blood flow, mean transit time, and permeability surface index (CBV, CBF, MTT, and PS respectively) were measured at the enhancing rim, non-enhancing central lesion, surrounding oedema area, and contralateral normal brain. All lesions were measured with the same amount of area of region of interest (ROI) at the same level. All measurements were done by a more than 10 years experienced neuroradiologist blindly from clinical data. The values of each parameter are shown on the screen of the work station collected.

In this study, the age range was from 11 to 65 years and the mean age (±SD) was 34.18±16.81 years. Highest incidence of brain abscess, 29.1 %, was found in 10 to 20 years’ age group followed by 20.0% between 21 to 30 years’ age group and 20.0% between 41-50 years’ age group. Statistical analysis of patients of both sexes has revealed that they were within similar age distribution (p value= 0.385). Mean±SD age of male was 36±3.101 years whereas the Mean±SD of female was 32± 3.337 years. Median age of both male and female was 35 and 28 years respectively. Out of 55 patients 30 were male and 25 were fema1e, male to female ratio was 1.2: 1.

Single lesion was present in 83.6% patients and 16.4% had multiple lesions in the brain. 94.5% patients had abscess in graywhite matter junction and rests had within white matter. 52.7% patients had brain abscess on right cerebral hemisphere followed by 43.6% on left hemisphere and 3.6% had on cerebellum. 94.5% lesions were hypodense on CT and rests had both hypo and isodense feature. CT feature of midline shifting was observed in 67.3% patients, 80% patients had sulcal and gyral effacement and 27.3% had ventricular dilatation (Table 2). CT scan revealed that maximum patients 23 (41.8%) had brain abscess on temporal lobe followed by frontal lobe (29.1 %), parietal lobe (10.90/0), occipital lobe (3.6%), in cerebellum (3.6%), 5 (9.1 %) patients had brain abscess on temporoparietal lobes and 1.8% had frontoparietal lobes (Table 3). East African Scholars Publisher, enhanced the feature to diagnose brain abscess was 100.0%, positive predictive value 94.5%, and accuracy 94.5%. Negative predictive value and specificity cannot be calculated (Table 4). Presence of hypodense feature was found a reliable sign of brain abscess because sensitivity, specificity, positive predictive value, negative predictive value, and accuracy 98.1 %, 66.7%, 98.1 %, 66.7% and 96.4% respectively. In our series, out of 52 pathologically diagnosed brain abscess patients, 51 (98.1 %) had hypodense CT feature. One (33.3%) 'Other lesions' had hypodense CT feature. CT evaluation of location of abscess in gray-white matter junction in our series, out of 52 pathologically diagnosed brain abscess patients, 51 (98.1%) had abscess in gray-white matter junction. One (33.3%) 'Other lesions' had abscess in this location. Presence of abscess in this location was found a reliable sign of brain abscess because sensitivity, specificity, positive predictive value, negative predictive value, and accuracy 98.1%,66.7%, 98.1%, 66.7% and 96.4% respectively.  In our series, out of 52 pathologically diagnosed brain abscess patients, 42 (80.80/0) had sulcal and ventricular effacement. Two (66.7%) 'Other lesions' had sulcal and ventricular effacement. Sulcal and ventricular effacement was found a reliable sign of brain abscess because sensitivity, specificity, positive predictive value, negative predictive value, and accuracy 80.8%, 33.3%,95.5%,9.1% and 78.2% respectively. This result is shown in table 5. Out of all cases 52 were diagnosed as brain abscess by CT and confirmed by cultural and cytopathological evaluation. They were true positive. Three cases cytopathological findings. They were false positive. No false negative and true negative case was diagnosed. Sensitivity of CT to diagnose brain abscess was 100.0%, positive predictive value 94.50/0, and accuracy 94.5%. Negative predictive value and specificity cannot be calculated. (Table 6)

Brain abscess is a serious, life-threatening condition which, until a decade ago, was associated with a mortality of about 40%. Over the last ten to fifteen years the mortality has fallen to less than 10%. ^[6,7] The mean±SD age of the patients of present study group was 34.18±16.81 years with a range of 11 to 65 years. Highest incidence of brain abscess, 29.1%, was found in 10 to 20 years’ age group followed by 20.0% between 21 to 30 years’ age group and 20.0% between 41-50 years’ age group. The age distribution was from 3 days to 81 years in a study conducted. Mean age of series was 18 years with a range 05 months to 55 years. Study group consisted of 66 male and 30 female patients, mean age 29.7 years (range 5-80 years), with 29 patients (30%) being under the age of 15 years. ^{[8, 9]}  Out of 55 patients of present study group 30 were male and 25 were female. Here male and female ratio was found 1.2: 1.

Sixty-seven patients with brain abscess who were managed over 19 years studied. Their series had a 2.5 to I male predominance. Male predominance picture of this series was comparable with us. ^[10] Male dominant picture was also reported. Out of 82 patients of their study group 58 were male and 24 were female. On CT 94.5% lesions were hypodense and rests were both hypo and iso dense feature. All patients of present study group had CT feature of edema around the lesions and presented with ring enhancement. CT feature of midline shifting was observed in 67.3% patients, 80% patients had sulcal and ventricular effacement and 27.3% had ventricular dilatation. ^{[11, 12]} The examined 29 patients with the diagnosis of brain abscess by computed tomography (CT). In 28 instances the CT finding was hypodense lesion with ring enhancement which became more marked after administration of the contrast substance. Some scientist Niv the most common sites of the brain abscess were the frontal (53%) and temporoparietal (28%) lobes. CT is highly sensitive (>95%) in detecting this type of lesion. Unfortunately, ring-enhancing lesions seen on CT images are not specific for brain abscess; cystic and necrotic neoplastic lesions, hematomas, and infarcted brain tissue may have the same CT characteristics. ^[13,14] In our series, out of 52 pathologically diagnosed brain abscess patients, 51 (98.1%) had hypodense CT feature. One (33.3%) 'Other lesions' had hypodense CT feature. We therefore consider that absence of hypo dense CT feature a very low possibility of being lesions other than brain abscess.

Brain abscesses are usually diagnosed on the basis of findings from CT and MR imaging, together with the clinical manifestations. CT scan thus can be regarded as a primary imaging modality in the diagnosis of brain abscess. The study was limited to the patients who underwent CT with subsequent operation & pathological examination. The ability to make a rapid diagnosis of a brain abscess is very important in order to provide the correct medical treatment. CT scan thus can be regarded as a primary imaging modality in the diagnosis of brain abscess.

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