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Biomedical subjects

R H Britt

Publications and source records attributed to R H Britt.

At least 37 records · Page 2Linked to original sources
PubMed1984

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.

Animals↗
PubMed1983

Staging of human brain abscess by computed tomography.

Precontrast and postcontrast computed tomographic (CT) scans of patients with brain abscesses were quantitatively studied to determine if the degree of encapsulation could be predicted. The findings in these cases correlated closely to the CT criteria for encapsulation previously established in an experimental model. Time-density curves of serial delayed postcontrast CT scans and the precontrast CT appearance yielded accurate criteria for determining the degree of encapsulation. The effect of corticosteroid treatment on contrast enhancement of brain abscess was also studied in one patient.

Brain Abscess↗
PubMed1983

Fusarium brain abscess. Case report.

The common soil fungus, Fusarium, is rarely pathogenic in man but occasionally causes serious disease, particularly in immunocompromised hosts. A case is reported of Fusarium brain abscess and meningitis occurring in a patient with chronic infectious mononucleosis syndrome and immunodeficiency. The patient died despite aspiration of the abscess and treatment with amphotericin B. This case demonstrates the importance of identifying the offending pathological organism through abscess aspiration in immunocompromised patients.

Adolescent↗
PubMed1983

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.

Adolescent↗
PubMed1982

Short term, high dose corticosteroids in computed tomographic staging of experimental brain abscess.

A short term, high dose corticosteroid treatment protocol was investigated to determine its clinical utility in staging an experimental brain abscess. Corticosteroids were shown to decrease the degree of contrast enhancement of brain abscess 12 h after administration but the magnitude of the effect was not consistent enough to be clinically useful in staging. The corticosteroid effect progressively diminished as the inflammatory lesion encapsulated over time. This effect emphasized that a decreasing ring diameter and not diminished contrast enhancement should be the CT criterion for brain abscess resolution.

Adrenal Cortex Hormones↗
PubMed1982

Quantitative analysis of methods for reducing physiological brain pulsations.

Normal movements of the mammalian brain, caused by the arterial and venous pressure fluctuations of each cardiac and respiratory cycle, have made obtaining stable intracellular recordings from neurons difficult. This study quantitated the movements of the cats' brainstem and examined the effects of traditional neurophysiological techniques used to reduce pulsation. Two components of brain movement were recorded: (1) an arterial component--relatively low amplitude (110-266 micrometers) and short duration (330-400 ms) excursions corresponding to the pressure wave of each cardiac systole [A-wave]; and (2) a pulmonary component--slower (10-12/min), high amplitude plateau-like displacement (300-950 micrometers) lasting for a time (2.4-5.1 s) corresponding to the inspiration of each respiratory cycle [P-wave]. Pneumothoraces and mechanical ventilation combined with elevating the animal's head reduced the pulmonary component by an average of 68% and the arterial component by 40%. Cerebrospinal fluid drainage could reduce the P-wave component of movement by as much as 50%. To reduce arterial pulsations below 100 micrometers, the mean arterial pressure (MAP) had to be lowered to less than 40 mm Hg, which was not compatible with maintaining normal brainstem auditory evoked responses. Residual movements at MAPs greater than 50 mm Hg were still sufficient to make stable intracellular penetration of small neurons difficult. The authors suggest the solution to this problem is the development of a cardiopulmonary bypass system which generates a non-pulsatile flow of oxygenated blood, described in a companion paper.

Animals↗
PubMed1982

High-resolution ultrasound evaluation of experimental brain abscess evolution: comparison with computed tomography and neuropathology.

Computed tomographic (CT) and high-resolution ultrasound (HRUS) imaging of experimental brain abscess were correlated with neuropathologic findings in nine mongrel dogs. The HRUS scan was more sensitive to different histologic features than the CT scan but both accurately delineated the evolution of the experimental brain abscess. All stages of abscess evolution were characterized by an appearance of an echogenic rim with a hypoechoic center. In the early stages the echogenicity of the abscess was related primarily to marked cellular infiltration, while in the late stages extensive collagen deposition correlated closely with the echo pattern. The size of the abscess in the cerebritis stages appeared smaller on the HRUS scan than on the CT scan because the latter modality detected the extensive cerebritis around the developing necrotic center whereas the HRUS scan did not. This discrepancy disappeared in the capsule stages. The HRUS scan provided a more accurate depiction of the neuropathologic characteristics of the necrotic than did the CT scan. Healing of the abscess, indicated by a decrease in size of the hypoechoic center, was accurately detected by the HRUS scan.

Animals↗
PubMed1982

The effect of short-term corticosteroid treatment on the CT appearance of experimental brain abscesses.

The effect of short-term corticosteroid treatment on contrast enhancement was investigated in an experimental brain abscess model. The degree of enhancement was reduced in the cerebritis stage, unaffected in the capsule stage, and intermediate in the transitional stage. The area and pattern of enhancement were also altered in the cerebritis stage. Although the magnitude of the entire cerebritis time-density curve (extended for 60 minutes) was decreased by the steroids, its configuration was unchanged. Prior to steroid administration, the 10- and 60-minute components of the curve discriminated between cerebritis and capsule stages, with the latter exhibiting a far lower 60-minute value. Implications for treatment of brain abscesses are discussed.

Animals↗
PubMed1982

Effects of sodium pentobarbital, ketamine, halothane, and chloralose on brainstem auditory evoked responses.

A parametric study was performed in cats comparing the effects on the brainstem auditory evoked response of four anesthetic agents used either in the operating room or the laboratory: sodium pentobarbital, ketamine, halothane, and chloralose. Each anesthetic agent was administered to each of four cats in varying sequence. Click-evoked brainstem auditory evoked responses (BAER) were compared for differences in wave form configuration, latencies, and amplitudes of the component peaks. Five distinct peaks (I to V) could be identified in the brainstem auditory evoked responses of every animal using each anesthetic agent. There were no statistically significant differences in mean latencies of the component peaks among anesthetic agents. Amplitude differences of the component peaks between animals using the same anesthetic agent were too large to be meaningfully compared. This study suggests that the click-evoked brainstem auditory response is a useful means of monitoring the integrity of the ascending auditory pathway during neurosurgical procedures as the wave form and latencies of the component peaks are not affected by a variety of parenteral and inhalation anesthetic agents.

Animals↗
PubMed1981

Long-term use of diazepam.

Plasma concentrations of diazepam and its major active metabolite nordiazepam were measured in 108 neurosurgical patients taking diazepam in doses of 5 to 40 mg/day for periods from one month to 16 years. Diazepam was used for relief of pain or muscle spasm, or anxiety and sleeplessness associated with these two symptoms, and was considered to be beneficial by 83% of the patients, although use of other drugs confounded this evaluation. Concentrations of total diazepam-nordiazepam ranged from 0 to 2,584 ng/mL, with nordiazepam being the predominant metabolite. "Low" concentrations (less than 250 ng/mL) were found in 35 of the 108 patients, with 19 having concentrations lower than 100 ng/mL. "High" concentrations (greater than 900 ng/mL) were found in 20 patients and did not occur more frequently than in other studies of long-term diazepam ingestion. Even with long-term use, diazepam seemed to retain its efficacy and did not lead to any clear-cut abuse.

Adult↗
PubMed1981

Intracranial infection in cardiac transplant recipients.

Infections have produced most of the deaths in the Stanford cardiac transplant program. Of the first 182 transplant recipients, 27 developed nonviral intracranial infections: meningoencephalitis/abscess in 16 patients, meningitis in 9, and rhinocerebral phycomycoses in 2. The responsible organisms included aspergillus, toxoplasma, candida, klebsiella, cryptococcus, coccidioides, listeria, mucor, and rhizopus. Characteristically, the areas of meningoencephalitis and abscesses were multiple and deep seated. Intracranial infections were invariably associated with pulmonary or disseminated infection with same organism. Computed tomographic (CT) brain scans in patients with meningoencephalitis often showed minimal, nonspecific, low-density lesions which usually did not exhibit contrast enhancement. At surgery the lesions were found to differ from typical pyogenic abscesses in that capsules were not well developed, and the aspirate consisted of necrotic fragments of edematous white matter and inflammatory cells rather than liquefied pus. Aspergillus infections of the central nervous system usually developed within the first three months after transplantation. Cases of meningitis occurred at variable times after transplantation, but approximately half appeared within 30 days after immunosuppressive therapy for treatment of rejection was increased. The prognosis for brain abscess depended on the causative organism. All patients with aspergillus infection died despite treatment with amphotericin B. The toxoplasma abscess responded to a combination of sulfadiazine and pyrimethamine. Meningitis was successfully suppressed or cured with appropriate treatment except for 1 patient with disseminated cryptococcosis.

Adult↗
PubMed1981

Occult arteriovenous malformation of the brainstem simulating multiple sclerosis.

A patient who proved to have an angiographically occult arteriovenous malformation of the brainstem and cerebellum was thought to have multiple sclerosis for 20 years, because of fluctuating brainstem symptoms and signs. Although the computed tomographic (CT) appearance of the lesion suggested a vascular malformation, because it bridged the subarachnoid space between the brainstem and cerebellum, an arteriogram was normal. This report stresses the importance of CT in making the diagnosos of occult arteriovenous malformations of the brainstem. On CT scan, these lesions generally have a high-density multiform appearance, which may enhance with contrast infusion. This lesion should be suspected clinically when there are fluctuating neurologic symptoms and signs attributable to the same neuroanatomic location within the brainstem. Surgical biopsy may confirm the diagnosis, but attempts to remove these lesions from the brainstem parenchyma are hazardous and probably are not indicated, considering the chronic and relatively benign course.

Adolescent↗
PubMed1981

Experimental study of high-resolution ultrasound imaging of hemorrhage, bone fragments, and foreign bodies in head trauma.

The accuracy of high-resolution ultrasound scans in detecting foreign bodies and hemorrhage within the brain was evaluated by comparison with computerized tomography (CT) scans and gross pathology. The test lesions were blood and foreign bodies consisting of bone, wood, and metal placed in the brain of an experimental animal. High-resolution ultrasound scans (10 MHz) performed in coronal and sagittal planes accurately delineated the position and spatial orientation of these foreign bodies and hemorrhage. Both hemorrhage and foreign bodies were echogenic compared to normal, hypoechoic brain parenchyma. Metal fragments had a highly characteristic echo pattern caused by sound reverberation within the object. Acute intracerebral hemorrhage produced an ultrasound image consisting of sharply circumscribed homogeneous echoes. The sonographic shape of intracerebral hemorrhage correlated closely with the area of increased density seen on the CT scan. High-resolution ultrasonography accurately delineated experimentally produced components of head trauma and may prove useful as an intraoperative imaging technique to facilitate surgery in head-injured patients.

Animals↗
PubMed1981

Balloon catheter occlusion for cavernous carotid artery injury during transsphenoidal hypophysectomy. Case report.

During transsphenoidal hypophysectomy for pituitary ablation in a patient with disseminated breast cancer, brisk arterial hemorrhage occurred during separation of adhesions between the pituitary gland and the wall of the cavernous sinus. Hemorrhage was controlled by placement of a Prolo balloon catheter into the internal carotid artery (ICA) that occluded the site of hemorrhage. The patient experienced no neurological sequelae. The cervical ICA was easily exposed for insertion of this double-lumen catheter. With the image intensifier already in position, injection of contrast material through the arteriography lumen allowed precise localization of the site of injury and directed positioning of the balloon for control of the hemorrhage.

Carotid Artery Injuries↗