Biomedical subjects

Martin Bendszus

Publications and source records attributed to Martin Bendszus.

43 records · Page 3Linked to original sources

PubMed2002

Hemodynamic effects of decompressive craniotomy in MCA infarction: evaluation with perfusion CT.

Decompressive craniotomy in hemispheric infarction has been reported to reduce mortality and improve outcome. Identifying tissue at risk and monitoring the benefit of craniotomy is hardly practical and has not been reported thus far. Perfusion CT was applied before and immediately after decompressive craniotomy in a patient with space-occupying middle cerebral artery (MCA) infarction. Before surgery, perfusion CT revealed malperfused but still vital tissue in the vicinity of the infarction core which returned to normal after decompressive surgery. The final infarct size did not exceed the area of the initial hypodensity on unenhanced CT scan. In critically ill patients, the practicability of perfusion CT allows for demonstration of tissue at risk around the infarct core in space-occupying MCA infarction. Moreover, it may be used to monitor the effect of decompressive craniotomy.

Cerebrovascular Circulation↗

PubMed2002

Brain damage after coronary artery bypass grafting.

BACKGROUND: Coronary artery bypass grafting (CABG) is associated with a risk for focal neurological deficits and neuropsychological impairment postoperatively. OBJECTIVES: To examine the brain damage after CABG using diffusion-weighted magnetic resonance imaging and (1)H-magnetic resonance spectroscopy (MRS) and to correlate the results with neurological and neuropsychological findings. PATIENTS AND METHODS: Thirty-five consecutive patients undergoing elective CABG were included. Patients underwent a neurological and neuropsychological examination before and after CABG. The magnetic resonance protocol was applied before and after (mean, 3 days) surgery and included a diffusion-weighted sequence and single-voxel MRS measurements in the frontal lobes. RESULTS: None of the patients revealed a new focal neurological deficit after surgery. Diffusion-weighted magnetic resonance imaging demonstrated new ischemic lesions in 9 (26%) of the patients. The presence of an ischemic lesion was not related to impaired postoperative test performance (P>.50). The apparent diffusion coefficient values in the cerebellum and the centrum semiovale exhibited an increase after surgery (P<.01), consistent with vasogenic edema. Following surgery, MRS revealed a significant decrease in the metabolite ratio of N-acetylaspartate-creatine (mean +/- SD, 1.69 +/- 0.20 vs 1.52 +/- 0.19; P<.001). The extent of deterioration in neuropsychological test performance after surgery was closely related to the degree of the N-acetylaspartate-creatine ratio decrease (P<.01). A follow-up MRS scan revealed a normalization of the N-acetylaspartate-creatine ratio, which accompanied the recovery in psychological test performance. CONCLUSIONS: Postoperative impairment in neuropsychological test performance is associated with a transient metabolic neuronal disturbance. Focal ischemic lesions after CABG are more frequent than the apparent neurological complication rate; however, they are not related to the diffuse postoperative encephalopathy.

Aged↗

PubMed2002

A new reproducible model of an epidural mass lesion in rodents. Part I: Characterization by neurophysiological monitoring, magnetic resonance imaging, and histopathological analysis.

OBJECT: The goal of this study was to characterize a new model of an epidural mass lesion in rodents by means of neurophysiological monitoring, magnetic resonance imaging, and histopathological analysis. METHODS: Changes in intracranial pressure (ICP), cerebral perfusion pressure (CPP), and laser Doppler flowmetry (LDF) values, intraparenchymal tissue partial oxygen pressure (PtiO2), and electroencephalography (EEG) activity were evaluated in the rat during controlled, epidural expansion of a latex balloon up to a maximum ICP of 60 mm Hg. The initial balloon inflation was followed by periods of sustained inflation (30 +/- 1 minute) and reperfusion (180 +/- 5 minutes). Histopathological analysis and magnetic resonance (MR) imaging were performed to characterize the lesion. The time to maximum balloon expansion and the average balloon volume were highly reproducible. Alterations in EEG activity during inflation first appeared when the CPP decreased to 57 mm Hg, the LDF value to 66% of baseline values. and the PtiO2 to 12 mm Hg. During maximum compression, the CPP was reduced to 34 mm Hg, the LDF value to 40% of baseline, and the PtiO2 to 4 to 5 mm Hg. The EEG tracing was isoelectric during prolonged inflation and the values of LDF and PtiO2 decreased due to accompanying hypotonia. After reperfusion, the CPP was significantly decreased (p < 0.05) due to the elevation of ICP. Both the LDF value and EEG activity displayed incomplete restoration, whereas the value of PtiO2 returned to normal. Histological analysis and MR imaging revealed brain swelling with a midline shift and a combined cortical-subcortical ischemic lesion beyond the site of balloon compression. CONCLUSIONS: This novel model of an epidural mass lesion in rodents closely resembles the process observed in humans. Evaluation of pathophysiological and morphological changes was feasible by using neurophysiological monitoring and MR imaging.

Animals↗

PubMed2002

A reproducible model of an epidural mass lesion in rodents. Part II: Characterization by in vivo magnetic resonance imaging.

OBJECT: The goal of this study was to characterize a novel epidural space-occupying lesion caused by balloon expansion in rodents by using sequential in vivo magnetic resonance (MR) imaging. METHODS: Ten Sprague-Dawley rats were intraperitoneally sedated. A trephination was performed over the left parietal cortex to attach a balloon-expansion device, which was secured with dental cement. Measurements were performed using a 1.5-tesla MR imaging device to obtain sequential T2-weighted and diffusion-weighted (DW) sequences in the coronal plane. A three-dimensional, constructed interference in steady state sequence was used for calculation of the balloon volume. The animal's temperature, heartbeat, and the arterial percentage of oxygen saturation were monitored continuously. After a baseline examination had been performed, the balloon was inflated for a 30-minute period until it reached a maximum volume of 0.3 ml; this procedure was followed by a period of sustained inflation lasting 30 minutes, balloon deflation, and a period of reperfusion lasting 3 hours. After perfusion fixation of the animals, morphometric analysis of the lesion size and examination of the percentage of viable neurons in the hippocampus were performed. Magnetic resonance imaging allowed for the precise visualization of the extension and location of the epidural mass lesion, narrowing of the basal cisterns, and development of a midline shift. A white-matter focus of hyperintensity, consistent with brain edema, developed, predominantly in the contralateral temporal lobe. During sustained inflation the volume of the balloon did not change and comprised 5 to 7% of total intracranial volume. During the same period the white-matter edema progressed further but no increased signal was revealed on DW images. After balloon deflation the brain reexpanded to the calvaria and imaging signs of raised intracranial pressure subsided. A cortical area of hyperintensity on T2-weighted images developed in the parietal lobe in the region of the former balloon compression. This area appeared bright on DW images, a finding that corresponded to an early cytotoxic edema. After deflation white-matter vasogenic edema in the temporal lobes regressed within 3 hours after reperfusion. The cortical edema in the parietal lobe and the ipsilateral basal ganglia became sharply demarcated. The histopathological results (that is, the extent of tissue damage) corresponded with findings of the authors' companion investigation, which appears in this issue. CONCLUSIONS: Magnetic resonance imaging allows for a precise and sequential in vivo monitoring of a space-occupying epidural mass lesion and visualizes the time course of vasogenic and cytotoxic brain edema. This rodent model of an epidural mass lesion proved to be reproducible.

Animals↗

PubMed2002

Sequential MR imaging of denervated muscle: experimental study.

BACKGROUND AND PURPOSE: MR changes in denervated muscles have been reported to occur within days up to several weeks after peripheral nerve damage. The purpose of this experimental study was to investigate the longitudinal changes in denervated muscles by using MR imaging. METHODS: In 12 Lewis rats, the left sciatic nerve was transected at the level of the proximal thigh. MR imaging of both legs was performed before and 1 hour, 24 hours, 48 hours, 7 days, 14 days, 28 days, and 2 months after the procedure. The MR protocol included T1-weighted spin-echo, T2-weighted double turbo spin-echo, and turbo inversion recovery magnitude (TIRM) sequences obtained in the axial plane. Signal intensities (T2-weighted double turbo spin-echo and TIRM sequences) and the T2 TR (T2-weighted double turbo spin-echo sequence) were recorded for the soleus, peroneal, and gracilis muscles of both sides. Moreover, the circumferences of both lower legs were determined on the basis of T1-weighted images. RESULTS: Twenty-four hours after denervation, a signal intensity increase in the denervated peroneal and soleus muscles was present on TIRM images. On T2-weighted images, only the peroneal muscle exhibited slightly increased signal intensities and T2 TR. Forty-eight hours after nerve transection, the denervated soleus and peroneal muscles revealed prolonged T2 TR and marked increased signal intensities on T2-weighted and TIRM images when compared with the contralateral side, which further increased at or less than 2 months after denervation. Muscle atrophy of the denervated muscles was present as early as 7 days after denervation and was also increased at follow-up examinations. CONCLUSION: The TIRM sequence is more sensitive than is T2-weighted imaging in the detection of signal intensity changes in denervated muscle. These changes occur as early as 24 (TIRM sequence) and 48 (T2-weighted sequence) hours, respectively, after complete transection of the sciatic nerve in rats and precede muscle atrophy. The sensitivity to early signal intensity changes in denervated muscles may support the use of MR imaging in the diagnosis of peripheral nerve lesions.

Animals↗

PubMedDate not supplied

Neurologic complications after particle embolization of intracranial meningiomas.

BACKGROUND AND PURPOSE: Preoperative embolization of meningiomas is frequently used to facilitate surgery and to reduce intraoperative blood loss. The purpose of this study was to evaluate the frequency of procedure-related neurologic complications during and after particle embolization of intracranial meningiomas. METHODS: Between 1996 and 2004, 185 consecutive patients underwent particle embolization of an intracranial meningioma. Devascularization was performed by means of superselective probing of the tumor-feeding vessels and ensuing free-flow embolization with spherical particles. All procedures were performed with systemic heparinization. RESULTS: Six patients (3.2%) had ischemic events with neurologic deficit. Two had amaurosis, and four patients presented with hemiparesis. Hemorrhage occurred in six patients (3.2%). In five of these patients, rapid microsurgical tumor removal resulted in a favorable outcome without persistent neurologic deficit. In one patient, massive intratumoral, subarachnoid, and subdural hemorrhage was lethal. CONCLUSION: Particle embolization of meningiomas is associated with a substantial risk of ischemic and hemorrhagic events. The individual risk-to-benefit ratio of embolization should be thoroughly considered.

Aged↗

PubMedDate not supplied

Iron particles enhance visualization of experimental gliomas with high-resolution sonography.

BACKGROUND AND PURPOSE: Intraoperative MR imaging and sonography are used for navigation during neurosurgical procedures. The purpose of this experimental study was to evaluate the potential of high-resolution sonography using superparamagnetic iron oxide (SPIO) particles as a contrast medium to delineate brain tumors and to relate these findings with those of MR imaging. METHODS: C6 gliomas were implanted in 36 rats. Eleven days after tumor implantation, the animals underwent MR imaging with a 1.5-T MR imaging unit. Twelve animals received gadopentetate dimeglumine immediately before the MR examination, 12 animals were injected with SPIO particles 24 hours before MR imaging, and 12 animals received no contrast agent. Immediately after MR imaging, the animals were sacrificed and their brains were removed and placed in saline. Sonography was performed instantly after brain removal. Brains were embedded in paraffin, and sections were stained for iron with Perl's stain and for macrophages with ED-1 immunohistochemistry. RESULTS: At MR imaging, the tumors appeared hyperintense on T2-weighted and gadolinium-enhanced T1-weighted images. After application of SPIO particles, they became markedly hypointense on T2-weighted images and hypo- to hyperintense on T1-weighted images. On sonograms, gliomas were iso- to slightly hyperechoic to normal brain parenchyma on nonenhanced and on gadolinium-enhanced images. After application of SPIO particles, tumors became markedly hyperechoic and were distinctly demarcated from the surrounding brain tissue. CONCLUSION: SPIO particles improved the detection and demarcation of the experimental gliomas on sonograms, which may improve intraoperative neuronavigation with sonography.

Animals↗