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Biomedical subjects

D R Enzmann

Publications and source records attributed to D R Enzmann.

At least 163 records · Page 9Linked to original sources
PubMedDate not supplied

MRI in varicella-zoster virus leukoencephalitis in the immunocompromised host.

Immunocompromised patients are at increased risk for CNS and disseminated varicella zoster virus (VZV) infection. In this report we present the MR findings in a leukemic patient with active, biopsy-proven VZV leukoencephalitis. The characteristic MR features of this infection were clustered subcortical plaque-like lesions demonstrating rapid demyelination. Active lesions enhanced with intravenous contrast medium administration. Edema and hemorrhage were not prominent early findings but developed as the infection evolved. These findings were strikingly similar to those reported in prior autopsy studies of immunocompromised patients with VZV leukoencephalitis.

Adolescent↗
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Gd-DTPA MR detection of blood-brain barrier opening in rats after hyperosmotic shock.

OBJECTIVE: Detection of blood-brain barrier (BBB) opening in neonates has required invasive methods not clinically applicable. We set out to develop a noninvasive approach to detect such opening. MATERIALS AND METHODS: Wistar rats were studied using MRI with Gd-DTPA contrast before and after injection of hyperosmotic solutions known to produce barrier opening. Arabinose was given via right carotid artery to produce unilateral barrier opening; urea was given via tail vein to produce bilateral opening; controls received normal saline. Next, all animals received Gd-DTPA via tail vein. RESULTS: Animals receiving carotid hyperosmotic injections showed increased signal in the ipsilateral brain hemisphere; those receiving venous hyperosmotic injections showed increased signal bilaterally. Similar increases were not found prior to administration of hyperosmotic agent or in saline controls. In both cases, barrier opening was detectable using the relative partitioning of Gd-DTPA between intrabarrier and extrabarrier structures, even in the absence of a hemispheric control. CONCLUSION: We conclude that MRI with Gd-DTPA contrast allows noninvasive detection of BBB opening in the rat.

Animals↗
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Progressive multifocal leukoencephalopathy: unusual MR findings.

A case of progressive multifocal leukoencephalopathy (PML) with a classic clinical presentation but with unusual pathological and radiographic findings is reported. The pathology revealed evidence of prior hemorrhage, and imaging studies revealed focal cerebral atrophy as well as contrast enhancement on MR scans. The contrast enhancement was visible only by utilizing magnetization transfer pulses on T1-weighted scans. The case report indicates that image criteria for PML may need to be redefined in the future.

Brain↗
PubMedDate not supplied

The technical characteristics of matched filtering in digital subtraction angiography.

The technical characteristics of a new digital fluorographic image processing method called matched filtering are presented. This technique, a type of extensive temporal integration, takes a weighted sum of images acquired during passage of a contrast bolus through some area of interest. The weight of each image is governed by the magnitude of the contrast bolus in that image. An essential requirement of the matched filter is that its integral be zero. It is shown for equal exposure rates and typical bolus characteristics that matched filtering provides a factor of two higher signal-to-noise ratio (SNR) than conventional methods for bolus transit times of 10 s or higher. Equilvalently, matched filtering can yield images with quality comparable to conventional digital subtraction angiography (DSA) at a factor of four less patient exposure. The SNR obtained with matched filtering is shown to be within 30% of an ideal bound. Comparisons of matched filtering to standard recursive methods and simple integration are made. Experimental canine studies are presented which compare matched filtering with conventional DSA.

Angiography↗
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Experimental Staphylococcus aureus brain abscess.

The virulent organism Staphylococcus aureus produced brain abscesses that were quantitatively and qualitatively different from those caused by less virulent organisms. S. aureus abscesses created larger lesions, as earlier ependymitis, delayed progress toward healing, and caused areas of inflammatory escape outside the collagen capsule. Imaging tests revealed similar findings: the abscesses were larger, had more extensive central necrosis, and showed earlier evidence of ependymitis. This virulent organism also demonstrated that white matter is more susceptible than overlying gray matter to destruction by infection. The pattern of spread and other histologic findings suggest that collagen capsule formation has less of an infection "containment" function than was previously thought.

Animals↗
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Optimizing MR imaging for detecting small tumors in the cerebellopontine angle and internal auditory canal.

Relative resolving power was used to determine the optimal MR imaging pulse sequence for detecting small tumors of the internal auditory canal and the cerebellopontine angle. Resolving power takes into consideration these important image characteristics: signal-to-noise ratio, contrast, and spatial resolution. The study was performed on a 1.5-T magnet using a 256 X 256 matrix and a 3-mm slice thickness. The TR ranged from 400-2000 msec; the number of excitations was either two or six; and the pixel size was 0.94, 0.78, or 0.63 mm. Theoretical calculations of relative resolving power were compared with the relative resolving power of 45 control patients and 15 patients with small tumors of the cerebellopontine angle or internal auditory canal. A TR of 800 msec was optimal from theoretical calculations and proved optimal in control and tumor patients. Scans obtained with TR = 2000 msec, TE = 80 msec were inferior to short TR scans; such scans could fail to detect intracanalicular tumors. The relative resolving power in patients exceeded theoretical calculations because of greater than expected image contrast caused by low CSF signal intensity secondary to CSF pulsation.

Adult↗
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Mycotic aneurysm in angiitis associated with herpes zoster ophthalmicus.

Varicella zoster (VZ) is an unusual cause of CNS angiitis, usually occurring in older patients and immunocompromised hosts. The infection most commonly presents as herpes zoster ophthalmicus with contralateral hemiplegia. Mycotic aneurysm formation associated with VZ angiitis is rare. We report two cases of VZ angiitis with mycotic aneurysm formation (both aneurysms eventually ruptured) and one case of probable VZ angiitis with distal carotid occlusion and cerebral infarction. The CT and angiographic appearances, clinical course, and histopathology are presented.

Adult↗
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Cerebral blood flow evaluation of arteriovenous malformations with stable xenon CT.

Twenty patients with supratentorial arteriovenous malformations (AVMs) were evaluated with angiography, conventional CT, and stable xenon CT to determine cerebral blood flow. Contralateral and ipsilateral regions of interest relative to the AVM were evaluated from cerebral blood flow maps and correlated with angiography. A significant decrease in cerebral blood flow was observed in the ipsilateral cortical gray matter adjacent to the AVM relative to the corresponding contralateral cortex (mean difference = 9.52 ml/100 g/min, p less than .01). The larger AVMs (greater than 8 cm3) were associated with a more marked decrease with a mean difference of 12.22 ml/100 g/min (p less than .02). Regions of interest were also chosen on the basis of angiographic findings, which suggested areas of decreased flow. Comparison of these areas with analogous contralateral areas also showed a significant decline in cerebral blood flow (mean difference = 8.86 ml/100 g/min); this decline was greater with larger AVMs (volume greater than 8 cm3), which had a mean difference of 11.38 ml/100 g/min (p less than .01). Our correlative study enabled us to pinpoint the regions most likely to have reduced flow from an AVM.

Adolescent↗
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Left-right temporal region asymmetry in infants and children.

Thirty-two consecutive cranial computed tomographic (CT) scans in normal infants ranging from 1 day to 3 years of age were evaluated for asymmetry of the temporal lobes as evidenced by differences in the size of the sylvian fissures. The left sylvian fissure was larger than the right in 23 of the 32 cases, which was statistically significant (p less than 0.0001). In five other cases the two sides were equal; in the four remaining cases, the right side was larger than the left. The results show that asymmetry of the temporal lobes can be demonstrated in vivo even at birth and that this asymmetry is a normal developmental difference between the two hemispheres and not secondary to an acquired abnormality.

Cerebral Aqueduct↗
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NMR imaging of experimental brain abscess: comparison with CT.

An experimental canine model of a brain abscess induced with alpha-streptococcus was imaged in the cerebritis and capsule stages by computed tomography (CT) with intravenous contrast enhancement and by nuclear magnetic resonance (NMR). An NMR imager equipped with a superconducting magnet operating at 3.5 kG was used for several imaging techniques. The NMR images were compared with the CT scans and with gross and microscopic neuropathologic findings. CT showed enhancement of the inflammatory focus at the site of capsule formation while the necrotic center retained its low-density appearance. Spin-echo NMR images demonstrated the presence and extent of abnormal infected brain tissue more accurately than contrast-enhanced CT. Spin-echo images showed the necrotic center, the surrounding inflammatory zone, and peripheral edema without discriminating distinctly between the latter two zones. Inversion-recovery NMR images depicted a lesion of lesser extent, showing the necrotic center circumscribed by the surrounding edematous brain tissue. The inversion-recovery technique was best for demonstrating gray- and white-matter contrast in normal brain and depicted edema as loss of contrast between the gray and white matter. NMR offers some advantages over CT in imaging brain abscess, and the variety of NMR imaging techniques is useful for characterizing the different pathologic areas.

Animals↗
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Intraoperative sonography through a burr hole: guide for brain biopsy.

Sonographic imaging of the brain was accomplished through a burr hole using a small, real-time, 5 MHz transducer in five patients. Brain tumors were accurately imaged, corresponding closely in morphology to the computed tomographic scan. Intraoperative sonography through a burr hole allows flexibility in technique and greatly facilitates brain biopsy procedures.

Biopsy↗
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Natural history of experimental intracerebral hemorrhage: sonography, computed tomography and neuropathology.

The evolution of intracerebral hemorrhage was investigated in a canine model by high resolution sonography, computed tomography (CT), and neuropathologic examination. In 12 dogs, a parietal lobe hematoma was introduced by craniotomy. The sonographic appearance of acute hemorrhage was characteristic and consisted of a sharply circumscribed, homogeneous, highly echogenic lesion, the size and shape of which correlated closely to the area of increased density seen on the CT scan. This changed within 3-4 days to an echogenic rim surrounding a hypoechoic center. Histologically, this change corresponded to a loss of integrity of individual red blood cells. This occurred earliest in the hemorrhage center causing a hypoechoic center, while intact red blood cells at the periphery accounted for the echogenic rim. Shortly after the red blood cells lost their biconcave shape they began to lose their hemoglobin causing the hemorrhage to become isodense with surrounding brain on the CT scan. Faint contrast enhancement by CT was noted at this early stage and was related primarily to a mononuclear perivascular infiltrate at the edge of the hemorrhage. A collagen capsule formed around the hemorrhage over a 2 week period. This capsule slowly replaced intact red cells as the cause of the now shrinking echogenic rim. This capsule was also responsible for the increasing ring contrast enhancement around the resolving hemorrhage. The sequence of image changes seen on both CT and sonography in this experimental model closely resembled the findings seen in intracerebral hemorrhage in patients.

Animals↗
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Experimental brain abscess: enhanced sonography and pathologic correlation.

A new sonographic contrast agent, gelatin-encapsulated nitrogen microbubbles, was introduced intraarterially to enhance the high-resolution sonographic scan of an experimental brain abscess. The echogenicity produced by the microbubbles correlated closely to the site and distribution of abscess neovascularity. The contrast agent aided in the detection of small necrotic centers in the late stages of abscess evolution when these centers were not visualized on noncontrast sonograms. The echogenic effect of the microbubbles was maximum immediately after injection; it decreased by 5 min and had virtually disappeared at 15 min.

Animals↗
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Infantile Krabbe disease: complementary CT and MR findings.

This case report of the infantile form of Krabbe disease in a 2 1/2-month-old boy illustrates the complementary findings that may be seen on CT and MR scans. The key finding on the CT scan was increased density in a bilateral symmetrical distribution involving the thalami with extension into the centrum semiovale. The MR scan, on the other hand, more clearly showed demyelination in the brain stem and cerebellum. In cases in which this involvement is minimal or absent, the MR scan may fail to detect an abnormality, and a CT scan will, therefore, still be necessary to detect characteristic abnormalities.

Brain↗