Search PubMedSearch

Biomedical subjects

M Misra

Publications and source records attributed to M Misra.

At least 19 recordsLinked to original sources

Juxtaorbital en plaque meningiomas. Report of four cases and review of literature.

Juxtaorbital spheroid wing or ridge meningiomas are the most common of the basal meningiomas. These are at times meningiomas en plaque, which in most patients do not have significant intracranial component. This article reviews the literature on en-plaque meningiomas and discusses the role of MR imaging and CT in the diagnosis of en-plaque meningiomas of the paraorbital region. The role of fat-suppression, gadolinium-enhanced, T1-weighted MR imaging is emphasized.

Adult

Evaluation and endovascular treatment of juxtaorbital vascular anomalies.

The evaluation of juxtaorbital anomalies with routine imaging, including CT and MR imaging, usually is insufficient for endovascular therapy planning. Cerebral angiography remains crucial to define detail necessary for endovascular therapy. This article provides an overview of the authors' approach and the endovascular therapies available to treat these lesions.

Aneurysm

Three-dimensional structure of HIV-1 Rev protein filaments.

The HIV-1 Rev protein facilitates the export of incompletely spliced and unspliced viral mRNAs from the nucleus. Rev polymerizes into two types of filaments in vitro. In the presence of RNA, Rev forms poorly ordered structures, while in the absence of RNA it polymerizes into regular hollow filaments. We have determined the helical structure of the latter filaments by analysis of cryo-electron micrographs, taking into account STEM measurements of mass-per-unit-length. They are made up of Rev dimers, arranged in a six-start helix, with 31 dimers in 2 turns, a pitch angle of 45 degrees, and an interstrand spacing of 3.8 nm. Three-dimensional reconstruction at 2.1 nm resolution reveals a smooth outer surface and a featured inner surface, with outer and inner diameters of approximately 14.8 and approximately 10.4 nm, respectively. The Rev dimer has a "top-hat" shape with a cylinder approximately 3.2 nm in diameter and approximately 2.2 nm high, pointing inward: the thinner rim areas pack together to form the filament wall. Raman spectroscopy shows polymerized Rev to have approximately 54% alpha-helix and 20-24% beta-sheet content. Electron microdiffraction of aligned filaments reveals a broad meridional reflection at approximately (0.51 nm(-1, suggesting approximate alignment of the alpha-helices with the filament axis. Based on these data, a molecular model for the Rev filament is proposed.

Dimerization

Failure of cerebral autoregulation in an experimental diffuse brain injury model.

The normal cerebral circulation has the ability to maintain a stable cerebral blood flow over a wide range of cerebral perfusion pressures and this is known as cerebral autoregulation. Autoregulation may be impaired in the injured brain. Closed head injury was induced in 28 Sprague-Dawley rats weighing 400-450 g. Four groups were studied: control and groups, head injured by weight drop from one meter height using 350 g, 400 g and 450 g respectively. CBF was monitored using laser-Doppler flowmetry along with monitoring of ICP and arterial blood pressure. If the correlation coefficient between CBF and CPP was > 0.85 and CPP was within normal range, loss of autoregulation was hypothesized. Loss of autoregulation was seen in all groups of injured rats during first four hours. A statistically significant difference (p = 0.041) was seen in the trequency of loss of autoregulation between injured and control animals. No loss of autoregulation was observed in the control group. In conclusion CBF and CPP provide information about loss of autoregulation in diffuse brain injury. Decrease in CBF and increase of ICP is observed as a result of loss of cerebral autoregulation. Knowledge of loss of autoregulation could help in the management of head injured patients.

Animals

Fluorosis.

Explore the source record for details and available documents.

Bone Diseases

Bipolar coagulation in neurosurgery.

Coagulation is an essential part of a surgical procedure, especially in neurosurgery. Beginning in the early years of this century, various techniques have been used to control bleeding at the surgical site. Over the years, these techniques have led to the invention of the bipolar coagulator and its modifications. Prevention of charring and tissue adhesion have been the goals of bipolar coagulator manufacturers all over the world; new techniques and different metallurgical compositions for the forceps have been tried to achieve these results. The NS2000, with its microprocessor-based controlled coagulative sequence, can be a good system for reducing tissue adhesion and charring under desired limits of low output power ranges provided by the system. Comparable results can also be obtained with the Malis CMC III and Synergy Malis systems with irrigation channels. These systems have the additional advantages of providing higher power outputs at lower panel settings and a maximum power output greater than that of NS2000. For neurosurgeons who need the additional option of cutting, the Malis CMC III is the recommended system.

Electrosurgery

Renal failure and deafness: branchio-oto-renal syndrome.

Branchio-oto-renal (BOR) syndrome is a rare autosomal dominant condition that may present with hearing loss, branchial cysts, and renal failure. The characteristic phenotypic expression of the full syndrome may be partial or complete, and a whole range of renal abnormalities may be present. Its similarity to Alport's syndrome may lead to misdiagnosis. We report here a case of adult-onset renal failure in a 44-year-old white man previously believed to have Alport's syndrome and a review the relevant literature.

Adult

Head registration techniques for image-guided surgery.

Localization of the pathological structures in relation to the surrounding anatomy and understanding of the surgical anatomy are probably the most important keys to successful neurosurgery. Image-guided surgery is an important tool for understanding an individual's anatomy and for precisely locating the lesion. Head registration is the most important step in image-guided surgery, required by every system in use today, although these systems show great differences. In this study, head registration techniques and user algorithms in 83 image-guided surgery cases were analyzed. Several types of fiducials including skin markers, bone fiducials, and the stereotactic frame were used for registration. Clinical applications, ease of use, and computer-calculated accuracy values for each type were compared. The average accuracy was 1.50 mm. X-spot skin markers are the fiducials most commonly used with CT scan. The stereotactic frame was the most accurate method, with an accuracy of 0.69 mm. Disc-shaped fiducials were used when MRI was the imaging modality; they provided an average accuracy of 2.62 mm. Head registration is an important part of image-guided surgery; the procedure used for registration should be based on the requirements of each individual case. Our results indicated that the stereotactic frame is the most accurate method of registration; however, skin markers provide reasonable accuracy with significant ease of use and patient comfort.

Adult

Neurovascular flow simulation review.

Computer simulation of the cerebral circulation has been carried out for three decades. We review the developments of cerebral circulation computer models of the last 30 years. Existing models are discussed in terms of fluid dynamics and possible clinical usage. Also the status and new achievements in some related research areas are summarized. Any new achievements in such areas would contribute to the progress of building a better model. A patient specific, highly predictive and reflective model could be a powerful clinical tool which would greatly benefit neurosurgeons and patients.

Arterial Occlusive Diseases

Transcranial cerebral oximetry in random normal subjects.

Near infrared optical spectroscopy is becoming a useful method for monitoring regional cerebral oxygenation status. The method is simple, reliable and noninvasive and the information which it provides is clinically significant in managing a growing number of neurological ailments. Use of this technique has been described previously by numerous authors. In the present study, regional cerebral oxygen saturation was measured at rest in 94 subjects randomly selected from a diverse population of individuals. This sample consisted of 38 males and 65 females (age range 18-70 years). There were 68 light-skinned individuals and 35 with darker skin comprising various ethnic and cultural backgrounds. Mean regional cerebral hemoglobin oxygen saturation was recorded as 67.14 +/- 8.84%. The association of the man regional cerebral hemoglobin oxygen saturation in various groups of individuals with relationship to their age, race, sex and skin color is examined.

Adolescent

Microsurgical anatomy of the short central artery.

We studied the origin, length, external diameter, disposition, branching patterns and the perforators of short central artery in the circle of Willis in eighty fresh, unfixed cerebral hemispheres (40 brains). We also examined the relationship of the short central artery, the recurrent artery of Heubner, and M1 perforators to the anterior perforated substance, caudate and putamen. The short central artery arises at 5.2 +/- 3.36 mm from the origin of the anterior cerebral artery, hidden and overlapped by the internal carotid artery bifurcation. The recurrent artery of Heubner arises distally to the origin of the short central artery. Four main anatomical variations were found: 1. Presence of short central artery and recurrent artery of Heubner (37.5%). 2. Isolated presence of the short central artery (27.5%). 3. Isolated presence of the recurrent artery of Heubner (21.25%). 4. Absence of short central artery and recurrent artery of Heubner (13.75%). Two different branching patterns were observed: 1. 2-4 straight perforators from the short central artery, perforators from the recurrent artery of Heubner and lenticulostriate from the most medial portion of the M1, in 42 of 80 hemispheres (52.5%). 2. 8-10 perforators from only short central artery in 10 of 80 hemispheres (12.5%) with absent or hypoplastic recurrent artery of Heubner and lenticulostriates from M1 and M2.

Cerebral Cortex

Ultrasonic perivascular flow probe: technique and application in neurosurgery.

Documentation and measurement of intraoperative cerebral blood flow during various neurosurgical procedures is not only valuable but also very informative. There are various methods by which qualitative and quantitative measurement of blood flow have been developed over the years. The use of perivascular ultrasonic flow more recently is fast gaining popularity. We describe the technique, principle and application of ultrasonic perivascular micro-flow probe quantitative measurement of selective vessel flow in neurosurgery.

Blood Flow Velocity

A differential response of diffuse brain injury on the concentrations of endothelin and nitric oxide in the plasma and brain regions in rats.

In the present study, we hypothesized that acute diffuse brain injury (DBI) in rats would produce an increase in endothelin-1 (ET-1), a potent vasoconstrictor, and/or nitric oxide (NO), a potent vasodilator, in plasma and brain areas in rats. DBI was induced in anesthetized male Sprague-Dawley rats (350-400 g) using a 350 g weight dropped from 1 meter height impact through a device designed by Marmarou et al., 1994. Blood plasma and brain tissue (cerebral cortex, diencephalon and brain stem) samples were collected for estimation of ET-1 and NO at zero or 6 h from rats (n = 6) subjected to DBI as well as control rats (n = 6), i.e., not subjected to DBI. In a separate group of animals, cerebral blood flow (CBF) was recorded at 0, 5, 10, 15, 30, 60, 120, 240 and 360 min after induction of DBI or sham-DBI. Acute DBI produced a significant decrease in CBF at 120 min after induction of DBI. Plasma levels of ET-1 was found to be significantly increased (from 0.89 +/- 0.09 to 2.09 +/- 0.29 pg ml-1), at 6 h following DBI. DBI produced a significant decrease in the levels of ET-1 in diencephalon (from 70.97 +/- 9.47 to 57.64 +/- 2.65 pg g-1). In contrast to ET-1, DBI produced a significant increase in the concentrations of NO in the diencephalon, cerebral cortex and brain stem at 6 h post DBI. It appears that DBI-induced increase in the levels of NO in brain regions which might be down regulating the synthesis of ET-1 in diencephalon. It is concluded that ET and NO homeostatic mechanisms may play a role in the regional and vascular responses associated with acute DBI.

Analysis of Variance

Comparison of the effect of etomidate and desflurane on brain tissue gases and pH during prolonged middle cerebral artery occlusion.

BACKGROUND: The authors compared the effects of etomidate and desflurane on brain tissue oxygen pressure (PO2), carbon dioxide pressure (PCO2), and pH in patients who had middle cerebral artery occlusion for > 15 min. METHODS: After a craniotomy, a probe that measures PO2, PCO2, and pH was inserted into cortical tissue at risk for ischemia during middle cerebral artery occlusion. A burst suppression pattern of the electroencephalogram was induced with etomidate (n = 6) or 9% end-tidal desflurane (n = 6) started before middle cerebral artery occlusion. Mean blood pressure was supported with phenylephrine to 90-95 mmHg. RESULTS: During baseline conditions, tissue PO2, PCO2, and pH were similar between the two groups (PO2 = 15 mmHg, PCO2 = 60 mmHg, pH = 7.1). During administration of etomidate before middle cerebral artery occlusion, tissue PO2 decreased in five of six patients without a change in PCO2 or pH. During administration of 9% desflurane, tissue PO2 and pH increased before middle cerebral artery clipping. Middle cerebral artery occlusion for an average of 33 min with etomidate and 37 min with desflurane produced a decrease in pH with etomidate (7.09 to 6.63, P < 0.05) but not with desflurane (7.12 to 7.15). CONCLUSION: These results suggest that tissue hypoxia and acidosis are often observed during etomidate treatment and middle cerebral artery occlusion. Treatment with desflurane significantly increases tissue PO2 alone and attenuates acidotic changes to prolonged middle cerebral artery occlusion.

Adult

Selection of cerebral aneurysms for treatment using Guglielmi detachable coils: the preliminary University of Illinois at Chicago experience.

OBJECTIVE: We present our initial experience with Guglielmi detachable coils (GDCs). The aim of this study was to determine the criteria for aneurysms, ruptured or unruptured, that are suitable for this technique. The importance of aneurysm geometry and its impact on the final results are discussed. METHODS: A retrospective analysis of 329 patients with 339 cerebral aneurysms that were treated at the University of Illinois Hospital at Chicago from May 1994 to June 1997 was conducted. One hundred eighty-five patients were treated surgically, and 144 were selected for treatment using GDCs. Of the 144 patients selected for GDC treatment, 55 patients with 55 aneurysms were admitted during the acute phase of subarachnoid hemorrhage and 89 patients with 97 aneurysms had nonruptured aneurysms or were treated after clinical recovery of previously ruptured aneurysms. All procedures were performed with the patients under general anesthesia and with systemic heparinization using live simultaneous biplane roadmapping, with the exception of the first four patients. These patients were treated before the installation of the biplane system. The percentage of aneurysm occlusion was determined at the end of each procedure. Follow-up angiography was scheduled to be performed at 6 months, 1 year, and 2 years after treatment. PATIENT SELECTION: For the initial 25 patients (Group 1), selection for coiling was restricted to nonsurgical candidates or patients in whom coiling was thought to be the best treatment choice, based on medical condition and location of the aneurysm. The geometry of the aneurysm was not considered to be an important factor in the selection for coiling. The remaining patients (Group 2) were selected for coiling based on aneurysm geometry, as determined by pretherapeutic angiography. Aneurysms that were considered to be favorable for coiling included those that had a dome-to-neck ratio of at least 2 and an absolute neck diameter less than 5 mm. RESULTS: The initial 25 patients (Group 1) were treated from May 1994 to February 1995. There were high morbidity and mortality rates, with 56% of the treated aneurysms occluded at 6 months. The remaining patients (Group 2) consisted of 119 patients with 123 aneurysms. There was no mortality directly related to the coiling procedure, and permanent morbidity was limited to 1.0%. Three patients (2.5%) developed transient neurological deficits secondary to the procedure, and seven patients (5.8%) experienced periprocedural complications that did not result in neurological sequelae. The morphological results were strongly correlated to the geometry of the aneurysms, with a complete occlusion rate of 72% among the acutely ruptured aneurysms and 80% among the nonacute aneurysms, when patients were selected for treatment based on the geometry of the aneurysms and the dome-to-neck ratio was at least 2. The occlusion rate dropped to 53% when selection was not based on aneurysm geometry and the dome-to-neck ratio was less than 2. A summary of the morphological outcomes for the Group 2 patients shows that 86% of the aneurysms that initially underwent coiling using GDCs were completely occluded (78% by coils alone, 3.0% in conjunction with surgery, and 5.0% with parent artery occlusion). Residual small neck remnants were present in 11% of the Group 2 aneurysms (3.0% were scheduled for surgical treatment of residual neck remnant growths not amenable to further endovascular treatment, and 8% were scheduled for initial 6-mo follow-up examinations). Death resulting from unrelated causes before initial follow-up occurred in 3.0% of the patients. CONCLUSION: These preliminary results suggest that using GDCs is a safe technique resulting in low morbidity and mortality rates for the treatment of intracranial aneurysms in appropriately selected patients. The percentage of complete aneurysm occlusion is related to the density of coil packing, which is strongly dependent on the geometry of the aneurysm. Optim

Acute Disease