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Biomedical subjects

L M Auer

Publications and source records attributed to L M Auer.

At least 19 recordsLinked to original sources
PubMed1992

Ultrasound stereotaxic endoscopy in neurosurgery.

Stereotaxic endoscopy assisted by laser- and video technique can be used in a circumscribed number of intracerebral lesions. In the present series of patients, ultrasound imaging has been used as a stereotaxic method to guide the tip of the endoscope to a target area in the depth of the brain via a burr hole in the cranial vault. Initial experience has been obtained in the evacuation of various intracerebral and ventricular as well as cerebellar haematomas; moreover, ventricular tumours can be laser-coagulated and resected. In cases of cystic hemispheric tumours biopsies can be taken under visual control and the inner surface coagulated with laser. The method is less traumatic compared to conventional neurosurgery.

Brain Neoplasms↗
PubMed1991

Acute effect of neodymium yttrium aluminium garment laser on the cerebral cortical structure, blood-brain barrier, and pial vessel behaviour in the cat.

Experimental brain lesions were created by Nd:YAG laser (wave length 1.06 microns) irradiation on the cerebral cortex of anaesthesized adult cats with 20 Watts impacts of 0.5, 1.0, 2.5, and 5.0 seconds exposure time through cranial windows. Histological changes, disruption of the blood-brain barrier (Evans blue extravasation) and pial vessel reaction (large vessels more than 100 microns and vessels smaller than 100 microns) were studied under constant PaCO2, blood pH, and mean arterial pressure. Histological changes of the lesions consisted of a zone of dense coagulation, a pale zone of homogeneous coagulation and an oedematous zone. Evans blue extravasation was uniformly seen extending from the histologically changed area into the surrounding tissue in all experiments. Pial arteries in the area with morphological changes showed pronounced dilatation (100.0 +/- 7.2%) and one third of these arteries were closed by thrombi. Pial arteries in the area of Evans blue extravasation but outside of histological changes also dilated (large arteries 60 +/- 4.1%, small arteries 77 +/- 5.9%). Pial arteries outside of the Evans blue extravasation were affected transiently and only in a very small zone: Within a distance of 200 microns from the Evans blue extravasation, large arteries initially dilated by 41 +/- 8.3%; small arteries dilated within 400 microns (42 +/- 3.7%). Within 4 minutes after irradiation arterial dilatation was again significantly reduced (p less than 0.01). It is concluded that no important vascular changes occur beyond the zones of histologically altered brain tissue.

Animals↗
PubMed1991

Fibrin tissue adhesive sealant for the prevention of CSF leakage following transsphenoidal microsurgery.

Fibrin glue (Beriplast, Behring or Tissucol, Immuno) was used for 126 sublabial transseptal transsphenoidal operations in 119 patients from April 1981 to March 1987 in a variety of sellar pathologies together with septal bone and spongycel to seal the sellar floor and the anterior wall of the sphenoid sinus. The incidence of postoperative rhinorrhea was 1.6%. A review of the literature revealed an incidence of 1.5%-9.6% with the use of autologous tissue for sellar packing such as fat or muscle; fibrin glue combined with autologous grafts led to postoperative rhinorrhea in 1%-4.4%. The present results support the view that sellar and sphenoidal sealing with fibrin glue instead of muscle or fat tissue does not raise the incidence of postoperative rhinorrhea.

Adenoma↗
PubMed1991

Cerebrovascular response to changes of cerebral venous pressure and cerebrospinal fluid pressure.

Using parietal cranial windows and multichannel videoangiometry, pial vessel responses were studied in cats during stepwise elevation of superior sagittal sinus pressure (Psss) to a level of 50 mmHg or reduction of CSF-pressure (PCSF). PCSF was monitored via a needle in the great cistern, known from previous studies to be identical to supratentorial CSF-pressure. During elevation of PSSS, large and small pial veins dilated by 14 +/- 6.1% from resting diameter. Small arteries remained unresponsive until they were dilated by 9 +/- 2.1% at the level of PSSS 50 mmHg. Large arteries dilated by 18 +/- 5.5% at the level of PSSS 50 mmHg. PSSS was always approximately twice as high as PCSF during increase of PSSS. During reduction of PCSF to -5 mmHg, pial veins also dilated, by 7.4 +/- 1% on the average. This observation suggests that normal PCSF is a result of mainly venous vascular pressure, and that the level of normal venous pressure is not dictated by PCSF but by the function and architecture of the cerebral vasculature. Since the rapid reduction of cerebral perfusion pressure CPP by elevation of venous pressure does not induce autoregulatory adjustment according to the level of CPP, but to the level of arterial transmural pressure, it is concluded, that the basic mechanism underlying autoregulation of CBF is myogenic.

Animals↗
PubMed1991

Hydroxyethyl-starch in transient experimental focal cerebral ischemia.

In a model of focal cerebral ischaemia in the cat (transorbital occlusion of the middle cerebral artery for 60 minutes, thereafter 6 hours reperfusion by clip removal), hydroxyethyl-starch (HAES) (ELOHES; Leopold Pharma GmbH, Graz, Austria) was administered intravenously before and during the ischaemic episode as a 6% or as a 10% solution in a randomised manner (6 animals each group). The size of the developing cerebral infarct was not significantly different when comparing the 6% and the 10% group with the controls (SALINE). Collateral circulation to the infarct border (pial arteries on the suprasylvian gyrus) was also not significantly different between the two groups, except for the first hour of reperfusion, where vessels of the 6% group were wider than vessels of the 10% group. At the infarct border (ectosylvian gyrus) small resistance vessels were significantly more dilated in the 6% than in the 10% group both during the occlusion period and during the reperfusion episode after removal of the clip. Pial arteries dilated less in both HAES-groups than in the controls. It can be assumed, that HAES-incuded decrease of plasma viscosity led to an elevation of blood flow velocity and blood flow quantity (CBF). But the latter might be counteracted by autoregulation of CBF, i.e. vasoconstriction. Thus, a possible positive effect of HAES might in part be counteracted by autoregulation, which explains that no significant therapeutic effect could be achieved.

Animals↗
PubMed1991

Unfavorable outcome following early surgical repair of ruptured cerebral aneurysms--a critical review of 238 patients.

Among 238 consecutive patients admitted early with ruptured cerebral aneurysms, surgical repair within 48-72 hours was feasible in 200 cases. Unfavorable outcomes among the latter 200 patients are analyzed and discussed in this paper. Preoperatively, 148 patients were in Hunt and Hess grades I-III, 33 were in grade IV, and 19 in grade V. After clipping of the aneurysm, all patients received a regimen of topical intracisternal and intravenous/peroral medication with the calcium antagonist nimodipine. The overall rate of unfavorable outcomes was 25%, ie, outcome with moderate or severe deficit or lethal outcome. The reasons for unfavorable outcomes among these 49 patients were the devastating effect of the bleed (severe subarachnoid hemorrhage or additional intracerebral hemorrhage) in 31 patients (15% of the 200 patients), a surgical complication in 11 (5.5%), preoperative rebleeding in three (1.5%), delayed ischemia from vasospasm in one (0.5%), and various others in three further patients (1.5%). Unfavorable outcome occurred in 11% of patients with preoperative grades I-III, in 52% of patients with grade IV, and in 16 of 19 patients with grade V. Among the 141 patients with subarachnoid hemorrhage but not intracerebral or intraventricular hematoma, 16 made an unfavorable outcome, ie, 11% versus 56% among patients with intracerebral hematoma/intraventricular hematoma on preoperative computed tomography scan. The present data seem to speak in favor of early surgery. Since half of the patients with intracerebral hematoma and poor outcome had suffered previous warning leaks, it appears to be a continuing challenge to diagnose warning leaks before a massive hemorrhage occurs.

Aged↗
PubMed1990

Practical application of intraoperative ultrasound imaging.

Intraoperative real-time ultrasound imaging (US) was used in over 500 patients to investigate which of the previously considered applications are of practical use in everyday neurosurgery. During all intraoperative applications for a wide variety of pathological conditions, small deep-seated as well as subcortically located lesions were detected with accuracy; in many instances they could be approached through smaller surgical exposures. US guidance was accurate in 209 cases for the stereotactic introduction of needles or endoscopes into various lesions: thus burrhole evacuation was performed on 148 intracerebral haematomas; in 16 patients endoscopic biopsy and resection of ventricular tumours was performed as well as biopsies of 39 hemispheric brain tumours and aspiration of a brain abscess in 6 instances. Seventy six gliomas were investigated by US imaging; the frequently unclear boundary between tumour and surrounding oedema was not better visualized than with CT or MRI. Moreover, US imaging for the detection of residual tumour towards the end of operation was unreliable. Postoperative imaging through burrholes or other cranial defects was mostly of unacceptably low quality for therapeutic decision making.

Biopsy↗
PubMed1990

Intraoperative ultrasound (US) imaging. Comparison of pathomorphological findings in US and CT.

Experience with the use of intraoperative ultrasound (US) imaging in over 300 patients are presented in this paper and discussed with special reference to various pathomorphologies as well as their identifiability within the brain/intracranium. In 201 of these patients, the pathomorphological peculiarities in US could be compared with preoperative CT findings. As a general result, all investigated lesions could be identified during intraoperative US investigations with the exception of small aneurysms. Most of the lesions gave at least partly higher echosignals than normal brain tissue, except arachnoid cysts. Size and shape of lesions were comparable in US and CT with the exception of some gliomas; in the latter group, the diffuse image in US was more akin to the situation likely to be found by the surgeon during operation, whereas CT used to give a misleading picture of a more or less clearly delineated tumour. US allowed more accurate differentiation between intratumoural necrosis and cysts than CT: the latter was misleading in many instances. At the present state of development, real time US imaging does not allow a histopathological diagnosis. The ease of handling and the high quality of morphological imaging, however, warrant a number of practical applications in daily neurosurgical practice.

Brain↗
PubMed1990

Disturbed cerebrospinal fluid circulation after subarachnoid hemorrhage and acute aneurysm surgery.

In 138 patients with ruptured cerebral aneurysms operated on within 48 to 72 hours after subarachnoid hemorrhage, an external ventricular drainage catheter was inserted before craniotomy and was used intermittently during the first week after surgery. In 51 patients, intracranial pressure (ICP) was measured intraoperatively. The majority of patients showed increased ICP intraoperatively irrespective of the preoperative Hunt and Hess grade and the amount of subarachnoid blood accumulation or intraventricular blood clot. Intraoperative drainage of cerebrospinal fluid allowed easy access for aneurysm dissection by making the brain slack in more than 90% of patients. Postoperative ICP measurements revealed that significant brain swelling did not occur in the majority of patients. In 7 patients, persistently elevated ICP (greater than 20 mm Hg) was recorded. Nine patients (8%) developed shunt-dependent hydrocephalus; all of these patients had suffered an intraventricular hemorrhage. Measurements of the volumes of cerebrospinal fluid drained did not allow prediction of shunt-dependent hydrocephalus.

Brain Edema↗
PubMed1989

Cerebrovascular response to elevation of ventricular pressure.

The behaviour of Pial vessels to levels of CSF-pressure between 10 and 100 mmHg induced by vetricular infusion of mock CSF, was observed in 6 cats under barbiturate and N2O anaesthesia, using the cranial window technique and videoangiometry. Supratentorial pressure (STP) equaled infratentorial pressure in the cisterna magna (CMP) throughou. No changes in pial arterial calibres were noted up to a CMP of 13 mmHg (i.e. a cerebral perfusion pressure (CPP) of 100 mmHg). Further increase of CMP to 45 mmHg induced significant arterial dilatation of 40 +/- 3.4%. With a further rise of ventricular fluid pressure (VFP) no marked further arterial dilatation occurred. Dilatation of arteries up to 100 um resting diameter and arteries between 100 and 250 um resting diameter and arteries between 100 and 250 um was not significantly different. When CPP approached 40 mmHg, arteries were still 47 +/- 3.6% dilated. Pial venous calibre did not vary by more than 20% during elevation of VFP. At CPP 47 mmHg, small and large veins were dilated by 14%. Single venous segments were compressed by crossing pial arteries and caused upstream venous congestion and distension.

Animals↗
PubMed1989

Endoscopic surgery versus medical treatment for spontaneous intracerebral hematoma: a randomized study.

A controlled randomized study of endoscopic evacuation versus medical treatment was performed in 100 patients with spontaneous supratentorial intracerebral (subcortical, putaminal, and thalamic) hematomas. Patients with aneurysms, arteriovenous malformations, brain tumors, or head injuries were excluded. Criteria for inclusion were as follows: patients' age between 30 and 80 years; a hematoma volume of more than 10 cu cm; the presence of neurological or consciousness impairment; the appropriateness of surgery from a medical and anesthesiological point of view; and the initiation of treatment within 48 hours after hemorrhage. The criteria of randomization were the location, size, and side of the hematoma as well as the patient's age, state of consciousness, and history of hypertension. Evaluation of outcome was performed 6 months after hemorrhage. Surgical patients with subcortical hematomas showed a significantly lower mortality rate (30%) than their medically treated counterparts (70%, p less than 0.05). Moreover, 40% of these patients had a good outcome with no or only a minimal deficit versus 25% in the medically treated group; the difference was statistically significant for operated patients with no postoperative deficit (p less than 0.01). Surgical patients with hematomas smaller than 50 cu cm made a significantly better functional recovery than did patients of the medically treated group, but had a comparable mortality rate. By contrast, patients with larger hematomas showed significantly lower mortality rates after operation but had no better functional recovery than the medically treated group. This effect from surgery was limited to patients in a preoperatively alert or somnolent state; stuporous or comatose patients had no better outcome after surgery. The outcome of surgical patients with putaminal or thalamic hemorrhage was no better than for those with medical treatment; however, there was a trend toward better quality of survival and chance of survival in the operated group.

Adult↗
PubMed1989

[The effect of neodymium yttrium aluminum garment laser on the cerebral blood vessel and blood brain barrier].

The effect of the laser energy to the cerebral vascular reactivity and the blood brain barrier. A Nd:YAG laser with 20 watt impacts of 0.5, 1.0, 2.5 and 5.0 seconds duration time were irradiated through the cranial window made at the parietal regions of anesthetized adult cats. The disruption of the blood brain barrier was examined by checking the degree of the extravasation of Evans blue dye administrated in the vein. The cortical vessel reactivity was observed through the cranial window and evaluated using an intravital microscope and a videoangiometer. The extravasation of Evans blue dye was seen uniformly extending from the histologically changed area into the surrounding tissue in all experiments. The extent of the extravasation of dye was 1 to 1.5 mm larger than the extent of the histologically changed area produced by laser irradiation. Pial arteries in the area with histological changes dilated markedly and some of them lost their blood stream. Pial arteries in the area of Evans blue extravasation, but outside it histological changes also dilated markedly. Furthermore, pial arteries within a distance of 200 to 400 microns from the edge of the Evans blue extravasation area also dilated moderately. A statistical estimation showed that the degree of dilatation of arteries in the area outside the histological change improved significantly in the time course of five minutes.

Animals↗
PubMed1988

Effects of vasospasm in the middle cerebral artery territory on flow velocity and volume flow. A computersimulation.

Recently blood flow velocity in large cerebral arteries became measurable non-invasively by transcranial Doppler sonography (TCD). The present study tries to quantify the relation between flow velocity and the more important volume flow in the middle cerebral artery (MCA) by means of computersimulation. A mathematical model of the MCA territory was developed. The model is able to take into account the non-Newtonian behaviour of blood viscosity and is also able to handle turbulant and laminar flow. Autoregulation is simulated by increasing or decreasing diameter of arteries as an answer to intraluminal pressure changes. Two processes are simulated: Vasospasm in the stem of the MCA, and vasospasm in the entire MCA territory. Results show that the relation between flow velocity and volume flow is rather complicated. Vasospasm in the MCA stem first leads to an increase of flow velocity at a constant level of volume flow. At higher grades of vessel constriction volume flow and flow velocity start to fall.

Animals↗
PubMed1988

Endoscopic neurosurgery.

This paper describes an ultrasound-guided, laser-assisted, and TV-controlled endoscopic technique which has been used so far in 133 patients for a variety of intracranial lesions. Following CT or MRI image reconstruction, and a decision on the placement of a 1 cm or a 2 cm burrhole, a 1 cm 5.0 mHz or 7.5 mHz intraoperative ultrasound probe is used to direct the endoscope from the burrhole to the target area. A 22.5 cm long rigid endoscope tube with an outer diameter of 6 mm with an inbuilt suction irrigation system, Neodymium Yag laser with 600 micron Quartz glass-fibre and an inlet for various microinstruments is then introduced. The attachment of a TV camera to the ocular lens allows the operator to control further surgical steps in the target area via the TV screen and thus warrants sterility in the operating field. The technique has been used for evacuation of 77 spontaneous intracerebral haematomas (lobar, putaminal, thalamic), 8 traumatic intracerebral haematomas, 13 ventricular haematomas, 8 cerebellar haematomas and 1 brainstem haematoma. Total or subtotal evacuation was achieved in 33% of intracerebral haematomas, removal of more than 50% of the clot in 55%. Twenty-four brain tumours (12 ventricular, 12 cystic cerebral or cerebellar tumours) were operated on for biopsy, evacuation of cyst, resection or removal of the cyst wall and/or laser irradiation of solid tumour or the inner cyst wall of cystic tumours. The complication rate probably related to surgery was 1.6%, morbidity 1.6%, mortality 0%. This high-tec endoscopic technique with its minimal surgical trauma and short operation time can be recommended as a low-risk alternative to conventional neurosurgical techniques.

Adult↗
PubMed1988

Prognosis after acute subdural or epidural haemorrhage.

In a series of 171 patients suffering acute subdural haemorrhage (SDH) (111 patients) or epidural haemorrhage (EDH) (60 patients) after closed head injury accumulated during the years 1978-1985 at the University Hospital of Graz, the mortality rate and the grade of clinical recovery were evaluated. The overall mortality in acute SDH was 57%, in acute EDH 25%, the percentages of good recoveries--full recovery and minimal neurologic deficit--25 and 58%, respectively. Outcome was found to be predominantly influenced by the preoperative state of consciousness, associated brain lesions, and, in comatose patients, the duration of the time interval between onset of coma and surgical decompression. When this interval exceeded two hours, mortality from SDH rose from 47 to 80% (good outcomes 32 and 4%, respectively). In acute EDH an interval under two hours lead to 17% mortality and 67% of good recoveries compared to 65% mortality and 13% of good recoveries after an interval of more than two hours. Age and concomitant injuries of other body regions proved to be of secondary importance.

Brain Injuries↗
PubMed1988

Early surgical repair of large intracranial saccular aneurysms.

Among 302 patients with cerebral aneurysms admitted between 1981 and 1986, 63 had a large (45) or giant (18) aneurysm with a diameter of more than 12 mm and 24 mm, respectively. 24 of these 63 patients were admitted early after a subarachnoid haemorrhage (SAH) so as to allow surgical repair within 72 hours. Eight of them were inoperable for various reasons and could not undergo definitive surgical repair and died. 16 patients underwent craniotomy and clipping of the aneurysm. 77% of the patients in preoperative grades I-IV made a good recovery with no or minimal neurologic deficit. During the same period 84% of patients with small aneurysms made a good recovery. The present data indicate, that large aneurysms rupture with a similar incidence compared to small aneurysms; saccular large ruptured aneurysms can be operated upon early with similar results as small aneurysms. However, devastating initial bleeds and poor outcome occur more frequently in patients with ruptured giant than in patients with small aneurysms. Most of the patients with ruptured giant aneurysms are comatose on early admission and cannot be considered for early surgery. Their poor prognosis is further reduced by a high rebleeding rate.

Aged↗
PubMed1988

Penumbra around chronic cerebral infarction?

In a series of 13 patients with cerebrovascular occlusive disease regional cerebral blood flow (rCBF) measurements (two-dimensional intravenous 133Xe clearance method) and quantitative EEG analysis (sensorimotor rhythms) as well as electronic measurement of handforce were performed before and during intravenous infusion of 1 microgram kg/min of one of the lipophilic dihydropyridine calcium channel blocker nimodipine (Nimotop). The aim of the study was to test the hypothesis of the existence of hypoperfusion (ischaemic penumbra) in the surroundings of chronic cerebral infarcts. All 3 parameters improved in one patient. Sensorimotor rhythms increased in 5 patients, rCBF in 3. EEG and rCBF improved in 2 patients. In 3 instances, a redistribution of rCBF in favour of the peri-infarct zone was noted (significant increase of rCBF from 35 +/- 2 SEM to 53 +/- 4 ml/100 g/min (p less than 0.01), whereas rCBF fell from 61 +/- 5 to 46 +/- 2 ml/100 g/min on a collimator remote from the infarct but in the infarcted hemisphere. The parallel improvement of rCBF and EEG in brain regions surrounding chronic infarcts in 3 patients was interpreted as functional improvement as a consequence of nimodipine-induced normalization of peri-infarct hypoperfusion, i.e. reversal of flow-dependent neuronal silence and/or dysfunction.

Adult↗