Biomedical subjects
L Steiner
Publications and source records attributed to L Steiner.
Long-term follow-up of radiosurgically treated arteriovenous malformations in children: report of nine cases.
Long-term follow-up results of nine children treated for cerebral arteriovenous malformation with a gamma unit are presented. Complete nidus obliteration was angiographically confirmed in six cases and significant decreases in arteriovenous malformation size were observed in the other three. There were no radiation-related deteriorations in physical or mental development. In seven patients who underwent endocrinological examination more than 3 years after irradiation, five were normal and the other two showed only low serum adrenocorticotropic hormone levels, which, however, did not necessitate replacement therapy. Neurodiagnostic imaging follow-up studies revealed no radiation-induced lesions in any of the nine cases.
Long-term results of radiosurgery for arteriovenous malformation: neurodiagnostic imaging and histological studies of angiographically confirmed nidus obliteration.
Detailed follow-up results for 25 patients treated for cerebral arteriovenous malformation (AVM) with a gamma unit are presented. Complete nidus obliteration was angiographically confirmed in 16 (73%) of 22 cases receiving full-dose irradiation. There were no radiation- or AVM-related mortalities. However, we did experience one case of radiation-related morbidity and one of angiography-related mortality, the autopsy findings of which are discussed. Computed tomography scan and magnetic resonance imaging follow-up studies of radiosurgically treated AVMs indicated that increased enhancement of the nidus after contrast or gadolinium administration could persist even after obliteration of the AVM was angiographically confirmed.
Clinical outcome of radiosurgery for cerebral arteriovenous malformations.
The clinical outcomes are described for 247 consecutive cases of arteriovenous malformation (AVM) treated with the gamma knife between April, 1970, and December 31, 1983. Headache resolved in 65 (66.3%) of the 98 patients presenting with this symptom and improved in an additional nine (9.2%). Of 59 patients admitted with seizures, 11 (18.6%) became seizure-free without anticonvulsant medication and an additional 30 patients (50.8%) became seizure-free with anticonvulsant medication. Pre-existing neurological deficits improved or totally disappeared following radiosurgery in 56.7% of affected cases. This improvement presumably occurred within the frame of the natural history. The protective effect of the ionizing beams against hemorrhage in incompletely obliterated AVM's is analyzed. To assess the rate of rebleeding, probability estimates were calculated using both the person-year method and the Kaplan-Meier life table. With the person-year method the actual rebleed rate is not too different from the values observed in the natural history of the disease (2% to 3%/yr). Analysis by Kaplan-Meier life-table estimates demonstrated a risk of nearly 3.7%/yr until 60 months after radiosurgery. Five years following treatment, the life table ends in a plateau which could be interpreted as an indication of decrease in the risk of hemorrhage. However, long flat regions at the right end of the life table do not imply that the real risk of rebleeding is negligible unless a large number of patients have been followed well into or beyond the flat region.
Outcome of radiosurgery for cerebral AVM.
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Radiosurgery and the double logistic product formula.
The double logistic product formula is proposed as a method for predicting the probability of developing brain necrosis after high dose irradiation of small target volumes as used in stereotactic radiosurgery. Dose-response data observed for the production of localized radiation necrosis for treating intractable pain with the original Leksell gamma unit were used to choose the best fitting parameters for the double logistic product formula. This model can be used with either exponential or linear quadratic formulas to account for the effects of dose, fractionation and time in addition to volume. Dose-response predictions for stereotactic radiosurgery with different sized collimators are presented.
Human tumor-lymphocyte interaction in vitro. III. T lymphocytes in autologous tumor stimulation (ATS).
The T-cell nature of the responding cells in autologous tumor stimulation (ATS) was proven by (1) E-rosette formation of lymphocytes attached to tumor cells during the early period of co-cultivation; (2) blast-transformed E-rosetting cells detectable at the end of the test period (day 6) and (3) the reactivity of T-enriched lymphocyte subset and unresponsiveness of T-depleted fractions. Preparation of tumor suspensions devoid of lymphocytes made it possible to carry out cross-tests between patients. Blastogenesis with allogeneic tumors was rare. The restricted autologous nature of the reaction is a strong indication for genuine tumor-relatedness.
Spontaneous healing of intracranial aneurysms after subarachnoid hemorrhage. Case report.
A case of spontaneous intra-aneurysmal thrombosis, verified angiographically, is reported in a patient with subarachnoid hemorrhage and without surgical intervention. The frequency of such an occurence and the factors involved are reviewed and discussed.
The value of repeat pan-angiography in cases of unexplained subarachnoid hemorrhage.
Four-vessel angiography was repeated in 56 patients with confirmed subarachnoid hemorrhage in whom the initial investigation was negative. Only one aneurysm was demonstrated. The results suggested that, with good technique, careful observation, and a complete four-vessel cerebral angiography, a false negative rate of less than 2% can be achieved. It is suggested that to repeat pan-angiography is seldom justified unless further bleeding episodes occur.
Cerebral blood flow and metabolism in the acute phase of experimental subarachnoid bleed.
Our experiment seems to confirm the hypothesis, implying an active CBF autoregulation as one of the interacting four survival mechanisms during an intracranial hemorrhage. While our present study has indicated that the autoregulation operates during the initial bleed, it is fully conceivable that the autoregulatory capacity may be exhausted after recurrent hemorrhages. Earlier experiments (Häggendal et al. [1970]) showed that autoregulation is easily abolished for prolonged periods after periods of intracranial hypertension. Further experiments are necessary to evaluate the capacity of the cerebral autoregulation to withstand repeated intracranial bleeds.
Titanium clips in neurosurgery for elimination of artefacts in computer tomography (ct) a technical note.
To eliminate the occurrence of artefacts produced by clips on the CT images, the use of titranium clips is suggested. Tests in vitro and in vivo indicate that clips manufactured from 0.2 mm thick 99.9 per cent titanium do not cause artefacts. They are resistant to corrosion, nontoxic, effective, easy to handle, relatively cheap, and are visible on plain X-ray films.
Characteristics and limits of tolerance in repeated subarachnoid hemorrhage in dogs.
The effects of repeated subarachnoid hemorrhages have been investigated experimentally in dogs. The main objectives were to determine the tolerance to repeated hemorrhage and to study the changes occurring during the repeated bleeds, in intracranial pressure, EEG, ECG, systemic arterial pressure and respiration. The natural course of an intracranial hemorrhage was simulated by shunting blood from a femoral artery through a drop recorder into five different sites in the craniospinal system: the chiasmatic cistern, a lateral ventricle, the cisterna magna, the lumbar subarachnoid space and into the cerebral tissue of the left frontal lobe. The hemorrhage was allowed to continue until it stopped spontaneously. Each bleed resulted in a transient rise in intracranial pressure to the level of the arterial pressure, followed by a return to a steady state value. The time taken for the attainment of the steady state was increasingly prolonged. The final steady state pressure increased with each bleed. Ultimately, a stage was reached where the hemorrhage resulted in a sustained high pressure at the level of the arterial blood pressure, producing failure of vital functions and an irreversibly isoelectric electroencephalogram. The average number of bleeds necessary to produce this state in the case of hemorrhage into brain parenchyma was 3 (range 2-4), into the lateral ventricle, 4 range 3-5), and into the cisterna chiasmatica, 5 (range 2-7). After 5 hemorrhages into the cisterna magna and the spinal subarachnoid space, a local resistance at the bleeding site was built up which prevented further bleeding.
Lethal mechanism in repeated subarachnoid hemorrhage in dogs.
The mechanism limiting the tolerance to repeated subarachnoid hemorrhages was analysed experimentally. Blood introduced by an extracorporeal femorointrathecal shunt or by injection, into five different sites of the cranio-spinal system in living and dead dogs, produced a progressive increase in the steady state CSF pressure after each subsequent bleed. The pressure increase was quantitatively related to the amount of blood entering the system. A comparison of the respective effects of injections of whole blood and of erythrocytes indicated that the red blood cells were the component which induced an increase in the outflow resistance by clogging the pathways of the cerebrospinal fluid. The increase in outflow resistance with each bleed resulted in a stepwise rise in pressure to a level incompatible with survival. The lethal volume of bleed was specific for each site of hemorrhage: namely for brain parenchyma 8.1 ml, lateral ventricle 16.2 ml, cisterna chiasmatica 17.7 ml, cisterna magna 30 ml, and spinal subarachnoid space 55 ml. The assumption that death might be a random event was discarded, the failure of vital functions being considered to be the result of the high intracranial pressure. Mock bleeds using intrathecal infusions of saline suggested that spatial decompensation rather than cumulative ischemic effects caused death.
Computer tomography in post-mortem examination of the brain and other specimens.
A technique is described for post-mortem examination of brain specimens employing computer tomography, for accurate comparison with in vivo scanning, including subsequent cutting of specimens in sections corresponding to tomographic layers measured. Potential application of this technique to diagnosis of mammary tumours is discussed.
Quantitative estimation of intracerebral and intraventricular hematoma by computer tomography.
A method to quantify the size of intracerebral hematoma by computer tomography was tested experimentally. The size of the lesion could be calculated with an error of +/- 3 to 9 per cent. By correlating the volume of the hematoma to the level consciousness in 62 patients, it was found that the volume which induced coma was rather specific, corresponding to about 6 to 7 per cent of the intracranial volume. This observation may lead to a reassessment of present therapeutic concepts.
Influence of absorbed dose and field size on the geometry of the radiation-surgical brain lesion.
Specimens from a number of patients locally irradiated in the thalamus for intractable pain with a multiple gamma beam technique have been examined. The geometry of well circumscribed necrotic lesions was ascertained. No correlation was seen between the dimensions of the lesions and the size of the field, 3 mm X 5 mm or 3 mm X 7 mm, within the clinically useful dose range, 16 to 25 krad.
Proceedings: Pathophysiology of repeated subarachnoid haemorrhage in dogs.
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