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Biomedical subjects

J Vajda

Publications and source records attributed to J Vajda.

At least 19 recordsLinked to original sources
PubMed1999

[Neurosurgery using the Gamma Knife].

Gamma Knife radiosurgery is a neurosurgical technique dedicated to treat a wide spectrum of intracranial pathologies. Radiosurgery is a method employing a single fraction of high dose ionizing radiation beams focused on the stereotactically defined intracranial target volume through the intact skull. This precise irradiation of intracranial volumes can necrotize the targeted cell mass--as in treatments of tumors and functional syndromes--or may induce certain biological effects in the target tissue-as in treatments of AVM's and epilepsy--without imposing a significant risk on the neighboring intact neural tissues. The clinical application of Gamma Knife includes a wide range of neurosurgical indications, such as treatments of arteriovenosus malformations, pituitary adenomas, craniopharyngiomas, meningiomas, vestibular schwannomas, gliomas, metastatic tumors, as well as functional neurosurgical syndromes, such as trigeminal neuralgia, extra-pyramidal dysfunctions, epilepsy, pain- and psychiatric syndromes. The clinical effect of irradiation is not immediate, it becomes detectable on follow up studies after a few months. The application of the technique is determined by the histological type, size and location of the pathology. Gamma Knife has evolved to become an established alternative to opened cranial surgery in certain cases with low morbidity and no mortality, offering a safe neurosurgical treatment for inoperable as well as operable lesions that carry significantly high surgical risk. In our review we present the technical and radiobiological principles, clinical indications, limitations and outcome results of this method. Our data are based on the practice and results of the Lars Leksell Center for Gamma Surgery, Department of Neurosurgery, University of Virginia, Charlottesville, Virginia, USA (Director: Ladislau Steiner dr.).

Arteriovenous Malformations↗
PubMed1997

Loss of Calbindin-D28K immunoreactivity from dentate granule cells in human temporal lobe epilepsy.

The loss of the calcium binding protein, Calbindin-D28k, from dentate granule cells has been observed in different animal models of epilepsy and in ischaemia. This decrease is accompanied by alterations of calcium and N-methyl-D-aspartate currents, which may explain the hyperexcitability of the dentate gyrus. In the present study, we found a loss of calbindin immunoreactivity from over 90% of the dentate granule cells in lobectomy samples from four of 10 temporal lobe epilepsy patients. In another four patients, over 50%, of dentate granule cells were devoid of calbindin immunoreactivity, whereas the remaining two cases showed a 20-30% decrease. Electron microscopy revealed a normal ultrastructure both in calbindin-containing and calbindin-negative granule cells. Both calbindin-positive and -negative mossy fibre collaterals participated in supragranular sprouting. As inferred from data in animal models, the lack of calbindin in dentate granule cells of human epileptic subjects is likely to result in hyperexcitability of the dentate gyrus, which may then function as a "motor" for seizures.

Adolescent↗
PubMed1996

Tumors of the cerebellopontine angle. Changing policy in treatment.

One hundred and twenty-six cases of cerebellopontine angle tumors with various histologies are presented. Results of 75 operated vestibular neurinomas, 22 meningiomas, and 16 tumors with other histologies are discussed. The method of irradiation and non-radical surgery may be an alternative for treatment.

Anastomosis, Surgical↗
PubMed1996

Aneurysm of the internal auditory artery: our experience and review of the literature.

The aneurysms of the internal auditory artery (IAA) situated distal from anterior inferior cerebellar artery (AICA)-IAA junction, are extremely rare lesions. A case of distal aneurysm if IAA is presented causing subarachnoid haemorrhage (SAH) and complete ipsilateral deafness. After the neurosurgical treatment the hearing of the patient definitely improved. The literature of distal aneurysms of AICA is reviewed focusing on the clinical features of these malformations, causing cerebello-pontine angel (CPA) symptoms with or without SAH.

Aneurysm, Ruptured↗
PubMed1992

Multiple intracranial aneurysms: a high risk condition.

There is still a relative silence in the literature on what policy should be followed in treating multiple aneurysms. The main risks are: bleeding of a formerly asymptomatic aneurysm during the haemodynamic tides of the peri-operative period; aneurysm(s) can be hidden on angiograms and tend to be overlooked easier in case of an already revealed aneurysm; misjudgement of the ruptured one as a silent additional aneurysm, therefore left for second stage surgery. This paper, based on a material of 330 operations for multiple aneurysms, focuses on these problems. It advocates the one stage complete repair of all lesions using both options of bilateral pterional craniotomies or the contralateral approach. But it also describes those silent aneurysms which safely could be clipped later. Hazards and disadvantages concerning the more aggressive surgery proved to be less significant than the natural history of multiple aneurysms represents.

Adult↗
PubMed1992

Management of pineal region tumours.

Pineal region tumours represent a colourful, challenging peculiarity of brain pathology. Views on their management are still much divided and controversial. Data of fifty patients with the whole palette of these tumours seen in the National Institute of Neurosurgery have been analysed in view of the result of management versus histology of these tumours. Findings of tumour marker studies have not at all been conclusive in predicting histology and outcome, however, cytology of the cerebrospinal fluid (CSF), if positive, pointed toward a very gloomy management result in all cases. Merits of infratentorial-supracerebellar, occipito-transtentorial approaches of direct surgery, palliative interventions and their timing, as well as that of irradiation are discussed in comparison with opinions and arguments from the literature. Shunt procedures alone proved to be dangerous in some cases by evoking haemorrhagic complications. In carefully selected cases microsurgical intervention gave the best possible results in expansively growing pineal region tumours. There is still place for irradiation and chemotherapy, again, in certain types of mass lesions.

Adolescent↗
PubMed1989

Propagation of focal epilepsies and the timing and targeting of surgical interventions. Illustrative case reports.

The mirror focus conception assumes propagation of epileptic excitation towards a homotopic area of the contralateral hemisphere inducing secondary focal discharges. Later, independent discharges can be initiated by this new area of epileptogenesis but initiation of seizures of the same or altered symptomatology--and not only interictal discharges--from a mirror focus has yet not been proved. Three cases will be presented where dynamism of the development of temporal lobe mirror focus have been followed. All cases give rise to several questions concerning selection and timing of surgical approach.

Adolescent↗
PubMed1989

The rhythmic properties of the motor system.

The resonance properties of the motor control circuits are basic features of the motor system. From our results, it can be concluded that, when the normally existing suppression mechanism weakens, external stimuli or internal impulses may elicit oscillations in the circuits according to the resonant frequency, and tremor will appear. It seems that the resonant frequency is between 5 and 8 Hz, as demonstrated by rhythmic voluntary movement, rhythmic elicited reflex movement and rhythmic modulated voluntary movement modulated by the stimulation of the central motor system.

Action Potentials↗
PubMed1989

Some basic features of the pathological and normal motor system studied by chronic deep electrodes.

Our stereotactic experiences in agreement with the literature showed, that different target points could influence the same motor disturbance. To choose the best target point or target point combinations we generally implant the electrodes into VL, Vim, CM, P, dentate nucleus and motor cortex. To ensure the correct sequence of therapeutic lesions we developed an investigation system, taking into consideration the resting and the working state of the motor system. We elicited events centrally (stimulation of the different target points) and peripherally (reflexes) and recorded the evoked potentials at the non-stimulated sites along with the motor and motor modulation effects in the appropriate muscles. The elicited events depend on the site of stimulation and registration and on the state of muscle activity. The centrally and peripherally elicited events influence each other. With our technique the elicited events and their functional dependency is most explicit within the motor system. The results help to explain some basic motor functions and help to answer some of our therapeutic questions.

Athetosis↗
PubMed1988

Contralateral approach to bilateral and ophthalmic aneurysms.

In a previous survey, we found a high incidence of fatal rupture of an unclipped aneurysm in patients with multiple aneurysms. To deal with this problem, we introduced a more vigorous technique that accesses aneurysms previously considered unapproachable during one operating session. Attempts were made to clip middle cerebral and ophthalmic aneurysms contralateral to the operative exposure. We have successfully clipped contralateral aneurysms of the posterior communicating artery when bilateral aneurysms were present. We have also used this contralateral approach successfully with single ophthalmic and proximal carotid aneurysms that pointed medially. We review the cases of 39 patients with 43 intracranial aneurysms operated from the contralateral side and present the surgical technique in relation to the angiographic findings.

Adult↗
PubMed1987

Investigation of trigeminal SEP with scalp and deep electrodes.

A special technique for stimulating and recording trigeminal somatosensory evoked potential (SEP) is described. Eleven healthy subjects and seven patients with chronically implanted deep electrodes have been investigated. Characteristic polyphasic waves were repeatedly observed. The recording of somatosensory evoked potential following trigeminal stimulation is a more difficult technique. This paper describes data in control subjects with scalp electrodes and data on patients with electrodes in the nucleus ventralis posteromedialis and cortical white matter. Depth recording may provide useful information about the origin, nature, and properties of trigeminal SEP.

Electrodes, Implanted↗
PubMed1987

Plasticity of the brain in respect of functional restoration after subarachnoid haemorrhage.

Subarachnoid haemorrhage caused by aneurysmal rupture constitutes a great impact on the brain and on the intracranial content as a whole, with emphasis on the subarachnoid spaces and arteries. The rupture is followed by a wide range of pathological alterations in the neural function and an outcome varying from neglected signs subsiding in a few days to immediate death. Two main factors seem to influence the different events after subarachnoid bleeding. One is the rupture itself which can be extremely variable in severity and in its immediate as well as late consequences. The other is the ability of all parts of the intracranial content to recover. In order to understand either of both the other should also be looked at and both have to be dealt with if we are to treat patients with an aneurysmal rupture properly. For this reason a grading of rupture will be given in respect of some characteristic events in the light of neural restoration. Clearing of CSF, resolution of brain oedema, restoration of impaired CBF, absorption of cisternal and parenchymal haematoma are all of importance. The majority of lesions which developed after the rupture are not fatal or irreversible and even the neural tissue destroyed by the impact or late ischaemia can be functionally replaced. Possible methods of treatment for attaining this functional restoration will be discussed.

Animals↗
PubMed1987

Separation of the tumor and brain surface by "water jet" in cases of meningiomas.

In the surgery of meningiomas one of the most delicate problems is the separation of the tumor from the brain surface. The authors generally recommend microsurgery to preserve the brain surface anatomically and functionally. For this purpose we have developed a new surgical technique according to our concepts of tissue care. After excavating the tumor from inside the tumor brain surface was separated by repeated "water jets" into the tumor arachnoideal space. The "water jet" was produced by an ordinary bulb syringe. The front pressure of the jets was 300-1000 mm of water and the side pressure 100-300 mm of water. In the tumor-arachnoideal space the spreading water (phys. NaCl) separates the brain from the tumor with utmost care. We operated on 55 meningiomas of different types with the "water jet" technique. The immediate results were anatomically excellent. Intraoperative and postoperative acute and late edemas appeared only in a few cases. The functions of the nearby brain were generally preserved. The surgery was uneventful when the tumor surface was smooth and the tumor was spherical. When the tumor surface was uneven, one part of the tumor extended under the dura as a thin layer or the tumor was multilobulated with expanded vessels between the lobules, more microseparation was necessary. We compared the results of the "water jet" technique with the results of the "pre-water jet" series. The surgery with the "water jet" technique was much shorter and its results were better than those of microsurgery alone.

Brain↗