Biomedical subjects

H Bertalanffy

Publications and source records attributed to H Bertalanffy.

At least 73 records · Page 4Linked to original sources

PubMed1997

Clinical significance of three-dimensional helical CT in neurosurgery.

The authors report about a 3-years experience with helical CT and 3-D surface reconstruction applied in neurosurgical patients. All examinations were performed in addition to preexisting diagnostic CT, MRI, or angiography. The aim of this study was to assess the clinical value of this method with regard to planning of the surgical approach to anterior, middle, and posterior skull base and spinal lesions. 75 examinations of 55 patients were analysed and ranked as follows: A = examination with significant additional information for neurosurgical planning of skull base or spinal procedures or for postoperative evaluation of the neurosurgical approach, B = examination with some useful information for the neurosurgical planning or postoperative control, however, without significant advantage as compared to established diagnostic methods, C = examination without significant additional information. Classification was performed independently by two experienced surgeons. Examinations of anterior, middle, and posterior skull base lesions including cerebral aneurysms were in the majority rated as helpful and significantly informative, (A = 21, B = 24, C = 9, n = 54). Three-dimensional imaging of the spine was of clinical value only in specific cases (A = 6, B = 6, C = 9, n = 21). The authors conclude that three-dimensional imaging is a valuable diagnostic tool for pre- and postoperative imaging of tumorous and vascular lesions adjacent to the skull base, allowing for optimal surgical approaches with minimal invasiveness.

Adult↗

PubMed1997

Fundamental electrophysiologic investigation of spinal cord: refractory period of feline conductive spinal cord evoked potential.

Refractory periods and recovery curves have been used to investigate the physiologic importance and disturbance of peripheral nerves, but the refractory periods of the central nervous system (CNS) have seldom been investigated. We estimated the refractory periods and the recovery curves of the ascending and descending conductive spinal cord evoked potentials (SCEP) in cats. The absolute refractory period of the first and second potentials of both the ascending and descending SCEP was approximately 0.4-0.5 ms. The amplitudes of the first potentials of the ascending and descending SCEP elicited by test stimuli exhibited significant differences, but their latencies did not differ significantly except at the interstimulus interval (ISI) of 1.5 ms, which implies that the same type of fibers was stimulated in the first potentials of the ascending and descending SCEP. The second potential of the descending SCEP elicited by test stimulus showed > 100% amplitude and a maximal recovery of 200% when the ISI was 3.0 ms. The third potential was produced in the test response more easily when a lower vertebral level (L4) was used as the recording site and the ISI was between 1.0 and 4.0 ms. We consider these phenomena to be the result of elimination of the synaptic inhibitory influence by the conditioning stimulus of the paired stimuli for the descending SCEP.

Action Potentials↗

PubMed1997

Endoscopic stereotaxy--an eight year's experience.

During the 10th meeting of the WSSFN in Maebashi in 1989, we discussed 'endoscopic stereotaxy', and presented our preliminary results. This technique was first designed to optimize stereotactic biopsy, but it proved to be effective for other neurosurgical indications as well, including endoscopic stereotactic evacuation of intraparenchymal and intraventricular space-occupying cysts, endoscopic stereotactic cystoventriculostomy, third ventriculostomy, evacuation of brain abscess and intracerebral hematoma, and retrieval of adherent or free-floating ventricular catheters. Our results with endoscopic stereotaxy in different indications are encouraging, compared to conventional microsurgical techniques and pure stereotactic techniques. From 1989 to 1997 we have performed more than 400 stereotactic endoscopic procedures. The mortality rate is below 1%, the operative morbidity is below 3%.

Biopsy↗

PubMed1997

Cognition and quality of life in patients after transcallosal microsurgery for midline tumors.

OBJECTIVE: The transcallosal route has been propagated as a safe approach to midline tumors. The present study was performed in order to elucidate the neurobehavioral late sequelae in patients after transcallosal microsurgery on near-midline tumors. EXPERIMENTAL DESIGN: The present study was performed retrospectively with a delay between surgery and follow-up examination ranging from 2 to 36 months (mean 10.2 months). SETTING: The study was performed in the Department of Neurosurgery, University Hospital of the University of Technology (RWTH) Aachen, Germany. PATIENTS: A consecutive series of 18 patients treated for an intracranial lesion by transcallosal surgery was included into the study. The patients had to be not younger than 16 and not older than 67 years. The age mean was 38.9 years (range 16 to 65 years). INTERVENTIONS: The surgical approach was performed along the falx cerebi under microneurosurgical conditions with direct use of the microscope after opening the dura. MEASURES: Beyond neurological examinations, the patients were submitted to an extensive neuropsychological testing battery. Furthermore, quality of life was examined by means of a questionnaire. RESULTS: Surgery was performed without persistent new neurological deficits. Cognitive deficits were found in short- and long-term memory, motor fine-coordination, reaction time, divided attention and fronto-cortical capacity. The quality of life was particularly impaired in the area of cognitive capacity in daily life. These findings could be related to the duration of preoperative symptoms and to the tumor location. CONCLUSIONS: The deficits found cannot be explained by surgical damage to the corpus callosum itself. Rather, they seem to correspond to an extra-callosal pathology. Further studies with a prospective evaluation of larger patient samples are called for in the future.

Adolescent↗

PubMed1996

Microsurgical management of ventral and ventrolateral foramen magnum meningiomas.

The authors report their experiences gained from 19 patients with ventral or ventrolateral foramen magnum meningiomas operated on via the dorsolateral, suboccipital transcondylar access route. It is emphasized that the microsurgical management of these lesions includes two important aspects which increase the safety of the procedure: a meticulous preoperative planning based on the microanatomical details of each patient, as well as an individualized tailoring of the surgical approach. There were no deaths, and, in the past 5 years, no neurological complications in this series. Gross total removal of the tumour was achieved in each case. It is concluded that microsurgical removal of ventral or ventrolateral foramen magnum meningiomas with this technique constitutes a safe and recommendable procedure.

Aged↗

PubMed1996

PET-study of intracranial meningiomas: correlation with histopathology, cellularity and proliferation rate.

The glucose metabolism of 62 meningiomas was measured by fluorine -18-2-fluorodeoxyglucose (FDG) PET and correlated with proliferation rate (Ki-67 index) and tumor cellularity. The mean metabolic rate (MRGlu) for meningiomas was 0.26 +/- 0.13 mikromol/g/min (range 0.08-0.62 mikromol/g/min). The relative tumor FDG-uptake (Q-MRGlu) (tumor/contralateral cortex) of all meningiomas was calculated with 0.73 +/- 0.37 (0.24-1.79). Differences of Q-MRGlu were significant between the groups with high vs. low cellularity (p < 0.01), increased vs. normal proliferation rate (p < 0.025) and low (WHO grade I) vs. higher (WHO grades II, III) graded tumors. In recurrent meningiomas (14 tumors) the glucose metabolism was not increased. The data show that 18 FDG-PET is suitable to serve as non-invasive predictor of tumor growth characteristics in meningiomas.

Adult↗

PubMed1996

Hemangioblastomas of the spinal cord and the brainstem: diagnostic and therapeutic features.

Hemangioblastomas of the spinal cord and the brainstem make up 4% of all spinal tumors and are less common than cerebellar hemangioblastomas. CT and MRI are essential for preoperative diagnosis. Nevertheless, cerebral and spinal angiography are also mandatory, since they allow a detailed study of the vascular situation, which is decisive for exact planning of a surgical strategy. The purpose of this study was to evaluate the diagnostic and therapeutic factors which influence surgical morbidity and postoperative outcome. Twelve patients harbouring spinal(8 cases) or medullary (4 cases) hemangioblastomas, all symptomatic with sensorimotor deficits corresponding to the level of the lesion were evaluated. All patients were treated in our department between December 1989 and September 1994. Complete resection of the lesion was achieved in each case. Postoperatively, none of the patients showed deterioration. Nine patients had immediate postoperative improvement of neurological signs and symptoms; in three patients the initial neurological deficits remained unchanged during the in-patient period. Late postoperative outcome demonstrated a clear improvement; in only one patient was there no change of the clinical signs, while in the other 11 patients a significant improvement of pre-existing neurological deficits was experienced. We conclude that microsurgical resection of spinal and medullary hemangioblastomas with low morbidity is feasible.

Adult↗

PubMed1996

Osteoplastic frontal sinusotomy and extradural microsurgical repair of frontobasal cerebrospinal fluid fistulas.

The choice of the surgical approach and operative technique for the management of cerebrospinal fluid (CSF) fistulas of the anterior cranial fossa are still a controversially discussed topic. Although "extracranial" approaches through the paranasal sinuses are becoming increasingly more popular among otolaryngologists and maxillo-facial surgeons, most neurosurgeons traditionally prefer the "intracranial" repair of CSF fistulas by a craniotomy. We present an approach through the frontal sinus for the repair of dural defects behind the posterior wall of the frontal sinus and at the floor of the anterior cranial fossa. The operative procedure comprises the following main steps: 1) exposure of the anterior wall of the frontal sinus by a bicoronal incision; 2) excision of the anterior wall without frontal burr holes; 3) bilateral removal of the posterior wall of the frontal sinus; 4) extradural inspection of the dura behind the frontal sinus and above the cribriform plate, ethmoidal roof, and orbital roof bilaterally; 5) closure of dural tears by direct suture and a periosteal graft; 6) reinsertion of the anterior wall of the frontal sinus and fixation with titanium micro plates. Twenty-five patients operated upon using this technique are described. The aetiology of the frontobasal lesion was traumatic in 23, and an ethmoid carcinoma in two. In all patients, the dural fistulas were successfully repaired during the initial procedure. One patient died from sudden circulatory arrest after an uneventful postoperative course of nine days. Otherwise, there were no postoperative complications. This technique affords atraumatic extradural inspection and repair of dural fistulas bilaterally behind the frontal sinus, and above the cribriform plate and the ethmoidal and orbital roofs with none or minimal brain retraction. It therefore allows early repair of CSF fistulas also in patients with severe brain injury. Although we consider the extradural closure of fistulas the method of choice, this approach also allows for a combined extradural-intradural procedure, thus enabling the surgeon to treat associated intradural pathologies, such as traumatic lesions or tumours of the frontal cranial base.

Adolescent↗

PubMed1996

Surgical approaches for vertebro-basilar trunk aneurysms located in the midline.

Fourteen cases of midline vertebro-basilar trunk aneurysms were operated on by four routes of surgical approach: middle fossa anterior transpetrosal approach (ATP), presigmoid transpetrosal approach (PTP), conventional lateral suboccipital approach (LSO) or suboccipital transcondylar approach (STC). There was no mortality, but the morbidity was different depending on the surgical approach. In basilar trunk aneurysms located higher than the internal auditory canal, excellent results were obtainable by ATP, especially in the case of posteriorly projecting aneurysms. For midline vertebral aneurysms located lower than the internal auditory canal, STC resulted in less surgical complications than LSO. Extradural resection of the jugular tubercle was necessary for aneurysms located on the distal vertebral artery at or close to the vertebro-basilar junction. For vertebro-basilar junction aneurysms located at the level of the internal auditory canal, hearing was preserved by STC, but not by ATP or PTP. However, choice of the surgical approach may depend on the direction of the aneurysm and the technical accessibility of the skull base. All these skull base approaches reduced surgical complications of retraction damage to the cranial nerves and the brain stem. This holds true for all aneurysms arising from the midline vertebro-basilar trunk.

Adult↗

PubMed1996

Strength-duration curve of conductive spinal cord evoked potentials in cats.

Strength-duration curves of the ascending and descending conductive spinal cord potentials (SCEPs) in cats were obtained using constant current stimuli. For the formulation of numeric indices of excitability, the rheobase is defined as the minimal current strength below which response cannot occur even if the current continues, and the chronaxie is defined as the minimal duration of a current required to evoke the potential at twice the rheobase strength. The chronaxies and rheobases were calculated from the constructed strength-duration curves. The purpose of this study is to produce strength-duration curves and to evaluate the utility of chronaxies and rheobases for SCEPs. This study showed the following results: (1) there was a hyperbolic relationship between stimulus strength and stimulus duration at threshold values, similar to that seen in peripheral nerves; (2) the ascending and descending tracts of SCEP were mediated through the same pathway (based on the similar chronaxies and rheobases); (3) following spinal cord compression the chronaxie and rheobase increased significantly (P < 0.05), which is similar to peripheral nerve disturbance. However, the rheobase decreased significantly following slight spinal cord compression (P < 0.05) and systemic cooling (P < 0.01), and the strength-duration curve shifted showing a tendency towards decrease of the galvanic threshold, therefore, amplitude augmentation with slight compression and with decrease in temperature seems to contribute to the reduction of the threshold. The strength-duration curve, the chronaxie and the rheobase may be useful in assessing spinal cord function.

Animals↗

PubMed1996

Microsurgical interhemispheric approach to dural arteriovenous fistulas of the floor of the anterior cranial fossa.

Six patients with a dural arteriovenous fistula (DAVF) of the floor of the anterior cranial fossa underwent microsurgical treatment. Two of them were operated using a conventional frontobasal approach, and four using an interhemispheric approach. The interhemispheric approach offers the advantages of sparing the frontal sinus, minimizing frontal lobe retraction, and providing a visual angle perpendicular to the floor of the anterior fossa and an excellent view of the fistula located on the cribriform plate at the level of the foramen caecum. Using the interhemispheric route, the malformation was occluded in all the cases by dividing the vascular connection between the dura of the cribriform plate and the intradural draining vein. There were no complications related to the surgical procedure. This route avoids some disadvantages of the more frequently reported frontobasal approach. It is therefore a recommendable alternative for the management of frontal DAVFs.

Adult↗

PubMed1996

Microsurgically produced bifurcation aneurysms in a rabbit model for endovascular coil embolization.

The authors present a detailed account of the microsurgical production of bifurcation aneurysms in chinchilla rabbits for basic studies of endovascular coil embolization of aneurysms. End-to-side anastomoses of both common carotid arteries (CCAs) were performed, and a venous pouch was fitted into the newly created bifurcation. These experimental aneurysms closely mimic human cerebral aneurysms in size and hemodynamic features. Sixty-three animals underwent operation. Fifteen animals died in the course of the experiment and 15 were excluded because of a CCA occlusion within the carotid bifurcation. Electrical detachable platinum coils, also known as Guglielmi detachable coils (GDCs), and tungsten mechanical detachable coils (MDCs) were used for the endovascular occlusion of 26 bifurcation aneurysms (16 rabbits were treated with GDCs and 10 with MDCs). Initially, complete angiographic obliteration (95%-100% occlusion of the aneurysm) was achieved in nine rabbits and incomplete obliteration (< 95% occlusion) was seen in 17 animals. Final angiography 3 to 6 months later demonstrated complete occlusion in only four and partial occlusion in 22 aneurysms. At present, the histopathological examination of 17 embolized aneurysms has revealed incomplete obliteration of all aneurysms, even in those three cases that were thought to be completely embolized according to angiographic criteria. A general overestimation of the radiological degree of aneurysm obliteration was found.

Animals↗

PubMed1995

[Endovascular treatment of cerebral aneurysms with selectively detachable platinum coils].

In 14 patients (eight men, six women; mean age 58 [31-72] years) with intracranial aneurysm (basilar artery in nine, anterior branches in five) the aneurysm was occluded by electrically detachable platinum coils, advanced into the aneurysm introduced via a percutaneously introduced catheter system, under local anaesthesia and fluoroscopic control. Ten patients had acute subarachnoid haemorrhage (stage II-IV). In two patients several sessions were required before complete occlusion was achieved. In one patient, with a basilar artery aneurysm, the aneurysmal wall was perforated (angiographically demonstrated contrast-medium extravasation), but this remained clinically asymptomatic. There has been no recurrence or renewed bleeding during a follow-up period of 6-12 months. The method is a highly promising addition to the micro-neurosurgical treatment of such aneurysms. However, as long-term results are still awaited, indications for using the method should be strict and only those patients should be so treated in whom operation would be associated with a high risk or who are inoperable.

Acute Disease↗

PubMed1995

Staging, scoring and grading of medulloblastoma. A postoperative prognosis predicting system based on the cases of a single institute.

Although recently survival of some medulloblastoma patients increased remarkably, it remains a serious diagnosis in others. In order to predict the postoperative prognosis in patients treated for medulloblastoma, a new staging, scoring and grading system was developed. Sixty-six patients operated on microsurgically between 1975 and 1990 at a single neurosurgical center were fully followed-up. No patient was excluded due to a poor postoperative course. Completion of commonly used radiotherapy protocols was attempted in all patients. Survival of patients was evaluated by the Kaplan-Meier method. The following 5 parameters were selected to define subgroups: patients' age, tumour location and histology, degree of resection and presence or absence of metastases. Patients older than 10 years had a better prognosis than individuals aged 10 or less (p < 0.01), patients with lateral tumours had a better prognosis than patients with midline tumours with brain stem infiltration (p < 0.05), patients with complete tumour resection had a more favourable prognosis than individuals with subtotal (p < 0.01) or partial resection (p < 0.001), patients without metastases at the time of diagnosis had a better prognosis than individuals without such evidence (p < 0.001), patients with the desmoplastic tumour variant had a better prognosis than patients with classical tumour histology (p < 0.01). According to the prognosis of a distinct subgroup, scoring points were distributed which correlated with the degree of inter-subgroup significances. The sum of a single patient's scoring points was called the total score. Based on this score, three groups of prognosis were distinguished.(ABSTRACT TRUNCATED AT 250 WORDS)

Adolescent↗

PubMed1995

Secondary manifestation of medulloblastoma: metastases and local recurrences in 66 patients.

Although primary treatment of medulloblastoma is now successful in a high percentage of patients, its secondary manifestations still bear a poor prognosis. Thorough studies of secondary manifestations are therefore pivotal to plan therapeutic approaches for the long-term management of medulloblastoma. Here we describe the incidence of secondary tumour manifestations in 66 patients of a single centre who underwent surgery for medulloblastoma between 1975 and 1990. No patient was excluded due to a poor postoperative course. Thirty-five patients showed evidence of secondary tumour growth. Of these, 17 suffered from local recurrence, and 27 developed metastastatic disease. The median latencies for secondary manifestations were 25 months for local recurrence (n = 17), 11 months for spinal metastases (n = 10), 15 months for supratentorial metastases (n = 8), 8 months for subleptomeningeal dissemination (n = 6), and 23 months for systemic metastases (n = 8). Two patients developed primary metastatic spread to the posterior fossa. Of 8 patients with supratentorial metastases, 6 developed fronto-basal lesions. In our patients, 89% of secondary lesions occurred within less than 3 years after primary diagnosis. 85% of patients with extra-axial tumour spread had been treated with a permanent shunt. Radical tumour resection and radiotherapy with 30 Gy to the neuraxis and 20 Gy boost to the posterior fossa was an important prognostic factor in this series. Patients with additional chemotherapy did not benefit significantly from this treatment. We conclude that optimal management of the primary lesions should aim at (i) total resection, (ii) avoid permanent shunting, and (iii) completion of the radiotherapy with inclusion of the medial frontobasal cisterns in the radiotherapeutic regimen. Our analysis suggests that adequate postoperative screening programmes should consist of 3-monthly scans of the neuraxis in the first three postoperative years and 6-monthly scans thereafter.

Adolescent↗

PubMed1995

Cavernous angiomas of the spinal cord clinical presentation, surgical strategy, and postoperative results.

Nine consecutive cases of surgically treated spinal cavernous angiomas are presented. Our series consists of 6 men and 3 women with the following intramedullary spinal location of the cavernomas: 4 cervical, 4 thoracic and 1 thoraco-lumbar. All 9 patients were symptomatic with signs of myelopathy and senorimotor deficits corresponding to the level of the lesion. Six patients underwent laminectomy and in three patients a hemilaminectomy was performed to approach the lesion. A complete resection of the cavernoma was achieved in each case. Five patients showed transient neurological deterioration, in three cases the neurological status remained unchanged, and one patient experienced a slight improvement of symptoms during the early postoperative period. At follow-up examination (mean 14 months postoperative), a clear improvement of the clinical signs was demonstrable in 6 patients, and a complete resolution of the pre-existing symptoms and signs was achieved in two individuals. In one case the clinical state remained unchanged. It is concluded that microsurgical resection is the treatment of choice in cavernomas of the spinal cord.

Adult↗

PubMed1995

Planning and surgical strategies for early management of vertebral artery and vertebrobasilar junction aneurysms.

Selection of the approach and technique for surgical repair of aneurysm of the vertebrobasilar artery system is mainly based on angiographic features. This report emphasizes that planning the surgical procedure should also include preoperative evaluation of the individual skull base configuration, as well as the relationship between aneurysm site and surrounding bony structures. These features are evaluated on thin slice CT scans using bone tissue algorithms and are particularly important for adequate exposure of distal vertebral artery (VA) or midline aneurysms, because these cases require drilling of the jugular tubercle. For the use of lateral approaches, the surgeon must be familiar with the extradural and intradural anatomy of the foramen magnum region and may rely on at least five anatomical landmarks for orientation during surgery: 1) the dural entrance of the vertebral artery; 2) the posterior condylar emissary vein; 3) the medial rim of the distal sigmoid sinus; 4) the hypoglossal canal; 5) the jugular tubercle. To increase the safety of the procedure, the authors recommend an individualized tailoring of the surgical approach according to the variable morphological situation of each patient.

Arteries↗

PubMed1994

Three-dimensional spiral CT for neurosurgical planning.

We carried out 22 examinations to determine the value of three-dimensional (3D) volumetric CT (spiral CT) for planning neurosurgical procedures. All examinations were carried out on a of the first generation spiral CT. A tube model was used to investigate the influence of different parameter settings. Bolus injection of nonionic contrast medium was used when vessels or strongly enhancing tumours were to be delineated. 3D reconstructions were carried out using the integrated 3D software of the scanner. We found a table feed of 3 mm/s with a slice thickness of 2 mm and an increment of 1 mm to be suitable for most purposes. For larger regions of interest a table feed of 5 mm was the maximum which could be used without blurring of the 3D images. Particular advantages of 3D reconstructed spiral scanning were seen in the planning of approaches to the lower clivus, acquired or congenital bony abnormalities and when the relationship between vessels, tumour and bone was important.

Adult↗