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W T Koos

Publications and source records attributed to W T Koos.

At least 37 records · Page 2Linked to original sources
PubMed1995

Intra-operative marking of neuroanatomical details--helpful for radiosurgery?

This report is a list of simple but effective techniques for marking important structures intra-operatively. During the last 2 years in 52 patients intra-operative marking techniques have been used. In 37 cases a small piece of fat has been taken. In 10 patients it was done by a radiopaque Barium impregnated silicon sphere and in 5 patients with a piece of a monofilament suture. Postoperative checks were done by conventional X-ray, computer tomography and Magnetic Resonance Imaging. The indication in all cases was to offer landmarks helpful for planning postoperative radiosurgery. In case of fat and radiopaque Barium impregnated silicone spheres the markings were always well defined and clear in contrast. In those cases where a piece of monofilament suture was used it was impossible to get clear postoperative information. In general there were no intra- or post-operative complications. All markers were well tolerated and no side effects have been observed so far. The advantages and disadvantages of each of these possibilities are described and discussed.

Adenoma↗
PubMed1995

The role of stereotactic biopsy in radiosurgery.

Radiosurgery offers a very powerful, minimally invasive therapeutic tool in the modern treatment of intracranial lesions. A direct contact with the lesion, as always takes place, e.g. in a stereotactic biopsy or microsurgical operation, is no longer an absolute prerequisite. Treatment planning is done using modern imaging techniques like computer assisted tomography (CT) or magnetic resonance imaging (MRI). Both provide high resolution and contrast images. The lesions can be displayed with high accuracy. The specificity of these techniques is adequate enough to provide neuropathological data which are a prerequisite for treatment? In 1991 we published a retrospective study in which the diagnosis based on CT was compared with the histological diagnosis following stereotactic biopsy on a series of 181 patients with intracranial processes. We could show clearly that CT alone does not offer a reliable basis for therapy planning. Overall CT-scan was inaccurate in 22% of the cases. Now in an additional series of 195 patients with intracranial processes, we have compared the MRI diagnosis with the neuropathological diagnosis. MRI results and the neuropathological diagnosis based on microsurgical operation were compared and evaluated according to the following criteria: 1. Absolute agreement between MRI and histological diagnosis. 2. No agreement between MRI and histological diagnosis. 3. Conditional agreement: the MRI result offered several differential diagnoses one of which was accurate.

Biopsy, Needle↗
PubMed1995

Interstitial irradiation of brain metastases.

Randomized studies have shown that survival in patients with single brain metastases is significantly higher after the combined treatment of surgical removal and whole-brain irradiation than after whole-brain radiation therapy alone. In patients with deep-seated lesions or those located in critical sites of the brain, as well as in cases in which the patient's general condition makes general anaesthesia difficult or impossible microsurgical resection usually cannot be performed or only with an increased surgical risk. Stereotactic radiosurgery, which can be done by means of convergent beam irradiation or by the implantation of highly loaded 125I seeds, provides an alternative to open procedures. In the following we report on our results using a stereotactic radiosurgical technique. A series of 20 treatments is presented, in which biopsy was performed and 125I seeds were implanted, both under stereotactic conditions in the same session. The 125I seeds were sealed in a teflon catheter, were left indwelling temporarily, and then removed after application of the prescribed radiation dose (6,000cGy at the tumour margin). There was only one recurrence in our series, complications occurred in only one patient by temporary aggravation of a pre-existing hemiparesis. Our results indicate that interstitial irradiation of brain metastases is a valuable, less stressful alternative to both open microsurgery as well as to stereotactic radiosurgical convergent beam irradiation.

Adult↗
PubMed1995

Stimulation of the ventral intermediate thalamic nucleus in tremor dominated Parkinson's disease and essential tremor.

Based on Benabid's experimental and clinical findings that low-frequency (50 Hz) electrical stimulation of the ventral intermediate thalamic nucleus may increase tremor, while higher frequencies (> 100 Hz) lead to suppression of the tremor, we implanted a stimulation electrode in 33 thalami among 27 patients. Six patients were implanted bilaterally. 23 suffered from Parkinson's disease, 4 from essential tremor. All patients had a drug-resistant tremor. The Vim target was calculated based on stereotactic ventriculography. An intra-operative neurophysiological target control was performed on all patients. After a monopolar (12 thalami) or quadripolar (21 thalami) lead was implanted we then connected it to a percutaneous extension lead. In the days following the surgery a test stimulation was performed. In all but one patient stimulation resulted in a suppression of the tremor. In a second procedure, a pulse generator (ITREL II; MEDTRONIC) was implanted and connected subcutaneously to the thalamic lead. After implantation of the pulse generator all patients stimulate chronically while some turn off the stimulator at night. In 21 thalami total suppression of tremor was observed, 6 showed major improvement, 4 only minor improvement. There was no significant effect on any other existing symptom of Parkinson's disease. Due to the proximity of Vim to the sensory thalamus the majority of the patients (27 thalami) report slight temporary paraesthesias when the pulse generator is turned on. Two report permanent paraesthesias when stimulation is on. In 4 cases a slight dysarthria occurs under stimulation. In 2 the dysarthria is marked. In one case dysequilibrium occurs under stimulation. All these side effects are reversible when stimulation is turned off. In 3 patients, the lead was displaced due to an insufficient lead fixation, thus making a second procedure necessary to correct the electrode position. We had one complication due to bleeding at the burr hole side. Follow-up ranges from 3 to 48 months. So far in no cases has the effect of stimulation worn off. In conclusion we regard Vim neurostimulation as an effective and safe alternative to conventional thalamotomy and recommend that it should be considered in cases in which drug therapy has failed to affect Parkinsonian or essential tremor. Moreover, we believe that this procedure is a less invasive and equally efficient alternative to classic thalamotomy and thus should be given preference.

Adult↗
PubMed1995

The retrosigmoid approach to acoustic neurinomas: technical, strategic, and future concepts.

The retrosigmoid approach continues to be the most widely employed strategy for the surgical resection of acoustic neuromas. The results with respect to facial nerve function are uniformly reported to be quite high. The great emphasis currently is upon improving results with regard to the conservation of useful hearing. This paper focuses on the anatomical and strategic surgical factors that we currently consider to be important to maximizing our current results. The future aspects of this trend toward improved success in conserving hearing in these patients is also discussed.

Humans↗
PubMed1995

Endoscopically assisted microneurosurgery.

Technological developments in neuroendoscopy are leading to an expansion of applications into the realm of microneurosurgical procedures. The new dimension that using an endoscope provides requires insight into different neuroanatomical aspects and a new kind of strategy in planning a microneurosurgical procedure. To gain some new insights into these exciting aspects of neurosurgery we have explored the sellar, parasellar, and posterior fossa regions in 50 fresh anatomical specimens and used various types of endoscopes to observe the surgically relevant neurotopographical details. We then utilized this experience in 33 clinical cases during microsurgical approaches for various lesions (posterior fossa tumors - 12 cases, sellar and parasellar tumors - 8 cases, trans-sphenoidal procedures for pituitary adenoma - 7 cases, transventricular procedures - 6 cases). In the laboratory we found that familiar neuroanatomical structures are seen in a completely different aspect from what we are accustomed. Orientation is at times difficult, which requires rehearsal and special handling of the endoscope for complex clinical procedures. We found that certain structures that are hardly noticed in routine anatomical views become very important when utilizing the endoscope (i.e., different arachnoid membranes and trabeculae). Importantly, the dimensions of a microsurgical approach can be greatly enlarged with the endoscope, making it possible to look behind structures and ''around corners''. We present our findings with respect to important anatomical details relevant to utilizing the endoscope as an adjunct to microneurosurgical procedures and our clinical data. We have concluded that the neuroendoscope can be a safe and helpful adjunct in many microneurosurgical procedures.

Endoscopy↗
PubMed1995

Computer-assisted multidimensional atlas for functional stereotaxy.

Functional stereotactic operations are currently performed primarily for medically uncontrollable Parkinson's disease and pain. In contrast to the targets in neuro-oncology, those in functional stereotaxy cannot be represented directly by modern imaging methods. The target co-ordinates must therefore be calculated with the aid of special stereotactic atlases. These are publications in which a model brain has been constructed from autopsy examinations on a number of brains, or the data obtained have been compiled in the form of tables and histograms on which the calculation is then based. The target can then be determined based on the classic stereotactic landmarks and reference lines, such as the anterior commissure (AC), the foramen of Monro (FM), the posterior commissure (PC) or the base line FM-PC or AC-PC and the height of thalamus, taking into account the interindividually different anatomical proportions. Since the computational procedures involve repetitious algorithms, it was obvious that such procedures should be run by a computer program. For the most common stereotactic targets, we have developed a computer program for data storage on the one hand and computation and graphic output on the other. The output can be displayed on the monitor and can also be plotted out on paper or overhead transparency. Calibrating between the program and printer renders a 1:1 reproduction, i.e. the graph can be superimposed directly onto original x-rays or images from computed tomography or nuclear magnetic imaging. The graph can be plotted in the three dimensions of the Cartesian co-ordinate system. An additional dimension can be attained by simultaneously including and plotting the data from different atlases and thus from different authors, including one's own data. In addition to the information capacity which this system offers, it also makes possible a considerable reduction in the time for computing the target while at the same time increasing the reliability.

Algorithms↗
PubMed1995

Detection of tumor necrosis factor-alpha protein and messenger RNA in human glial brain tumors: comparison of immunohistochemistry with in situ hybridization using molecular probes.

Tumor necrosis factor-alpha (TNF alpha) protein and messenger (m)RNA distribution was studied in biopsy samples of glial brain tumors, using immunohistochemistry and in situ hybridization with molecular probes, to investigate the role of this cytokine in tumor proliferation and immunological host defense. Focal expression of TNF alpha was detected in four of four glioblastomas, one of two anaplastic astrocytomas, and four of five low-grade astrocytomas, regardless of their subtype or grade of malignancy, but in none of the normal peritumoral brain tissues used as controls. The TNF alpha protein and mRNA were present in reactive astrocytes and protoplasmic tumor cells, confined to areas of leukocyte or T-lymphocyte infiltrating, and less pronounced in tumor cells at the edge of necrosis. Additionally, TNF alpha reactivity was found in infiltrating macrophages and perivascular microglia. Immunohistochemistry and in situ hybridization for TNF alpha showed comparable reaction patterns and numbers of TNF alpha-positive cells, even though the sensitivity of in situ hybridization was significantly higher. Quantitative evaluation of TNF alpha protein, TNF alpha mRNA, and leukocyte infiltration revealed a significant positive correlation between the TNF alpha-positive reactive astrocytes and the number of lymphocytes present in corresponding areas. Together, these data lead to the conclusion that TNF alpha in reactive astrocytes and monocytic cells within tumor areas of high leukocyte infiltration and in tumor cells at the border of necrosis may represent one defense pathway of the immune system against tumor proliferation.

Adolescent↗
PubMed1991

Proliferation in pituitary adenomas: measurement by MAb KI 67.

The monoclonal antibody MAb KI 67 reacts with a nuclear antigen throughout the entire cell cycle and allows easy evaluation of proliferating tumour cells on routinely prepared smear and frozen sections. 120 pituitary adenomas were investigated by use of the monoclonal antibody KI 67 in a two-step avidin-biotin-peroxidase complex (ABC) technique. The KI 67 labelling index (LI) ranged in all adenomas from 0.2 to 4.6%. In 90 cases of transphenoidally operated adenomas the dura of the sella floor was investigated histologically. Adenomas with histologically proven dural infiltration showed a statistically significant higher KI 67 LI (p less than 0.001) compared to non-invasive adenomas.

Adenoma↗
PubMed1991

Modifications of temporal approaches: anatomical aspects of a microneurosurgical approach.

All subtemporal approaches have in common the risk of temporal lobe damage. To reduce the retraction of the temporal lobe we combine two synergistic modifications of temporal approaches to reach the prepontine space. The first is the temporary resection of the zygomatic arch which allows to bring the temporalis muscle more caudally and subsequently allows an anterior subtemporal approach with only minimal temporal lobe retraction. The second modification is the resection of the apex of the petrous bone after incision of the tentorium. This provides an excellent view into the posterior fossa between the trigeminal nerve medially, the internal carotid artery caudally and the internal auditory canal laterally. The anatomical aspects of a microneurosurgical approach regarding these modifications are reported and discussed.

Brain Neoplasms↗
PubMed1991

Diagnostic potential of stereotactic biopsy of midline lesions.

The technique of CT-guided stereotactic biopsy is described and its reliability is discussed based on the experiences with a series of 1747 procedures. We could show that stereotactic biopsy has an overall diagnostic accuracy of 95% and therefore is a safe and reliable tool for planning the therapeutic strategy.

Biopsy↗
PubMed1988

Criteria for preservation of vestibulocochlear nerve function during microsurgical removal of acoustic neurinomas.

A careful examination of the shape, location and course of the 8th cranial nerve in medium-sized and large tumours exhibits three distinct variants. In all cases where cochlear function was preserved, the type III variant (12%) in the cranial nerve tumour relationship was observed. The author's experience clearly indicates that, if a tumour is resected in toto, anatomical nerve continuity cannot be preserved in the type I and II variants (48%, respect. 40%). However, in the type I and II variants the patients invariably had preoperative hearing loss. The important criteria which must be considered in order to preserve cochlear function when extirpating acoustic neurinomas are an anatomically intact nerve, the origin of the tumour and its direction of spread, further more the shape, location and course of the 8th nerve components, the quality of preoperative cochlear nerve function, the pattern of vascularization of the statoacoustic nerve and the inner ear, and lastly, but not least a possible infiltration of the vestibular and/or cochlear nerves by the tumour itself. Objective hearing function could be preserved in 62% of small neurinomas (grade II) and 10% of large tumours (grades III and IV).

Audiometry, Pure-Tone↗
PubMed1985

Statistics of intracranial midline tumors in children.

Of the 1,280 pediatric brain tumors seen at the Department of Neurosurgery, University of Vienna, until December 1984 57% involved the midline. Midline tumors were supratentorial in 40% of cases and infratentorial in 60%. The distribution of different tumor types in the various anatomical regions follows the known sites of predilection of brain tumors. Orienting diagrams show their rates in numerical terms, in various regions as well as their "clinical" malignancy.

Austria↗
PubMed1985

Problems of surgical technique for the treatment of supratentorial midline tumors in children.

In this presentation the authors describe briefly their thoughts on microsurgical management of certain typical brain tumors arising from within and adjacent to the third ventricle the surgical treatment of which has for many years been essentially conservative, not infrequently without histological verification of the type of the tumor or even of the presence of a real neoplasm.

Brain Neoplasms↗
PubMed1985

Nimodipine treatment of ischemic neurological deficits due to cerebral vasospasm after subarachnoid hemorrhage. Clinical results of a multicenter study.

Intravenous Nimodipine was administered to 109 patients (65 female and 44 male) with either pre- or post-operative progressive neurological deterioration from cerebral vasospasm following subarachnoid hemorrhage from a ruptured aneurysm. In 91 of the patients the efficacy of Nimodipine in relieving ischemic symptoms was assessed and in all of the 109 patients the tolerance was evaluated. The aneurysms were related to following arteries: anterior communicating artery (41%), middle cerebral artery (24%), internal carotid artery (10%), vertebro-basilar arteries (4%) and others (5.5%); 11% of the patients had multiple aneurysms. On 16 of the 91 patients no surgery was performed. On 16% of the remaining 75 patients surgery was performed within 72 hours after the hemorrhage, 57% were operated between day 4 and day 15 and 29% after day 16. The ischemic neurological deficits occurred preoperatively in 67% of the patients and post-operatively in 23%. At the beginning of treatment 84% of the patients were graded III-V according to the Hunt and Hess grading system. Most of the patients received doses of 24-48 mg Nimodipine daily as constant i.v. infusion for 7-10 days. The grade of neurological deficit at the end of the treatment was evaluated according to the Glasgow Outcome Scale. 59 (65%) of the patients showed complete recovery or marked improvement of the ischemic symptoms while 22% remained unchanged and 11% died due to severe vasospasm. Administration of Nimodipine seemed to be more efficient in cases where treatment was started within 24 hours. In the patient group which was treated pre-operatively, recurrent hemorrhage was recorded in 8% of the patients.(ABSTRACT TRUNCATED AT 250 WORDS)

Adult↗
PubMed1984

Hydrocephalus in infancy and childhood: diagnosis and indication for operation.

Improvement of the prognosis for children suffering from hydrocephalus requires prompt diagnosis and reliable indication of surgical treatment. Today, intrauterine hydrocephalus is detectable within the first three months of pregnancy; in infancy, before the cranial sutures have fused, pathological growth of the head is the principal sign confirming together with anatomical examinations (ultrasound, CT scan) the indication of operative treatment. In later childhood, surgical treatment is only definitely indicated by symptoms and morphological examination of clearly active hypertensive hydrocephalus. Intermittently normotensive hydrocephalus (not "normal-pressure-hydrocephalus"!) showing symptoms adapted to childhood, however, often requires exact examination of intracranial pressure dynamics, including quantitative volume provocation test. "Step-by-step-procedure" is advisable (Table III).

Cerebrospinal Fluid Shunts↗
PubMed1984

Reconstruction of the facial nerve in acoustic neurinoma surgery. Juxtapontine-intratemporal nerve graft.

Five cases of large acoustic neurinomas (diameter 2.5 cm) with involvement of the facial nerve in the tumour capsule are presented. The preoperative function of the facial nerve was normal. During surgery, in order to achieve a radical tumour removal, the facial nerve was severed juxtapontine. Reconstruction was performed at the same procedure using a 5-6 cm long sural nerve graft. Thus the central juxtapontine stump was joined to the peripheral stump in the facial nerve canal of the petrous bone. After six months, all five patients exhibited a well functioning mimic and a good eyelid function. At the one year control four patients had normal nerve function clinically and one patient still showed asymmetrical mimic.

Adult↗