W. Th. Koos

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

SummaryBased on Benabids 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 Parkinsons 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 Parkinsons 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 drag 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.

Frameless stereotactic guided neurosurgery: Clinical experience with an infrared based pointer device navigation system

SummaryAn infrared based frameless stereotactic navigation device (Easy Guide Neuro) was investigated for its clinical applicability, registration/application accuracy and limitations in a standard operating room set-up.In a five-month period 40 frameless stereotactic procedures (23 female, 17 male, mean age 46.4, yrs range 10–83) including 36 craniotomies and 4 spinal surgery procedures were performed. Image registration, data transfer and operation planning using skin fixed fiducials (between 5–10, mean 6.6) and CCT in 12 patients/MRI in 28 patients, generally was done the day before surgery.Clinical applicability was proven in all procedures with an additional time for pre-operative imaging and system application in the OR of 50 min mean (35–120 range). A useful registration was achieved in 39/40 patients (97.5%) with a registration accuracy of 3.4 mm (range 1.8–6.7) for brain surgery cases and 14.4 mm (6.8–25) for spine cases. This resulted in intra-operative application accuracy values for brain surgery of 4.2 mm mean (range 1–12). Enhanced registration/application accuracy values over the test period from 4.2/3.8 mm mean (Cases 1–20) up to 3.2/2 mm mean (Cases 21–40) was observed. In spinal surgery an application accuracy of 11.3 mm mean (range 5–20) was found. An intra-operative re-calibration because of system-head drift was necessary in none of the patients, nevertheless, application accuracy degradation due to brain shift was detected in every case.In conclusion, the system allowed a time sufficient accurate frameless intra-operative localisation guidance in cavernoma, meningioma, glioma, and brain metastasis surgery. In spinal surgery, the application accuracy exceeded clinical usefulness due to high registration inaccuracy using skin markers.

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.

Contour-guided brain tumor surgery using a stereotactic navigating microscope.

OBJECTIVE The benefit of intraoperative radiological data integration in approach planning and resection of brain tumors using a computer navigating microscope (MKM Zeiss) was investigated. METHODS Since February 1995, out of 86 MKM-guided surgical procedures, 53 contour-guided tumor cases (24 females, 29 males, mean age 51.6) including 16 metastasis, 14 glioblastomas, 10 low-grade gliomas, 6 anaplastic gliomas, 3 meningiomas and 4 others were performed. The preoperative planning was based on CT in 42 cases and Magnetic Resonance Tomography (MRT) in 11 cases using skin markers (4-9, mean 6). Neuroradiologically defined tumor contours were transferred into the ocular of the microscope and projected into the operating field during the procedure. RESULTS The advantages of the system were: (1) preoperative approach planning; (2) minimal, accurate skin incision and craniotomy; (3) intraoperative detection of deep seated lesions or lesion components; (4) determination of lesion boundaries; (5) minimized traumatization in/near eloquent areas. Mean registration accuracy improved from 5.3 mm for the first 10 cases up to 2 mm for the last 18 cases. In glioma surgery, the system provided exact definition of radiologically planned resection borders. In meningioma surgery, it allowed a tailored craniotomy, dura opening and resection, lowering the risk of recurrence. In metastasis surgery, it provided a safe approach to deep and eloquent located lesions. CONCLUSION Contour-guided operation planning and resection guidance using the investigated navigating microscope provides additional security to avoid some potential risks in brain tumor surgery.

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.

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 patients 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.

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.

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.

Timing of surgery for ruptured aneurysms--experience from 800 consecutive cases.

SummaryIn the Department of Neurosurgery, University of Vienna, about 800 patients with intracranial aneurysms have been operated since 1958. The distribution of age, sex, and the localization of the aneurysms correspond roughly to the international statistics. From our experience it is apparent that the level of consciousness and responsiveness is the most important factor in deciding the choice and time of treatment on the one hand and the further fate of the patient on the other. The authors therefore use some modification of the five-grade system of Hunt and Hess to stress the importance of the level of consciousness and the neurological deficits.As far as timing of surgery is concerned, the earliest possible microsurgical treatment for patients in grades I and II seems the method of choice, primarily to avoid rebleeding. Patients with impaired and/or fluctuating consciousness, neurological deficits and rather severe signs of meningeal irritation were operated as soon as the clinical picture became stable or showed a tendency to improve. Grade V patients were operated only if a life-threatening space occupying intracerebral haematoma was encountered my means of a CT scan. Nevertheless the authors have tried to avoid any too rigid routine and to adjust their decisions on therapeutic measurements according to the needs of the individual patient.

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.