Malignant brain oedema after radiosurgery of a medium-sized vestibular schwannoma.

CASE REPORT: We present a patient with an unusual malignant brain oedema occurring after gamma knife radiosurgery of a medium-sized vestibular schwannoma. CLINICAL PRESENTATION: A 62-year-old female with a large vestibular schwannoma underwent partial microsurgical resection; 6 months later she underwent a second intervention with gamma knife radiosurgery for a medium-sized tumour remnant. With a latency period of 6 months after radiosurgery, she presented with progressive neurological deterioration. Serial magnetic resonance imaging revealed progression of the tumour and of the perifocal oedema which finally extended up to the ipsilateral internal capsule. The patient became comatose. INTERVENTION: The tumour was nearly completely removed via a standard retrosigmoid craniotomy. Histopathological examination demonstrated increased mitotic activity compared to the initial histology. The patient became conscious 10 days after surgery and recovered slowly. Surprisingly, the brain oedema resolved rapidly. The CT scan obtained 11 days after surgery showed almost complete disappearance of the oedema. CONCLUSION: Although rare, radiosurgery of medium-sized vestibular schwannomas causing brainstem compression may lead to life-threatening tumour progression and malignant brain oedema. Therefore, microsurgical gross total resection should be the preferred treatment option in vestibular schwannomas causing significant brainstem compression.

[Endoresection of large uveal melanomas after pretreatment by single-dose stereotactic convergence irradiation with the leksell gamma knife--first experience on 46 cases]. / Endoresektion grosser Melanome der Uvea nach stereotaktischer Single-dose-Vorbestrahlung mit dem Leksell Gamma-Knife -- Erste Erfahrungen an 46 Fällen.

BACKGROUND: The aim of this non-comparative, consecutive case series is to evaluate the short-term results after endoresection of large uveal melanomas in combination with pretreatment with stereotactic gamma knife radiosurgery. METHODS: Between March 2000 and November 2002, forty-six patients with large uveal melanomas underwent stereotactic radiosurgery followed by endoresection of the tumour via a standard three-port vitrectomy including laser photocoagulation and silicone oil tamponade. The average tumour height was 9.5 mm. The minimum dose delivered to the tumour volume was 25 Gy. RESULTS: The median follow-up time was 410 days. In 40 cases (87 %), the eye was retained with a VA of 20/200 or better in 30 cases (65.2 %) and 20/63 or better in ten cases (21.7 %). In 12 eyes with a follow-up of >/= 0.5 years, the median VA was 20/80 after silicone oil removal and cataract surgery had been performed. Six eyes (13 %) were enucleated due to serious complications caused by the radiosurgery (3 cases) or endoresection (3 cases). In 13 patients (28.2 %), additional major surgery was required. Seven patients developed liver metastases during follow-up and six patients died. No local tumour recurrences were observed. CONCLUSIONS: Eyes with large uveal melanomas can be salvaged by stereotactic radiotherapy followed by endoresection.

[Stereotactic radiosurgery using the Gamma Knife for large uveal melanomas]. / Stereotaktische Konvergenzbestrahlung grosser uvealer Melanome mit dem Gamma-Knife. Vorläufige Ergebnisse bei 100 Patienten.

BACKGROUND: We report the results over 3 years with stereotactic radiosurgery using the Gamma Knife for large and unsuitably located uveal melanomas. PATIENTS AND METHODS: A total of 100 patients (51 male, 49 female) have been treated since 1997 following a standardised treatment protocol (outpatient single-shot treatment, maximum dose 50 Gy, tumour margin dose min.25 Gy, retrobulbar anaesthesia alone for globe fixation). The localisation and/or dimension of the tumours did not allow radiation brachytherapy with Ru106 plaques. Of the tumours 18 were located in the ciliary body, 61 were located at the posterior pole, and 21 were located in the mid-periphery. All patients were followed and tested ophthalmologically and neuroradiologically at regular intervals. The 1-year follow-up data were available for 73 patients, 2-year follow-up data for 33 patients and 3-year follow-up-data for 17 patients. RESULTS: Before therapy the maximum apical tumour height (MAH) was median 7.8 mm (95% CI 2.9-12.5 mm): 1 year after treatment (73 patients) the MAH was median 5.7 mm (95% KI 2.4-10.2 mm),2 years after treatment (33 patients) the MAH was median 4.3 mm (95% KI 2.2-8.8 mm),and 3 years after treatment (17 patients) the MAH was median 4.6 mm (95% KI 2.4-8.5 mm). All differences to the MAH of the corresponding patients before treatment were statistically significant (paired t-test). Within the first year after treatment seven patients were enucleated due to a painful secondary glaucoma,within the second year after radiation two patients (one tumour recurrence, and one secondary glaucoma) and within the third year one more patient (tumour recurrence) was enucleated. CONCLUSIONS: Our 3-year results demonstrate that radiosurgery using the Gamma Knife is beneficial in achieving a local tumour control in 98% of eyes with large and unsuitably located uveal melanomas. The risk for a secondary enucleation is highest in the first year after treatment with a favourable overall rate of 10%. Due to the excellent local tumour control rate we decreased the maximum dose to 40 Gy (min.tumour margin dose 20 Gy) in the subsequently treated patients.

[Endoscopic resection of malignant melanomas of the uvea after preoperative stereotactic single dose convergence irradiation with the Leksell gamma knife]. / Endoresektion maligner Melanome der Uvea nach präoperativer stereotaktischer Einzeldosis-Konvergenzbestrahlung mit dem Leksell-Gamma-knife.

In cases of large volume and highly prominent melanomas of the uvea, it is rare for conventional methods of radiation therapy to enable salvage of the globe or even residual functionality of the affected eye. Complications due to the massive amount of accumulated necrotic tissue often necessitate subsequent enucleation of the blinded eye. Tumor-destroying, single-dose convergence irradiation (radiosurgery) of such tumors applied shortly before endoresection can represent a possible therapeutic alternative in these types of cases.

First clinical experience with the automatic positioning system and Leksell gamma knife Model C. Technical note.

In May of 1999, the first Leksell Model C gamma knife was installed at the Gamma Knife Zentrum in Krefeld, Germany. The authors recount their experience with this latest technical gamma knife development. Until the end of 1999, extensive physical and technical tests were performed and the system's hardware and software were continuously improved and adapted to the user's needs. By the end of 1999, 163 GKSs had been performed using the new functionality of the Model C in manual or "trunnion" mode. The trunnions, the two parts of the system that fix the patient headframe to the gamma knife when the isocenter positions, are checked manually. During the same period the new automatic positioning system (APS) was extensively tested and refined so that the first APS treatment could be performed in January 2000. Fifty GKSs have been performed with the APS capability of the Model C. It was possible to use APS alone in 74% of surgeries whereas in 14% some shots were given with APS and some with trunnions. In 12%, GKS was scheduled and planned for APS, but due to unexpected technical (6%) or mechanical (6%) reasons the treatment had to be performed manually. At present there are some spatial restrictions with Model C in APS mode when compared with the Model B. The most significant restriction is the narrow space for the patient's shoulders, especially when deep-seated lesions are treated. Through mechanical changes of the APS motor housing and some modifications of and to the motor driven couch adjustment, these limitations will be reduced in the future. The APS treatment runs smoothly and fast. In no case did any relevant safety error occur during GKS. The more stringent mechanical limitations of the APS compared with the Model B means that frame placement on the head is more critical than before.

Surgery and radiotherapy compared with gamma knife radiosurgery in the treatment of solitary cerebral metastases of small diameter.

OBJECT: The aim of this retrospective study was to compare treatment results of surgery plus whole-brain radiation therapy (WBRT) with gamma knife radiosurgery alone as the primary treatment for solitary cerebral metastases suitable for radiosurgical treatment. METHODS: Patients who had a single circumscribed tumor that was 3.5 cm or smaller in diameter were included. Treatment results were compared between microsurgery plus WBRT (52 patients, median tumor dose 50 Gy) and radiosurgery alone (56 patients, median prescribed tumor dose 22 Gy). In case of local/distant tumor recurrence in the radiosurgery group, additional radiosurgical treatment was administered in patients with stable systemic disease. Survival time was analyzed using the Kaplan-Meier method, and prognostic factors were obtained from the Cox model. The patient groups did not differ in terms of age, gender, pretreatment Karnofsky Performance Scale (KPS) score, duration of symptoms, tumor location, histological findings, status of the primary tumor, time to metastasis, and cause of death. Patients who suffered from larger lesions underwent surgery (p < 0.01). The 1-year survival rate (median survival) was 53% (68 weeks) in the surgical group and 43% (35 weeks) in the radiosurgical group (p = 0.19). The 1-year local tumor control rates after surgery and radiosurgery were 75% and 83%, respectively (p = 0.49), and the 1-year neurological death rates in these groups were 37% and 39% (p = 0.8). Shorter overall survival time in the radiosurgery group was related to higher systemic death rates. A pretreatment KPS score of less than 70 was a predictor of unfavorable survival. Perioperative morbidity and mortality rates were 7.7% and 1.6% in the resection group, and 8.9% and 1.2% in the radiosurgery group, respectively. Four patients presented with transient radiogenic complications after radiosurgery. CONCLUSIONS: Radiosurgery alone can result in local tumor control rates as good as those for surgery plus WBRT in selected patients. Radiosurgery should not be routinely combined with radiotherapy.

[Profile of ambulatory radiosurgery with the gamma knife system. 1: Method and multicenter irradiation concept]. / Profil der ambulanten Radiochirurgie mit dem Gamma-Knife-System. Teil 1: Methode und multizentrisches Bestrahlungskonzept.

Radiosurgery represents a minimally invasive radiologic method for the treatment of intracranial tumours and arteriovenous malformations. In 1994 the radiosurgical device 'Leksell Gamma Knife' (LGK) was installed in a dedicated logistic environment for outpatient treatments. High quality requirements have to be met for radiosurgery. The target point accuracy taking into account the whole system was shown to be reliably below 0.5 mm whereas the spatial therapeutic resolution was 0.035 cm3. Quality parameters of the dose plan were evaluated for the first 500 consecutive treatments. These values and examples of dose plans were used to emphasize the advantages of the treatment principle with multiple isocenters. An analysis of data in the literature revealed that there is no uniform standard of treatment available in radiosurgery. A highly significant correlation between a risk prediction model for the stereotactic linear accelerator on the one hand and a different model for the LGK on the other could be shown. This result could be helpful in order to proceed towards a more uniform treatment standard in radiosurgery and to improve overall treatment results.

[Profile of ambulatory radiosurgery with the gamma knife system. 2: Report of clinical experiences]. / Profil der ambulanten Radiochirurgie mit dem Gamma-Knife-System. Teil 2: Klinischer Erfahrungsbericht.

Gamma Knife radiosurgery (GKRS) was applied in 500 consecutive treatments for 445 patients within 2 years. Indications were arterio-venous malformations (93 patients), schwannomas of cranial nerves (75 patients), meningiomas (79 patients; 73 of the tumors involving the skull base), pituitary adenomas (40 patients), craniopharyngiomas (13 cases), gliomas (13 cases), rare indications (12 cases), and brain metastases (126 patients). In arterio-venous malformations two complications were observed whereas two other patients underwent surgery due to intracranial hemorrhage in the latent period after GKRS. In all cases follow-up with MRI showed evidence of an active obliteration process. Out of 24 patients with a follow-up over 1 year, angiography revealed complete obliteration in 9 patients so far. A partial obliteration was evidenced by MRI in 15 cases. In benign tumors (meningiomas and vestibular schwannomas) tumor control rates of 88% and 89% were achieved, respectively. Treatment related side effects were mild and rare; no facial palsy occured after primary Gamma Knife treatment. GKRS was particularly effective in inoperable skull base meningiomas. Cerebral metastases were controlled in 89.5% by a single Gamma Knife treatment. The mean survival period was 11.8 months. In patients receiving a single Gamma Knife treatment the mean survival time was 9.1 months. For patients undergoing multiple (up to 5) sessions of GKRS (because of new tumors) the mean survival period was 17.2 months. MRI showed evidence of adverse radiation reactions in 10/124 patients (8.1%) which were symptomatic in 3 patients (0.8%). The results obtained in patients with cerebral metastases emphasize that GKRS alone is as effective as the combined treatment of these lesions by surgery and fractionated radiotherapy. Our results demonstrated an attractively high therapeutic gain factor of Gamma Knife treatment in key indications of radiosurgery.

Computer assisted brain surgery for small lesions in the central sensorimotor region.

The capacity of a new optical navigation device is demonstrated by six microsurgical procedures for small subcortical lesions within the central sensorimotor strip. This small series is aimed at less invasive resection in this functionally critical region, independently of primary diagnosis and outcome. Guided by high resolution CT imaging data five brain tumours and one cavernous angioma was selectively located and most sparingly removed without additional sensorimotor deficit. In two cases improvement of a pre-operative paresis was observed immediately after surgery. Thanks to light-weight freehand pointing instruments and a ranging accuracy of +/- 1 mm, damage to functionally important brain areas and vessels was avoided by using uncommonly oblique, e.g., transsulcal ways of access which would hardly have been possible even with guidance by conventional stereotaxy. The demanding systematic cortical stimulation of the precentral gyrus applied in three cases was only sensitive in infiltrating tumours-e.g., low grade astrocytomas-where for want of adjuvant therapy it was essential to proceed to the extreme limits of resection. In general, precise anatomical localisation by computer aided surgery (CAS) is sufficient in small central lesions which guarantees minimally invasive surgery. The potential of this new, soon commercially available optical navigation system in (neuro) surgery, quality control and teaching is discussed.

Microstereometrically guided cortical stimulation for the intraoperative identification of the central motor strip.

A rangable stimulation tool based on the sonar microstereometric system has been developed for the intraoperative identification of the central motor strip. The elicited motor evoked potentials (MEPs) were recorded with surface electrodes and displayed together with the corresponding stereometric coordinates of the stimulation site. MEP data were overlaid in 'real time' on preoperatively scanned CT images on a computer screen. The system has been used during open microsurgical procedures in 6 patients with small tumors near the central motor strip or related 'eloquent' areas. Three operations have been performed under local anesthesia, 3 under general anesthesia. It was possible to operate on tumors located closely to functionalal relevant areas of the brain not only stereotactically, but also with function guidance.

Micro-stereometry: a frameless computerized navigating system for open microsurgery.

We are introducing a new type of ultrasonic-based three dimensional (3D) ranging system for the localization of small hand-held surgical tools to be used during operation in open and stereotactic brain surgery. The new device has been extensively tested in the laboratory and showed a linear localization accuracy of +/- .4 mm. The calibration of the system is automatically done by an active calibration frame as well as by pointing to fiducial markers. The position of the tool is sent to a visualization unit and overlaid in realtime on preoperatively scanned computed tomography (CT) and magnetic resonance imaging (MRI) pictures. First clinical tests showed the improved accuracy, handling, and versatility of the new stereometric navigation system, which will soon become the backbone of a computer-aided surgery (CAS) system with a variety of locatable tools.

Ranging accuracy test of the sonic microstereometric system.

We have recently introduced a new type of ultrasonic-based, three-dimensional ranging system for the localization of small handheld surgical tools to be used during operation in open stereotactic brain surgery. This targeting system has now been extensively laboratory tested during thousands of measuring cycles with a CNC-based measuring table. The typical accuracy found in a single direction was 0.4 mm and better. The accuracy vector in space was 0.897 mm (n = 2312). The test-retest accuracy was typically 0.4 mm. With the given accuracy, the system is suitable for all ranging tasks in open stereotactically guided microsurgery.

Stereo-microvision. Development of an opto-electronic operating microscope.

A novel opto-electronic operating microscope has been designed and clinically tested. It consists of a small camera microscope, a central electronic unit, and a stereoscopic video monitor. Advanced miniaturization permitted ergonomics superior to those of conventional optomechanical microscopes. Electronic imaging facilitates coupling to an ultrasound navigation system which enables the neurosurgeon to verify the location of the focus in real time, correlated with CT and MRI pictures. A fully computerized, digital operating microscope will now be developed based on this prototype.

Sonic stereometry in microsurgical procedures for deep-seated brain tumors and vascular malformations.

A frameless computerized navigating system was successfully employed in 20 cases of open microsurgical operations on deep-seated brain tumors and vascular malformations. Localization in space was made by measuring the traveling time of sonic waves (24 kHz) in air. This allowed the construction of mechanically simple, lightweight freehand targeting instruments. The tips can be localized with a measuring accuracy of +/- 1 mm intracranially on the basis of computed tomographic scans. This thoroughly redesigned sonic stereometrical device is being optimized for everyday use; magnetic resonance imaging, digital substraction angiography, and other diagnostic modalities will be implemented. Some perspectives on "computer-aided (neuro)surgery" are discussed.

Compensation of human stance perturbations: selection of the appropriate electromyographic pattern.

Perturbations of stance evoke purposive EMG patterns which are directed to hold the body's centre of gravity over the feet. Dorsiflexing rotation of the feet is followed by a monosynaptic stretch reflex response in the gastrocnemius muscle, succeeded by a late compensatory tibialis anterior activation. Backward translation of the feet elicits only a compensatory polysynaptic EMG response in the gastrocnemius muscle, while an early gastrocnemius response is absent. The amplitude modulation of the gastrocnemius H-reflex has been investigated during the early part of the two modes of perturbation. Only during translational perturbation a progressive decrease in gastrocnemius H-reflex amplitude started within 5 ms after onset of displacement. The degree of the reduction in amplitude in the former perturbation was dependent on the displacement velocity. Only the contact forces (torques) differed between the two modes of perturbations within the first 10 ms after onset of perturbations. It is suggested that signals from pressure receptors within the body are responsible for the early change in H-reflex amplitude during translational perturbations and it is concluded that the simplest spinal reflex is under very rapid and powerful moment-to-moment control by changes in peripheral feedback. In view of a strong reciprocal modulation of monosynaptic and polysynaptic reflex responses, the later purposive EMG responses may be determined by early changes in presynaptic inhibition of group I afferents.

[Microsurgical removal of deep vascular malformations using sonar-stereometry]. / Mikrochirurgische Entfernung tiefliegender Gefässmissbildungen mit Hilfe der Sonar-Stereometrie.

The advantages of a new, dynamic sonar technology in open stereotactic microsurgery are demonstrated by means of three surgical procedures for deep-seated vascular malformations that are not easy of access. With this method, targets can be aimed at without using rigid, obstructive pointing devices as in conventional stereotaxy. On the contrary, it is possible to take advantage of preformed anatomical spaces reaching the lesion most carefully by means of light-weight, free-hand on-target instruments. The spatial information, correlated with a CT data set, is displayed in real time with an accuracy of +/- 1 mm. Additional image data from MR and digital angiography can be used interactively.

Body sway stabilization in human posture.

Electromyographic (emg) responses and joint movements of the leg were analysed in subjects standing with eyes closed on a sinusoidally moving treadmill (0.16 Hz or 0.33 Hz, amplitude 33 cm). Activity in antagonistic leg muscles was reciprocally modulated, with a predominant gastrocnemius activation during deceleration of forward movement and tibialis anterior activation during deceleration of backward movement of the treadmill. In these phases, it was necessary to compensate for sway induced by body inertia. The match between treadmill movement and emg activity was better for the gastrocnemius than for the tibialis anterior muscle. The characteristic pattern of leg muscle emg activity is suggested to be modulated predominantly by vestibulo-spinal reflexes partly because treadmill movements did not evoke muscle strength, and partly because patients with loss of vestibular function showed basic alterations in the emg pattern and could only compensate for the slow sinus while standing unsupported.

A basic posture control mechanism: the stabilization of the centre of gravity.

Holding the body's centre of gravity steady represents the crucial variable for the stabilization of posture in upright stance in man. The visual, vestibular and muscle proprioceptive systems have all been shown to contribute to sway stabilization. Nevertheless, earlier work has suggested that an additional receptor system is needed to signal the position of the body's centre of gravity relative to the support surface, i.e., the feet. This proposed receptor system should be 'gravity' dependent. To evaluate the properties of this receptor system, an experiment was designed under simulated 'microgravity', in water immersion. An approximately linear relationship was found between contact force and impulse directed EMG response amplitudes in the leg muscles. Out of water loading of the subjects resulted in no further increase of the response amplitude. A gain control mechanism for postural reflexes which is dependent on body weight was demonstrated. In a further experiment it could be shown that the receptors for this mechanism are distributed along the vertical axis of the body: it is suggested that these force-dependent receptors are pressure receptors within the joints and the vertebral column.

Interlimb coordination of stance in children: divergent modulation of spinal reflex responses and cerebral evoked potentials in terms of age.

EMG responses in the gastrocnemius (GM) and tibialis anterior muscles (TA) of both legs together with cerebral evoked potentials (CP), were recorded following perturbations of stance on a treadmill with split belts, in two age groups of children. Unilateral displacements were followed by ipsilateral short latency and bilateral long latency EMG responses. The CP was similar in both tasks. When displacements were simultaneously induced in opposite directions, a significant reduction in the long latency components of EMG responses occurred, while the amplitude of the CP was maximal in this condition. In the older children the CP and long latency EMG responses were larger and the short latency reflex potentials smaller in all conditions compared to the younger children. It is concluded that (1) CP and EMG responses reflect a divergent modulation of a given somatosensory input; (2) developmental changes are reflected in alterations in the amplitude of CP and EMG responses; (3) there is no evidence of transcortically mediated muscle responses.

[CT/MRI correlated stereometry with ultrasound in brain surgery]. / CT/MRI-korrelierte Stereometrie mit Ultraschall für Hirnoperationen.

Today the accuracy of medical imaging systems lies between +/- 0.5 mm (CT) and +/- 2.5 mm (MRI). In neurosurgery the overall uncertainty may reach the dimension centimetres. A non-tactile ultrasonic measurement system is described that allows three-dimensional measurement with a theoretical accuracy of +/- 0.1 mm in a frequency range between 50 and 70 kHz. In practice the accuracy is better than +/- 1 mm with a repetition rate of 10 per second for the x,y,z-data sets.