Direct surgery for intra-axial lesions of the brainstem was done for 9 cases : seven cases in the pons (2 cavernous angiomas, 3 gliomas, 2 metastatic tumors) and two in the medulla oblongata (one cavernous angioma, one glioma), by suboccipital craniectomy. For the lesions in the pons, the supra or infrafacial approach was made. Cavernous angiomas were totally removed. Metastatic tumors were gross-totally removed. Gliomas were partially removed except one case in the medulla oblongata which was removed gross-totally. Suprafacial approach was taken in 5 cases and infrafacial approach was in 2. As surgical results, 7 cases showed improvement of symptoms, and 2 cases, which were operated by infrafacial approach, showed worsening. Cavernous angiomas are good candidate for total removal. Infrafacial approach will required more meticulous procedures than the suprafacial triangle.
In order to define the optimal treatment for an AVM patient, the probability of cure and the management risk following the treatment must be estimated before the treatment. Here, Gamma Knife surgery has an advantage over microsurgery and embolization with it's reproducibility within the variability of the individual radiation sensitivity. Based on more than 2000 treatments, we have developed models to predict the probability for obliteration, the risk for radioinduced complications and the probability for a post treatment hemorrhage within the first two years following a Gamma Knife treatment. The factors determining the overall outcome are the absorbed dose in the target and the brain, the AVM volume and location and the age and clinical history of the patient. The probability for obliteration equals 35, 69* ln (Dmin) -39, 66 and is AVM volume independent. The risk for radioinduced complications relates to the average dose in the 20cm3 tissue receiving the most radiation, and it is also related to the clinical history of the patient and the AVM location. Finally, the risk for post treatment hemorrhage increases with the age of the patient, and is higher for larger AVM. It decreases with increasing amount of radiation given, and it is independent of the clinical history of the patient. For retreatments, the model for prediction of obliteration is valid, but the risk for radioinduced complications is higher and the risk for post treatment hemorrhage lower as compared to following the first treatment.
Bleeding in the latency period before obliteration considerably worsens the prognosis of cerebral arteriovenous malformations (AVMs). Bleeding risk should be considered and total obliteration should performed as early as possible. In this study we investigated factors related to early obliteration following Gamma Knife radiosurgery and proposed a grading system for AVMs. Forty-six patients with cerebral AVMs followed angiographically within twelve months after Gamma Knife radiosurgery were analyzed. Four factors, volume, type (categorized by our own method), location, and marginal dose were found to be correlated with early obliteration rate. We scored these factors, and categorized the scores into a grade 0 to 6 Gamma Knife Score (GKS), and evaluated the obliteration rate of each grade. The total obliteration rate in twelve months according to grade was : grades 0 and 1, 61.9% grades 2 and 3, 36.0%, grades 4 and 5, 16.7%. AVMs with a low GKS (grades 0 and 1) had a high early obliteration rate and seemed suitable for Gamma Knife radiosurgery. Since early obliteration is difficult to obtain in the high grade group, endovascular surgery should be considered to reduce the GKS before Gamma Knife radiosurgery.
Surgery of midline lesions is difficult in many cases and often only partial removal is possible. Between May 1992 and April 1997, 81 patients with midline lesions were treated radiosurgically. The lesions were located in the hypothalamic region (25), thalamus (20), third ventricle (2), quadrigeminal plate (9), pons (13), fourth ventricle (4), pineal region (4) and other locations (4). Forty-eight patients were male and 33 were female. Histologically, there were 56 benign cases (13 arteriovenous malformations, 11 low grade gliomas, 20 craniopharyngiomas, 5 meningiomas, 3 hamartomas, 4 miscellaneous) and 25 malignant cases (10 metastases, 10 high grade gliomas, 2 medulloblastomas, 3 miscellaneous). Clinical and radiological follow-up was obtained in 71 patients (88%). In all patients the treatment was well tolerated. Radiographic response could be achieved in 39 of 68 tumor patients (57%). A complete obliteration was seen in 6 arteriovenous malformations (60%) 2 years after radiosurgery. A second radio-surgical procedure was necessary in 2 patients because of incomplete obliteration after 3 years. According to our experience, we can conclude that radiosurgery appears to be effective as adjuvant treatment of midline lesions.
In order to identify the best strategy for the treatment of acoustic schwannomas, we analyzed the role of tumor size and its relation to successful gamma knife radiosurgery. Seventy-seven patients who had had been followed up for more than 2 years after radiosurgery were analyzed from the view points of tumor control and functional outcome. They were divided into 2 groups; 55 cases had no prior surgery (group A), and 22 cases had undergone previous surgery (group B). Of the latter group, 7 cases with large tumors were treated by radiosurgery after intentional surgical resection to minimize functional damage. They were classified as the B-I sub-group, with the other 15 cases being referred to as the B-S sub-group. The actuarial reduction rate of all cases at 2, 3 and 4 years was 68%, 80% and 83%, respectively. There were 2 cases (2.6%) who needed surgical extirpation after radiosurgery. Large sized tumors were less controlled than small to medium sized tumors (p = 0.0008). Useful hearing was preserved in 88% of all cases and no patient suffered worse permanent facial dysfunction. Comparing the groups, the pre-radiosurgical hearing (Gardner & Robertson classification) of A to B-S or B-I was 2.5 to 4.7 (p = 0.063) or 3.3 (p =0.24), and facial functions (House & Brackmann grading) were 1.0 to 2.5 (p = 0.006) or 1.3 (p =0.13), respectively. Gamma knife radiosurgery may be a good choice in small to medium sized tumors, especially in patients with useful hearing. Combined therapy for large tumors with intentional partial removal followed by radiosurgery also appears to offer an excellent functional outcome.
Transsphenoidal surgery usually represents first line treatment for pituitary adenomas with the aim of removing the tumor, decompressing the optic apparatus and, in secreting tumors, eliminating the hypersecretion. Gamma Knife radiosurgery is indicated for tumor remnants or recurrences in or above the sella including those invading the cavernous sinus and also as initial treatment in patients who are unable to tolerate an open surgical procedure and where medication has failed. In this study, the target definition was retrospectively studied and when necessary corrected in 10 acromegalic patients, 8 with Cushing's disease, and 12 with prolactinomas undergoing Gamma Knife radiosurgery. The dose plan was analyzed and the volume of the target covered by a minimum of 15, 20, 25, 30 and 35Gy was estimated. A dose/volume profile for each treatment was created and correlated to the endocrinological and clinical outcome. Cure, according to strict endocrinological criteria, was seen in 6 of the acromegalic patients, in 2 of the patients with ACTH hypersecretion, and in 2 of the patients with prolactinomas. Analysis of these profiles, also for the patients with partial effect, show that a minimum radiation dose of 20Gy may be adequate to eliminate the hypersecretion in acromegalic patients whereas a dose of at least 25Gy may be required in patients with Cushing's disease and prolactinoma.
Endovascular treatment is an excellent alternative as a less invasive procedure to treat cerebrovascular disease. Percutaneous transluminal angioplasty and thrombolysis for occlusive disease, obliteration of intracranial aneurysms with coils, artery occlusion for large aneurysms, and embolization of dural arteriovenous fistulas and cerebral arteriovenous malformations are described with illustrative cases. Although endovascular treatment for cerebrovascular diseases is being developed and the indications are becoming broader, combination treatment with microsurgery and radiosurgery should also be considered in an attempt to achieve better results.
A major aim of minimally invasive neurosurgery is to preserve function in the brain and cranial nerves. Based on previous results of radiosurgery for central lesions (19 craniopharyngiomas, 46 pituitary adenomas, 9 meningeal tumors), combined micro-and/or radiosurgery was applied for large lesions compressing the hypothalamus and/or brainstem. A basal interhemispheric approach via superomedial orbitotomy or a transcallosal-transforaminal approach was used for these large tumors. Tumors left behind in the hypothalamus or cavernous sinus were treated with radiosurgery using a gamma unit. Preoperative hypothalamo-pituitary functions were preserved in most of these patients. Radiosurgical results were evaluated in patients followed for more than 2 years after treatment. All 9 craniopharyngiomas decreased in size after radiosurgery, although a second treatment was required in 4 patients. All 20 pituitary adenomas were stable or decreased in size and 5 of 7 functioning adenomas showed normalized values of hormones in the serum. All 3 meningeal tumors were stable or decreased in size after treatment. No cavernous sinus symptoms developed after radiosurgery. We conclude that combined micro-and radio-neurosurgery is an effective and less invasive treatment for large central lesions compressing the hypothalamus and brainstem.
Treatment of some large, deep-seated arteriovenous malformations is still a challenge to neurosurgeons. Recent development of non-invasive imaging modalities has increased the chance of finding asymptomatic AVM's, for which evaluation of risk and benefit of treatment is more complicated than in symptomatic cases. Currently there are three major treatment options for AVM : microsurgical removal, radiosurgery, and intravascular embolization. It is not easy task for us neurosurgeons to choose the best single modality or combination of modalities for individual patients, who have different types of onset, neurological deficits, size and location, and social background. After the installation of the Gamma Knife in November 1991, we established an “AVM Treatment Board”. It consists of vascular neurosurgeons, endovascular neurosurgeons, and radio-neurosurgeons, and meetings are twice a month. Every AVM case referred to us is presented to the board, and treatment strategy is selected after a discussion among experts who know the advantages and drawbacks of each treatment modality. This paper describes this board system in detail and emphasizes the importance of gathering expertise in decision making.