Stereotactic radiosurgery with the linear accelerator: treatment of arteriovenous malformations.

An original stereotactic radiosurgical approach coupling a) Talairach's stereotactic methodology, b) a specially devised mechanical system, and c) a linear accelerator is detailed. The authors present their preliminary results on 66 patients with nonsurgical intracranial arteriovenous malformations. The doses delivered for treatment varied from 20 to 70 Gy. Doses of no more than 40 Gy were used in 80% of patients. An angiographic study was performed when the computed tomographic scan controls showed relevant modifications of the lesion volume. Total obliteration was obtained in 27 of the 41 patients (65.8%) who were followed up for at least 24 months. The percentage of the cured patients is significantly higher when a) the entire malformation is included in the 75% isodose (96%) and b) the maximum diameter of the lesion is less than 12 mm (81%). Two patients died of rebleeding at 18 and 29 months after treatment.

Comparison of 1-year follow-up evaluations of patients with indication for pallidotomy who did not undergo surgery versus patients with Parkinson's disease who did undergo pallidotomy: a case control study.

UNLABELLED: Many reports published during the past 5 years have shown evidence of the beneficial effect of posteroventral pallidotomy (PVP) in large groups of patients for up to 3 years, but none of them have compared patients who underwent surgery with a control group. OBJECTIVE: To compare the evolution of Parkinson's disease symptoms at 1-year follow-up between patients who underwent surgery and those who did not. MATERIAL AND METHODS: Ten patients with idiopathic Parkinson's disease refractory to treatment who were included in the Core Assessment for Intracerebral Transplantation program for PVP did not undergo surgery because financial support was lacking. These patients were followed up for 1 year as if they had been operated on and were finally compared with 10 patients having similar characteristics in whom PVP had been performed during the same period of time. RESULTS: There were no significant differences at basal evaluation in the motor section scores of the Unified Parkinson's Disease Rating Scale between those patients who underwent surgery and those who did not, but a significant reduction in Unified Parkinson's Disease Rating Scale motor score in the group who underwent surgery at 1-year evaluation was found (P < 0.006). Dyskinesias, which was nonsignificantly different at basal evaluation, showed, at the 1-year follow-up, a significant reduction in the group who underwent surgery (P < 0.04). Scores from the subsets of the Unified Parkinson's Disease Rating Scale addressing rigidity, tremor, and bradykinesia also proved significantly different at the 1-year follow-up. The slope of the line generated by the two evaluations for each group showed a negative value in the group who underwent surgery (value of -0.21) and a positive value in the group who did not (value of 0.148). CONCLUSION: At the 1-year follow-up, microelectrode-guided PVP produced significant changes in patient motor status and disease progression versus a comparable group of patients who did not undergo surgery during the same period of time.

[Multiple-beam stereotaxic irradiation]. / Irradiation stéréotaxique multifaisceaux.

The "Talairach" stereotactic multibeam irradiation system developed by the authors allows to irradiate selectively small intracranial or intraorbital lesions localized in the Talairach stereotactic system. The centre of the target volume is placed in the isocentre of rotation of a linear accelerator (160 degrees), a special head fixation allows for a stepwise rotation of the head (145 degrees) around the centre of the lesion. Special collimators adapt the width of the high energy photon beam to the dimensions of the target (some millimeters to 3 cm), creating a high dose radiation field limited to the lesion (deep AVM, pituitary adenomas, small gliomas in critical areas etc.).

[Radiosurgical treatment of minor intracranial arteriovenous malformations by using a linear accelerator]. / Traitement radiochirurgical avec accélérateur linéaire des "petites" malformations artério-veineuses intra-crâniennes.

This study deals with 43 patients with cerebral arteriovenous malformations (AVMs) of a maximum of 20 mm in diameter. All of them were radiosurgically treated with a linear accelerator in stereotatic conditions (UMIC). The delivered doses vary from 20 gys to 50 gys. Thirty-seven were controlled angiographically and 35 of them showed the disappearence of the AVM. Different parameters can modify the results: delivered dose, the size and shape of the lesion, target-volume, peripheral lesion isodosis (75%), location, underestimation of the size or dose. These results show that small lesions are best to treat than larger ones, particularly because their volume enables us to encompass them more easily. The uniformity of this series is related to the homogenous size of the treated AVMs, thus avoiding the discussion of global, unclear, results.

[Current experience of stereotaxic irradiations in the treatment of hemispheric gliomas (author's transl)]. / L'expérience actuelle des irradiations stéréotaxiques dans le traitement des gliomes hémisphériques.

Authors present a short review of the techniques and results of the stereotactic focal irradiations (S.I.) used at present in France for the treatment of small "active" gliomas localized in high risk areas (functional and vital) of the brain. These techniques include the temporary interstitial implantation of 192Ir wires, possibly associated with external irradiation and the treatment of active glioma cysts by intracystic injection of colloidal beta emitters such as 90Y and 186Re. The risk of immediate (surgical) and late (radiation) functional loss is low and the overall results at 3 years are satisfactory in particular with small well delimited astrocytomas. Such treatments can be associated to surgical reduction of the tumor volume or to other forms of irradiation according to the data of stereotactic localization studies including biopsy.

[Stereotaxic diagnosis and treatment of colloid cysts of the 3d ventricle. Apropos of 7 cases]. / Diagnostic et traitement stéréotaxique des kystes colloïdes du troisième ventricule. A propos de 7 cas.

The clinical and anatomical results of the treatment of 7 colloid cysts of third ventricle by stereotaxic aspiration are reported. A history of increased intracranial pressure was reported in all patients (4 females aged of 12, 16, 28, 38 years; 3 males aged of 36, 54, 59 years). A ventricular shunting device has been inserted in 4 patients. Pre-operative clinical findings were: signs of increased intracranial pressure (1 case), isolated memory disturbances (3 cases); motor weakness, memory disturbances and psychomotor slowness (2 cases); 1 of the 2 last cases had also thymic disturbances. Clinical examination was normal in 1 patient. CT-Scan revealed 5 hyperdense lesions, 3 with slight enhancement; 1 hypodensity encircled by an hyperdense ring without enhancement, 1 not enhancing isohypodensity. 6 colloid cysts were between the Foramens of Monro, 1 in the posterior third ventricle. Cyst volume ranged from 1.8 to 6.3 cc. (m: 3.4). Biventricular hydrocephalus was present in all but 1 patient. Stereotaxic aspiration of the cyst performed according to Talairach's system resulted in a release of C.S.F. circulation in all cases. 3 colloid cysts were aspirated completely, 4 were reduced to 3%, 11%, 12%, 33% of the initial volume. Post-operatively 2 patients presented with a transient meningeal reaction, 1 with a transient "myoclonic" syndrome. In 1 "completely aspirated" case a control CT-Scan showed, 5 years later, a small hyperdensity corresponding to 4% of the initial cyst volume. All patients lead a normal and useful life (Follow-up: 8-78 months, m: 45). Neurological examination is normal in 6 cases and shows a pre-existent facial asymmetry in 1. Ours results suggest that stereotaxic investigation should be the first safe procedure in order to achieve both diagnosis and treatment of colloid cysts of third ventricle.

[Stereotaxic treatment of expanding cysts in craniopharyngiomas by endocavitary beta-irradiation (Re-186; Au-198; Y-90)]. / Traitement stéréotaxique des kystes expansifs de crânio-pharyngiomes par irradiation endocavitaire bêta (Re 186; Au 198; Y 90).

The authors report the results of 17 intracystic injection of colloidal 186 rhenium, 2 colloidal 198 gold, and 1 colloidal 90 yttrium for endocavitary treatment of 18 cystic craniopharyngiomas (16 pts during a period ranging from January 1975 till July 1982. Follow-up studies ranging from 12 to 72 months (m: 36 m) revealed that all craniopharyngiomas cysts were effectively treated with cessation of fluid formation, progressive shrinkage of the formerly expansive cysts, and finally cyst obliteration in 75% of the cases. No early or late side-effects were observed during the entire observation period. Late reexpansion of one craniopharyngioma cyst, observed at 11 months, was successfully treated by a second injection. Leakage of colloid isotope into the CSF spaces during the "test" or "therapeutic" injections occurred in 18% of the global number of injections, however no clinical complications were observed. On the basis of a clinical dosimetric study a 30 000 rads wall-dose, not exceeding 40 000 rads is actually considered as the safer dose for endocavitary treatment of craniopharyngioma.

Radiosurgery with a linear accelerator. Methodological aspects.

Based on the concepts of Leksell and on recommendations of different Swedish physicists on the use of linear accelerator for radiosurgical use, we developed a new methodology coupling the Talairach stereotactic system with a commercial linac. Anatomical facts encouraged us to use coronal angles of irradiation employing the angular displacement of the linac above the horizontal plane. Different coronal planes are obtained by rotation of the stereotactic frame. The center of the irradiated target coincides with the irradiation and rotation center of the linear accelerator. Multiple targets can be irradiated in the same session. We use as recommended a secondary collimator in heavy alloy. Special software was prepared after different dosimetric controls. The use of a PC allows us to employ 1-6 targets and different collimators to displace the isocenters in order to obtain geometrical isodose modification, and to change the value of each irradiation arc or portions of each arc in some minutes. Simple or sophisticated neurosurgical strategies can be applied in the treatment of frequently irregular shape and volume AVMs.