The associated targets methodology and the multi-isocenters radiosurgery treatment planning system Artemis-3D.

A new radiosurgical methodology, the "associated targets methodology" has been developed and tested by our group for the irradiation of complex cerebral arteriovenous malformations using our treatment planning system Artemis-3D. For the treatment of the arteriovenous malformations we used 15 MV photons generated by a Saturne 43 Linac, eight additional collimators (6-20 mm in diameter), the Betti fixation seat and the Talairach stereotactic frame. The successive steps of the associated targets' methodology are: -the prescription of a peripheral minimal therapeutic effective dose corresponding to the 60-70% cumulated isodose range; -the compartmentalization of the target volume into several sub-volumes, each of them having its own isocenter, collimator, irradiation space and isocenter dose weight; -the 3-dimensional computation and graphics requirements, and dose volume analysis; -the optimization evaluation criteria taking into account the dose inside and outside of the lesion. Two treatment planning software versions of Artemis-3D exist; the first one was developed for the sitting position and later for the supine treatment position, the second version is a multi-modalities imagery radiosurgical treatment planning system based on more powerful computers. Different types of stereotactic frames have been integrated. Three-dimensional visualization, stereotactic CT imaging, and angiography can be used for the sitting or supine position. We started using this methodology in 1990, and treated 44 patients during that year. For 26 single isocenter arteriovenous malformations, the obliteration rate was 22/26 (85%). In the 18 multi-isocenters irradiation cases, the overall obliteration rate was 11/18 = 61%. An example of successfully irradiated complex arteriovenous malformation is discussed to illustrate the methodology. With this three-dimensional methodology we have improved the results obtained during the first period (1986 to 1989) of our radiosurgical practice in which we used a two dimensional planification approach.

[Stereotaxic laser interstitial thermotherapy. A new alternative in the therapeutic management of some brain tumors]. / La thermothérapie interstitielle laser stéréotaxique. Une nouvelle alternative dans la prise en charge thérapeutique de certaines tumeurs cérébrales.

Laser Interstitial Thermo Therapy (ITT) is a new procedure which has been performed only a few times in our department as well as in foreign services. The aim of an ITT is to increase the temperature of a tumoral target which has been perfectly determined stereotactically. In the center of the target, i-e at the extremity of the laser fibre, temperature reaches 80 degrees 90 degrees C and creates a coagulation necrosis. At the periphery of the target, temperature must be 41 degrees-43 degrees C so as to create a selective lesion of the pathological tissue due to proteinic and enzymatic denaturation. The authors present their experience based on 8 patients who underwent an ITT between June 1990 and October 1991. A stereotactic determination of the tumor is first performed; then two routes are determined for the laser-fibre (Nd-YAG 1.06 microns, fiber diameter: 400 mu) and for the thermic electrode. The ITT itself is performed a few days later (P = 3-5w, time: 800-1200 seconds). Laser heat effects are monitored with MRI controls (H5, H24, D8 then monthly). The authors insist on the importance of a long follow-up so as to be sure of the complete inocuity of such a treatment. It is the only way to broaden and develop laser-ITT procedures as therapeutic alternatives for certain deep-seated intracerebral tumors.

[Treatment of various dyskinesias by intermittent thalamic stimulation]. / Traitement de certaines dyskinesies par stimulation thalamique intermittente.

Abnormal movements or dyskinesias are associated with hyperpathia and hyperalgesia in a number of conditions such as post amputation jumping stumps pseudothalamic syndromes following cerebro vascular accidents and in some cases of demyelinating diseases. Intermittent electrical stimulation of the specific sensory nucleus of the thalamus (I.T.S.) controls at the same time pain and dyskinesias with the same long lasting effect. In some cases where dyskinesias are associated with sensory deafferentation, but not with chronic pain or hyperpathia, the same positive effect of thalamic stimulation on the control of abnormal movements is achieved while in other cases of tremor or dyskinesias without sensory deafferentation such as parkinsonism, intention tremor etc.. the efficacy of I.T.S. is nil. Hence, discriminative sensory deaffrentation is the common link between the cases of tremor or dyskinesias that use to respond to I.T.S. which is up to now the only therapy of proven efficacy in such conditions.

[Transformation of body scheme caused by thalamic stimulation. Thalamic stimulation for painful phantom limb (author's transl)]. / Modification du schéma corporel sous stimulation thalamique. A propos des stimulations thalamiques pour membres fantômes douloureux.

Intermittent stimulation of the parvo cellular portion of the nucleus ventralis posterolateralis (VLP) was able to control both pain and phantom limb phenomenon. The authors insist upon the transformation of the "body scheme" caused by an operation which does not alter the somesthesic function. The sensorial delusion of a phantom limb is probably related to an insufficiency of sensitive information at thalamus level.

Control of dyskinesias due to sensory deafferentation by means of thalamic stimulation.

Intermittent stimulation of the parvocellular portion of the nucleus ventralis posterolateralis (V.P.L.) by means of chronically implanted electrodes and stimulus generator was performed in 124 patients for the control of chronic intractable pain. Among these, 11 showed spontaneous abnormal movements within the painful area: 6 post amputation "jumping stumps"; 4 pseudothalamic syndromes and 1 Von Benedikt's syndrome following a cerebrovascular accident. Electrical stimulation of the V.P.L. was able to control both pain and abnormal movements in all cases. The technique was applied with an equally good result in a case of choreoathetotic syndrome without pain but with severe sensory disturbances following a demyelinating process. Attempts made to control action tremor, parkinsonism and other dyskinesias not associated with sensory deafferentation in 12 cases failed. The same mechanism seems to be responsible for pain and dyskinesia in cases of sensory deafferentation, and thalamic stimulation might work as a substitute for sensory information delivered to the nucleus ventralis posterolateralis.

[Present state of pain surgery]. / Etat actuel de la chirurgie de la douleur

This report presented to the Société de Neurochirurgie de Langue Française is based on 34 years of unique practice in neurosurgical management of pain; during that long period the author and his associates have collected an unusually large experience in almost every field of neurosurgical management of pain; they have improved or fully devised several new techniques which allow them to ground an appreciation of the procedures still worthy to be used in various pain syndromes. The first part of the report deals with "Cybernetics of pain". This rather long chapter is based both on classical data and personal observations on man during and following operations, meant to relieve pain. Though supporting HEAD and HOLMES, theory on Control of protopathic by epicritic Stimuli, the authors consider that the type of pain associated with noxious stimulation as representative of just one among other types of pain, not induced by nociception and not associated with protection reflexes. Sensory deafferentation as can be produced by amputations, herpes zoster, dorsal column or medullary lesions, cannot be included in Sherrington's scheme of psychical mechanisms associated with protection reflexes and yet is responsible for most of the chronic unbearable and often intractable pain. Moreover, an important modulation of pain as such depends on conditioning, on inherited and acquired patterns of behaviour and on a multiplicating factor which is provisionally named "algogenic neurosis". The fact that an intact nucleus ventralis posterolateralis is a necessity for a "no pain status" tends to prove that this thalamic nucleus acts as a major inhibiting relay on the pain integrating system and for several additional reasons is the level of integration of epicritic versus protopathic stimuli in case of true nociception...