Victor A. Fasano

Photocoagulation of Cerebral Arteriovenous Malformations and Arterial Aneurysms with the Neodymium: Yttrium-Aluminum-Garnet or Argon Laser: Preliminary Results in Twelve Patients

Six arteriovenous malformations (AVMs) and five arterial aneurysms (AAs) were treated with either argon or neodymium:yttrium-aluminum-garnet laser irradiation; one AVM was treated with both. All AVMs were occluded completely, leaving adjacent tissue untouched and preserving the regional vascularization. Photocoagulation produced varying effects on AAs: in one case an intraoperative rupture was sealed, in two cases the volume of an ectasia was reduced when the bleeding and thinner areas were coagulated, and in one case a saccular aneurysm was progressively and completely obliterated while the patency of the parent artery was preserved. These preliminary results are satisfactory; more experience will indicate how and when these new techniques can replace traditional ones or be used in combination with them.

The effects of new technologies on the surgical management of brainstem tumors.

Nuclear magnetic resonance, real-time and A-scan ultrasonography, and computerized CO2 lasers were recently introduced for diagnosis and surgical treatment of brainstem tumors. These new technologies offer many advantages: safe but aggressive surgery on the brainstem, the possibility of performing a correct histologic diagnosis, and an exact indication for radiotherapy. Eleven tumors were operated on in our series: seven were intrinsic and four protruded out from the axis. Patients with high-grade malignant tumors died from 5 to 12 months after treatment, whereas those with pilocytic astrocytoma are still alive and leading useful lives.

Observations on the use of three laser sources in sequence (co2‐argon‐nd: yag) in neurosurgery

In neurosurgical practice the laser can be considered an additional instrument to improve conventional techniques, or even a new method of treatment of some cerebral lesions. A complete laser surgery requires the association of three laser sources in combination. The CO2 laser is useful for cutting small lesions in important brain areas. Nd: YAG is particularly suitable for tumor surgery‐allowing a deeper destruction with predictable effects associated with a more complete hemostasis. The combination Nd: YAG‐Argon has clear indications for irradiation of the vessels.

Principles of Laser Surgery

Lasers have provided the means to operate on tissue without mechanical contact thus reducing the manipulation of the surrounding healthy structures and the need for tissue retraction. The operative field is under constant vision without obstruction by solid instruments which are used much less in laser surgery. Hemostasis is improved and laser permits surgery in coagulopathies.

Treatment of cerebral arterio-venous malformations with laser.

The surgical application of the laser in the treatment of vascular diseases of the brain is based on its characteristic to perform an immediate or delayed modification of the vessel wall either by shrinking the collagenous fibres or by intraluminal thrombosis. Personal researches have been carried out to study the histological modifications of the vessel wall in normal arteries following laser irradiation with Nd:YAG. On this basis we have treated arterio-venous malformations (AVMs) in man. The laser enables radical surgery with a complete preservation of the healthy tissue surrounding the lesion because of reduced manipulation and the absence of intraoperative haemorrhage. Doppler technique and real-time ultrasonography are mostly suitable in the identification of the small deep-seated AVMs localizing the site of the malformation and the reactive glial tissue surrounding the lesion. The main indications are small AVMs located in critical areas of the brain.

The CO2 Laser in Neurosurgery

While in ophthalmology and other branches of surgery (plastic surgery, gynaecology, otorhinolaryngology etc.), the laser has now become part of operative routine, in neurosurgery this has only recently become true and applies to very few medical centres. Thus, the operation by S. Stellar1, 2, 3 in 1969, for the removal of a cerebral glioma, remained for a long time an isolated instance. Heppner and Ascher4 used the laser systematically at the Neurosurgical Clinic of the University of Graz, starting in 1976; Perria in Genoa, also from 1976; and this Institute of Neurosurgery5 of the University of Turin, starting from 1977. We can deduce the limitations and possible counter-indications of the laser from the experience gained at these medical centres, as well as from papers presented at conferences.

Cryoanalgesia. Ultrastructural Study on Cryolytic Lesion of Sciatic Nerve in Rat and Rabbit

The sciatic nerve was exposed to cryoinjury at different freezing patterns in albino rats and rabbits and the frozen nerves were serially examined with electron microscopy from the time of cryolitic lesion (--60 degrees C for 3 minutes) for up to 28 days. The cryolesion was characterized by a total degeneration of the myelin fibers, while non-myelin fibers and vessels seemed less affected. Regeneration began 8 days after cryolysis. A peculiar pattern was the absence of Schwann cells, while the basal membrane around regenerating axons remained intact. The hypothesis that the basal membrane might play a role is discussed.

New technologies in neurosurgery: Effects on the conventional techniques and anaesthesiological considerations

New technologies have been recently introduced into neurosurgery: laser sources, ultrasonic aspiration, intraoperative echotomography and intraoperative Doppler flowmeter. The aim of this work, showing the use of these instruments in different neurosurgical operations, is to discuss the effective improvements of the surgical techniques when comparing new and traditional technologies. The laser is able to concentrate high energies in restricted areas allowing a maximum selectivity. Having a superficial destructive effect with associated hemostasis, CO2 and argon are suitable in dissection maneuvers. Nd:YAG produces a high thermal diffusion, consenting a deeper and extended tissue removal and a considerable reduction of intraoperative blood loss also in vascularized tumors. A promising field of application of the laser is the treatment of cerebral vascular malformations. In arterio-venous malformations the irradiation of the nidus with Nd:YAG produces a rapid obliteration of the pathologic vessels. This technique avoids the isolation of the feeding arteries and reduces the manipulation of the surrounding tissue. In small saccular aneurysms an argon laser is used to produce a shrinkage of the dilatation with consequent occlusion of the malformation. The ultrasonic aspirator is used in the tumoral surgery to obtain a more rapid demolition of the mass by fragmentation and suction. Intraoperative echotomography consents a sharp topographic localization of the lesion, particularly in deeper cerebral areas, providing data on the nature of solid tumors. The intraoperative Doppler flowmeter is useful for identification of the feeding arteries and the shunt of the small deep-seated arterio-venous malformations consenting a dynamic evaluation of the operation. General anaesthesia in neurosurgical procedures is favourably influenced by laser use. Conventional anaesthetic techniques, however, must be modified to avoid the harmful effect of the laser, depending on the movements of the brain surface, which may switch the laser beam to adjacent tissues, and become particularly dangerous when the laser is used near high functional structures or when the laser is driven by a computer.

Laser Effect on Normal Nervous Tissue (CO2-Nd: YAG). Histological Data

The tissue changes following application of lasers to rabbit brain were studied by Beck et al. in 19791 using CO2 and Nd: YAG lasers.

Preliminary Experiences with Argon and Nd: YAG Scalpel Laser in Neurosurgery

The possibility to approach a lesion performing a no-touch surgery is generally considered one of the main advantages of the laser. This property is expecially useful for the treatment of small deep-seated lesions (intraventricular, midline and brain stem tumors).