The use of the Nd-YAG laser in neurosurgery

Use of Laser in Arteriovenous Malformation Surgery

BACKGROUND

Arteriovenous malformation surgery is particularly demanding owing to the need to control bleeding of small, deep white matter vessels during and after removal of the nidus; this is probably one of the most critical moments of arteriovenous malformation surgery. The aim of this article is to describe a useful technique based on the use of tweezers to temporarily stop the blood flow followed by coagulation with the thulium laser.

METHODS

Surgery was performed in 20 patients with unruptured cerebral arteriovenous malformations. In each case, the superficial feeder vessels were easily coagulated with nonstick bipolar tips. The finer and deeper feeder vessels were coagulated with use of tweezers and thulium laser.

RESULTS

All patients were treated successfully. Optimal intraoperative hemostasis was achieved.

CONCLUSIONS

Results were good with no postoperative complications. Our results could encourage a more standardized use of the described technique.

Effect of dexamethasone, barbiturate and hypothermy on edema induced by CO2 laser brain lesion in the dog: light and electron microscopic study

Experiments were carried out to compare the effectiveness of dexamethasone, a barbiturate, and hypothermy on experimental cerebral edema caused by CO2 laser in dogs. Experimental brain lesions were created over the right frontal cortex of the dogs through the intact dura mater with CO2 laser energy (40 W impact, 0.5 second duration, for a total time of 4 seconds on a 12.5 mm surface). Animals were divided into four groups and treated with dexamethasone, a barbiturate, hypothermy, and a crystalloid (control group). The brains were examined 48 hours after injury. Histologically all brain lesions showed three distinct layers with a vaporized center bordered by a zone of coagulation necrosis surrounded by edema. The main finding in the surrounding coagulation and edematous layers was dilatation of the vessels. Hemorrhage was sometimes observed mainly in the edematous layer. The effect of these therapies on the laser lesion and the effectiveness of these therapies on surrounding cerebral edema were evaluated by both light and electron microscopy. The control group showed significantly greater edema than the dexamethasone group. There was only a minimal difference between the control group and the barbiturate group, and there was no significant difference in amount of edema between control group and the hypothermy group. There was less edema in the dexamethasone group than in the other ones. These data suggest that dexamethasone inhibits edema in CO2 laser lesions with the same efficacy as shown in the treatment of vasogenic edema.

A new 1.9-mu wavelength laser for neurosurgery

The 1.9-mu wavelength component of a 1.9/1.06-mu two-wavelength laser with near-continuous wave properties was tested for its potential use in neurosurgery. The 1.9-mu wavelength has tissue-ablative capabilities, while the 1.06-mu wavelength (Nd:YAG) is suitable for achieving hemostasis. The advantages of the 1.9-mu wavelength over the CO2 laser include its ability to transmit through silica fiberoptic delivery systems and its deeper penetration in water (approximately 100 mu, a depth 10 times greater than for the CO2 laser), which is compatible with irrigation during ablation. To test the effectiveness of the laser, bilateral craniotomies were performed in anesthetized rats immobilized in a stereotactic frame. Under an operating microscope, lesions were made on the cortex by delivering the 1.9-mu laser beam through a 400-mu fiber at an average power of 1 W over a range of fluences. Subjective intraoperative observations were notable for minimal bleeding, absence of charring when the tissue was irrigated with a thin stream of saline, and uniform lesion formation. For comparison, lesions were generated with a commercially available continuous-wave CO2 laser at equivalent power and fluences. Histological specimens were divided into three groups based on the study after laser application: acute (30 minutes), subacute (48 hours), and chronic (14 days). The extent of thermal injury for the 1.9-mu laser in the acute lesions was quantitatively and histologically similar to that generated by the CO2 laser. Regions of injury extended approximately from the apex of the lesion, and crater depths generated by both lasers were similar (250 to 750 mu) in the range of fluences investigated (1.25 to 10 kJ/sq cm). Subacute and chronic histological specimens demonstrated inflammatory and repair responses that correlated with the acute injury regions in both the 1.9-mu and CO2 laser-treated specimens. This study demonstrates a neurosurgical potential for a new two-wavelength laser that ablates tissue effectively with limited thermal injury. The 1.9-mu laser is comparable to the widely used CO2 laser but offers several unique advantages, including the ability for delivery through a fiberoptic system and to irrigate tissue during use.

Nd:YAG-laser in the microsurgery of frontobasal meningiomas

Forty-three patients with big frontobasal meningiomas underwent a microsurgical removal of the tumor. The 1.32 microns Nd:YAG-laser has proved useful in this prospective series particularly with the contactless shrinkage of the tumors and the necrotization of the dural and bony attachments. Tumor shrinkage was achieved by radiating the tumor surface with the Nd:YAG-laser. This technique facilitated the microsurgical dissection and reduced the blood loss by half. The Nd:YAG-laser necrotization of the dural and bony attachments reduced the recurrence rate following grade two resections from 20% to zero. The postoperative quality of life was excellent with a complete rehabilitation in 76% of the patients. The use of the 1.32 microns Nd:YAG-laser improved significantly the results of microsurgery for frontobasal meningioma.