Neurosurgical applications of the 2-μm thulium laser: histological evaluation of meningiomas in comparison to bipolar forceps and an ultrasonic aspirator.

Objective: The authors evaluated the histological effects of the 2-μm thulium laser on meningioma tissue, comparing them to the results obtained using bipolar forceps and an ultrasonic aspirator.

Methods: The authors analyzed nine samples of intracranial meningiomas. Four slices were obtained for every sample, and one incision was performed on each slice. Two incisions were made with a 2-μm thulium laser (one set to a 6 W and another set to a 12 W power level). One incision was made using a bipolar forceps and the other using an ultrasonic aspirator. Tissue was addressed and analyzed. Upon microscope analysis, three zones of laser action were identified: (A) a central crater; (B) a vaporized zone; and (C) a shrunken layer. These three layers were measured and compared.

Results: When addressed with the laser, all nine meningiomas presented a crater having an average depth of 1 mm. Three layers were clearly distinguished and measured: A (average depth: 0.8 mm at 6 W and 1.24 mm at 12 W); B (average depth: 0.32 mm at 6 W and 0.72 mm at 12 W); and C (average depth: 0.39 mm at 6 W and 0.44 mm at 12 W). On slices treated with bipolar forceps incisions, only zones B and C were identified. Ultrasonic aspirator incisions showed a deeper A zone (average depth: 2.93 mm), no B zone, and a tiny C zone (average depth: 0.16 mm).

Conclusions: Thulium laser can be safely used for the surgical removal of intracranial meningiomas; beyond 2 mm under the surface of action, no tissue alterations were found. The lesions produced on meningiomas were characterized by vaporization and shrinking. When compared with bipolar forceps, the thulium laser offers cutting precision and vaporization of the tissue. When compared to the cavitron ultrasonic surgical aspirator (CUSA), the laser offers shrinking and coagulation of small vessels.