James E. Boggan

Neurilemmoma of the fourth cranial nerve. Case report.

✓ A tumor of the trochlear nerve sheath with an unusual but diagnostic presentation is described. The rarity of reported cases may reflect failure to differentiate tumors originating from the trochlear and trigeminal nerves.

Comparison of the brain tissue response in rats to injury by argon and carbon dioxide lasers

This study compares the acute and chronic response of brain tissue to injury by equal power density, focused argon (Ar) and carbon dioxide (CO2) laser beams. A cortical incision from 0.2-second laser pulses of 12.5 X 10(3) W/cm2 power density was made in the exposed cortex of 32 rats using either the CO2 or the Ar laser. The brains were examined at intervals from 1/2 hour to 1 month after injury. Histologically, all brain incisions were sharply demarcated hemispheroidal defects with a vaporized center bordered by a zone of coagulation necrosis surrounded by edema. The laser incisions were found to be of equal depth (less than 1 mm). The average cortical surface diameter of the CO2 laser incision was 0.86 mm for a focused beam spot size 0.45 mm in diameter, compared with 0.65 mm with the Ar laser, which had a focused beam spot size 0.15 mm in diameter. In both incisions, some delayed depth effect was observed. A progression of the tissue necrosis by approximately 17% was observed during the first 24 hours after injury. During the first 4 hours after injury, the Evans blue blood-brain barrier defect (EBBD) surrounding the cortical incisions averaged 5.80 mm2 for the CO2 incision and 0.888 mm2 for the Ar incision. In both types of brain incision, the EBBD appeared to resolve by 24 hours after injury. At 1 month after injury, a core of coagulation necrosis surrounded by mild fibrillary gliosis was observed. At the power density and focused beam spot sizes used, there was no significant difference in the overall brain tissue response to Ar and CO2 laser lesions.

Past, Present, and Future Usage of Lasers in Clinical Neurosurgery

Technological innovations have had significant impact on the delivery of neurosurgical care. The introduction of lasers into the armamentarium of surgical instruments has provided neurosurgeons with a method of tissue removal that is more delicate than those previously available. At present, the primary application for lasers in neurological surgery is in the ablation of critically placed neoplastic tissues. Because the interaction of laser energy with tissue is inherently hemostatic, this relatively nontouch technique of removing neoplasms decreases blood loss. Tissue coagulation or removal can be accomplished without mechanical manipulation; therefore damage to surrounding normal tissues is less. In addition, evoked responses and EEG can be monitored continuously during laser surgery so that aspects of the surgical procedure that compromise neural function can be immediately recognized and remedied. Competent use of surgical lasers results in precise and hemostatic ablation of target tissue with decreased likelihood of damage to adjacent normal structures. Although these assets are particularly valuable in neurosurgery, the percentage of cases in which laser use is “a must” is probably less than 10%.1

PHOTORADIATION THERAPY OF THE RAT 9L GLIOSARCOMA BRAIN TUMOR MODEL.

The uptake, distribution, and retention of hematopophyrin derivative (HPD) in the rat 9L gliosarcoma brain tumor model has been evaluated using a digitized video fluorescence technique. In addition, histopathologic examination, and survival studies have been used to assess the in vivo cytotoxic effects of photoradiation therapy (PRT) in this model.The uptake, distribution, and retention of hematopophyrin derivative (HPD) in the rat 9L gliosarcoma brain tumor model has been evaluated using a digitized video fluorescence technique. In addition, histopathologic examination, and survival studies have been used to assess the in vivo cytotoxic effects of photoradiation therapy (PRT) in this model.