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Object The treatment of insular tumors is controversial. Surgical treatment is associated with a higher morbidity rate than other therapies. The present work presents a new method in which the descending motor pathways are monitored during surgery for insular tumors. Methods Intraoperative monitoring was performed in a combination of 2 techniques. The motor cortex was stimulated with a transcranial electrical stimulus. In addition, direct subcortical stimulation was performed with an electrical anodal monopolar stimulus. Compound motor action potentials (CMAPs) were recorded from target muscles. Results Fifteen patients were included in this preliminary study. Following transcranial stimulation, CMAPs were recorded in all cases. Subcortical stimulation was successful in 12 cases. Significant CMAP alterations were recorded in 5 patients. There were no false-negative results in the series. Conclusions The technique presented here is a safe method. It allows a quantitative monitoring of motor function and functional mapping of the pyramidal tract during insular surgery.

Intraoperative electrical stimulation of the motor cortex is a sensitive method for intraoperative mapping and monitoring of this region. Two different stimulation techniques have been established, the bipolar and monopolar techniques. Controversy exists regarding the most suitable method. Both methods have advantages and disadvantages and different electrophysiological backgrounds. The present study is a review of the electrophysiological basis of direct cortical electrical stimulation of the motor cortex. Both methods are discussed and their field of application is presented.

Background Posterior lumbar interbody fusion (PLIF) surgery is a commonly used procedure for degenerative lumbar instability. Locally harvested bone is usually inserted into intervertebral cages to increase fusion rate. The fusion rate without bone application remains unknown. Our aim was to analyze retrospectively the fusion rates of intervertebral polyetheretherketone (PEEK) and titanium cages in PLIF surgery that were implanted without bone grafting using three-dimensional computed tomography (CT) scanning. Material and Methods Forty patients (age 43–83 years) with mono- or bisegmental degenerative instability were included. PEEK cages were used in 28 segments (25 patients), and titanium cages were used in 17 segments (15 patients) undergoing PLIF surgery plus pedicle screws. The primary outcome parameter was radiologic fusion rate measured by CT at follow-up. Secondary parameters included rate of implant failure and adjacent segment disease. Results No difference in mean age between groups was identified (PEEK: 69 ± 10 years; titanium: 62 ± 13 years). Mean follow-up was 39 ± 13 months in PEEK and 24 ± 12 months in the titanium group. Radiologic fusion rate was 32% of operated segments in PEEK and 53% in the titanium group. Screw loosening/adjacent-level disease was observed in 8% and 8% in the PEEK group and in 0% and 7% in the titanium group, respectively. Conclusion Radiologic fusion rates of PEEK and titanium cages without bone grafting is low in PLIF surgery, and therefore bone grafting should be performed if possible. Rate of implant failure and adjacent-level disease remains low despite reduced osseous fusion in the operated segments.

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