側頭骨, 頭蓋底手術におけるナビゲーションシステムの検討

抄録

Image-guided surgery has made marked progress in ENT, especially in sinonasal surgery. However, in temporal and skull base surgery, its accuracy level is insufficient. We investigated the usefulness of image-guided system in temporal and skull base surgery involving eight patients (three acoustic neurinoma, one facial neurinoma, two jugular foramen neurinoma, and two petroclival meningioma). The level of accuracy was acceptable in image-guided surgery for patients with acoustic and facial neurinoma. However, errors were noted in patients with jugular foramen neurinoma and petroclival meningioma. We had to discontinue the use of the image-guided system in two patients because of gross errors. Errors tended to occur in extended operations and with deeper operative fields.
We considered the following as causes of and solutions for errors. The first cause is a skin shift of the retroauricular and occipital area occurring on preoperative scannning. Generally, when patients underwent a preoperative CT scan, they would lie in a supine position using a pillow, which pushed the occipital skin. Therefore the scan data was distorted near the occipital area. In order to prevent this skin shift, a small and somewhat stable pillow is necessity. The second cause is skin shift occurring in the surgical position. A ventilation tube required to maintain general anesthesia and some electrodes to monitor nerve functions were placed on the patient's face. They strain the patient's facial skin, thereby causing skin shift. We must be careful to prevent this. The third cause is instability of the reference frame. We usually use a reference frame fixed to a neurosurgical head holder. The system consists of long arms and multiple joints between the head holder and reference frame. The development of a noninvasive and stable reference frame is awaited. The last cause is carelessness in registration. As mentioned above, the image guided-system receives inaccurate data due to skin shift. If we performed registration of the deformed portion near the occipital area, some errors may be observed. We must pay more attention to any difference between of the intra- and preoperative data regarding the head.