C. Matula

The course of the prevertebral segment of the vertebral artery: Anatomy and clinical significance

BACKGROUNDnThe so called pretransverse or prevertebral segment of the vertebral artery is defined from its origin at the subclavian artery to its entry into the respective transverse foramen. In surgery, angiography, and in all noninvasive procedures it is of great importance to know the exact details of the course and the origin of this segment of the vessel as well as in which percentages real abnormalities can be found.nnnMETHODSnThe VI segment of the vertebral artery was investigated both in anatomic preparations and clinical studies. A total of 402 vertebral arteries were evaluated (70 anatomic preparations in different forms, 181 patients, 95 angiographies of the aortic arch, and 86 color coded doppler sonographies).nnnRESULTSnA contorted course was found in 157 (39%) cases. The plane of tortuosities demonstrated by the respective vessels was found to be horizontal in 40 (44.9%) cases, sagittal in 30 (33.7%) cases, and frontal in 19 (21.4%) cases. In 51 (32.5%) cases the contorted pathway was on the right side, and in 106 (68%) cases, on the left. A hypoplasia was found in 16 (10%) cases--11 (4.8%) right and 5 (2.2%) left. We further differentiated the convexity lying either medially or laterally in the transverse or frontal plane, or oriented dorsally or ventral in the sagittal plane. The exact location of the origin of the artery on the circumference of the subclavian artery (47% cranial, 44% dorsal, 3% ventral, 6% caudal) and also the average values of length and diameter are described. No significant differences between tortuous and nontortuous vessels were found with respect to length and diameter. A real abnormality of the origin of the vertebral artery was found in 8 (3.5%) cases.nnnCONCLUSIONSnThe described morphologic variations and frequencies of the VI segment of the vertebral artery have clinical applications in a wide field of pathologies in that region. To know about these findings seems to be very important not only in diagnosis (angiography, color coded doppler sonography) but also in their surgical and endovascular treatment.

Meningiomas of the Space of the Cavernous Sinus

During the years 1985 to 1992, we encountered 59 patients with meningiomas involving the space of the cavernous sinus. In 29 of these patients, meningiomas were primarily located within the space of the cavernous sinus and were operated on without mortality and with low morbidity. A small subtemporal surgical approach was favored, which allowed initial tumor resection from the posterior aspect, where the Parkinsons triangle is wide, thus avoiding the additional morbidity of large-scale approaches. According to the relationships of the all-important cranial nerves passing within the lateral wall of the cavernous sinus, we divided the primary intracavernous meningiomas into four types, which reflected not only the preoperative cranial nerve deficit but also the feasibility of surgical resection. Cranial nerve function deteriorated after operations in 14% of oculomotor nerves, in one abducent nerve, in 58% of trochlear nerves, and in 21% of trigeminal nerves. We encountered improvement of function in 43% of oculomotor nerves, in 50% of abducent nerves, and in approximately 30% of the second and third but in only 7% of the first branches of trigeminal nerves. There was no improvement in trochlear nerve function. Improvement of oculomotor nerve function was observed only in moderately impaired nerves, which indicates that surgery should be undertaken early to preserve or improve oculomotor nerve function.

Intraoperative Computed Tomography Guided Neuronavigation: Concepts, Efficiency, and Work Flow

Image-guided surgery is currently considered to be of undisputed value in microsurgical and endoscopical neurosurgery, but one of its major drawbacks is the degradation of accuracy during frameless stereotactic neuronavigation due to brain and/or lesion shift. A computed tomography (CT) scanner system (Philips Tomoscan M) developed for the operating room was connected to a pointer device navigation system for image-guided surgery (Philips EasyGuide system) in order to provide an integrated solution to this problem, and the advantages of this combination were evaluated in 20 cases (15 microsurgical and 5 endoscopic). The integration of the scanner into the operating room setup was successful in all procedures. The patients were positioned on a specially developed scanner table, which permitted movement to a scanning position then back to the operating position at any time during surgery. Contrast-enhanced preoperative CCTs performed following positioning and draping were of high quality in all cases, because a radiolucent head fixation technique was used. The accuracy achieved with this combination was significantly better (1.6:1.22.2). The overall concept is one of working in a closed system where everything is done in the same room, and the efficiency of this is clearly proven in different ways. The most important fact is the time saved in the overall treatment process (about 55 h for one operating room over a 6-month period). The combination of an intraoperative CCT scanner with the pointer device neuronavigation system permits not only the intraoperative control of resection of brain tumors, but also (in about 20% of cases) the identification of otherwise invisible residual tumor tissue by intraoperative update of the neuronavigation data set. Additionally, an image update solves the problem of intraoperative brain and/or tumor shifts during image-guided resection. Having the option of making an intraoperative quality check at any time leads to significantly increased efficiency, improves the operating work flow because of the closed-system concept, and offers an integrated solution for improved patient work flow and clinical outcome.

Neuroanatomical Details Under Endoscopical View — Relevant for Radiosurgery?

Both, neuroendoscopy and radiosurgery, are upcoming techniques in neurosurgery and become nowadays more and more important. In planning radiosurgical interventions it is very important to have both, the information about the morphology of the pathology itself, and also a clear understanding from the surrounding structures. Neuroendoscopic techniques gives the possibility to demonstrate well known structures without prior dissection. This paper focuses on these anatomical informations which might be relevant in planning further radiosurgical interventions especially in cases of the vascularization of the cranial nerves and the arachnoid membranes, these structures appears much more complex than described in common neuroanatomical textbooks. Endoscopic techniques also better demonstrate the real in vivo relationships and gives so a better understanding for interpreting planning MRI and CT scans. We therefore consider that neuroanatomical studies under a neuroendoscopical view are very important and could be very helpful in planning radiosurgical intervensitons.

Intra-Operative Marking of Neuroanatomical Details — Helpful for Radiosurgery?

This report is a list of simple but effective techniques for marking important structures intra-operatively. During the last 2 years in 52 patients intra-operative marking techniques have been used. In 37 cases a small piece of fat has been taken. In 10 patients it was done by a radiopaque Barium impregnated silicon sphere and in 5 patients with a piece of a monofilament suture. Postoperative checks were done by conventional X-ray, computer tomography and Magnetic Resonance Imaging. The indication in all cases was to offer landmarks helpful for planning postoperative radiosurgery. In case of fat and radiopaque Barium impregnated silicone spheres the markings were always well defined and clear in contrast. In those cases where a piece of monofilament suture was used it was impossible to get clear postoperative information. In general there were no intra- or post-operative complications. All markers were well tolerated and no side effects have been observed so far. The advantages and disadvantages of each of these possibilities are described and discussed.