The area around the foramen magnum

Transcription

1 OPERATIVE NUANCES FAR-LATERAL APPROACH TO THE CRANIOCERVICAL JUNCTION Giuseppe Lanzino, M.D. Peoria, Illinois Sergio Paolini, M.D. Peoria, Illinois THE FAR-LATERAL APPROACH is an extension of the standard suboccipital approach, designed to maximize exposure of the lateroventral craniocervical junction. Following a basic principle of cranial base surgery, the angle of view is increased by bone removal. Bone removal involves the most lateral part of the inferior occipital squama and the posterior arch of C1. Drilling of various portions of the occipital condyle further increases the exposure. Transposition of the vertebral artery is seldom required. The far-lateral approach allows a tangential, unobstructed view of the lateroventral cervicomedullary area and can be applied effectively to manage with a heterogeneous spectrum of pathological lesions involving this area. The technical aspects of the procedure are briefly illustrated in this report. Neurosurgery 57[ONS Suppl 3]:ONS-367 ONS-371, 2005 DOI: /01.NEU Robert F. Spetzler, M.D. Division of Neurological Surgery, Barrow Neurological Institute, St. Joseph s Hospital and Medical Center, Phoenix, Arizona Reprint requests: Giuseppe Lanzino, M.D., 530 NE Glen Oak, Peoria, IL lanzino@uic.edu Received, October 28, Accepted, March 9, The area around the foramen magnum and the craniocervical junction is the site of a variety of different vascular, neoplastic, and degenerative lesions. The farlateral approach has proved to be very helpful in the management of the majority of these lesions (2, 5, 7, 9). We describe the basic technique to treat a variety of lesions in this area. Several modifications of this approach have been described (1, 3, 8). We usually let the location and type of lesion dictate the exact type of approach used. In most cases, however, the current approach with minor variations has proven more than adequate for the majority of lesions located ventrolateral to the brainstem and upper cervical cord. POSITIONING Position is the key for correct conduct of the approach. We use a modified park-bench position (Fig. 1). This modification improves venous return and minimizes injury to the brachial plexus, especially during long procedures. Dropping the contralateral shoulder also increases the amount of cranial flexion and rotation. The contralateral arm is positioned below the level of the body in a dependent position, foam-padded and taped to the Mayfield stand. The table is extended several centimeters by the use of a Plexiglas board. The head of the patient is positioned so that the ipsilateral (to the lesion) mastoid is at the highest point of the surgical field. Three key movements of the head are made before it is fixed in a modified Mayfield headholder: 1) the head is flexed so that the chin is 1 cm from the sternum; 2) the head is then rotated contralaterally to the lesion, maximally increasing the angle between the atlas and the foramen magnum; and 3) the head is laterally flexed approximately 30 degrees toward the contralateral shoulder (Fig. 2). The ipsilateral shoulder is pulled gently toward the feet to open the angle between the patient head and the shoulder itself to increase the range of movement of the surgical microscope. A roll is placed under the dependent axilla and between the knees. The entire body is secured with adhesive tape so that the table can be rotated safely and properly during the surgical procedure as needed. INCISION (see video at web site) The incision starts at the tip of the ipsilateral mastoid, continues above the superior nuchal line, then curves to the midline and down to the level of C3 (Fig. 3). It is important to maintain midline orientation by palpating the spinous processes of the upper cervical vertebrae. The skin flap is then elevated. Preservation of a muscle cuff at the level of the superior nuchal line is helpful to correct approximation of the musculature at the end of VOLUME 57 OPERATIVE 4 OCTOBER 2005 ONS-367

2 LANZINO ET AL. FIGURE 1. Illustration showing the patient in the modified park-bench position for far-lateral exposure ( 1990, Barrow Neurological Institute). EXPOSURE the procedure and in prevention of a cerebrospinal fluid leak. Although knowledge of the anatomy of the muscle layers is of utmost importance to the surgeon, we usually prefer taking down the muscles in a single flap, which is rotated anteriorly. Fish hooks attached to rubber bands are the preferred mode of retraction for two main reasons: 1) they provide a dynamic form of retraction, which can be easily adjusted by repositioning the Leyla bar to which the rubber bands are attached under tension; and 2) by applying downward pressure to the retracted tissues, they flatten the edges of the wound, decreasing the depth of the operative field. In taking down the muscle and skin flap, several landmarks are identified and followed. The transverse process of C1 is a valid landmark for the lateral exposure. Exposure of the ipsilateral lamina of C2 also helps in obtaining adequate lateral exposure even in patients with short, thick necks. After the spinous processes of C1 and C2 are identified, the lamina of C2 is exposed, as is the ipsilateral portion of the posterior arch of C1. The posterior arch of C1 is followed laterally to the sulcus arteriosus, which marks the medial limit of the vertebral artery. Although, in previous descriptions of this approach, we stressed the importance of exposure and skeletonization of the vertebral artery, with increased experience, we no longer think that this maneuver is necessary. It is important to localize and identify the vertebral artery itself along FIGURE 3. Illustration showing the skin incision, which starts at the tip of the ipsilateral mastoid, continues above the superior nuchal line, then curves to the midline and down to the level of C3 ( 1990, Barrow Neurological Institute). with its surrounding venous plexus so that the artery can be easily protected during drilling of the posterior portion of the occipital condyle. Exposure and skeletonization of the vertebral artery is required in cases in which proximal control of the artery in its extradural portion is important. After the position of the sulcus arteriosus and the vertebral artery is identified, the ipsilateral posterior arch of the atlas is removed, either with the footplate of a high-speed drill or with rongeurs (Fig. 4). The lip of the foramen magnum is then FIGURE 2. Illustration showing three key movements of the head, which are made before it is fixed in a modified Mayfield headholder: 1) the head is flexed so that the chin is 1 cm from the sternum; 2) the head is then rotated contralaterally to the lesion, maximally increasing the angle between the atlas and the foramen magnum; and 3) the head is laterally flexed approximately 30 degrees toward the contralateral shoulder. The contralateral arm is dropped below the level of the body and padded well ( 1990, Barrow Neurological Institute). FIGURE 4. Illustration showing removal of the ipsilateral portion of the posterior arch of C1. The horizontal portion of the vertebral artery is identified at the level of the sulcus arteriosus. Although, at the beginning of our experience, we routinely exposed and mobilized the vertebral artery, this maneuver is not necessary unless proximal control of the vessel is required in its extradural portion (from, J Neurosurg). ONS-368 VOLUME 57 OPERATIVE 4 OCTOBER

3 FAR-LATERAL APPROACH TO THE CRANIOCERVICAL JUNCTION exists regarding how much condyle needs to be drilled (4, 6, 10, 11), we usually let the lesion dictate how much removal of the condyle is necessary. For tumors of the ventrolateral brainstem and upper cervical cord, minimal condyle removal is necessary because the surgeon creates additional room as the tumor is removed. In such cases, the tumor already has created an avenue of approach by displacing critical surrounding neurovascular structures. For aneurysms of the distal vertebral artery, drilling of the posterior third of the condyle, so that a flat angle of exposure is obtained after opening the dura, offers satisfactory exposure. As mentioned previously, the approach is then tailored to the specific needs of the lesion and the surgeon, and additional extensions/modifications of this basic approach can be made. DURAL OPENING FIGURE 5. Illustration showing the craniotomy, including the most lateral part of the occipital squama to the inferior rim of the foramen magnum (from, J Neurosurg). identified and a small craniotomy is performed with the aid of the high-speed drill. The craniotomy is extended as far laterally as possible and to the midline medially (Fig. 5). The next key step is drilling of the condyle (Fig. 6). Although debate We usually open the dura in a curvilinear fashion (Fig. 7). After the dura is opened, the exposure obtained encompasses the lower cranial nerves to C2 (Fig. 8). Superior extension of this basic approach allows the surgeon to follow lesions up to the internal auditory meatus. CLOSURE A watertight dural closure either primarily or with duraplasty prevents cerebrospinal fluid fistulae and postoperative pseudomeningocele formation. The dural closure often is augmented with fibrin glue. The craniotomy flap is replaced with miniplates. If the ipsilateral portion of the posterior arch of C1 is removed with the high-speed drill, it can be reconstituted at the end of the procedure with miniplates. As mentioned pre- FIGURE 6. Illustration showing the most posterior portion of the occipital condyle and articular mass of C1, which are drilled while the vertebral artery is protected. We usually drill enough of the posterior third of the condyle to obtain a flat area of approach to the ventrolateral brainstem (from, J Neurosurg). FIGURE 7. Illustration showing the curvilinear dural incision. The laterally hinged dural flap is sutured to the suboccipital muscles, maximizing the lateral-to-medial exposure ( 1990, Barrow Neurological Institute). VOLUME 57 OPERATIVE 4 OCTOBER 2005 ONS-369

4 LANZINO ET AL. 7. Sen CN, Sekhar LN: An extreme lateral approach to intradural lesions of the cervical spine and foramen magnum. Neurosurgery 27: , Sen CN, Sekhar LN: Surgical management of anteriorly placed lesions at the craniocervical junction: An alternative approach. Acta Neurochir (Wien) 108:70 77, Spetzler RF, Grahm TW: The far-lateral approach to the inferior clivus and the upper cervical region: Technical note. Barrow Neurol Inst Q 6:35 38, Vallee B, Besson G, Houidi K, Person H, Dam HP, Rodriguez V, Meriot P, Senecail B: Juxta- or trans-condylar lateral extension of the posterior suboccipital approach: Anatomical study, surgical aspects [in French]. Neurochirurgie 39: , Vishteh AG, Crawford NR, Melton MS, Spetzler RF, Sonntag VKH, Dickman CA: Stability of the craniovertebral junction after unilateral occipital condyle resection: A biomechanical study. J Neurosurg Spine 90:91 98, FIGURE 8. Illustration showing a tangential view of the bulbomedullary junction, the lower cranial nerves, and the intradural vertebral artery on opening of the dura. CN, cranial nerve; PICA, posteroinferior cerebellar artery (from, J Neurosurg). viously, leaving a cuff of muscle immediately below the insertion of the muscles on the superior nuchal line greatly facilitates tight closure of this layer, decreasing the incidence of postoperative subcutaneous fluid collections. The skin is then closed with suture. CONCLUSION The far-lateral route is a versatile approach to a variety of lesions located ventrolateral to the brainstem and upper cervical cord. It allows adequate exposure of the important neurovascular structures in this region with no or minimal retraction. Modifications on this theme can be applied as the lesion requires. This approach should be in the armamentarium of any surgeon treating patients with lesions in these areas. REFERENCES 1. Baldwin HZ, Miller CG, van Loveren HR, Keller JT, Daspit CP, Spetzler RF: The far lateral/combined supra- and infratentorial approach: A human cadaveric prosection model for routes of access to the petroclival region and ventral brain stem. J Neurosurg 81:60 68, Bertalanffy H, Seeger W: The dorsolateral, suboccipital, transcondylar approach to the lower clivus and anterior portion of the craniocervical junction. Neurosurgery 29: , George B, Dematons C, Cophignon J: Lateral approach to the anterior portion of the foramen magnum: Application to surgical removal of 14 benign tumors Technical note. Surg Neurol 29: , George B, Lot G, Tran Ba HP: The juxtacondylar approach to the jugular foramen (without petrous bone drilling). Surg Neurol 44: , Heros RC: Lateral suboccipital approach for vertebral and vertebrobasilar artery lesions. J Neurosurg 64: , Nanda A, Vincent DA, Vannemreddy PS, Baskaya MK, Chanda A: Farlateral approach to intradural lesions of the foramen magnum without resection of the occipital condyle. J Neurosurg 96: , COMMENTS Lanzino et al. have described the far lateral approach to anterolateral lesions at the craniocervical junction. As they mention in their introduction, their description of the procedure is an extension of the lateral suboccipital approach to this area. I would like to clarify a few issues for the reader. The approach as described here would work for the clipping of a vertebrobasilar system aneurysm or a foramen magnum meningioma; in other words, this approach would suffice only for an intradural pathological process. I differ in several respects in managing both intradural and extradural lesions in this area. I position the patient in a lateral decubitus position with no forward flexion or lateral rotation of the head so as not to compromise the already compressed cervicomedullary junction and also to avoid distorting the orientation of the vertebral artery in its passage from C2 to the dura. The skin incision is placed laterally, and the muscles in most instances are dissected in layers to make this into a wide and shallow exposure and avoid piling up the muscles on the sides. This maneuver also allows exposure of a wide arc, so that the surgeon has a lateral as well as a posterolateral perspective. A posterior perspective is almost never needed for these lesions; hence, exposure of the spinous processes is not necessary. The vertebral artery is a key figure in these lesions, and hence, we dissect and isolate the vessel as it turns around the articulation of the occiput and C1 to its dural entry. This is especially needed for tumors that encase the artery and extradural tumors, which tend to be extradural and intradural. If needed, it can also be isolated all the way down to the C2 transverse foramen. For intradural tumors, we incise the dura all around the entry site of the artery so that the vessel can be moved around freely, facilitating its separation from the tumor and also allowing an unimpeded view of the area in front of the craniocervical junction. In certain extradural tumors that extend down to C1 or C2, the artery may be released from the C1 transverse foramen and mobilized posteriorly to gain additional caudal visualization. Drilling of the occipital condyle is used selectively in dealing with intradural processes. In my experience, the shape of the foramen magnum as well as the size of the lesion influences this maneuver. In principle, drilling the posterior portion of the condyle allows the surgeon to gain room in front of the vertebral artery so as to incise the dura around the artery and release it. This is helpful for a deep foramen magnum and a relatively small tumor. In summary, the principle of approaching an intradural lesion at the anterior craniocervical junction involves a trajectory that follows the vertebral artery into the foramen magnum in a caudal-to-cephalad direction so that the surgeon enters the foramen magnum from a lateral perspective aiming cephalad from a predominantly upper cer- ONS-370 VOLUME 57 OPERATIVE 4 OCTOBER

5 FAR-LATERAL APPROACH TO THE CRANIOCERVICAL JUNCTION vical exposure, avoiding manipulation of the brainstem and the lower cranial nerves. Chandranath Sen New York, New York Lanzino et al. have provided an excellent pictorial description of their approach to the foramen magnum. This report is well illustrated and details the technical nuances associated with both opening and closure and the amount of drilling for the occipital condyle. As we have previously stated, the degree of occipital condyle resection is more the surgeon s choice and does not necessarily add to better exposure, especially for intradural lesions (1). More recently, I have begun to favor a linear incision and have not found any increase in cerebrospinal fluid leaks. This is an excellent illustration of the armamentarium that exists for anterior foramen magnum, vascular degenerative, and benign tumor lesions. Anil Nanda Shreveport, Louisiana 1. Nanda A, Vincent DA, Vannemreddy PS, Baskaya MK, Chanda A: Far-lateral approach to intradural lesions of the foramen magnum without resection of the occipital condyle. J Neurosurg 96: , The authors have refreshed our understanding of the far lateral approach to the craniocervical junction with this article. This has been in vogue for quite some time. However, they do point out that the vertebral artery does not need to be transposed at all times, nor does there need to be significant removal of the occipital condyle, to gain a satisfactory view of the ventrolateral cervicomedullary junction. There are a wide variety of pathological lesions that can be handled in this region, from the mid clivus down into the cervical canal. This reviewer uses a straight prone position so as not to distort the upper cervical anatomy. The table then performs the rotation to allow for line-of-sight visualization through the operating microscope. The advantage of the procedure is that destabilization of the craniocervical region is not performed, as would occur with a true far lateral exposure with removal of the occipital condyle. Arnold H. Menezes Iowa City, Iowa This is a short but precise description of the far-lateral approach, which I call the posterolateral approach (as opposed to the anterolateral approach). I fully agree with all the statements and details given, especially those about the vertebral artery. This vessel is surrounded by a periosteal sheath enclosing the perivertebral venous plexus. It does not have to be opened. This leads to troublesome bleeding before hemostasis is attained and does not bring any benefit in the exposure. The end of the vertebral artery groove corresponds to the medial aspect of the lateral mass occipital condyle junction. Thus, most of the time, the bone resection should not extend beyond this point. For the opening of the dura, the curvilinear incision is a nice option, because closure is much easier. In the past, I used to perform a contraincision toward the vertebral artery, but like cerebellopontine angle exposure, I have abandoned it most of the time nowadays. In fact, in the vast majority of patients, the elasticity of the dura permits us to retract it up to the bone and thus not lose any space. The only point on which I differ is the positioning of the patient. I still prefer the semisitting position with hypervolemia and a G-suit so as to keep the venous pressure positive and to avoid air embolism. This position is less comfortable for the surgeon s arms, but the surgical field easily remains nicely clean. Bernard George Paris, France New Prices for Color Illustrations in Neurosurgery Lippincott Williams & Wilkins, the publisher of Neurosurgery, is pleased to announce a reduction in the price charged to authors for color figures in their articles. The new cost for 1 color figure will be $400; the cost for each additional color figure is $100. The submission of illustrations in digital format is highly encouraged. Please refer to the Journal s Information for Contributors for full details on the formatting requirements. VOLUME 57 OPERATIVE 4 OCTOBER 2005 ONS-371