J Neurosurg 72:513-516, 1990

The versatile frontal sinus approach to the floor of the anterior cranial fossa Technical note JOHN A. PERSING, M.D., JOHN A. JANE, M.D., PAUL A. LEVINE, M.D., AND ROBERT W. CANTRELL, M.D. Departments of Plastic and Reconstructive Surgery, of Neurosurgery, and of Otolaryngology Head and Neck Surgery, University of Virginia Health Sciences Center, Charlottesville, Virginia A technique to expose the anterior cranial base is described with entry through the anterior and posterior walls of the frontal sinus. Burr holes are avoided in the visible portion of the forehead. Expansion of the operative field may be accomplished, if necessary, by supplemental superior frontal or supraorbital rim osteotomy. The technique is rapid, safe, and provides excellent operative exposure and superior cosmetic results. KEY WORDS cranial base surgical approach

frontal sinus

C

RANIOFACIAL resection for tumors with both a cranial and a facial c o m p o n e n t is an established operative approach. 3'~4 C o m m o n t u m o r types treated in this manner include the esthesioneuroblastoma, invasive tumors of the nasopharynx and paranasal sinuses, mesenchymal tumors of the cranial base, and benign intracranial tumors, such as the tuberculum meningioma with extension into the facial skeleton. Specific treatments of these t u m o r types, however, are varied. Most of the surgical approaches described previously require a frontal craniotomy; 4'8'~'~2 however, this procedure can be time-consuming and disfiguring, particularly if burr holes are placed in the region of nonhair-bearing forehead skin. To deal with these problems, we have developed an approach to the paramedian anterior cranial base which is rapid, safe, and cosmetically superior to previously described techniques, while maintaining excellent intraoperative visualization of the t u m o r region. This approach is made available by capitalizing on the unique architectural relationship of the frontal sinus to the anterior cranial base. Description of Technique

The procedure is used for patients with an anterior cranial fossa t u m o r in a median or paramedian location J. Neurosurg. / Volume 72/March, 1990

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with facial region extension. A 6-ft anteroposterior Caldwell view of the skull is obtained to determine the exact size and location of the frontal sinus. An x-ray template of the frontal sinus is outlined. This template, allowing for a magnification factor (usually 1.3:1), is to be used intraoperatively to outline the perimeter of the frontal sinus, and is therefore sterilized. 1o Following induction of general anesthesia, the patient receives a lumbar cistern drain. A bicoronal skin incision is made, followed by subgaleal dissection of the anterior scalp flap. The periosteum of the frontal bone is elevated, separately, to the region of the nasion. The x-ray template is placed on the frontal bone to determine the anatomical location of the frontal sinus. The correct orientation is aided by reference to identifiable landmarks, most c o m m o n l y the frontonasal suture and the superomedial orbital rims. The perimeter of the template is marked with blue dye. An oscillating saw is used to cut through the outer table of the frontal sinus along this perimeter line (Fig. la). The blade is oriented obliquely into the center of the sinus to assure osteoto m y within the confines of the sinus, and to develop an endocranial shelf, onto which the anterior wall of the sinus m a y be returned at the completion of the procedure. 513

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FIG. 1. Intraoperative drawings, a: A sterilized x-ray template is used to outline the frontal sinus perimeter osteotomy, b: The anterior wall of the frontal sinus is fractured forward, exposing the posterior sinus wall for burr-hole placement, c: Following removal of the posterior wall of the frontal sinus, the crista galli is removed to aid visualization of the olfactory fiber associated dura.

FIG. 2. Intraoperative drawings, a: Olfactory fibers and dura are severed and cerebrospinal fluid is allowed to drain freely, until all of the fibers to be transected have been released. The dura is closed with two parallel continuous sutures incorporating all of the openings in the dura (inset). b: The opening into the frontal sinus may be expanded superiorly (A) or laterally (B), if additional operative exposure is required, c: Osteotomy of the cranial base is performed under direct visualization. The anterior table of the frontal sinus is elevated and the mucosa removed from its intrasinus surface. A shaping burr is used to remove the intraosseous mucosal remnants. With the aid of a perforator, access is gained to the epidural space through the posterior wall of the frontal sinus (Fig. lb). With blunt dissection, the sagittal sinus is carefully freed from the posterior wall of the frontal bone and frontal sinus. The posterior wall of the frontal sinus is removed by rongeur to expand visualization of the epidural space. The scope of exposure includes the medial orbital roofs and midline cranial base, to the level of the tuberculum of the sella turcica. Visualization is aided by cerebrospinal fluid (CSF) removal through the lumbar cistern drain. If the t u m o r extends into the posterior ethmoid region, the crista galli is removed with the aid of the air drill and bordering malleable retractors to avoid injury to the adjacent frontal dura (Fig. 1c). The dura adjacent to the individual olfactory fibers is divided. No attempt is made to close openings in the dura at this stage and CSF is allowed to drain freely to further aid in visualization of the floor of the anterior cranial fossa, without brain retraction. After division of fibers as far posteriorly as desired (Fig. 2a), the dura 514

may be closed with a continuous suture, avoiding timeconsuming interrupted suture closure or unreliable silver-clip ligatures. After the frontal dura is sealed, a gauze pad is placed temporarily on the dura to further support the suture line and to lessen direct contamination of the dura during the subsequent osteotomy of the anterior cranial base into the nasoethmoid region. Remarkably, even in patients with a small frontal sinus, excellent exposure of the anterior cranial base is obtained, without undue brain retraction. If, however, there is inadequate visualization of the t u m o r site, the dura and sagittal sinus may be elevated from the endocranial surface of the frontal bone and a second or "extended" frontal craniotomy may be performed without placement of additional frontal burr holes (Fig. 2b). The extension may be cephalad into the frontal bone or lateral into the supraorbital rim, incorporating the orbital roof, if desired, as described previously. 6 An osteotome and sagittal saw are used to free up the bone segment of the cranial base for resection (Fig. 2c). If the bone resection required extends to the level of the optic nerves at the orbital apex, it is useful to make a separate opening in the dura in order to directly visualize the optic nerves intradurally while making the J. Neurosurg. / Volume 72/March, 1990

Frontal sinus approach to anterior cranial base

FIG. 3. If resection of the cranial base must extend to the orbital apex, a separate opening in the dura (arrow) may be made to achieve direct visualization of the optic nerves intradurally. This technique is helpful in avoiding injury to these nerves.

final posterior osteotomies (Fig. 3). In this case, the potential morbidity from an additional opening in the dura is outweighed by the benefit of greater definition of the course of the optic nerve during the osteotomy. Most anterior cranial-base resections involving just the ethmoid and anterior sphenoid regions do not require bone reconstruction. Larger cranial-base resections, however, may require bone replacement, and other techniques such as vascularized-vault 9 or split cranialvault bone reconstruction m a y be more useful in these instances. Closure of the frontal sinus osteotomy site is accomplished by plugging the nasofrontal ostia with either muscle, minced bone, or fat. The dural suture lines are reinforced with fibrin glue obtained from the patient's own plasma. 2.17 Coverage of the cranial-base defect is accomplished by the periosteal (not galeal) flap based anteriorly on the supraorbital and supratrochlear vessels, unsupported or supported by a bone graft to the anterior cranial fossa floor. The flap is secured to bone by two sutures at the right and left osteotomy perimeters, supported by fibrin glue. Additional support in the form of an obturator m a y be gained by previous attachm e n t of a free fat (abdominal) graft to the osteotomy perimeter with suture through preplaced drill holes. The anterior wall of the frontal sinus is returned and secured to the adjacent frontal bone with wire or fixation plates (Fig. 4). Discussion Craniofacial resection for anterior cranial-base tumors extending into the paranasal sinuses, or vice versa, is becoming a more c o m m o n l y performed procedure. Initial procedures designed to treat this condition involved an extensive single or staged bifrontal craniotomy, in combination with a facial resection of the J. Neurosurg. / Volume 72~March, 1990

FIG. 4. Postoperative appearance of a patient following a frontal sinus intracranial approach, supplemented by a lateral rhinotomy facial approach.

tumor. These procedures were lengthy, but the tumors were resected fully, demonstrating the feasibility of the approach. Attention is now being directed at further refinement of the technique to make it more safe, efficient, and aesthetic. A n u m b e r of i m p r o v e m e n t s have been developed for the treatment of the facial portion of this t u m o r to include less noticeable incisions on the face (hidden in natural crease lines) 7,15 and nasal degloving procedures to avoid external incisions. A similar, parallel approach has been taken to the cranial portion of this surgical effort. Initially, bifrontal craniotomies were associated with burr-hole defects in the glabellar region, frontal hair line, and pterion. Although it has been considered a justified aesthetic defect for i m p r o v e m e n t in periods of survival, this concept is no longer tenable. T u m o r treatment regimens have significantly improved, leading to longer survival times such that these deformities are too readily visible and cause too great a long-term morbidity. As one of the goals of this surgical procedure is to allow the patient to return to normal activity, disfigurement works counter to the goal. Operative approaches were developed to gain access to the anterior cranial base while avoiding frontal burr holes; however, these still required a large frontal craniotomy. 4 The approach presently described avoids a large unneeded craniotomy, which m a y not only be time-consuming but also m a y jeopardize function by exposure of additional brain parenchyma. One concern that the surgeon might have, however, is the potentially smaller area of visibility afforded by 515

J. A. Persing, et al. this procedure. With an average-sized sinus, this is not a problem as craniofacial tumors involving the cranial base are best visualized by an approach which gives direct access to the t u m o r (parallel to and at the level of the base), without brain retraction. In previous approaches where entry into the frontal sinus has been avoided, excessive retraction of the frontal lobes may be necessary to gain access to the cranial base. However, if the patient has a small, even virtually absent, frontal sinus, the approach along the plane of the anterior cranial base is preferred over methods requiring frontal lobe elevation; if additional exposure is required, it may be gained by increasing bone removal to include more than the frontal sinus. In this way, the presently described approach modifies previously described approaches to the cranial base through the frontal sinus. ~3 Almost limitless exposure may be gained using the frontal sinus to visualize the epidural space. The dura may be safely retracted and the craniotomy may be expanded superiorly or laterally without the placement of additional disfiguring frontal burr holes. One concern might be contamination of the operative field by entry into the frontal sinus. Resection of craniofacial tumors through the nasal cavity renders the question of contamination moot, because it is a necessary consequence of a one-stage resection procedure. A useful adjunct in the treatment of these patients is the use of autologous fibrin glue, acting as an effective immobilizer of tissue so that biological wound repair may occur as rapidly as possible. We believe that it may reduce the risk of postoperative CSF leaks. 16 Using the patient's own blood to obtain the fibrin obviates the additional risk of acquired i m m u n e deficiency syndrome (AIDS) and hepatitis. 2'~7 The periosteum has served as an effective support and barrier for dural closure, as has been reported previously. 1,5 In contrast to techniques that employ the galea for reconstruction of the dura, '3 it is faster (because of well-developed cleavage planes), safer (because it does not remove blood supply to the anterior scalp flap), and less deforming (because it does not remove or injure frontalis muscle function). Overall, the presently described technique is safe, simple, rapid, and versatile. Because of this, it is now being used as the preferred approach for treatment of anterior cranialbase tumors at our institution. Acknowledgments

The authors wish to thank Dr. William Spotnitz for helpful review, Mona Banton and Debra Shaffer for editorial assistance, and Craig Luce, M.S., for the medical illustrations contained within this manuscript.

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References

1. Abul-Hassan HS, von Drasek Aschev G, Acland RD: Surgical anatomy and blood supply of the fascial layers of the temporal region. Plast Reconstr Surg 77:17-24, 1986 2. Alterbaum R, Williams L, Requena R, et al: Autologous fibrin glue (a new method of preparation). Surg Forum 36:544-546, 1985 3. Cantrell RW, Ghorayeb BY, Fitz-hugh GS: Esthesioneuroblastoma: diagnosis and treatment. Ann Otol Rhinol Laryngol 86:760-765, 1977 4. Colohan ART, Jane JA, Park TS, et al: Bifrontal osteoplastic craniotomy utilizing the anterior wall of the frontal sinus: technical note. Neurosurgery 16:822-824, 1985 5. Horowitz JH, Persing JA, Nichter LS, et al: Galeal - pericranial flaps in head and neck reconstruction: anatomy and application. Am J Surg 148:489-497, 1984 6. Jane JA, Park TS, Pobereskin LH, et al: The supraorbital approach: technical note. Neurosurgery 11:537-542, 1982 7. Levine PA, Scher PL, Jane JA, et al: The craniofacial resection, eleven year experience at the University of Virginia: problems and solutions. J Otolaryugol Head Neck Surg (In press, 1990) 8. McCarthy JG, Zide BM: The spectrum of calvarial bone grafting: introduction of the vascularized calvarial bone flap. Plast Reconstr Surg 77:10-18, 1984 9. McCarty CS: The Surgical Treatment of Intracranial Meningiomas. Springfield, Ill: Charles C Thomas, 1961 10. Montgomery WW: Osteoplastic frontal sinus operation: coronal incision. Ann Otol Rhinol Laryngol 74:821-830, 1965 11. Morley TP: Tumors of the cranial meninges, in Youmans JR (ed): Neurological Surgery. Philadelphia: WB Saunders, 1973, Vol III, pp 1388-1411 12. Odom GL, Woodhall B: Supratentorial skull flaps. J Neurosurg 25:492-501, 1966 13. Schramm V: Anterior craniofacial resection, in Sekhar L, Schramm V (eds): Tumors of the Cranial Base. Diagnosis and Treatment. Mt Kisco, NY: Futura, 1987, pp 265-278 14. Schramm V: Cranial resection, in Sasaki CT, McCabe BF, Kirchev JA (eds): Surgery of the Skull Base. Philadelphia: JB Lippincott, 1984, pp 43-6 l 15. Schramm VL, Myers EN: How I do it: head and neck. A targeted problem and its solution. Lateral rhinotomy. Laryngoscope 89:1077-1091, 1978 16. Shaffrey CI, Spotnitz WB, Shaffrey ME, et al: Fibrin glue augmentation of dural tears - - experience with 136 patients. Neurosurgery (In press, 1990) 17. Spotnitz WD, Mintz TD, Avery N, et al: Fibrin glue from stored human plasma. An inexpensive and efficient method for local blood bank preparation. Am Surg 53: 460-462, 1987 Manuscript received July 10, 1989. Address reprint requests to." John A. Persing, M.D., Department of Plastic Surgery, Box 376, University of Virginia Health Sciences Center, Charlottesville, Virginia 22908.

.i.. Neurosurg. / Volume 7 2 / M a r c h , 1990

The versatile frontal sinus approach to the floor of the anterior cranial fossa. Technical note.

A technique to expose the anterior cranial base is described with entry through the anterior and posterior walls of the frontal sinus. Burr holes are ...
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