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Sphenoid sinus cerebrospinal fluid leaks

2006; Elsevier BV; Volume: 17; Issue: 1 Linguagem: Inglês

10.1016/j.otot.2006.01.010

1557-9395

Bradford A. Woodworth, Jeffrey G. Neal, Rodney J. Schlosser,

Cerebrospinal fluid and hydrocephalus

There are a number of special considerations regarding endoscopic repair of cerebrospinal fluid (CSF) leaks and encephaloceles occurring in the sphenoid sinus. The sphenoid sinus is formed by the anterior and middle cranial fossae, is in close proximity to the internal carotid artery and optic nerve, and may have extreme lateral pneumatization that limits accessibility via normal endoscopic routes. Although CSF leaks and encephaloceles can occur anywhere within the sphenoid sinus, they are generally divided into a medial, perisellar type and a lateral, sphenoid recess type. The diverse etiologies of sphenoid sinus CSF leaks make it essential to have a thorough understanding of the underlying pathophysiology, and treatment principles and treatment options to achieve excellent outcomes. The specific surgical approach for a sphenoid sinus skull base defect is dependent on the exact site of the defect within the sphenoid sinus. Once an appropriate endoscopic approach with wide local exposure is obtained, reconstruction of the skull base is dependent on the etiology of the leak and other factors, including the underlying intracranial pressure. This article will highlight the surgical techniques and perioperative care relevant to sphenoid CSF leaks and encephaloceles. There are a number of special considerations regarding endoscopic repair of cerebrospinal fluid (CSF) leaks and encephaloceles occurring in the sphenoid sinus. The sphenoid sinus is formed by the anterior and middle cranial fossae, is in close proximity to the internal carotid artery and optic nerve, and may have extreme lateral pneumatization that limits accessibility via normal endoscopic routes. Although CSF leaks and encephaloceles can occur anywhere within the sphenoid sinus, they are generally divided into a medial, perisellar type and a lateral, sphenoid recess type. The diverse etiologies of sphenoid sinus CSF leaks make it essential to have a thorough understanding of the underlying pathophysiology, and treatment principles and treatment options to achieve excellent outcomes. The specific surgical approach for a sphenoid sinus skull base defect is dependent on the exact site of the defect within the sphenoid sinus. Once an appropriate endoscopic approach with wide local exposure is obtained, reconstruction of the skull base is dependent on the etiology of the leak and other factors, including the underlying intracranial pressure. This article will highlight the surgical techniques and perioperative care relevant to sphenoid CSF leaks and encephaloceles. Until recently, encephaloceles of the lateral recess of the sphenoid sinus were relatively undocumented.1Buchfelder M. Fahlbusch R. Huk J.W. et al.Intersphenoidal encephaloceles–A clinical entity.Acta Neurochir (Wien). 1987; 89: 10-15Crossref PubMed Scopus (51) Google Scholar, 2Daniilidis J. Vlachtsis K. Ferekidis E. et al.Intrasphenoidal encephalocele and spontaneous CSF rhinorrhea.Rhinology. 1999; 37: 186-189PubMed Google Scholar, 3Landreneau F.E. Mickey B. Coimbra C. Surgical treatment of cerebrospinal fluid fistulae involving lateral extension of the sphenoid sinus.Neurosurgery. 1998; 42: 1101-1105Crossref PubMed Scopus (72) Google Scholar These lesions evolve from the herniation of temporal lobe tissue through a middle cranial fossa defect lateral to the foramen rotundum and vidian canal (Figure 1). These patients have excessive pneumatization of the pterygoid process, with an attenuated sphenoid sinus recess roof and skull base. This increases the likelihood of defects developing in the floor of the middle fossa.4Reynolds J.M. Tomkinson A. Grigg R.G. et al.A LeFort I osteotomy approach to lateral sphenoid sinus encephaloceles.J Laryngol Otol. 1998; 112: 679-681Crossref PubMed Google Scholar Other factors, including elevated cerebrospinal fluid (CSF) pressures, may contribute to the development of these CSF leaks. Patients with spontaneous CSF leaks frequently have increased CSF pressure, which increases hydrostatic force at the weakest sites of the skull base. The increased CSF pressures seen in this subset of patients lead to the highest rate (range 50% to 100%) of encephalocele formation and the highest recurrence rate after surgical repair of the leak (range 25% to 87%), compared with less than 10% for most other etiologies.5Gassner H.G. Ponikau J.U. Sherris D.A. et al.CSF Rhinorrhea 95 consecutive surgical cases with long term follow-up at the Mayo Clinic.Am J Rhinol. 1999; 13: 439-447Crossref PubMed Scopus (97) Google Scholar, 6Hubbard J.L. McDonald T.J. Pearson B.W. et al.Spontaneous cerebrospinal fluid rhinorrhea Evolving concepts in diagnosis and surgical management based on the Mayo Clinic experience from 1970 through 1981.Neurosurgery. 1985; 16: 314-321Crossref PubMed Scopus (181) Google Scholar, 7Schick B. Ibing R. Brors D. et al.Long-term study of endonasal duraplasty and review of the literature.Ann Otol Rhinol Laryngol. 2001; 110: 142-147PubMed Google Scholar Underlay bone grafts add support and help prevent encephalocele herniation and disruption of the repair. In addition, lumbar drains and acetazolamide are recommended to lower documented increase of the intracranial pressure. Sinonasal tumors and skull base neoplasms can create sphenoid sinus CSF leaks directly through erosion of the anterior cranial fossa (superior) or middle cranial fossa (posterior and lateral), or indirectly secondary to therapeutic treatments for the tumor (Figure 2, Figure 3). One of the most common causes of sphenoid CSF leaks is from transsphenoidal pituitary resection. In 1 study, CSF leaks after transsphenoidal surgery occurred in 6.0% of cases.8Shiley S.G. Limonadi F. Delashaw J.B. et al.Incidence, etiology, and management of cerebrospinal fluid leaks following trans-sphenoidal surgery.Laryngoscope. 2003; 113: 1283-1288Crossref PubMed Scopus (127) Google Scholar Persistent malignant tumor after resection and repair will continue to erode the skull base and contribute to sphenoid sinus CSF leaks. Prior chemotherapy or radiation creates significant healing difficulties because of poor vascularity of the wound bed.Figure 3Coronal magnetic resonance image showing a large pituitary adenoma with disruption of the sellar diaphragm, predisposing to an intraoperative CSF leak.View Large Image Figure ViewerDownload (PPT) Sphenoid sinus CSF leaks may result from blunt or penetrating trauma. Traumatic disruption of the sphenoid sinus walls can create an obvious CSF leak or present years later with meningitis, delayed leak, or encephaloceles. Although more than 70% of traumatic CSF leaks close with observation or conservative treatment, a 29% incidence of meningitis has been reported in long-term follow-up when treated nonsurgically.9Bernal-Sprekelsen M. Bleda-Vazquez C. Carrau R.L. Ascending meningitis secondary to traumatic cerebrospinal fluid leaks.Am J Rhinol. 2000; 14: 257-259Crossref PubMed Scopus (127) Google Scholar Functional endoscopic sinus surgery and neurologic surgery are the 2 most common surgeries leading to iatrogenic skull base defects. Significant defects can result from powered instrumentation if they occur during bone resection near the skull base. A CSF leak can occur in the roof of the sphenoid sinus during routine sphenoidotomy. An expansile mucocele or tumor can create dehiscences in the sphenoid roof that are more susceptible to iatrogenic CSF leak during instrumentation. Congenital encephaloceles were initially divided into sincipital, also referred to as anterior or frontoethmoidal, and basal encephaloceles. The basal-type encephaloceles are intranasal in location and have been variously described as transethmoidal, sphenoethmoidal, sphenomaxillary, spheno-orbital, transsphenoidal, and transtemporal.10David D.J. Cephaloceles Classification, pathology, and management—A review.J Craniofac Surg. 1993; 4: 192-202PubMed Google Scholar Clinically, transsphenoidal encephaloceles are the only congenital type found in the sphenoid sinus. Abiko et al11Abiko S. Aoki H. Fudaba H. Intrasphenoidal encephalocele Report of a case.Neurosurgery. 1988; 22: 933-936Crossref PubMed Scopus (32) Google Scholar further noted 2 types of transsphenoidal meningoencephaloceles: the intrasphenoidal and the true transsphenoidal. The former describes meningoencephaloceles extending into the sphenoid sinus but confined by its floor. The latter describes those encephaloceles traversing the floor of the sphenoid sinus and protruding into the nasal cavity or nasopharynx. The true transsphenoidal-type encephaloceles, which are transmitted through the sphenoid bone, will most commonly have coexisting abnormalities of the face, optic system, and brain, corresponding to the median cleft face syndrome.12Moore M.H. Lodge M.L. David D.J. Basal encephalocoele Imaging and exposing the hernia.Br J Plast Surg. 1993; 46: 497-502Abstract Full Text PDF PubMed Scopus (20) Google Scholar High surgical risks may be encountered with transsphenoidal encephalocele in the early infantile period because the pituitary-hypothalamic structures are usually incorporated in the herniated encephalocele of this age group.13Peter J.C. Fieggen G. Congenital malformations of the brain–A neurosurgical perspective at the close of the twentieth century.Childs Nerv Syst. 1999; 15: 635-645Crossref PubMed Scopus (28) Google Scholar Presentation in adults is rare because congenital facial anomalies are subtle or absent, and diagnosis is delayed until rhinorrhea occurs, a visual field defect becomes evident, hormonal deficiency is noted, or an epipharyngeal mass is discovered. In adults, the intrasphenoidal type of congenital encephalocele has reportedly had a good outcome with transsphenoidal repair, but a true transsphenoidal meningoencephalocele must be viewed with caution because of the complexity of the distorted anatomy and involvement of vital structures.14Jabre A. Tabbaddor R. Samaraweera R. Transsphenoidal meningoencephalocele in adults.Surg Neurol. 2000; 54: 183-188Abstract Full Text Full Text PDF PubMed Scopus (50) Google Scholar Before any surgical intervention, it is essential to establish firmly the diagnosis of CSF leak to differentiate CSF rhinorrhea from other causes of rhinorrhea. The most commonly accepted method of differentiating CSF from nasal secretions is testing for beta-2 transferrin. Because only 0.17 mL is needed for testing, this provides a very reliable, accurate, noninvasive method to establish the diagnosis of an active CSF leak, with a low incidence of false-positives and false-negatives.15Schlosser R.J. Bolger W.E. Nasal cerebrospinal fluid leaks Critical review and surgical considerations.Laryngoscope. 2004; 114: 255-265Crossref PubMed Scopus (173) Google Scholar, 16Skedros D.G. Cass S.P. Hirsch B.E. et al.Sources of error in use of beta-2 transferrin analysis for diagnosing perilymphatic and cerebral spinal fluid leaks.Otolaryngol Head Neck Surg. 1993; 109: 861-864PubMed Google Scholar Beta trace protein is another noninvasive marker that is very specific for CSF and is used most commonly in Europe.17Bachmann Beta-trace protein An unknown marker for cerebrospinal fluid leaks.Laryngoscope. 2005; 115: 756PubMed Google Scholar Preoperative imaging studies for sphenoid CSF leaks and encephaloceles generally consist of both coronal and axial computerized tomography (CT) to provide important bony detail that is useful in the surgical approach. The unique orientation of the sphenoid sinus with both anterior and middle cranial skull base contributing to the superior and posterolateral walls, respectively, necessitates coronal and axial imaging to evaluate these areas. If the patient is unable to collect fluid for a noninvasive study, such as beta-2 transferrin, then a CT cisternogram can be both diagnostic and assist in localization of the defect. Magnetic resonance imaging is particularly useful for sphenoid meningoencephaloceles because they identify brain parenchyma and CSF that have herniated into the sinus. Alternative studies, such as radioactive cisternograms, are less useful for localizing defects and confirming the diagnosis of CSF rhinorrhea, and are not often used. After obtaining appropriate preoperative studies, we generally begin each case with rapid sequence intubation, to minimize the risk of pneumocephalus. We then inject intrathecal fluorescein, as previously described,15Schlosser R.J. Bolger W.E. Nasal cerebrospinal fluid leaks Critical review and surgical considerations.Laryngoscope. 2004; 114: 255-265Crossref PubMed Scopus (173) Google Scholar which is extremely useful for localizing the exact site of the skull base defect. For most cases, our neurosurgical service then places a lumbar drain. This drain can be useful in cases that show increased CSF pressures or when a repair is somewhat tenuous. If not needed, it is easily removed at the end of the case. Simple defects in the central sphenoid or perisellar regions can be approached through a direct parasagittal endoscopic approach. After topical and injected vasoconstriction, the middle turbinate can be gently lateralized, and the inferior portion of the superior turbinate is resected. Just medial to the superior turbinate within the sphenoethmoidal recess, the natural os of the sphenoid can be identified. A wide sphenoidotomy is then performed using straight mushroom and Kerrison punches. Additional midline exposure can be gained by resecting the posterior portion of the nasal septum and the intersinus septum. If the defect is more laterally located, a transethmoidal approach to the sphenoid sinus is chosen. A complete endoscopic ethmoidectomy is performed, with identification of the natural ostium of the sphenoid after perforation of the basal lamella and resection of the inferior third of the superior turbinate. The sphenoidotomy is extended laterally to the medial orbital wall and lateral wall of the sphenoid sinus as needed. Skull base defects of the middle cranial fossa in the lateral recess of the sphenoid sinus are difficult to access by the midline transeptal/parasagittal or transethmoidal approaches and ultimately require an endoscopic transpterygoid approach (Figures 4 and 5).18Bolger W.E. Endoscopic transpterygoid approach to the lateral sphenoid recess Surgical approach and clinical experience.Otolaryngol Head Neck Surg. 2005; 133: 20-26Crossref PubMed Scopus (117) Google Scholar A complete ethmoidectomy, wide maxillary antrostomy, and wide sphenoidotomy are performed first. To gain access to the pterygopalatine fossa, the posterior wall of the maxillary sinus is removed. The internal maxillary artery and its branches are identified, and transposed inferiorly or clipped and divided. Within the pterygopalatine fossa, meticulous dissection of the vidian nerve and the maxillary division of cranial nerve V will avoid untoward morbidity. The anterior face of the sphenoid sinus that has pneumatized into the pterygoid plates is curetted or drilled away to gain exposure of the lateral recess of the sphenoid sinus. We generally preserve the neurovascular bundle that travels from the vidian canal to join V2 to avoid postoperative problems with lacrimation.Figure 4(A) Endoscopic medial maxillary antrostomy with an incised, laterally based posterior maxillary sinus wall mucosal flap. MT, middle turbinate. (B) The mucosal flap is elevated laterally and the posterior maxillary wall drilled away to show the pterygopalatine fossa (PPF). The internal maxillary artery (IMA) may be clipped or reflected inferiorly for access to the anterior wall of the pneumatized lateral recess of the sphenoid. (C) Coronal cross-section of herniated encephalocele lateral to foramen rotundum (V2) into the pneumatized lateral recess (arrow). (D) The maxillary division of trigeminal nerve (V2) and vidian nerve are preserved in the pterygopalatine fossa. The anterior face of the lateral recess has been drilled or curetted away with exposure of the encephalocele. (E) After the encephalocele is reduced and the mucosa stripped, a fascia graft is placed to cover the skull base defect.View Large Image Figure ViewerDownload (PPT)Figure 5Triplanar imaging of the transpterygoid approach to a sphenoid sinus lateral recess encephalocele through the pterygopalatine fossa. The posterior wall of the right maxillary sinus has been opened and the lateral recess exposed. Note the bony skull base defect lateral to foramen rotundum. (Color version of figure is available online.)View Large Image Figure ViewerDownload (PPT) Once adequate identification and exposure of the skull base defect have been obtained using 1 of the aforementioned surgical approaches, the recipient bed is prepared by removing several millimeters of mucosa surrounding the bony defect. Any encephaloceles are reduced or ablated using bipolar cautery as much as possible. Malleable suction monopolar cautery devices can be shaped to reach difficult areas in the anterior and lateral skull base but should be avoided near the optic nerve or carotid artery. Meticulous hemostasis is mandatory while ablating the encephalocele to avoid retraction of the sac into the cranial cavity with subsequent intracranial hemorrhage. After reduction of the encephalocele, if a lumbar drain has been placed preoperatively, the drain is opened, and CSF is shunted into the collection bag. Removing 10-15 mL of CSF and then positioning the bag to establish a flow rate of 5-10 mL/hour will facilitate graft placement by allowing the encephalocele base to be reduced intracranially. We prefer a multilayer repair technique on all CSF leaks that consists of an underlay graft placed in the epidural space and an overlay graft placed intranasally beneath the bony skull base. It is at this point that the precise etiology of the CSF leak/encephalocele impacts our surgical decision making. If the patient has a spontaneous CSF leak or another condition associated with increased CSF pressures, we generally attempt to place a rigid underlay graft, such as bone, into the epidural space (Figure 6). Leaks from other etiologies that have normal intracranial pressures probably do not require rigid grafting and can be repaired successfully by using soft tissue grafts for both underlay and overlay. Options for rigid grafting include bone grafts from the nasal septum, turbinates, or mastoid. Septal bone provides significant strength as is easily trimmed to shape using through cutting sinus instruments. Turbinate bone is often thin and may have a shape that does not conform to the native skull base. Mastoid bone can be sculpted to the precise shape needed but requires additional time to harvest and thin using an otologic drill. We typically do not use cartilage because of its thickness, tendency to fracture, and lower structural strength when compared with bone grafts. A variety of soft tissue materials may be used for underlay or overlay grafts, including temporalis fascia, cadaveric dermis or fascia, or free mucosal or mucoperichondrial grafts. We caution against the use of mucosal grafts placed in the epidural space in an underlay fashion. Mucoceles, meningitis, and other intracranial complications have been seen when contaminated mucosa is placed intracranially. Fascia or dermal grafts are recommended when the surgeon believes a soft tissue underlay graft is needed. In addition, abdominal fat may be used as the primary graft material, or a piece of fascia can be placed over the defect, and abdominal fat can serve a secondary supportive function. In this case, the abdominal fat provides support to the fascia and is readily cleared from the sphenoid sinus. Multiple layers of absorbable packing are then placed within the sphenoid sinus. A removable finger cot can be placed over the face of the sphenoid to prevent inadvertent removal of the absorbable packing. Lumbar drains are very useful in the repair of sphenoid CSF leaks for a variety of reasons. They can assist in a questionable diagnosis with the preoperative injection of intrathecal fluorescein to identify the leak. In patients with spontaneous CSF leaks and possibly increased intracranial pressure, they can temporarily lower that pressure and assist the placement of graft materials. These patients will also have increased pressure postoperatively because of overproduction of CSF, with the absence of a release valve mechanism. This increase in CSF pressure against a closed defect can dislodge the graft materials and lower the chance of success. Maintaining a lumbar drain in these individuals for 2-3 days postoperatively can increase the chance of successful repair. Acetazolamide is a diuretic of the carbonic anhydrase inhibitor type that is a useful adjunct in patients with increased CSF pressure. It can decrease CSF production up to 48% in these individuals and may decrease the chance of a recurrent CSF leak or new CSF leak from skull base erosion. As with any diuretic, periodic electrolyte monitoring is necessary to correct imbalances that develop. Patients are limited to light activity for 6 weeks postoperatively. All patients are placed on a stool softener and are seen every 1-2 weeks postoperatively for a very conservative endoscopic debridement. This procedure is performed to maintain patency of the paranasal sinuses on the side of the defect and repair to avoid stasis of secretions and bacterial infections. By 6 weeks postoperatively, patients are returned to relatively normal activity levels, and little packing remains. Careful preoperative evaluation and localization of the sphenoid defect, and a thorough understanding of underlying etiologies are essential in the selection of the best possible surgical approach and skull base reconstruction for repair of sphenoid sinus CSF leaks and encephaloceles. Endoscopic techniques are highly effective in the repair of both midline and lateral sphenoid lesions.