Учебники / Computer-Aided Otorhinolaryngology-Head and Neck Surgery Citardi 2002
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A thorough endoscopic evaluation, as well as imaging studies such as CT and/or MRI, are essential for preoperative planning.
Histologically benign, centrally localized tumors seem to constitute the most widely accepted characteristics making endoscopic resections suitable.
The surgical approach is dependent upon the surgeon’s experience. Whether or not a surgeon can perform a complete resection undoubtedly depends on his or her experience and skill. In the hands of skilled endoscopists, the use of telescopes to visualize and achieve complete resection of the mass is possible in most cases.
Recurrence seems to occur in an inverse relation to the completeness of tumor removal irrelevant of the elected surgical approach.
Close follow-up will be required for adequate reporting of disease control. This should include long-term serial endoscopic evaluations ( 10 years).
In all cases, close postoperative surveillance is essential. Close follow-up and routine utilization of the sinus telescopes allows for early detection of recurrence. In the absence of malignant transformation, recurrent inverted papillomas generally have been seen to exhibit a relatively slow growth rate and small (i.e., millimeters) recurrences can be easily removed in the office setting through endoscopic means. This obviates the need for a subsequent return to the operating room (beyond the initial procedure) in the vast majority of these patients.
16.4.1.2 Juvenile Nasopharyngeal Angiofibroma
Juvenile nasopharyngeal angiofibromas (JNAs) are histologically benign, slowgrowing, locally invasive, highly vascular tumors that are most frequently found in boys and young men between 14 and 25 years of age [33,34]. The most common presenting symptoms include epistaxis and nasal obstruction. Associated symptoms vary depending on tumoral extension into adjacent structures. Despite their histologically benign nature, rich vascularization gives these tumors the potential for life-threatening complications secondary to bleeding or intracranial extension. The submucosal centrifugal growth makes these lesions obligatorily extradural, even in cases with intracranial extension.
Rarely encountered in adults, it is believed that JNAs exhibit spontaneous regression. In addition, documented cases exist in which subtotal resection or incomplete radiotherapy have come to achieve tumor regression [34]. Whether the tumoral involution observed in these cases was entirely due to spontaneous regression or to devascularization of the residual tumor secondary to surgery or radiation therapy remains unknown.
Indentation of the posterior wall of the maxillary sinus and the superior orbital fissure (the Holmann-Miller sign) is suggestive but not pathognomonic of
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this entity [35]. Other diagnostic imaging techniques such as CT, MRI, magnetic resonance angiography (MRA), and conventional angiography all have contributed to the improved preoperative assessment of tumor extent, intracranial extension, and feeding vessels. Angiography with preoperative embolization has shown to be a significant adjunct in the management of these lesions reducing intraoperative blood loss and improving intraoperative visualization [7,8,36].
Various modalities of treatment have been proposed for this entity. Radiotherapy has been shown to halt tumor growth [7,37]. However, its effects on the growth of the craniomaxillofacial skeleton, along with its potential carcinogenic effects, should limit its use for surgically unresectable tumors or potentially lifethreatening complications.
Surgical excision has been considered curative when complete resection is attained. The surgical goal is to achieve tumor resection with minimal neurological sequelae while minimizing the intraoperative blood loss and postoperative morbidity. In addition, the male craniomaxillofacial skeleton continues to grow until approximately the second decade of life. Hence, soft tissue elevation, maxillofacial osteotomies, and the use of metal plate fixations may potentially lead to subsequent asymmetric growth. These factors have to be considered when selecting a surgical approach for the resection of JNAs. The endoscopic approach offers a potential advantage over most of the external approaches, since the endoscopic approach is minimally disruptive to these developing anatomical structures, but still offers the capacity for adequate long-term disease control.
For cases of JNAs with limited extension to the nasopharynx, nasal cavity, ethmoid and sphenoid sinus, or pterygopalatine fossa, the endoscopic approaches compare favorably with the external approaches [6–8]. Early experience in a relatively small number of patients suggests that adequate tumor control may be attained with minimal disruption to uninvolved soft or bony tissue and little difference in morbidity. It has been noted that tumor recurrence occurs in direct proportion to its clinical stage, with overall recurrence rates being around 10%. The recurrence rate rises in cases with intracranial extension [37,38–40]. In the surgical management of JNAs, CAS may be useful in delineating the boundaries of the pterygomaxillary fossa and identifying the structures adjacent to the tumor margins (such the ICA, cavernous sinus, and clivus).
16.4.1.3 Mucoceles
Mucoceles are gradually expansile, epithelial-lined lesions filled with inspissated secretions. These lesions may erode the bony confines of the nasal cavity with the potential for intracranial or intraorbital penetration. Although many etiologies have also been proposed, mucoceles have been theorized to develop as a direct result of obstruction to the sinus ostium [41,42]. Rapid expansion of the mucocele may occur secondarily to acute infection (mucopyocele) with subsequent rupture that spreads infected material into contiguous orbital or intracranial stuctures.
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Several authors have compared endoscopic with external approaches (i.e., Lynch-Howarth and frontal sinus obliteration procedures). Excellent results have been reported utilizing the endoscopic approach with minimal morbidity or complications [9–12]. However, at times this may require an extended frontal or sphenoid sinusotomy to widely marsupialize the cavity [43]. Today, CAS facilitates wide decompression of mucoceles that previously required an external or combined approach because of anatomic limitations and previous surgery. CAS may also be useful during endoscopic marsupialization of mucoceles, in which surgical access would otherwise be difficult because the inflammatory process has altered the standard surgical landmarks. Even mucoceles in the lateral aspect of the frontal sinus can be drained with computer-aided endoscopic techniques. In the event that frontal obliteration is indicated, CAS may also be used to plan the osteotomy cuts [44].
16.4.1.4 Meningoceles and Encephaloceles
Meningoceles or encephaloceles may present in the nose and paranasal sinuses with potentially adverse consequences (Figure 16.8). Cerebrospinal fluid (CSF) rhinorrhea and subsequently meningitis may ensue if these lesions are left untreated. The surgical literature documents many series of patients whose CSF leaks were repaired endoscopically [13–16]. In fact, the endoscopic repair of meningoceles and encephaloceles is attainable in most cases. The successful endoscopic repair of most skull base defects is now possible with one simple outpatient procedure in more than 90% of the patients. The use of CAS also allows identification of the bony and dural defect margins to minimize the chances of inadvertent intracranial resection of brain parenchyma (as in the case of an encephalocele) and subsequent injury to intracranial structures (Figure 16.9).
16.4.1.5 Other Benign Tumors
There have been numerous case reports of histologically benign tumors undergoing successful endoscopic resection. Immature teratomas and fibrous dysplasia
FIGURE 16.8 A meningoencephalocele from the anterior crnail fossa may intrude into the paranasal sinuses. This anterior skull base defect (indicated by the arrow) is well seen on this coronal sinus CT.
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FIGURE 16.9 (A) CT scans can accurately show the extent of paranasal osteomata. This CT shows a very large ethmoidal osteoma, which was causing significant exophthalmos CAS may be used to identify the boundaries during central debulking of this type of lesion with powered instrumentation. The thinned outer shell can then be safely removed transnasally. (B) Nasal endoscopy in the same patient shows a large submucosal mass that fills most of the superior nasal vault and middle meatus.
have both been treated by endoscopic resection [17,18]. Further generalizations regarding the treatment of these benign lesions cannot be made since no surgeon has had sufficient experience upon which to draw definitive conclusions.
Osteomas of the nasal and paranasal sinus region have also been endoscopically resected. However, most of the published cases report endoscopically assisted external approaches [19,20]. When osteomas are restricted mainly to the medial maxilla or ethmoid sinus, these lesions are thinned with a cutting bur from a central to peripheral direction entirely through an endoscopic approach (Figure 16.9). CAS allows for localization of the orbital and intracranial margins of dissection and thereby facilitates adequate thinning of the osteoma. In this way, the osteoma’s outer shell can be easily removed in a piecemeal fashion through the nose.
16.4.2Endoscopic Resection of Malignant Lesions of the Sinonasal Region and Anterior Skull Base
Until recently, endoscopic resection has been advocated strictly for debulking of malignant neoplasms. Such an approach has been reported for the palliation of
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sinonasal melanoma; this partial tumor removal can improve the patient’s quality of life but not his or her life expectancy [45,46]. More recently, there have been a few reports on endoscopic resection of malignant sinonasal disease [21–24]. All of these have been small case series of patients undergoing endoscopically assisted craniofacial resection. Most of the malignant lesions have been hemangiopericytomas or esthesioneuroblastomas of the anterior skull base.
CAS may be useful in defining the lateral and superior tumor margins of resection at the bony skull base and orbit [47]. Critical neurovascular pedicles may be identified and preserved. As mentioned previously, CAS may not be as useful once the cranial cavity is entered or after the skull base and intracranial structures have been significantly distorted by the surgery, since current CAS systems do not reflect the manipulations induced by the actual surgical procedure.
16.5CONCLUSION
Over the past several years, minimally invasive endoscopic techniques for the surgical management of sinonasal tumors and anterior skull base lesions have garnered increasing interest. Early reports have suggested that endoscopic techniques are at least comparable to standard approaches and may even offer specific advantages that the standard approaches cannot duplicate. All of these procedures require detailed understanding of critical anatomical relationships, which may be altered by the underlying disease process. CAS offers relatively straightforward ways for better comprehension of these surgical landmarks. CT and MR review at the CAS workstation, coupled with surgical planning and simulation, may actually reduce potential morbidity and enhance surgical results. Furthermore, intraoperative surgical navigation, which provides specific localization information, may provide invaluable guidance for the surgical procedure, especially if the procedure is performed under endoscopic visualization. Strategies that incorporate endoscopic approaches and CAS may emerge as the preferred method for the management of sinonasal tumors and other lesions of the anterior cranial base.
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13.RR Casiano, D Jassir. Endoscopic cebrospinal fluid rhinorrhea repair: Is a lumbar drain necessary? Otolaryngol Head Neck Surg 121(6):745–750, 1999.
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16.JA Burns, EE Dodson, CW Gross. Transnasal endoscopic repair of cranionasal fistulae: a refined technique with long-term follow-up. Laryngoscope 106(9 Pt 1):1080– 1083, 1996.
17.RL Voegels, W Luxemberger, H Stammberger. Transnasal endoscopic removal of an extensive immature teratoma in a three-month-old child. Ann Otol Rhinol Laryngol 107:654–657, 1998.
18.K Ikeda, H Suzuki, T Oshima, A Shimomura, S Nakabayashi, T Takasaka. Endonasal endoscopic management in fibrous dysplasia of the paranasal sinuses. Am J Otolaryngol 18(6):415–418, 1997.
19.K Al-Sebeih, M Desrosiers. Bifrontal endoscopic resection of frontal sinus osteoma. Laryngoscope 108:295–298, 1998.
20.AM Seiden, YI El Hefny. Endoscopic trephination for the removal of frontal sinus osteoma. Otolaryngol Head Neck Surg 112:607–611, 1995.
21.A Blokmanis. Endoscopic diagnosis, treatment, and follow-up of tumours of the nose and sinuses. J Otolaryngol 23(5):366–369, 1994.
22.N Bhattacharyya, NL Shapiro, R Metson. Endoscopic resection of a recurrent sinonasal hemangiopericytoma. Am J Otolaryngol 18(5):341–344, 1997.
23.ER Thaler, M Kotapka, DC Lanza, DW Kennedy. Endoscopically assisted anter-
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ior cranial skull base resection of sinonasal tumors. Am J Rhinol 13(4):303–310, 1999.
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17
Computer-Aided Otologic
and Neurotologic Surgery
Eric W. Sargent, M.D., F.A.C.S.
Michigan Ear Institute, Farmington Hills, Michigan
17.1INTRODUCTION
Otology and neurotology, like sinus surgery, challenge surgeons in ways that make image guidance potentially useful. Both disciplines deal with vital structures whose anatomy may be obscured or altered by disease. The minute structures of the ear, such as the labyrinthine facial nerve and cochlea, test the resolution of currently available computer-aided surgery (CAS) technology.
Like other disciplines, the majority of otologic and neurotologic procedures can be more easily performed without CAS using well-established and relatively invariable landmarks. Operations such as stapedotomy, tympanoplasty, tympanomastoidectomy, and labyrinthectomy, for example, benefit little from intraoperative surgical navigation. Other surgical challenges potentially benefit from CAS in extreme circumstances. During cochlear implantation of an ossified or malformed cochlea, for example, CAS surgical navigation can aid in placing the electrode close to the neural elements. In surgery for external auditory canal atresia, CAS may allow delineation of the facial nerve and ossicular mass while drilling proceeds, potentially reducing the risk to these structures.
In the author’s experience, procedures in which CAS technology offers the most potential use can be divided into two categories. Cases in which anatomy is
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distorted by pathology, as in large acoustic tumors, benefit from image guidance. Although not discussed in this chapter, we have used image guidance when removing massive cerebello-pontine angle tumors since CAS can help delineate the tumor/brainstem interface. Cases in which unreliable landmarks obscure vital structures also gain from CAS. Intraoperative surgical navigation is especially useful in these instances. This category includes middle cranial fossa procedures, petrous apex drainage procedures, and retrosigmoid dissection of the internal auditory meatus for acoustic neuroma. CAS would be of little benefit in neurotologic procedures like retrosigmoid vestibular nerve section or vascular decompression where landmarks are clear and the structures of interest are easily visible.
In this chapter, the author’s experience with CAS in otology and neurotology will be reviewed so that the reader may understand the applications and potential pitfalls of this technology in otology, neurotology, and lateral skullbase surgery. Two procedures that exemplify the type of otologic operations for which CAS is best suited will be presented. In this regard, CAS, including preoperative surgical planning and intraoperative surgical navigation, has the greatest utility during middle cranial fossa surgery [1] and petrous apex surgery.
17.2MIDDLE CRANIAL FOSSA SURGERY
Since its reintroduction in 1961 by William House [2], the middle cranial fossa (MCF) approach to the internal auditory canal (IAC) has been used for a variety of indications. For vestibular schwannomas located laterally in the IAC, the MCF approach allows preservation of hearing. For patients with intractable vertigo due to unilateral labyrinthopathy and serviceable hearing, the MCF approach to the vestibular nerve is an alternative to retrolabyrinthine or retrosigmoid vestibular nerve section. It can be used in revision nerve section procedures as well. No matter the indication, however, the MCF approach is a technical challenge.
In the lateral end of the IAC the margin for error is slight. Posterior to the lateral IAC is the ampullate end of the superior semicircular canal (SSC), and anterior to the lateral IAC is the basal turn of the cochlea. Millimeters separate the structures. The facial nerve becomes more superficial in the lateral IAC as it rises to the geniculate ganglion located in the floor of the MCF and is thus more exposed to potential injury. Landmarks are not as apparent in the MCF as in other approaches through the temporal bone, making dissection more difficult.
Without the benefit of CAS, the surgeon may choose a number of strategies to orient the dissection. The greater superficial petrosal nerve may be located in the facial hiatus and traced backward to the geniculate ganglion [3,4]. The IAC may then be located medial to the geniculate ganglion. Alternatively, the superior semicircular canal may be used as the primary landmark and traced forward until