Endoscopic Surgery of the Paranasal Sinuses and Anterior Skull Base (ISBN 9783137494027) © 2008 Georg Thieme Verlag

46 2 Endoscopic Anatomy of the Nose and Paranasal Sinuses

Fig. 2.39 Medial wall of the antrum in an anatomical dissection (Prof. Dr. J. Lang, Würzburg, Germany). The prelacrimal recess (∗ ) protrudes in an anterosuperior direction, in front of the bulge of the nasolacrimal canal. It is difficult to assess by intranasal endoscopy. A paper millimeter scale lies in the maxillary ostium, and the internal maxillary artery is marked in red (→ ). b Fig. 2.40a The natural primary antral ostium is usually not round but is split up and very variable in shape (straight telescope with a view through a left-sided anterior antral window). b Coronal CT projection demonstrating the true structure of the so-called primary maxillary ostia: narrow channels (arrows), not windows. On both Frontal sinus sides are paradoxically curved middle turbinates with a right concha within frontal bone bullosa.

Middle nasal concha Left orbit recess. From this point a ﬂat groove can be followed as it Nasal runs upward and medially to form the boundary between septum the posterior wall and roof of the antral cavity. The junc- Nasal cavity tion between the roof and anterior wall is usually smooth. The surgeon learns to recognize the typical contours, usu- Birth Inferior ally bilaterally symmetric, in order to preserve the thin turbinate 1 year wall of the orbit during sharp dissection. The anterior 4 years wall of the antral cavity slopes outward, and tapers infe-

riorly (Fig. 2. 42 c ). Fig. 2 .42a–d 7 years Palate 12 years Maxillary sinus The bony canal of the infraorbital nerve may form a Adult Molar tooth within maxilla sagittal bulge running anteriorly in the roof of the antral cavity, providing a valuable landmark (Fig. 2. 42 b ). It must Fig. 2.41 Increase of the extent of the frontal and maxillary cavities not be confused with mucosal bands that often run from with age. Preoperative knowledge of their individual size is particu- the medial to the lateral walls of the antral cavity under larly important for endoscopic sinus surgery during childhood.

its roof (Fig. 2. 43). Fig. 2 .43

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cd Fig. 2.42a Endoscopic view of the left posterior wall of the antral tion of the three different colored regions. View with a 70 ° telescope cavity through an inferior meatal antrostomy. The zygomatic recess introduced through a window in the inferior meatus. d Alveolar re- lies on the right side ( ∗ ) (70 ° telescope). b Left antral roof with prom- cess of a left antral cavity with the root of a molar tooth ( ∗ ). The pos- inent canal of the infraorbital nerve ( ∗ ). View with a 70 ° telescope terior wall of the antrum is marked in blue, the anterior wall in yel- through an inferior meatal antrostomy. c The left anterior antral wall low. View with a 70 ° telescope through an inferior meatal antros- shown in yellow, bordering onto the roof shown in pink, and the pos- tomy. terior wall in blue. The zygomatic recess lies at the point of intersec-

Fig. 2.43 Mucosal fold ( ∗ ) in a left antral cavity. View with a 70 ° Fig. 2.44 Abnormal extension of the ethmoids into the maxillary telescope through an inferior meatal antrostomy. sinus with protruding giant cells (coronal CT).

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a b Fig. 2.49 a, b Intranasal middle meatal antrostomy. b The punch is pushed in a strictly horizontal direction with the jaws a First step: application of a pointed 45 ° upward-cutting ethmoid slightly open. A small window is created by closing the forceps forceps immediately above the center of the inferior turbinate. and removing fragments that are grasped.

Fig. 2.50 The left lateral nasal wall of an anatomical dissection with a small middle meatal antrostomy ( ∗ ) at the typical site above the center of the inferior turbinate, immediately above its upper edge, Fig. 2.51 A small middle meatal antrostomy ( ∗ ) seen through a directly under the posterior end of the uncinate process. The win- straight telescope from in front. The middle turbinate has been dow may be considerably widened above, anteriorly, and posteriorly pushed slightly medially and upward. The uncinate process and the from this point. ethmoid bulla are visible.

Fig. 2.52 A large middle meatal antrostomy as seen through a 70 ° telescope, and the posterior wall of the antrum beyond it. The over- hanging middle turbinate conceals the uncinate process and the bulla.

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Fig. 2.53 Topography of the supraturbinate part of the lateral nasal wall in the plane of a proper fenestration, in a frontal section of a dissected specimen. The antral opening of the maxillary ostium lies very close to the floor of the orbit above a fold. If the nasal wall is always perforated in a strictly horizontal direction above the dorsum of the turbinate bone, the orbit is always out of reach of the instru- ment. c Fig. 2.54 a–c Transoral fenestration of the maxillary cavity. a The sublabial skin incision in the upper oral vestibule. b Exposure of the translucent bone in the canine fossa. c Limited bone resection with a chisel has preserved the anterior mucosa. A small bony frame protects the infraorbital nerve ( arrow).

ab Fig. 2.55 a, b Transcanine endoscopy of the maxillary cavity. b Cranial view of the inferior orbital wall. a Direct inspection (0 ° telescope) of the posterior wall bending down from the floor of the orbit with the primary ostium on its Fig. 2.55 c–e ୴ left side.

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Seiden and Stankiewicz 1998; Lowry and Brennon 2002). Every defect in the anterior bony wall, however, implies the danger of ingrowing subcutaneous soft tissues. The following approaches are available: • Endoscopic, limited opening of the frontal sinus from below (widening of the frontoethmoidal junction zone). • Limited intracavitary manipulations controlled by angled- or fiber-optics, laser surgery. • Combined external–endonasal approaches utilizing the endoscope as monitor of remote manipulations in minimal-access surgery for trauma and tumor growth. • A limited external frontal sinus procedure using the Fig. 6.42 Posteroanterior ethmoidectomy (schematic drawing). endoscope and plastic repair of the small defect in the The upward-biting punch follows the skull base safely with its blunt anterior wall of the frontal sinus, with preservation of head. the bony framework. If necessary, a mucocele is mar- supialized and tumors are reduced in size within the cavity before removal. Treatment of infl ammatory The second principle is complete opening of the cells complications by such conservative surgery is still de- to guarantee healing of the chronic polypoid mucosal in- veloping, and demands intensive postoperative care. flammation. Remaining cells are often the point of origin of persistent disease. These two aspects therefore led us to develop complete ethmoidectomy, in which an entirely Operative Technique visible ethmoid compartment is created with no remaining narrow areas and no remaining cells. The resulting Preliminary Observations wide upper nose was a new and surprising experience, which did not lead to drying of the regenerating mucosa The restricted access to the often extensive and recessed or to the development of ozena. frontal sinus limits transnasal frontal sinus surgery. Whereas the view into all recesses may be satisfactory for diagnostic purposes, many therapeutic manipulations are ill-advised because the necessary instruments cannot Operations on the Frontal Sinus be monitored endoscopically. However, much can be achieved, contrary to what Indications might be expected, including the generous transnasal fenestration of the floor of the frontal sinus, which suf- • Recurrent empyema of the frontal sinus fices for the treatment of most cases of sinusitis when • Chronic frontal sinusitis combined with circumscribed dissection of the frontal • Auxiliary drainage of osteitic complications infundibulum. Many other problems such as stenosis, • Auxiliary endonasal aproach together with external foreign bodies, and occasionally mucopyoceles can be operations for frontal trauma or foreign bodies tackled if this procedure is combined with a small trans- • Biopsy and removal of small tumors, and tumorlike le- frontal portal to allow the introduction of an endoscope sions or instruments. When choosing between a transfacial or intranasal procedure, the safety of the patient is more important than avoiding a facial scar. Principles Recent developments of combined instruments for fi - ber-optic monitoring and laser delivery have opened new The goal of the endoscopic operation from below is the options. restoration of ventilation and drainage. For this purpose, a recanalization of the frontal sinus infundibulum is often Exposure of the Frontal Infundibulum sufficient, and provides mucosal recovery also in remote recesses. Preservation of mucosa and thus of mucociliary The prerequisite for endoscopic exposure of the frontal transport are preconditions, especially in the frontoeth- sinus from the nose is removal of the anterior part of the moidal transition as a bottleneck. Limited pathological ethmoid area as far as the base of the skull. If the most changes can be removed endoscopically. For more diffi - anterior ethmoid cells have been opened intranasally cult intracavitary manipulations, combined external–en- during an anterior ethmoidectomy, the blunt probe usu- donasal approaches are recommended (Gross et al. 1995; ally glides smoothly into the frontal infundibulum. The

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use of force and of pointed bougies is dangerous. An endoscope with an angled telescope should be used to expose the anterior ethmoid. Bony overhangs, coarse mucosal tags, and polyps in- terfering with the view into the frontal duct should be removed under vision (see Fig. 6.43). The curved Bolger spoon curette (see Fig. 4.8 ) is a useful and safe pathfi nder for this purpose. These obstacles are often not present, so that removal of the most anterior cells leads directly into the frontal sinus. In those cases with a well-developed cell system, the frontal duct can easily be widened to a diameter of 4–5 mm by removing small remaining septa with the punch, curette, or rasp. This step improves the prospects of healing of chronic sinusitis and prevents ob- struction by scar tissue. If a curved suction tube 4 mm in diameter passes without resistance, the frontal duct will usually be found to be wide enough. The resulting opening suffi ces for suction of thickened secretions and for the removal of polyps or cysts with the curved forceps. Further procedures are un- necessary, even if the mucosa is thickened and humped, because of the excellent recuperative capacity of the frontal sinus mucosa. Care must be exercised when tearing off mucosal tags Fig. 6 .43 Frontal sinusotomy using the sharp curette to break because resulting reparative granulation tissue can lead down the anterior ethmoid cells. to the formation of cicatricial stenosis and formation of new bone. On no account must the mucosa around the entire circumference be damaged, as this leads to a ring Sharp forceps and rasps are sometimes inadequate for of scar tissue. the often hard bone, and in this case the diamond burr If the endoscope does notexpose the nasofrontal duct should be used to resect the bone on one side in an ante- and the anterior ethmoid cells apparently end blindly, or rior direction (but not in a circular manner) in front of the if only a narrow nasofrontal duct is visible, broad fenes- nasofrontal duct. Since ideal angled diamond burrs have tration of the floor of the frontal sinus may be indicated not yet been developed, the arch of bone hanging down (Weber et al. 2001), but the author usually omits this ex- from the agger nasi must be straightened and the anterior tension of the procedure if the ethmoiditis is not exten- wall of the duct itself must be drilled gradually (Fig. 6.44). sive and radiography has shown good aeration of the One finger of the left hand holding a long speculum frontal sinus with no mucosal swelling. On the other should be placed on the medial canthus to detect perfora- hand, when there is no view into the frontal sinus, exter- tion of the bone in this area immediately, and thus pre- nal sinusotomy might be carried out for massive intra- vent damage to the lacrimal ducts. The drill must be irri- cavitary polyposis indicating a severe disorder of drain- gated with cool saline solution, which is sucked out of the age and aeration of the sinus. It is likewise indicated for nasopharynx with a curved tube. the removal of frontal mucoceles, foreign bodies, and tu- If a circular lesion of the mucosa has been produced, mors (see below). and the newly created window does not appear to be wide enough, then a spacer should be retained for 2–3 weeks to prevent stenosis (Hosemann et al. 2003). The Transnasal Frontal Sinusotomy frontal duct may appear to be patent during the fi rst Three concepts are important: weeks to be followed by cicatricial stenosis some weeks 1. Ifthe nasofrontal duct has a visible diameter of only later. 1–2 mm and appears incapable of ensuring satisfactory 2. Sometimes the search for the frontal duct with the en- drainage for extensive polyposis of the frontal sinus, it doscope proves fruitless. However, if radiographs have should be widened to form a broad duct extending as far shown the presence of a developed frontal sinus, a careful as the frontal infundibulum. This procedure corresponds endoscopic examination should be carried out. This ma- to the concept of isthmus surgery. Although the surgeon neuver is particularly delicate and demanding because is now aware of the direction of dissection, widening of inadvertent perforation of the anterior skull base is life- the duct is often more difficult than perforation of the threatening. The surgeon should orientate himself by the cells by the above-described method because the cells are transverse bar formed by the anterior ethmoid artery, usually small and few in number. and proceed forward from there. At the same time the

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roof of the maxillary sinus below, high up to the angle Endoscopic and Microscopic Surgery between ethmoid and frontobasis. In fact, such complete uncovering is only appropriate for major approaches into on the Anterior Skull Base the orbit. Smaller targets like limited subperiosteal ab- scesses or mucoceles can be approached via a circum- Indications scribed resection of the medial orbital wall (see Fig. 7. 3 c ). • Foreign body, injury, fracture, dural defect The procedure starts with a partial resection and me- • Malformation, fi stula, meningocele dialization of the middle turbinate (see pages 54 and • Infl ammatory complications 106), and continues with an anteroposterior ethmoidec- • Neoplasia and tumorlike lesions tomy of sufficient length exposing the medial orbital wall. • Combined neurorhinosurgical approach The latter is then opened using a semi-sharp dissector for infracturing the lamina papyracea and removing the bone plates. Principles The underlying periosteum, the periorbita, may have a strong texture resisting an incision, and can be well vas- Transnasal ethmoidectomy provides a limited but direct cularized. After a first horizontal incision with a sharp endoscopic or microscopic view of the inferior surface of sickle knife, the periorbita is opened on demand. the anterior base of the skull (rhinobasis) from below, Orbital fat will always protrude and become a visual reaching from the frontal sinus over the central areas obstacle. A broad medial protrusion may be the aim in around the cribriform plate back to the sphenoid cavity case of orbital decompression for endocrine orbitopathy, with the sella turcica within its roof. Utilizing angled en- but if it hampers the exposure of a circumscribed target it doscopes or direct microscopy, the surgeon achieves a must be reduced or removed. Bipolar coagulation has superb exposure, allowing precise management of local- proved useful to shrink the mass and to erect a superfi cial ized skull base lesions with minimal invasion, in contrast partition at the level of the orbital wall. One should be to the inevitable injury with neurosurgical approaches concerned not to injure the medial long eye muscle with from above, such as temporary cerebral displacement instruments or cautery. Short compression with gauze and abrasion of olfactory fi bers. For these reasons endo- soaked in diluted epinephrine helps to keep the orbital scopic skull base surgery has gained increasing interest contents blood free for better identification, but a caveat during recent years (Husain et al. 2003; Lopatin et al. is needed: Direct application of epinephrine near the op- 2003; Tosun et al. 2003; Casler et al. 2005). Besides this, tic nerve may induce a spasm of the central optic artery the endoscopic access can expose suprabasal structures and thus provoke blindness. Any removal of circum- like the pituitary gland or tumors of the anterior cerebral scribed neoplasia or tumorlike lesions requires optimum fossa. Combined neurorhinosurgical endoscopic ap- visualization for precise dissection of the lesion and min- proaches, on the other hand, allow a complete exposure imal destruction of healthy tissue. Ultrasound- or MRI- of the anterior skull base up to the optic chiasm, in com- based navigation might become extremely valuable for bination with a one-stage revision of the paranasal pneu- this purpose, as are appropriate microinstruments such matization from above. They also spare more invasive as the ball-tipped dissector and small double-cup forceps transfacial and subcranial approaches. from ear surgery. The incision of an orbital abscess (see Chapter 7) is left open to the ethmoid. In other cases, a closure of the open- Operative Technique ing in the orbital wall appears useful, which can be achieved by grafting a piece of mucoperiosteum, taken The anterior part of the anterior skull base is formed by from the inferior turbinate, over the defect with fi xation the posterior wall of the frontal sinus and the roof of the by fibrin glue and ethmoidal packing. orbit. In the middle lies the roof of the ethmoid, and pos- Lesions lateral and dorsal to the bulb and superior to teriorly the sphenoid plane and the roof of the sphenoid the optic nerve are more safely exposed from above (see sinus (see Fig. 2. 68). The exposure of the ethmoid and below) or via an infratemporal approach . Both ouver- sphenoid roof described for the intranasal endoscopic tures require additional microsurgical rather than endo- technique in the previous section was related only to dis- scopic techniques. Inferior orbital fractures (blowout section of the anterior skull base from below (Fig. 6.80). fractures) are managed by an infraorbital transfacial The posterior wall of the frontal sinus is suitable for only a pproach or transantrally if very small. very limited endoscopic manipulation, but the superior and posterior walls of the sphenoid sinus are well within the reach of endoscopy. Endoscopy of the anterior base of the skull is indicated for lesions of the anterior and middle ethmoid roof, especially the cribriform plate, for the olfactory rim, and for

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Fig. 6.80 The anterior skull base (rhinobasis) exposed endoscopically. The surgical field is framed by the thinned middle turbinate medially and the orbital wall laterally. Dorsally, the choana opens close to a large antrostomy (right). Anteriorly (top of the picture), a shadow marks the entrance to the frontal sinus. An oblique fibrous scar (∗ ) forms a small threshold behind which the skull base appears deeper in a groove because the fenestrated oblique ground lamella of the middle turbinate descends from the skull base. Left ethmoidal roof (70 ° telescope).

the walls of the sphenoid sinus, whereas lesions of the sphenoid plane requiring attention are rare. For these reasons, anterior ethmoidectomy is the method of choice for access to the anterior base of the skull, followed by c posterior ethmoidectomy with opening of the sphenoid sinus. Individual circumstances will decide which of these is used for adequate exposure. Particular proce- Fig. 6.81 a–b Transnasal endoscopic closure of a dural fistula in a dures do not need to be described further at this point. defect of the anterior skull base (schematic drawing). Ethmoidectomy in these circumstances naturally includes a E xcision of a proper graft from the inferior turbinate of the contra- the radical removal of the mucosa as far as this is neces- lateral side. sary. b The excised material with its three layers: thin bony plate in its center with periosteum around, and a mucosal cover. According to the extent of the lesion, a suffi cient por- c I nsertion of the free combined mucoperiosteal bone graft into tion of the ethmoids is exenterated by an anteroposterior the defect. The superficial mucosal layer should overlap the edges or posteroanterior ethmoidectomy. Particular attention is of the exposed bony breach. paid to a broad visualization of the compromised area. For this purpose a superior plastic correction of the nasal septum and a reduction of the middle and superior turbi- transition, and the sphenoid. In these regions, the fi xa- nates may be indicated. The mucoperiosteal lining cover- tion of a free graft on the exposed inferior surface of the ing the ethmoid roof is then circumcised and removed skull base (onlay technique) must suffi ce (Fig. 6.81 a–c). from the involved area until healthy bone margins are Its margins have to overlap the adjacent healthy bone by identifi ed. at least 1–2 mm and are fixed to the bone with fi brin tis- These borders have to be exposed by at least 1–2 mm. sue adhesive. This mucoperiosteal patch works as a free If possible, the overlying dura mater is dissected free graft. It should fit snugly into the exposed area and must from the underlying bone at the same distance in order to not be laid over neighboring mucosa. The technique is enable the interposition of a free graft (underlay tech- not difficult if the surgeon is familiar with bimanual en- nique). This maneuver, carried out with a curved semi- doscopy. After removal of as much of the middle turbi- sharp dissector, and controlled by the endoscopic or mi- nate as necessary, the ethmoid cells are cleared up to the croscopic visualization, is not difficult in plane areas. It base of the skull. Once the fi stula has been found becomes questionable or impossible at the incorporation (Fig. 6 . 82 a, b), the neighboring mucosa is removed deli- of the nasal septum or superior conchae within the skull cately from the edge over a distance of 2–4 mm using fi ne base, also at the fossa olfactoria, the frontoethmoidal curved double forceps. If the fistula reaches the nasal

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7 Complications of Sinusitis

Indications Operative Technique

• Perifocal inflammation of facial soft tissues Orbital Complications • Chemosis, nasolacrimal stenosis • Orbital abscess or phlegmon, optic nerve neuritis Orbital complications are most frequently due to an ag- • Mucopyocele gressive infection of the ethmoid. Blockade of the maxil- • Osteitis, osteomyelitis lary and frontal sinuses gives rise to tailback of secretions, • Meningitis, brain abscess thus provoking mucoceles with diplopia or pain as pre- • Focal spread senting symptoms. Chronic conjunctivitis, blepharitis, and epiphora can be caused by chronic rhinosinusitis with or without stenosis of the nasolacrimal duct. Ophthalmological ex- Principles amination including probing and irrigation of the duct and radiological diagnosis will then indicate conservative Inflammatory invasions of soft tissues and bone beyond or eventually rhinosurgical treatment of the underlying the borders of the paranasal sinuses are termed compli- disease, which means an endoscopic revision of the adja- cations. They may involve adjacent structures or remote cent sinuses, and a microscopic dacryocstorhinostomy if areas by superficial or hematogenous dissemination. In necessary (see Chapter 6). the past, radical eradications, mostly with external ap- Rhinogenous orbital cellulitis and subperiostal ab- proaches, exposing the starting point at a paranasal sinus scess are regularly caused by invasive infl ammation from together with the healthy neighborhood were regarded the ethmoid through the lamina papyracea into the orbit. as mandatory. Modern endoscopic surgery has changed This proliferation is especially easy during childhood. The the strategy: Sanitation of the focus by one of the stan- alarming symptoms of chemosis and orbitalprotrusion dard operations described in Chapter 6 in facultative (Fig. 7. 2 ) are, therefore, generally addressed in infants by combination with an eventual neurosurgical or ophthal- an initially conservative treatment under ophthalmologi- mological intervention supported by high-dosage antibi- cal supervision over 24–36 hours before ethmoidectomy osis has proved successful. It must be stressed that early should become necessary. perifocal edema and phlegmon during childhood should In adults, this decision is facilitated by the evidence of only reluctantly be treated with surgery (Fig. 7.1 ). chronic ethmoiditis (Fig. 7.3 a–c). Endoscopic total eth-

Fig. 7.1 Initial orbital complication from rhinitis in an infant show- Fig. 7.2 Orbital complication from rhinosinusitis with periocular ing a swollen and reddened upper lid and chemosis. venous congestion, edema, and slight protrusio bulbi.

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a c Fig. 7.3 a–c Advanced sinugenic orbital complication. b N ecrotizing maxilloethmoiditis ( < ) in the CT scan. The medial or- a The facial aspect with periocular inflammation, chemosis, and bital wall (arrow) is eroded and deflected by a subperiosteal ab- protrusio bulbi. scess. c I ncision of the prominent periorbita after ethmoidectomy releases the abscess (∗ ).

moidectomy is carried out according to the technique described in Chapter 6. A limited resection of the lamina papyracea is added, and the localized abscess is opened by a vertical incision of the periosteum with a sickle knife. A mild and careful spreading with a small Blakesley forceps will completely empty the abscess cavity, which should be monitored, and if necessary this manipulation process should be repeated the next day under local an- esthesia and endoscopic visualization. Mann et al. (1997) had to repeat the maneuver in 6 of 26 children with a periorbital abscess. The healing process may be supported by insertion of a soft strap of cotton for 1–2 days. Orbital invasion from frontal sinusitis, clinically suggested by the lateroinferior displacement of the eye- ball (Fig. 7.4 ), will be detected on CT. It will be addressed by a frontal sinusotomy, if possible, endoscopically, combined with an anterior ethmoidectomy and medial orbi- totomy. A deep retrobulbar abscess (Fig. 7.5 ) originating from the posterior ethmoid may be drained endonasally, but the risk of injuring the optic nerve must be balanced against the higher expense but greater safety of a trans- Fig. 7.4 Severe lateroinferior displacement of the left eye due to cranial approach. A modiﬁed endoscopic Lothrop proce- frontoethmoidal sinusitis with orbital phlegmon. dure has been recommended for cases with extension of

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