Paranasal sinus imaging S. JAMES ZINREICH, MO, Baltimore. Maryland
The Inability of plain radiographs to yield conclusive Information about the ostlomeatal complex In sinusitis Is no longer a significant problem. Computed tomography (CTI. magnetic resonance Imaging (MRII, and Improved endoscopic technology now enable almost complete exploration of the sinus anatomy and the pathophysiology of sinus disease. Nasal endoscopy provides a clear view of the anterior nasal cavltyIncluding the middle meatus-In patients with symptoms of sinusitis. However, the maxIllary ostia are stilidifficult to visualize directly. CT Isrequired for noninvasive evaluation of deep ostlomeatal air passages and posterior ethmoid and sphenoid sinuses. MRI of the nasal cavity and paranasal sinuses, although of limited use for displaying nasal morphology. Is even more sensitive than CT In Identifying fungal concretions and neoplasms. (OTOLARVNGOL HEAD NECK SURG 1990;103:863.)
For
100 years after Darwin published his thesis. the human hand stayed at the top rung of the evolutionary ladder. Thumb-to-finger apposition went uncontested ~ntil, in the early 1960s, a famous challenge appeared ID the medical literature: Could the hand differentially retain or expel solid, liquid. or gas? No. the proctologist author answered. This pinnacle of evolution belonged to another organ system-the anal sphincter. Until now, the sinuses have been jousted to a lower rung of human evolution, topping only the upright spine, still better suited to moving about on all four extremities. Yet congestion of wintertime upper respiratory infections (URIs) regularly relegated the paranasal sinuses to lower throwback status. After all. more patients go to their physicians for sinusitis than for backache. All this changed as color. three-dimensional images have documented the exquisite nature of the previously mysterious sinus passages. New understanding of the functional integrity of the ostiomeatal complex has revolutionized the diagnosis and treatment of sinus disease-and suddenly thrust the nasal passages into Contention for top rank in the "pecking order" of human evolutionary attainment. The gauntlet has been thrown down: Which body system is capable of constant recycling and movement of fluids to humidify, warm, and filter inspired air? Only the paranasal sinuses.
Muoocillary Clearance The primary physiologic roles of the nasal passages-humidification, warming. and removal of particulate matter from inspired air-are well docu-
23/0/24794
mented. The role of mucociliary clearance is less well defined. The thin layer of mucus covering the inner surface of sinuses receives the largest deposits of inhaled large particulate matter. The cilia and the thin mucous layer here are in constant motion in predetermined pathways toward the various sinus ostia. If mucosal transport of bacteria, mucus. and debris is obstructed, that sinus becomes susceptible to infection. Mucociliary clearance in the frontal sinuses advances along the septal wall to the sinus roof, then moves laterally along the roof and medially along the floor toward the ostium. Messerklinger' recognized that backflow resulting from recirculation in the frontal recess may be a cause of initial infection. In the maxillary sinus. mucociliary movement is toward the ostium. It starts at the sinus floor and radiates along the wall of the sinus superiorly. Even in the presence of nasal antral windows after inferior meatotomy, intended to clear mucus from the maxillary sinus. mucociliary movement persists in its upward movement toward the sinus ostium. Unobstructed flow through the ostiomeatal complex and its narrow communicating passages within the sinus ostia is integral to mucociliary clearance and ventilation. It is of particular importance that the anterior and posterior ethmoid sinus channels be patent because the primary sites for mucociliary drainage include the anterior middle meatus and the posterior sphenoethmoid recess. With anatomic distortion or even minor swelling, two mucosal layers may become opposed and lead to stenosis or obstruction in the ostiomeatal complex. Reduced aeration or accumulated secretions in the major maxillary and frontal sinuses then appear to predispose again to infection. On the basis of these observations, the guiding prin-
863
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Fig. 1. CT display of inflammatory disease. CT scan through the anterior ethmo id sinus reveals a patentlelt Infundibulum (da shed arrow). The right (R) infund ibulum (solid arrow) Isobstructed .Minimum muco pe riostea l thickening is present within the right maxillary sin us (open arrow) and ethmoid bulla
n.
Fig. 2. CT display of an anatomic variation . Axial scan through the anterior ethmoid sinus reveals a right [R) concha bullose t).
ciple of management has become the reversal of the sinusiti s cycle involving the ostiomeatal complex. Understanding how to do this has been the focus of a line of research yielding techniques and knowledge that have dramatically changed standards of care of patients with sinusitis.
Sclentlftc Evolution As early as 1893, Caldwell" noted a functional relationship between the ostia of the frontal maxillary and anterior ethmoid sinuses, indicating that maxillary sinusitis may be a result of other disease in this area. In 1926, Hajek et al. J emphasized that stenosis occurs
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Volume 103 Number 5 Part 2 November 1990
Paranasal sinus Imaging
chiefly in the "nose itself' in acute sinusitis, whereas the middle meatus was implicated in cases of chronic stenosis. Later studies by Messerklinger," Proctor," and Hilding 6 stressed the ethmoid sinus as a common site of primary infection that led to disease in the frontal and maxillary sinuses. . The frontal and maxillary sinuses nevertheless continued to be the focus of the clinical evaluation of pa~ients with symptoms of sinusitis. Physicians virtually Ignored the ethmoid sinuses because the mainstay of Sinusitis diagnosis-plain sinus radiography-never ~uggested the importance of the ostiomeatal complex In sinus health and disease. When refined endoscopic instrumentation, computed tomography (CT), and magnetic resonance imaging (MRI) clearly showed the incidence and location of inflammatory disease within the Complex (Fig. l), 4.7.8 clinical emphasis shifted dramatically. It has now become well demonstrated that anatomic abnormalities playa role in chronic sinusitis (Fig. 2). Persistent, low-grade inflammation in the ethmoid sinus, which apparently may have few localizing symptoms, can predispose to recurrent infection in the maxillary and / or frontal sinuses.
165
...sc
Standard Radiography Is there still a place for standard radiography in clinical evaluation of sinusitis? The answer is equivocal, depending on the situation. Plain radiographs still provide noninvasive and fast evaluation of the lower third of the nasal cavity and the maxillary, frontal, sphenoid, and posterior ethmoid sinuses. These observations are inadequate, however, for evaluation of the anterior ethmoidal air cells, the upper two thirds of the nasal cavity, and the infundibular, middle meatus, frontal recess air passages. Computed Tomography While conventional plain radiographs readily demOnstrate maxillary and frontal sinus disease, they provide limited views of the anterior ethmoid cells, the upper two thirds of the nasal cavity, and the frontal recess." In these areas, CT can provide specific diagnosis and display the underlying causes of sinusitis in patients with chronic or recurrent acute sinusitis; in the latter, CT examination is delayed until antibiotic therapy controls acute exacerbation. CT can clarify anatomic relationships and variations that may playa role in sinusitis; it may also guide endoscopic surgery. To afford optimal demonstration of the anterior ethmoid sinuses and ostiomeatal structures, CT imaging is performed in the coronal planes. Sectional imaging of the maxillofacial area shows accurate soft tissue definition in the nasal cavity, paranasal sinuses, orbit, and
p
A
Fig. 3. Anatomy of the anterior ethmoid sinus. Soglttal reconstructed cross-sectton (5C) through the middle of the ethmoid sinusreveals the frontal sinus (F). frontal recess (curved arrow). ethmoid bulla (8),uncinate process (U), sinuslateralls (SL), bosal lamella (Bi), sphenoid sinus (5). bony palate (8P), hiatus semllunarls (dashed curved line), middle meatus t'). middle turbinate (2), Inferior turbinate (1). posterior (P), and anterior (A).
intracranial compartment. Highly contrasting densities identify air within the bony sinuses, fat within the orbit, and soft tissues outlined by air in the nasal cavity. CT thus enables the clinician to identify and evaluate systematically each frontal sinus, frontal recess, uncinate process, infundibulum, maxillary sinus, maxillary sinus
Downloaded from oto.sagepub.com at CAMBRIDGE UNIV LIBRARY on June 5, 2016
OIolaryngologVHead and Neck surgery
866 ZINREICH
.c.
Fig . Chronic sinusitis on Waters view and CT. A, Waters view obtained 8 hours before the CT exam ination revea ls bilateral frontal and maxillary sinus mucoperiosteal thickening . B, The CT examination also reveals bilatera l and anter ior ethmoid sinus disease and provides Improved display of the relationship with the adjacent bra in and orb it.
ostia. ethmoid bulla. sinus laterali s, middle meatus. posterior ethmoid sinus cell s. sphenoid sinus. and the sphenoid rece ss (Fig. 3) . CT examination . usually performed after medical treatment of sinusitis. can reveal the extent of mucosal disease deep in the ostiomeatal complex III (Fig. 4) . Resolution of secondary inflammatory changes affords a more accurate display of the regional anatomy and therefore provides a better "guide" for the surgical procedure. In our evaluation of CT examination of the nasal
cavity and paranasal sinuses of 23 patients with clini cally established chronic sinusitis. mucoperiostial inflammation was present in the anterior ethmoid sinus in 78% of patients; in the maxillary sinus. 66%; frontal sinus. 34%; posterior ethmoid sinus. 31%; sphenoid sinus . 16%. and in 16% of the patients . no mucosal inflammation was detected . These results confirmed the observations of investigators who concluded-before the advent of endoscopy and CT-that the ethmoid sinus is the seat of
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Fig. 6. Three-dimensional CT shows the location of the sphenoid sinus septum (small arrows) and its relationship to the cavernous Interna l carotld artery (large arrow) . Fig. 5. three-dImensional CTof the nasal cavl1yand paranasol slnuses. The frontal sinuses (green) and maxillary sinuses (red) are shown posteriorly. The orientation of the Infundibula (white arrows) and location of the frontal recess (black arrows) are shown.
disease and the site from which inflammation extends into the frontal and maxillary sinuses.t":" Combined Nasal Endoscopy and OT The complementary nature of endoscopy and CT cannot be overstressed. Endoscopy only displays the surface mucosa of the ethmoid cells. whereas CT shOWS it in depth (Figs. 5 and 6). displaying the deeper air chambers that are hidden from the telescope. is particularly indispensable in diagnosing surgically correctable sinus disease. but the presence on CT of a change as significant as sinus opacification. for example. is not necessarily sufficient to justify surgical intervention. Changes identified by CT should be correlated with symptoms and endoscopic findings. CT may reveal an anatomic abnormality that predisposes sinusitis; however. its therapy-be it medical or surgical-should be based on the combined information extracted from the radiographic and clinical evaluations .
cr
Magnetic Resonance Imaging (MRI) While early reports were enthusiastic for use of MRI in studying the paranasal sinuses. its use to diagnose sinusitis may have some limitations.
In an effort to ascertain whether the abnormal appearance of nasal mucosa on MRI in patients free of nasal symptoms or history of nasal disease may be a result of the natural alternating congestion and decongestion in the normal nasal cycle. we studied five healthy adult volunteers. II In each subject. we performed three to four MRI studie s over an 8-hour period . using both Tl- and T2-weighted images. (Tl-weighted images define regional anatomy. whereas T2-weighted images display pathologic changes.) The signal intensity and size changes of the inferior turbinate over the test period were consistent with the normal nasal cycle . During the congested phase. all subjects demonstrated significantly increased signal intensity in the ethmoid sinus. but not in the frontal. maxillary. and sphenoid sinuses. We concluded that the appearance of normal nasal mucosa during the edematous phase of the nasal cycle on T2-weighted images can resemble pathologic change and that MRI may have limited usefulness in the evaluation of patients with suspected sinusitis . We also inferred from the study that changes within the ethmoid sinus during the nasal cycle indicate that neural control may playa greater role in the functioning of the paranasal sinuses than previously thought. The normal cycle is believed to be regulated by autonomic tone under hypothalamic control. Several studies have suggested that individuals may have the potential to achieve some degree of voluntary control .":" For example. some people are capable of changing air flow
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from one nasal passage to another during yoga breathing exercises, presumably through conscious control of the autonomic nervous system. Despite MRI's limitations in evaluating sinusitis, it is more sensitive than CT in detecting fungal infections, perhaps because of the presence of calcium and ferromagnetic elements in the fungal concretions. 16 In addition, with its superior soft tissue resolution, MRI can differentiate neoplastic processes from inflammatory diseases in 90% of patients. 17
II.
12.
13. 14.
CONCLUSION Improved imaging of the sinuses-especially the anterior ethmoid sinuses-is leading toward optimal diagnosis of diseases of the nasal cavity and paranasal sinuses. The increased use of endoscopy and CT confirm the importance of ostiomeatal disease and anatomic deformities of the middle meatus in the pathogenesis of sinusitis. Nasal endoscopy should supplement clinical evaluation in all patients with chronic or recurrent acute sinusitis. CT should be used when endoscopy fails to explain symptoms of sinusitis. CT shows extent of mucosal disease deep in the ostiomeatal complex. Through its accurate definition of the soft tissues of the nasal cavity, paranasal sinuses, orbit, and intracranial compartment, it optimally displays the regional anatomy and therefore should be performed on every patient who is to undergo a surgical procedure to treat sinusitis. MRI can be helpful in the diagnosis of fungal sinusitis and neoplastic processes. REFERENCES I. MesserkJinger W. On the drainage of the normal frontal sinus of man. Acta Otolaryngol 1967;63:176-81. 2. Caldwell OW. The accessory sinuses of the nose: an improved method of treatment for suppuration of the maxillary antrum. NY Med J 1893;S8:S26. 3. Hajek M, Heitger JO, Hansel FK,trans. Pathology and treatment of the inftammatory diseases of the nasal accessory sinuses. St. Louis: CV Mosby Co, 1926. 4. Messerklinger W. Endoscopy of the nose. Baltimore: Urban and Schwartzenberg, Inc., 1978. S. Proctor OF. The nose, paranasal sinuses and pharynx. In: Walters W, ed, Lewis-Walters practice of surgery. Hagerstown, Md: WF Prior Co., 1966;4:1-37. 6. Hilding AC. Physiologic basis of nasal operations. Calif Med 19S0;72:103-7. 7. Kennedy OW, Zinreich SJ, Rosenbaum AE. Johns ME. Functional endoscopic surgery. Theory and diagnostic evaluation. Arch Otolaryngol 1985;111 :S76-82. II. Stammberger H. Endoscopic endonasal surgery-Concepts in treatment of recurring rhinosinusitis. Part I. Anatomic and pathophysiologic considerations. OrOLARYNOOL HEAD NECK SURG 19116;94:143-7. 9. Som PM. The paranasal sinuses. In: Bergeron RT, Osborn AG. Som PM. eds. Head and neck imaging excluding the brain. SI. Louis: CV Mosby Co.• 1984:S-143. 10. Zinreich SJ, Kennedy OW, Rosenbaum AE, Gayler.BW, Kumar
IS.
16. 17.
AJ, Stammberger H. Paranasal sinuses: CT imaging requirements for endoscopic surgery. Radiology 1987;163:769-7S. Zinreich SJ, Kennedy OW, Kumar AJ. Rosenbaum AE. Arrington JA. Johns ME. MR imaging of normal nasal cycle: comparison with sinus pathology. J Comput Assist Tomogr 1988; 12:1014-9. Eccles R, Eccles KSJ. Asymmetry in the autonomic nervous system with reference to the nasal cycle. migraine, anisocoria and Meniere's syndrome. Rhinology 1981;19:121-S. Eccles R. The central rhythm of the nasal cycle. Acta Otolaryngol 1978;86:464-8. Eccles R, Lee RL. The inftuence of the hypothalamus on the sympathetic innervation of the nasal vasculature of the cat. Acta Otolaryngol 1981;91:127-34. Eccles R. Elwell 0, Lee RL. Nasal vasoconstriction induced by electrical stimulation of the cat hypothalamus. J Physiol (Lond) 1979;293:48P. Zinreich SJ, Kennedy OW, Malat J, et al. Fungal sinusitis: diagnosis with CT and MR imaging. Radiology 1988;169:439-44. Som PM, Braun IF. Shapiro MD, Reed OL, Curtin HO, Zimmerman RA. Tumors of the parapharyngeal space and upper neck: MR imaging characteristics. Radiology 1987;164:823-9.
DISCUSSION Dr. Kennedy: The indications for computed tomography (CT) in patients with sinusitis should perhaps be made clearer to primary care physicians-not just why a CT scan may be needed, but the appropriate timing of the examination. Will you comment on that, Dr. Zinreich? Dr.Zinrelch: The primary role of the CT examination in sinusitis is to define the anatomy before anticipated surgery in patients, with a firm diagnosis based on nasal endoscopy and an exhaustive history. The role of CT is not only to provide the surgeon a good anatomic "map," but to demonstrate why the patient may have the recurring symptoms-in other words, to show exactly where surgical correction may be effective. For this purpose, there must be as little mucosal inflammation as possible, so adequate medical therapy should precede the CT examination. Mucosal thickening is frequently present in normal, nonsymptomatic patients; therefore, surgery should not be solely based on the CT findings. Dr. Kennedy: Chronic sinusitis is a complicated, multifactorial problem, and what is seen on CT is just one aspect of it. On the other hand, it is possible to have significant, symptomatic ostial obstruction without CT changes. In fact, CT findings always underestimate the amount of disease present; when mucosal thickening is seen on CT, one can be sure it is really there. The question is, is the thickening causing the patient's symptoms? That is the reason we select patients for CT on the basis of nasal endoscopy and an extensive history. Dr, Druce: Can you comment on the use of the lim-
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November 1990
Paranasal sinus Imaging
ited, four-slice CT scan versus the conventional full examination? Dr. Zinrelch: The limited examination may be valuable if one is sure, on the basis of medical or surgical therapy, that the sinusitis is limited to a particular area. For example, if there is disease only in the anterior ethmoid sinus and CT information is needed for further therapy. a limited scan may be all that is needed. Dr.Reilly: Does the standard radiographic series have any practical value? Dr. Zinrelch: When an examination is ordered. one has specific questions in mind. In the acute state. if one is Worried about intracranial or intraorbital extension. as well as wishing to confirm the acute process, standard radiographic films might suffice. However, if confronted with a patient with established chronic sinusitis and surgery is contemplated, the underlying anatomy and the extent of disease will not be optimally displayed on plain films. Dr. Avant: How can the primary care physician identify those of his patients who require endoscopy and/or CT? Dr. Kennedy: If the symptoms are severe, and if symptoms persist despite all the usual medical treatments, and a careful history indicates that the problem is indeed a sinus-related one, it is time for the patient to have an endoscopic examination by an otolaryngologist, and a CT examination if the findings are inconclusive. It is important to remember that many patients ascribe any headache to sinusitis. Things that point to sinusitis, even in the presence of normal radiographic findings, include a history of recurrent infections that tend to get better after therapy with antibiotics or topical decongestants. Dr. Avant: Then you would find it acceptable for a primary care physician to treat two or three episodes of acute sinusitis over a year before sending the patient for additional studies? Dr. Kennedy: Yes, if the symptoms are not remarkable. A patient with severely debilitating headache or
869
facial pain associated with unconfirmed sinusitis deserves immediate nasal endoscopy and, if that is not diagnostic, CT. After three or so office visits for presumed recurrent acute sinusitis within a year, I would recommend nasal endoscopy and perhaps a CT examination, regardless of the severity of the symptoms. I would not recommend CT for any patient with sinusitis before endoscopy, however. Dr. Reilly: Would you ever consider CT examination before doing endoscopy, or send a patient with a normal endoscopic examination for CT? Dr. Kennedy: In general, I use nasal endoscopy as a screening test for CT. If a patient has an outstanding history of severe headache or debilitating facial pain, I may want a CT examination in the face of a normal endoscopy. Also, a patient with presumed bacterial sinusitis whose plain radiographs repeatedly show abnormal air-fluid levels merits CT evaluation, even if endoscopy shows normal results. Dr. Zinrelch: I would like to stress that endoscopy may provide all the infermation you want, so it should be used before CT, since the latter involves radiation. Dr. Avant: If both nasal endoscopy and CT show normal findings, does that rule out sinusitis as the cause of a patient's symptoms? Dr. Kennedy: No. A patient with normal sinus mucosa who encounters intermittent ostial obstruction for the first time will report the severest headache he or she has ever encountered. This patient also appears to be at greater risk for an intracranial complication than the patient with thickened sinus mucosa, which is less sensitive to pain. This is not an easy diagnosis to make, and a high index of suspicion is extremely important to it. Dr. Reilly: Sinus endoscopy requires not only trained clinical skills but diligence and dedication to thorough examination. Physicians who lack either adequate training or frequent experience with the techniques should send their patients to physicians who perform endoscopy regularly and well.
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The Inability of plain radiographs to yield conclusive Information about the ostlomeatal complex In sinusitis Is no longer a significant problem. Computed tomography (CTI. magnetic resonance Imaging (MRII, and Improved endoscopic technology now enable almost complete exploration of the sinus anatomy and the pathophysiology of sinus disease. Nasal endoscopy provides a clear view of the anterior nasal cavltyIncluding the middle meatus-In patients with symptoms of sinusitis. However, the maxIllary ostia are stilidifficult to visualize directly. CT Isrequired for noninvasive evaluation of deep ostlomeatal air passages and posterior ethmoid and sphenoid sinuses. MRI of the nasal cavity and paranasal sinuses, although of limited use for displaying nasal morphology. Is even more sensitive than CT In Identifying fungal concretions and neoplasms. (OTOLARVNGOL HEAD NECK SURG 1990;103:863.)
For
100 years after Darwin published his thesis. the human hand stayed at the top rung of the evolutionary ladder. Thumb-to-finger apposition went uncontested ~ntil, in the early 1960s, a famous challenge appeared ID the medical literature: Could the hand differentially retain or expel solid, liquid. or gas? No. the proctologist author answered. This pinnacle of evolution belonged to another organ system-the anal sphincter. Until now, the sinuses have been jousted to a lower rung of human evolution, topping only the upright spine, still better suited to moving about on all four extremities. Yet congestion of wintertime upper respiratory infections (URIs) regularly relegated the paranasal sinuses to lower throwback status. After all. more patients go to their physicians for sinusitis than for backache. All this changed as color. three-dimensional images have documented the exquisite nature of the previously mysterious sinus passages. New understanding of the functional integrity of the ostiomeatal complex has revolutionized the diagnosis and treatment of sinus disease-and suddenly thrust the nasal passages into Contention for top rank in the "pecking order" of human evolutionary attainment. The gauntlet has been thrown down: Which body system is capable of constant recycling and movement of fluids to humidify, warm, and filter inspired air? Only the paranasal sinuses.
Muoocillary Clearance The primary physiologic roles of the nasal passages-humidification, warming. and removal of particulate matter from inspired air-are well docu-
23/0/24794
mented. The role of mucociliary clearance is less well defined. The thin layer of mucus covering the inner surface of sinuses receives the largest deposits of inhaled large particulate matter. The cilia and the thin mucous layer here are in constant motion in predetermined pathways toward the various sinus ostia. If mucosal transport of bacteria, mucus. and debris is obstructed, that sinus becomes susceptible to infection. Mucociliary clearance in the frontal sinuses advances along the septal wall to the sinus roof, then moves laterally along the roof and medially along the floor toward the ostium. Messerklinger' recognized that backflow resulting from recirculation in the frontal recess may be a cause of initial infection. In the maxillary sinus. mucociliary movement is toward the ostium. It starts at the sinus floor and radiates along the wall of the sinus superiorly. Even in the presence of nasal antral windows after inferior meatotomy, intended to clear mucus from the maxillary sinus. mucociliary movement persists in its upward movement toward the sinus ostium. Unobstructed flow through the ostiomeatal complex and its narrow communicating passages within the sinus ostia is integral to mucociliary clearance and ventilation. It is of particular importance that the anterior and posterior ethmoid sinus channels be patent because the primary sites for mucociliary drainage include the anterior middle meatus and the posterior sphenoethmoid recess. With anatomic distortion or even minor swelling, two mucosal layers may become opposed and lead to stenosis or obstruction in the ostiomeatal complex. Reduced aeration or accumulated secretions in the major maxillary and frontal sinuses then appear to predispose again to infection. On the basis of these observations, the guiding prin-
863
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OtolaryngologyHead and Neck Surgery
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Fig. 1. CT display of inflammatory disease. CT scan through the anterior ethmo id sinus reveals a patentlelt Infundibulum (da shed arrow). The right (R) infund ibulum (solid arrow) Isobstructed .Minimum muco pe riostea l thickening is present within the right maxillary sin us (open arrow) and ethmoid bulla
n.
Fig. 2. CT display of an anatomic variation . Axial scan through the anterior ethmoid sinus reveals a right [R) concha bullose t).
ciple of management has become the reversal of the sinusiti s cycle involving the ostiomeatal complex. Understanding how to do this has been the focus of a line of research yielding techniques and knowledge that have dramatically changed standards of care of patients with sinusitis.
Sclentlftc Evolution As early as 1893, Caldwell" noted a functional relationship between the ostia of the frontal maxillary and anterior ethmoid sinuses, indicating that maxillary sinusitis may be a result of other disease in this area. In 1926, Hajek et al. J emphasized that stenosis occurs
Downloaded from oto.sagepub.com at CAMBRIDGE UNIV LIBRARY on June 5, 2016
Volume 103 Number 5 Part 2 November 1990
Paranasal sinus Imaging
chiefly in the "nose itself' in acute sinusitis, whereas the middle meatus was implicated in cases of chronic stenosis. Later studies by Messerklinger," Proctor," and Hilding 6 stressed the ethmoid sinus as a common site of primary infection that led to disease in the frontal and maxillary sinuses. . The frontal and maxillary sinuses nevertheless continued to be the focus of the clinical evaluation of pa~ients with symptoms of sinusitis. Physicians virtually Ignored the ethmoid sinuses because the mainstay of Sinusitis diagnosis-plain sinus radiography-never ~uggested the importance of the ostiomeatal complex In sinus health and disease. When refined endoscopic instrumentation, computed tomography (CT), and magnetic resonance imaging (MRI) clearly showed the incidence and location of inflammatory disease within the Complex (Fig. l), 4.7.8 clinical emphasis shifted dramatically. It has now become well demonstrated that anatomic abnormalities playa role in chronic sinusitis (Fig. 2). Persistent, low-grade inflammation in the ethmoid sinus, which apparently may have few localizing symptoms, can predispose to recurrent infection in the maxillary and / or frontal sinuses.
165
...sc
Standard Radiography Is there still a place for standard radiography in clinical evaluation of sinusitis? The answer is equivocal, depending on the situation. Plain radiographs still provide noninvasive and fast evaluation of the lower third of the nasal cavity and the maxillary, frontal, sphenoid, and posterior ethmoid sinuses. These observations are inadequate, however, for evaluation of the anterior ethmoidal air cells, the upper two thirds of the nasal cavity, and the infundibular, middle meatus, frontal recess air passages. Computed Tomography While conventional plain radiographs readily demOnstrate maxillary and frontal sinus disease, they provide limited views of the anterior ethmoid cells, the upper two thirds of the nasal cavity, and the frontal recess." In these areas, CT can provide specific diagnosis and display the underlying causes of sinusitis in patients with chronic or recurrent acute sinusitis; in the latter, CT examination is delayed until antibiotic therapy controls acute exacerbation. CT can clarify anatomic relationships and variations that may playa role in sinusitis; it may also guide endoscopic surgery. To afford optimal demonstration of the anterior ethmoid sinuses and ostiomeatal structures, CT imaging is performed in the coronal planes. Sectional imaging of the maxillofacial area shows accurate soft tissue definition in the nasal cavity, paranasal sinuses, orbit, and
p
A
Fig. 3. Anatomy of the anterior ethmoid sinus. Soglttal reconstructed cross-sectton (5C) through the middle of the ethmoid sinusreveals the frontal sinus (F). frontal recess (curved arrow). ethmoid bulla (8),uncinate process (U), sinuslateralls (SL), bosal lamella (Bi), sphenoid sinus (5). bony palate (8P), hiatus semllunarls (dashed curved line), middle meatus t'). middle turbinate (2), Inferior turbinate (1). posterior (P), and anterior (A).
intracranial compartment. Highly contrasting densities identify air within the bony sinuses, fat within the orbit, and soft tissues outlined by air in the nasal cavity. CT thus enables the clinician to identify and evaluate systematically each frontal sinus, frontal recess, uncinate process, infundibulum, maxillary sinus, maxillary sinus
Downloaded from oto.sagepub.com at CAMBRIDGE UNIV LIBRARY on June 5, 2016
OIolaryngologVHead and Neck surgery
866 ZINREICH
.c.
Fig . Chronic sinusitis on Waters view and CT. A, Waters view obtained 8 hours before the CT exam ination revea ls bilateral frontal and maxillary sinus mucoperiosteal thickening . B, The CT examination also reveals bilatera l and anter ior ethmoid sinus disease and provides Improved display of the relationship with the adjacent bra in and orb it.
ostia. ethmoid bulla. sinus laterali s, middle meatus. posterior ethmoid sinus cell s. sphenoid sinus. and the sphenoid rece ss (Fig. 3) . CT examination . usually performed after medical treatment of sinusitis. can reveal the extent of mucosal disease deep in the ostiomeatal complex III (Fig. 4) . Resolution of secondary inflammatory changes affords a more accurate display of the regional anatomy and therefore provides a better "guide" for the surgical procedure. In our evaluation of CT examination of the nasal
cavity and paranasal sinuses of 23 patients with clini cally established chronic sinusitis. mucoperiostial inflammation was present in the anterior ethmoid sinus in 78% of patients; in the maxillary sinus. 66%; frontal sinus. 34%; posterior ethmoid sinus. 31%; sphenoid sinus . 16%. and in 16% of the patients . no mucosal inflammation was detected . These results confirmed the observations of investigators who concluded-before the advent of endoscopy and CT-that the ethmoid sinus is the seat of
Downloaded from oto.sagepub.com at CAMBRIDGE UNIV LIBRARY on June 5, 2016
VOlume 103 Number 5 Port 2 NoItember 1990
Paranasal sinus Imaging
167
Fig. 6. Three-dimensional CT shows the location of the sphenoid sinus septum (small arrows) and its relationship to the cavernous Interna l carotld artery (large arrow) . Fig. 5. three-dImensional CTof the nasal cavl1yand paranasol slnuses. The frontal sinuses (green) and maxillary sinuses (red) are shown posteriorly. The orientation of the Infundibula (white arrows) and location of the frontal recess (black arrows) are shown.
disease and the site from which inflammation extends into the frontal and maxillary sinuses.t":" Combined Nasal Endoscopy and OT The complementary nature of endoscopy and CT cannot be overstressed. Endoscopy only displays the surface mucosa of the ethmoid cells. whereas CT shOWS it in depth (Figs. 5 and 6). displaying the deeper air chambers that are hidden from the telescope. is particularly indispensable in diagnosing surgically correctable sinus disease. but the presence on CT of a change as significant as sinus opacification. for example. is not necessarily sufficient to justify surgical intervention. Changes identified by CT should be correlated with symptoms and endoscopic findings. CT may reveal an anatomic abnormality that predisposes sinusitis; however. its therapy-be it medical or surgical-should be based on the combined information extracted from the radiographic and clinical evaluations .
cr
Magnetic Resonance Imaging (MRI) While early reports were enthusiastic for use of MRI in studying the paranasal sinuses. its use to diagnose sinusitis may have some limitations.
In an effort to ascertain whether the abnormal appearance of nasal mucosa on MRI in patients free of nasal symptoms or history of nasal disease may be a result of the natural alternating congestion and decongestion in the normal nasal cycle. we studied five healthy adult volunteers. II In each subject. we performed three to four MRI studie s over an 8-hour period . using both Tl- and T2-weighted images. (Tl-weighted images define regional anatomy. whereas T2-weighted images display pathologic changes.) The signal intensity and size changes of the inferior turbinate over the test period were consistent with the normal nasal cycle . During the congested phase. all subjects demonstrated significantly increased signal intensity in the ethmoid sinus. but not in the frontal. maxillary. and sphenoid sinuses. We concluded that the appearance of normal nasal mucosa during the edematous phase of the nasal cycle on T2-weighted images can resemble pathologic change and that MRI may have limited usefulness in the evaluation of patients with suspected sinusitis . We also inferred from the study that changes within the ethmoid sinus during the nasal cycle indicate that neural control may playa greater role in the functioning of the paranasal sinuses than previously thought. The normal cycle is believed to be regulated by autonomic tone under hypothalamic control. Several studies have suggested that individuals may have the potential to achieve some degree of voluntary control .":" For example. some people are capable of changing air flow
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from one nasal passage to another during yoga breathing exercises, presumably through conscious control of the autonomic nervous system. Despite MRI's limitations in evaluating sinusitis, it is more sensitive than CT in detecting fungal infections, perhaps because of the presence of calcium and ferromagnetic elements in the fungal concretions. 16 In addition, with its superior soft tissue resolution, MRI can differentiate neoplastic processes from inflammatory diseases in 90% of patients. 17
II.
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13. 14.
CONCLUSION Improved imaging of the sinuses-especially the anterior ethmoid sinuses-is leading toward optimal diagnosis of diseases of the nasal cavity and paranasal sinuses. The increased use of endoscopy and CT confirm the importance of ostiomeatal disease and anatomic deformities of the middle meatus in the pathogenesis of sinusitis. Nasal endoscopy should supplement clinical evaluation in all patients with chronic or recurrent acute sinusitis. CT should be used when endoscopy fails to explain symptoms of sinusitis. CT shows extent of mucosal disease deep in the ostiomeatal complex. Through its accurate definition of the soft tissues of the nasal cavity, paranasal sinuses, orbit, and intracranial compartment, it optimally displays the regional anatomy and therefore should be performed on every patient who is to undergo a surgical procedure to treat sinusitis. MRI can be helpful in the diagnosis of fungal sinusitis and neoplastic processes. REFERENCES I. MesserkJinger W. On the drainage of the normal frontal sinus of man. Acta Otolaryngol 1967;63:176-81. 2. Caldwell OW. The accessory sinuses of the nose: an improved method of treatment for suppuration of the maxillary antrum. NY Med J 1893;S8:S26. 3. Hajek M, Heitger JO, Hansel FK,trans. Pathology and treatment of the inftammatory diseases of the nasal accessory sinuses. St. Louis: CV Mosby Co, 1926. 4. Messerklinger W. Endoscopy of the nose. Baltimore: Urban and Schwartzenberg, Inc., 1978. S. Proctor OF. The nose, paranasal sinuses and pharynx. In: Walters W, ed, Lewis-Walters practice of surgery. Hagerstown, Md: WF Prior Co., 1966;4:1-37. 6. Hilding AC. Physiologic basis of nasal operations. Calif Med 19S0;72:103-7. 7. Kennedy OW, Zinreich SJ, Rosenbaum AE. Johns ME. Functional endoscopic surgery. Theory and diagnostic evaluation. Arch Otolaryngol 1985;111 :S76-82. II. Stammberger H. Endoscopic endonasal surgery-Concepts in treatment of recurring rhinosinusitis. Part I. Anatomic and pathophysiologic considerations. OrOLARYNOOL HEAD NECK SURG 19116;94:143-7. 9. Som PM. The paranasal sinuses. In: Bergeron RT, Osborn AG. Som PM. eds. Head and neck imaging excluding the brain. SI. Louis: CV Mosby Co.• 1984:S-143. 10. Zinreich SJ, Kennedy OW, Rosenbaum AE, Gayler.BW, Kumar
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16. 17.
AJ, Stammberger H. Paranasal sinuses: CT imaging requirements for endoscopic surgery. Radiology 1987;163:769-7S. Zinreich SJ, Kennedy OW, Kumar AJ. Rosenbaum AE. Arrington JA. Johns ME. MR imaging of normal nasal cycle: comparison with sinus pathology. J Comput Assist Tomogr 1988; 12:1014-9. Eccles R, Eccles KSJ. Asymmetry in the autonomic nervous system with reference to the nasal cycle. migraine, anisocoria and Meniere's syndrome. Rhinology 1981;19:121-S. Eccles R. The central rhythm of the nasal cycle. Acta Otolaryngol 1978;86:464-8. Eccles R, Lee RL. The inftuence of the hypothalamus on the sympathetic innervation of the nasal vasculature of the cat. Acta Otolaryngol 1981;91:127-34. Eccles R. Elwell 0, Lee RL. Nasal vasoconstriction induced by electrical stimulation of the cat hypothalamus. J Physiol (Lond) 1979;293:48P. Zinreich SJ, Kennedy OW, Malat J, et al. Fungal sinusitis: diagnosis with CT and MR imaging. Radiology 1988;169:439-44. Som PM, Braun IF. Shapiro MD, Reed OL, Curtin HO, Zimmerman RA. Tumors of the parapharyngeal space and upper neck: MR imaging characteristics. Radiology 1987;164:823-9.
DISCUSSION Dr. Kennedy: The indications for computed tomography (CT) in patients with sinusitis should perhaps be made clearer to primary care physicians-not just why a CT scan may be needed, but the appropriate timing of the examination. Will you comment on that, Dr. Zinreich? Dr.Zinrelch: The primary role of the CT examination in sinusitis is to define the anatomy before anticipated surgery in patients, with a firm diagnosis based on nasal endoscopy and an exhaustive history. The role of CT is not only to provide the surgeon a good anatomic "map," but to demonstrate why the patient may have the recurring symptoms-in other words, to show exactly where surgical correction may be effective. For this purpose, there must be as little mucosal inflammation as possible, so adequate medical therapy should precede the CT examination. Mucosal thickening is frequently present in normal, nonsymptomatic patients; therefore, surgery should not be solely based on the CT findings. Dr. Kennedy: Chronic sinusitis is a complicated, multifactorial problem, and what is seen on CT is just one aspect of it. On the other hand, it is possible to have significant, symptomatic ostial obstruction without CT changes. In fact, CT findings always underestimate the amount of disease present; when mucosal thickening is seen on CT, one can be sure it is really there. The question is, is the thickening causing the patient's symptoms? That is the reason we select patients for CT on the basis of nasal endoscopy and an extensive history. Dr, Druce: Can you comment on the use of the lim-
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ited, four-slice CT scan versus the conventional full examination? Dr. Zinrelch: The limited examination may be valuable if one is sure, on the basis of medical or surgical therapy, that the sinusitis is limited to a particular area. For example, if there is disease only in the anterior ethmoid sinus and CT information is needed for further therapy. a limited scan may be all that is needed. Dr.Reilly: Does the standard radiographic series have any practical value? Dr. Zinrelch: When an examination is ordered. one has specific questions in mind. In the acute state. if one is Worried about intracranial or intraorbital extension. as well as wishing to confirm the acute process, standard radiographic films might suffice. However, if confronted with a patient with established chronic sinusitis and surgery is contemplated, the underlying anatomy and the extent of disease will not be optimally displayed on plain films. Dr. Avant: How can the primary care physician identify those of his patients who require endoscopy and/or CT? Dr. Kennedy: If the symptoms are severe, and if symptoms persist despite all the usual medical treatments, and a careful history indicates that the problem is indeed a sinus-related one, it is time for the patient to have an endoscopic examination by an otolaryngologist, and a CT examination if the findings are inconclusive. It is important to remember that many patients ascribe any headache to sinusitis. Things that point to sinusitis, even in the presence of normal radiographic findings, include a history of recurrent infections that tend to get better after therapy with antibiotics or topical decongestants. Dr. Avant: Then you would find it acceptable for a primary care physician to treat two or three episodes of acute sinusitis over a year before sending the patient for additional studies? Dr. Kennedy: Yes, if the symptoms are not remarkable. A patient with severely debilitating headache or
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facial pain associated with unconfirmed sinusitis deserves immediate nasal endoscopy and, if that is not diagnostic, CT. After three or so office visits for presumed recurrent acute sinusitis within a year, I would recommend nasal endoscopy and perhaps a CT examination, regardless of the severity of the symptoms. I would not recommend CT for any patient with sinusitis before endoscopy, however. Dr. Reilly: Would you ever consider CT examination before doing endoscopy, or send a patient with a normal endoscopic examination for CT? Dr. Kennedy: In general, I use nasal endoscopy as a screening test for CT. If a patient has an outstanding history of severe headache or debilitating facial pain, I may want a CT examination in the face of a normal endoscopy. Also, a patient with presumed bacterial sinusitis whose plain radiographs repeatedly show abnormal air-fluid levels merits CT evaluation, even if endoscopy shows normal results. Dr. Zinrelch: I would like to stress that endoscopy may provide all the infermation you want, so it should be used before CT, since the latter involves radiation. Dr. Avant: If both nasal endoscopy and CT show normal findings, does that rule out sinusitis as the cause of a patient's symptoms? Dr. Kennedy: No. A patient with normal sinus mucosa who encounters intermittent ostial obstruction for the first time will report the severest headache he or she has ever encountered. This patient also appears to be at greater risk for an intracranial complication than the patient with thickened sinus mucosa, which is less sensitive to pain. This is not an easy diagnosis to make, and a high index of suspicion is extremely important to it. Dr. Reilly: Sinus endoscopy requires not only trained clinical skills but diligence and dedication to thorough examination. Physicians who lack either adequate training or frequent experience with the techniques should send their patients to physicians who perform endoscopy regularly and well.
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