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Acs0204 Head And Neck Diagnostic Procedures


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Acs0204 Head And Neck Diagnostic Procedures

  1. 1. © 2004 WebMD, Inc. All rights reserved. ACS Surgery: Principles and Practice 2 HEAD AND NECK 4 HEAD AND NECK DIAGNOSTIC PROCEDURES — 1 4 HEAD AND NECK DIAGNOSTIC PROCEDURES Adam S. Jacobson, M.D., Mark L. Urken, M.D., F.A.C.S., and Marita S.Teng, M.D. Head and neck surgery deals with a wide range of pathologic con- esophagus. The pharynx is subdivided into the nasopharynx, the ditions affecting the upper aerodigestive tract and the endocrine oropharynx, and the hypopharynx. organs of the head and neck. As in other areas of the body, the causes of these conditions can be inflammatory, infectious, con- Nasopharynx genital, neoplastic, or traumatic. This chapter discusses the diag- The nasopharynx extends from the posterior choanae to the nostic approach to head and neck disorders, with particular inferior surface of the soft palate. Malignancies of the nasophar- attention to cancer. ynx can present as nasal obstruction, epistaxis, tinnitus, headache, diminished hearing, and facial pain. Anatomic Considerations Oropharynx The head and neck can be conceptualized by dividing it into The oropharynx extends from the junction of the hard and soft the following segments: (1) nasal cavity and paranasal sinuses, (2) palates and the circumvallate papillae to the valleculae. It includes the oral cavity, (3) pharynx, (4) larynx, (5) salivary glands, and (6) soft palate and uvula, the base of the tongue, the pharyngoepiglottic thyroid [see Figure 1]. and glossoepiglottic folds, the palatine arch (which includes the ton- sils and the tonsillar fossae and pillars), the valleculae, and the later- NASAL CAVITY AND PARANASAL SINUSES al and posterior oropharyngeal walls. Carcinomas of the oropharynx The nasal vault and paranasal sinuses are a complex labyrinth can present as pain, sore throat, dysphagia, and referred otalgia. of interconnected cavities. These cavities are lined with mucous membranes and are normally well aerated. The nasal vault itself Hypopharynx is divided into two equal halves by the nasal septum. There are The hypopharynx extends from the superior border of the three paired turbinates in the nasal cavity, which further subdi- hyoid bone to the inferior border of the cricoid cartilage. It includes vide the nasal vault from cephalad to caudal, creating the superi- the pyriform sinuses, the hypopharyngeal walls, and the post- or, middle, and inferior meatuses. cricoid region (i.e., the area of the pharyngoesophageal junction). The ethmoid sinus is the most complicated of the paranasal Malignancies of the hypopharynx can present as odynophagia, sinuses; it is also known as the ethmoid labyrinth [see Figure 2]. dysphagia, hoarseness, referred otalgia, and excessive salivation. The maxillary sinus lies within the body of the maxilla and is the LARYNX largest of the paranasal sinuses. The frontal sinus lies within the frontal bone and is divided into two asymmetrical halves by an The larynx is subdivided into the supraglottis, the glottis, and intersinus septum. The sphenoid sinus lies posterior to the nasal the subglottis [see Figure 3]. It consists of a framework of carti- cavity and superior to the nasopharynx. It too is an asymmetri- lages that are held together by extrinsic and intrinsic musculature cally paired structure that is divided by an intersinus septum.The and lined with a mucous membrane that is topographically sphenoid sinus remains the most dangerous sinus to manipulate arranged into two characteristic folds (the false and true vocal surgically because of the surrounding vital structures (i.e., the cords). Neoplasms of the larynx can present as hoarseness, dysp- carotid artery, the optic nerve, the trigeminal nerve, and the vid- nea, stridor, hemoptysis, odynophagia, dysphagia, and otalgia. ian nerve). Tumors within the nasal vault or the paranasal sinuses present Supraglottis as nasal airway obstruction, epistaxis, pain, and nasal discharge. The supraglottis extends from the tip of the epiglottis to the They can originate in any of the paranasal sinuses or the nasal junction between respiratory and squamous epithelium on the cavity proper and often remain silent or are mistakenly treated as floor of the ventricle (the space between the false and true cords). an infectious or inflammatory condition, with a consequent delay Carcinomas of the supraglottis can present as sore throat, in the diagnosis. odynophagia, dysphagia, and otalgia. ORAL CAVITY Glottis Anatomically, the oral cavity extends from the vermilion bor- The space between the free margin of the true vocal cords is der to the junction of the hard and soft palates and the circum- the glottis.This structure is bounded by the anterior commissure, vallate papillae. It includes the lips, the buccal mucosa, the upper the true vocal cords, and the posterior commissure. The most and lower alveolar ridges, the retromolar trigones, the oral tongue common symptom of carcinoma of the glottis is hoarseness. (anterior to circumvallate papillae), the hard palate, and the floor of the mouth. Subglottis The subglottis extends from the junction of squamous and res- PHARYNX piratory epithelium on the undersurface of the true vocal cords The pharynx is a tubular structure extending from the base of (approximately 5 to 10 mm below the true vocal cords) to the the skull to the esophageal inlet. Superiorly, it opens into the nasal inferior edge of the cricoid cartilage. The most common symp- and oral cavities; inferiorly, it opens into the larynx and the tom of carcinoma of the subglottis is hoarseness. 1
  2. 2. © 2004 WebMD, Inc. All rights reserved. ACS Surgery: Principles and Practice 2 HEAD AND NECK 4 HEAD AND NECK DIAGNOSTIC PROCEDURES — 2 Sphenoidal Sinus Superior Sagittal Sinus Concha Suprema Frontal Sinus Superior Concha Falx Cerebri Middle Concha Pharyngeal Orifice of Auditory Tube Inferior Concha Straight Sinus Oral Part of Tongue Sublingual Fold Pharyngeal Recess Pharyngeal Part of Tongue Salpingopharyngeal Fold Epiglottis Palatine Tonsil Hyoid Bone Oral Part of Pharynx Laryngeal Part of Pharynx Vocal Fold Thyroid Cartilage Figure 1 The anatomic structures of Esophagus the head and neck are shown. SALIVARY GLANDS Clinical Evaluation Salivary glands are subdivided into major and minor salivary The diagnostic approach to the upper aerodigestive tract begins glands.The major salivary glands consist of the parotid glands, the with a thorough history, starting with a detailed evaluation of the submandibular glands, and the sublingual glands. The minor sali- chief complaint. Once the chief complaint has been defined (e.g., vary glands are dispersed throughout the submucosa of the upper neck mass, hoarseness, hemoptysis, or nasal obstruction), it must be aerodigestive tract. Classically, benign neoplasms present as pain- further characterized. The physician must determine how long the less, slow-growing masses. A sudden increase in size is usually the problem has been present and whether the patient has any associ- result of infection, cystic degeneration, hemorrhage into the mass, ated symptoms (e.g., pain, paresthesias, discharge, change in voice, or malignant transformation. Malignant neoplasms also usually dyspnea, hemoptysis). In addition, it is important to ask about re- present as a painless swelling or mass. However, certain features cent infection (e.g., of the ear, mouth, teeth, or lungs) and previous are strongly suspicious for a malignancy, such as overlying skin medical treatment. Once a complete history of the chief complaint involvement, fixation of the mass to the underlying structures, has been obtained, the physician should elicit a more comprehen- pain, facial nerve paralysis, ipsilateral weakness or numbness of the sive general medical history from the patient, including pertinent tongue, and cervical lymphadenopathy. past medical history, past surgical history, medications, allergies, social history (tobacco, ethanol, I.V. drug use), and family history. THYROID After completion of the history, the next step is to perform a The thyroid gland performs a vital role in regulating metabol- comprehensive physical examination. This begins with a thor- ic function. It is susceptible to benign conditions (e.g., nodule, ough inspection of the entire surface of the head and neck, with goiter, and cyst), inflammatory disease (e.g., thyroiditis), and malig- a focus on gross lesions, areas that are topographically abnor- nancies. Additionally, congenital anomalies of the thyroid, such mal, and old scars from previous injuries or procedures. The as a thyroglossal duct cyst, can present later in life.Thyroid lesions examination should proceed in an orderly fashion from superi- can present as pain, hoarseness, dyspnea, or dysphagia. or to inferior. Next, the inspection focuses on the mucosal sur- On the posterior aspect of the thyroid gland reside the four faces of the upper aerodigestive tract. parathyroid glands. These glands play a vital role in maintaining Although an accurate history and careful physical examination of calcium balance. Parathyroid adenomas and, rarely, carcinomas the head, neck, and mucosal surfaces are the most important steps can develop. in evaluating a lesion in this part of the body, this clinical evaluation
  3. 3. © 2004 WebMD, Inc. All rights reserved. ACS Surgery: Principles and Practice 2 HEAD AND NECK 4 HEAD AND NECK DIAGNOSTIC PROCEDURES — 3 Frontal Sinus Ethmoid Sinuses Turbinate Ostium Bones Maxillary Sinus Nasal Airway Figure 2 The paranasal sinuses are shown. usually provides only a working diagnosis.The head and neck sur- 60º, and 90º), which allow for visualization of structures that are in- geon must then proceed in a stepwise fashion to further clarify the accessible by simple anterior rhinoscopy. Rigid nasal endoscopy is diagnosis and, in the case of neoplasm, to perform an accurate staging. especially useful for visualizing deeper structures and structures that Radiographic techniques allow the head and neck surgeon to vi- are not in a straight axis from the nasal aperture. sualize the mass and determine its characteristics (i.e., to differenti- ate between solid and cystic lesions), as well as determine its anatomic associations. Ultrasonography, magnetic resonance imag- Indirect Laryngoscopy ing, and computed tomography each provides a unique view of the Indirect laryngoscopy has been used since the 1800s for visualiz- pathology in question and thereby helps narrow the differential di- ing the pharynx and larynx. In this technique, the head light source agnosis. Acquisition of a tissue specimen for cytologic or histologic illuminates the mirror, which in turn illuminates the laryngophar- analysis, or both, is the next step. Fine-needle aspiration (FNA) is ynx [see Figure 5].The patient is seated in the sniffing position and often utilized at this stage in the workup, provided that the location protrudes the tongue while a warmed laryngeal mirror is intro- of the mass lends itself to a safe procedure. If the lesion is located duced firmly against the soft palate in the midline to elevate the deep in the neck near vital structures, image-guided FNA can be at- uvula out of the field (gently, so as not to elicit the gag reflex).The tempted before resorting to an open biopsy. If the lesion is on a mu- image seen on the mirror can be used to assess vocal cord mobility, cosal surface of the upper aerodigestive tract, an endoscopic biopsy as well as to inspect for a mass or foreign body of the larynx or phar- is performed. Often, a panendoscopic procedure is performed at ynx.This technique can be performed rapidly and is inexpensive. this point to accurately map the lesion, obtain a tissue specimen, and, in patients with cancer, assess the rest of the upper aerodiges- tive tract for a synchronous primary tumor. Endoscopic Procedures After a histologic diagnosis has been made and correlated with Endoscopic evaluation of the upper aerodigestive tract is cru- the imaging information, the patient and physician can have a com- cial in establishing a definitive diagnosis. The equipment used prehensive discussion of the pathology, the stage of the disease, and consists of both rigid and flexible laryngoscopes, bronchoscopes, the selection of therapy. and esophagoscopes. Many of these techniques can be performed in the office setting, providing the surgeon with an array of meth- ods for gaining the information necessary for a working diagnosis Nasal Diagnostic Procedures and, in some cases, for performing a therapeutic intervention. Operative endoscopy is performed to obtain a definitive diagno- ANTERIOR RHINOSCOPY sis, to stage tumors, and to rule out synchronous lesions.There is Using a variety of different light sources that provide both illu- no substitute for thorough examination and biopsy of a lesion mination and coaxial vision, the head and neck surgeon can view with the patient under general anesthesia. Regardless of the endo- the nasal vault through a nasal speculum [see Figure 4].This tech- scopic method used, an adequate biopsy specimen must be nique is performed both before and after nasal decongestion, with obtained for a histologic diagnosis. particular attention to mucosal color, edema, and discharge and FLEXIBLE RHINOLARYNGOSCOPY the effect of vasoconstriction. Limited visualization of the nasal septum, the turbinates, and the vault is also possible with this Flexible rhinolaryngoscopy is currently one of the most com- technique. monly used techniques for visualizing the nasal cavity, the sinus- es, the pharynx, and the larynx. The technique utilizes a small- RIGID NASAL ENDOSCOPY caliber flexible endoscope and can be performed in an office set- The rigid nasal endoscope comes with a variety of lens angles (0º, ting [see Figure 6]. Before the procedure, the patient’s nasal cavity
  4. 4. © 2004 WebMD, Inc. All rights reserved. ACS Surgery: Principles and Practice 2 HEAD AND NECK 4 HEAD AND NECK DIAGNOSTIC PROCEDURES — 4 Epiglottis ESOPHAGOSCOPY Esophagoscopy plays an important role in the evaluation of Vestibule of patients with dysphagia, odynophagia, caustic ingestion, trauma, Hyoid the Larynx ingested foreign bodies, suspected anomalies, and upper aerodi- Bone gestive tract malignancies. This procedure may be performed with either a flexible or a rigid scope. Vestibular Flexible Esophagoscopy Fold The primary application for flexible esophagoscopy is diagno- sis. The procedure is particularly useful in elderly patients with limited spinal mobility and in patients with short, thick necks. The flexible esophagoscope is used with local anesthesia and Vocal sedation in a monitored setting.To facilitate control of secretions Fold and the passage of the instrument, the patient is placed in a flexed Thyroid position and lying on one side. Using insufflation, the surgeon Cartilage visualizes and enters the cricopharyngeus and carries out a safe Vocal Muscle and detailed visual study of the esophagus. If a malignancy is sus- pected, either a brush specimen is sent for cytology or a cup for- ceps is used to acquire a specimen for histologic analysis. Infraglottic Rigid Esophagoscopy Cricoid Cartilage Space Rigid esophagoscopy can be used to treat a variety of problems, including foreign bodies, hemorrhage (e.g., from esophageal varices), and endobronchial tumors. Rigid esophagoscopes [see Fig- ure 8] are used with the patient under general anesthesia.The pa- Trachea tient is placed in the supine position with the neck extended. The esophagoscope is then passed along the right side of the tongue, with the endoscopist using the left hand to cradle the instrument. The right hand is used for stabilization of the proximal end of the Figure 3 Cross-sectional anatomy of the larynx is shown. scope, suctioning, and insertion of instruments through the lumen of the esophagoscope. The lip of the esophagoscope is positioned anteriorly for manipulation of the epiglottis and visualization of the is decongested and anesthetized for maximum visualization and pyriform sinus and the arytenoids.The scope is then passed along minimal discomfort. In the procedure, the examiner threads the the pyriform sinus into the cricopharyngeus (i.e., the superior end of the scope into the nasal aperture along the floor of the esophageal valve). The left thumb is then used to advance the in- nasal cavity. As the scope is advanced, the examiner can visualize strument down the esophagus. If no major lesions are noted on in- the nasal cavity proper for any evidence of lesions or masses. sertion of the esophagoscope, a careful inspection of the mucosa Once the scope approaches the nasopharynx, it is directed inferi- should be made during withdrawal of the instrument. orly and advanced slowly, allowing direct visualization of the entire pharynx and larynx. DIRECT LARYNGOSCOPY Direct laryngoscopy has the advantage of permitting both diag- nostic and therapeutic intervention [see Figure 7]. It is performed with the patient under general anesthesia and intubated.The pro- cedure allows for direct visualization of the pharynx and the larynx and permits the surgeon to perform biopsies and remove small le- sions. At the same time, the surgeon has the opportunity to palpate the structures of the oral cavity, the oropharynx, and the hypo- pharynx, which cannot be properly palpated in an awake patient. The laryngoscope can also be suspended from a table-mount- ed Mayo stand (for hands-free use), and a microscope can be maneuvered into focal distance to allow magnified visualization of the glottis and subglottis. During a microscopic direct laryn- goscopy, small lesions or topographic abnormalities can be better characterized and removed if desired. Some examples of lesions that can be diagnosed by direct laryngoscopy are vocal cord polyps, leukoplakia, intubation granulomas, contact ulcers, webs, nodules, hematomas, and papillomatosis. Additionally, small malignant lesions of the vocal cords can be examined and ablat- ed or extirpated by using a CO2 laser under direct microlaryngo- scopic guidance. Figure 4 Shown is an assortment of nasal specula.
  5. 5. © 2004 WebMD, Inc. All rights reserved. ACS Surgery: Principles and Practice 2 HEAD AND NECK 4 HEAD AND NECK DIAGNOSTIC PROCEDURES — 5 Figure 5 Shown is a laryngeal mirror. Such an instrument is used for indirect laryngoscopy. BRONCHOSCOPY visualized, the instrument is threaded anteriorly to allow visualiza- Bronchoscopy provides clinically useful information by direct tion of the glottis. The bronchoscope is then passed between the inspection of the tracheobronchial tree. Like esophagoscopes, vocal cords and into the trachea. At this point, ventilation may be bronchoscopes come in both flexible and rigid forms. The flexi- resumed either by positive pressure or by jet ventilation techniques ble bronchoscope is used primarily for diagnosis.The value of the (ventilating bronchoscopes have a side port for attachment of the rigid bronchoscope lies in its therapeutic applications, which tubing from the ventilator).The patient’s head is manipulated with include foreign-body removal, removal of bulky tumors, intro- the endoscopist’s right hand so as to direct the tip of the broncho- duction of radioactive materials, and placement of stents. scope and permit bilateral exploration of the major airways. Flexible Bronchoscopy PANENDOSCOPY The flexible fiberoptic bronchoscope is usually used with local The term panendoscopy refers to the combination of direct anesthesia and sedation in a monitored setting (e.g., an operating laryngoscopy (with or without microscopic assistance), esopha- suite). After local anesthesia and decongestion of the nasal vault goscopy, and bronchoscopy. Together, these three procedures with topical tetracaine and 1% phenylephrine, the flexible scope is provide a complete examination of the entire upper aerodigestive gently passed along the nasal floor into the nasopharynx, where tract. In cancer patients, this combination of procedures allows the tip of the scope is angled inferiorly to permit visualization of the examiner to create a detailed map of the tumor, as well as to the pharynx.The instrument is then advanced slowly into the glot- rule out synchronous primary tumors. tis (between the true vocal folds) and into the tracheobronchial tree. After a visual inspection of the airway has been completed, a Biopsy Procedures specimen can be retrieved by means of brush biopsy, broncho- alveolar lavage, or a biopsy forceps. FINE-NEEDLE ASPIRATION Rigid Bronchoscopy FNA is often used to make an initial tissue diagnosis of a neck Rigid bronchoscopy [see Figure 9] is performed with the patient mass. The advantages of this technique include high sensitivity under general anesthesia. The patient is placed in the supine posi- and specificity; however, 5% to 17% of FNAs are nondiagnostic. tion with the neck hyperextended. The bronchoscope is then Another advantage of FNA is speed: If a cytologist or a patholo- passed along the right side of the tongue, with the endoscopist gist is available, diagnosis can often be made within minutes of using the left hand to cradle the instrument.The instrument is ini- the biopsy. tially held almost vertically until it reaches the posterior pharyngeal FNA is performed with a 10 ml syringe with an attached 21- wall, at which point it is slowly guided into a more horizontal posi- to 25-gauge needle. Larger needles are more likely to result in tion.While advancing the scope, the endoscopist cradles the instru- tumor seeding.The patient is positioned to allow for optimal pal- ment with the fingers of the left hand, providing guidance and pro- pation of the mass. The skin overlying the mass is prepared with tecting the patient’s lips and teeth. Once the tip of the epiglottis is a sterile alcohol prep sponge. Local anesthesia is not necessary. The mass is grasped and held in a fixed and stable position. The needle is introduced just under the skin surface. As the needle is advanced, the plunger of the syringe is pulled back, to create suc- tion. Once the mass is entered, multiple passes are made without exiting the skin surface; this maneuver is critical in maximizing specimen yield. After the final pass is completed, the suction on the syringe is released and the needle withdrawn from the skin. If a cyst is encountered, it should be completely evacuated and the fluid sent for cytologic analysis. A drop of aspirated fluid is placed on a glass slide. A smear is made by laying another glass slide on top of the drop of fluid and pulling the slides apart to spread the fluid. Fixative spray is then applied. Alternatively, wet smears are placed in 95% ethyl alcohol and treated with the Papanicolaou technique and stains. FNA has several advantages over excisional biopsy. An FNA requires only an office visit, with minimal loss of time from work for the patient. In contrast, excisional biopsy is commonly per- formed in an operating room, so the patient must undergo pre- operative testing. Patients with a significant medical history may require formal medical clearance. An excisional biopsy exposes Figure 6 A small-caliber flexible laryngoscope is used for rhino- the patient to the risks of anesthesia, postoperative wound infec- laryngoscopy. tion, and tumor seeding.
  6. 6. © 2004 WebMD, Inc. All rights reserved. ACS Surgery: Principles and Practice 2 HEAD AND NECK 4 HEAD AND NECK DIAGNOSTIC PROCEDURES — 6 a b Figure 7 Shown are (a) normal vocal folds directly visualized via (b) a rigid laryngoscope. ULTRASOUND-GUIDED FNA neck. Palpable masses in the neck [see 2:3 Neck Mass] can be Ultrasonographic guidance of FNA enables the surgeon to ob- assessed for changes in size, for association with other local struc- tain a cytologic specimen of deeper or nonpalpable masses that are tures, and for character (i.e., solid, cystic, or complex). Applica- not amenable to standard FNA. Real-time imaging of the needle’s tions of ultrasonography include assessment of masses such as passage allows the surgeon to plot a more accurate trajectory and thyroglossal duct cysts, branchial cleft cysts, cystic hygromas, sali- avoid underlying vital structures. Furthermore, it provides an image vary gland tumors, abscesses, carotid body tumors, vascular of the mass, allowing its characterization as solid, cystic, or hetero- tumors, and thyroid masses. Additionally, ultrasonography com- geneous.With cystic or complex masses, it is imperative to place the bined with FNA and cytologic evaluation can provide both a tip of the needle into the wall to increase specimen yield. detailed visual description and an accurate cytologic evaluation of masses in the neck [see Ultrasound-Guided FNA, above]. CT-GUIDED FNA COMPUTED TOMOGRAPHY CT -guided FNA is most commonly employed to diagnose poor- ly accessible or deep-seated lesions of the head and neck. Like ultra- A CT scan with intravenous contrast is often the first-line sound-guided FNA, CT-guided FNA provides visualization of the imaging technique used to evaluate a mass of the neck and to as- needle as it is passed through the tissue and into the underlying sess for pathologic adenopathy. CT has proved to be an effective structures, thus allowing a more accurate needle trajectory and method for primary staging of tumors and lymph nodes. Addition- avoidance of underlying vital structures. Additionally, visual guid- ally, it has been shown to be effective in studying capsular pene- ance of the needle greatly increases the likelihood of obtaining a tration and extranodal extension. It is clearly superior to MRI in specimen from the mass rather than the surrounding tissues. evaluating bone cortex erosion, given that MRI cannot assess bone cortex status at all. CT scans are also widely used for post- treatment surveillance in cancer patients. Imaging Procedures MAGNETIC RESONANCE IMAGING Because many of the deep structures of the head and neck are inaccessible to either direct evaluation by palpation or indirect MRI avoids exposing the patient to radiation and provides the evaluation via endoscopy, further information must be obtained investigator with superior definition of soft tissue. For example, by radiography. Imaging procedures such as CT, MRI, ultra- MRI can differentiate mucous membrane from tumor, as well as sound, and positron emission tomography (PET) scanning per- detect neoplastic invasion of bone marrow. In patients with nasal mit the diagnosis and analysis of pathologic conditions affecting cavity tumors, MRI can distinguish between neoplastic, inflam- these deep structures, including the temporal bone, skull base, matory, and obstructive processes. MRI is also valuable in assess- paranasal sinuses, soft tissues of the neck, and larynx. ing the superior extent of metastatic cervical lymphadenopathy (i.e., intracranial extension). A disadvantage of MRI is its limited ULTRASONOGRAPHY ability to show bone detail; it therefore cannot detect invasion of Ultrasonography is a safe and inexpensive method of gaining bone cortex by a neoplasm. Furthermore, an MRI scan is signif- high-resolution real-time images of the structures of the head and icantly more expensive than a CT scan. Figure 8 Shown is a rigid endoscope.
  7. 7. © 2004 WebMD, Inc. All rights reserved. ACS Surgery: Principles and Practice 2 HEAD AND NECK 4 HEAD AND NECK DIAGNOSTIC PROCEDURES — 7 a b Figure 9 (a) Rigid bronchoscopes incorporate stainless-steel tubes of varying length and diameter. The beveled distal end of this Hopkins bronchoscope facilitates mobilization of the epiglottis during intubation; the side ports permit ventilation and use of suction catheters. (b) Illumination is provided by fiberoptic rods that are inserted into the bronchoscope. POSITRON EMISSION TOMOGRAPHY False negative scans occur when tumor deposits are very small PET scanning is a functional imaging technique that measures (i.e., 3 to 4 mm or less in diameter). Thus, micrometastases are tissue metabolic activity through the use of radioisotopically not reliably detected using an FDG-PET image. Furthermore, a tagged cellular building blocks, such as glucose precursors. A false negative scan can occur if the PET scan is performed too range of physiologic tracers has been developed for PET imag- soon after radiation therapy. ing, with the glucose analogue 2-deoxy-2-[(18)F]fluoro-D-glu- The role of PET imaging in head and neck oncology is rapid- cose (FDG) the most commonly used. FDG has a half-life of 110 ly expanding. Currently, the majority of PET imaging used in minutes. Once given to the patient, FDG is taken up by glucose head and neck oncology is FDG based. FDG-PET is actively transporters and is phosphorylated by hexokinase to become being used to look for unknown primary lesions and second pri- FDG-6-phosphate (FDG-6-P). Further metabolism of FDG-6- maries, to stage disease before therapy, to detect residual or P is blocked by the presence of an extra hydroxyl moiety, which recurrent disease after surgery or radiation therapy, to assess the allows FDG-6-P to accumulate in the cell and serve as a marker response to organ preservation therapy, and to detect distant for glucose metabolism and utilization. metastases. Because false positive and false negative PET scans Because neoplastic cells have higher rates of glycolysis, localized do occur, accurate interpretation of PET scans requires a thor- areas of increased cellular activity on PET scans may represent neo- ough understanding of the potential confounding factors. plastic tissue. In this respect, PET is very different from CT and MRI, PET/CT which depict tissue structure rather than tissue metabolic activity. Because FDG is nonspecifically accumulated in glycolytically PET/CT is essentially an FDG-PET scan that has been coreg- active cells, it demarcates areas of inflammation as well as neo- istered with a simultaneous CT scan to allow the radiologist to plastic tissue, which can lead to a false positive scan. Muscular precisely correlate the area of increased cellular activity with the activity during the scan can also lead to areas of increased uptake anatomic structure. This technique removes some of the guess- in nonneoplastic tissue. Furthermore, healing bone, foreign body work involved with interpreting an area of increased activity on a granulomas, and paranasal sinus inflammation can produce false simple PET scan and provides the physician with a morphologic positive results. correlate for the area of increased uptake. Recommended Reading AJCC Cancer Staging Manual, 5th ed. Lippincott Cummings C: Otolaryngology Head and Neck Cancer Institute, National Institutes of Health, 2004. Raven, Philadelphia, 1997 Surgery, 3rd ed. Mosby – Year Book St. Louis, 1998 Bailey B: Head and Neck Surgery – Otolaryngology, Som P: Head and Neck Imaging, 4th ed. Mosby, St. Acknowledgments 3rd ed. Lippincott Williams & Wilkins, Philadelphia, Louis, 2003 Figure 1 Tom Moore. 2001 Surveillance Epidemiology and End Results. National Figures 2 and 3 Alice Y. Chen.