Neoplastic Fixation to the Prevertebral ... - ResearchGate

Neoplastic Fixation to thePrevertebral Compartment bySquamous Cell Carcinoma of theHead and NeckLaurie A. Loevner1Ingrid L 0111David M. Yousem1’2Kathleen 1. Montone3Erica R. Thaler2Ara A. Chalian2Gregory S. Weinstein2Randal S. Weber2OBJECTIVE. The purpose of this study was to determine the accuracy of MR imaging indetermining fixation of squamous cell carcinomas to the prevertebral space.MATERIALS AND METHODS. MR images of 15 patients with large pharyngeal carcinoma(n = 13) or laryngeal carcinomas with pharyngeal extension (n = 2) were retrospectivelyreviewed independently by two head and neck radiologists who were unaware of the surgicalfindings. MR images were evaluated for four criteria in the prevertebral longus muscle complex:muscle concavity, irregular tumor-muscle interface, T2 hyperintensity, and enhancement. Allpatients underwent panendoscopy where fixation or mobility of the tumor relative to the prevertebralfascia was assessed by manual manipulation. Tumors in six patients were fixed to the prevertebralspace and inoperable. In nine patients whose tumors were not fixed, open neckexplorations were performed and tumors were resected in seven patients. MR findings werecompared with panendoscopy in all patients and with intraoperative assessment in nine patients.RESULTS. Eleven of 15 patients had at least two of the MR imaging criteria present. Noneof the MR findings were both sensitive and specific for tumor fixation. Although muscle concavityand enhancement each had a sensitivity of 88%, both criteria suffered from low specificity(14% and 29%, respectively). An irregular tumor-muscle interface and muscle T2hyperintensity were criteria that suffered from both low sensitivity and specificity. Accuracyof the imaging criteria independently ranged from 53% to 60%.CONCLUSION. Although abnormal muscle contour, T2 hyperintensity, and enhancementare frequently present in neck carcinomas that are fixed to the prevertebral space, thesefindings may also be present in patients in whom the tumor is mobile and resectable. MR imagingmay not be able to differentiate between neoplastic fixation and nonneoplastic changesin the prevertebral space.Received September 9, 1997; accepted after revisionNovember 6, 1997.Supported bythe Radiological Society of North AmericaResearch and Education Fund, Scholar Award Grant1 Department of Radiology, University of PennsylvaniaMedical Center, 3400 Spruce St, Philadelphia, PA 19104.Address correspondence to L A. Loevner.2Department of Otorhinolaryngology, Head and NeckSurgery, University of Pennsylvania Medical Center,Philadelphia, PA 19104.3Department of Pathology, University of PennsylvaniaMedical Center, Philadelphia, PA 19104.AiR 1998;170:1389-13940361-803X/98/1705-1389© American Roentgen Ray SocietyT he treatment of squamous cell carcinomaof the head and neck iscomplex. The need for and type ofsurgery are guided by the site of origin of theprimary tumor and stage of disease at the timeof clinical presentation. Staging is determinedby many factors, including tumor size and origin,submucosal spread into the deep spacesof the neck, cartilage invasion, lymphadenopathy,and distant metastases. Direct visualizationcombined with endoscopy is sensitive inevaluating the mucosa of the aerodigestivetract [1-3]. However, even extensive neoplasticinfiltration of the deep spaces surroundingthe upper aerodigestive tract is often difficultto detect on physical and endoscopic examination.As a result, disease is frequently understagedclinically [4].Radiologic imaging has played an increasinglyimportant role in the staging of headand neck cancer, including the detection ofclinically occult lymphadenopathy, cartilageinvasion, and tumor spread into the submucosalspaces of the neck [5-12]. However, investigationinto the ability of imaging topredict the presence of tumor spread to theprevertebral compartment has been scant.Neoplastic spread directly into the prevertebralspace or fixation of tumor to the prevertebralfascia is significant in that it usuallyrenders the tumor inoperable and often incurable[13]. Presently, neoplastic fixation andextension to the prevertebral space may onlybe determined intraoperatively by manualmanipulation under general anesthesia. Fixedtumors are deemed inoperable and surgery isAJR:170, May 1998 1389

Loevner et ai.aborted. Therefore, it would be extremelyvaluable to be able to reliably determine thepresence or absence of prevertebral fixationby preoperative imaging.The purpose of this study was to determinethe usefulness of MR imaging in detectingneoplastic spread to the prevertebralspace in patients with advanced oropharyngeal,hypopharyngeal, and laryngeal cancer.To do this, MR imaging findings were comparedwith observations during panendoscopyand open neck exploration.Materiais and MethodsThe MR images of 57 patients with primarypharyngeal orlaryngeal cancer seen in a 3-year penod(1993-1996) in the head and neck cancer centerat our institution were retrospectively reviewed.The MR images were evaluated for preservation ofthe prevertebral fat between the tumor and the prevertebralmusculature (longus colli-longus capitiscomplex). The retropharyngeal fat plane is readilyidentified on unenhanced Ti-weighted MR imagesbecause of its hyperintensity relative to surroundingtissues in the neck (muscle and lymphoid tissue)(Fig. 1). This fat plane at the tumor-muscleinterface was obliterated in 20 patients; however,five patients were eliminated from the study becauseno clinical or intraoperative assessment wasavailable. The MR images of the remaining 15 patients(nine men, six women), who had a mean ageof62 years (range, 48-78 years), were selected forinclusion in this study. All patients had squamouscell carcinoma with the site of origin in theoropharynx (n = 8), the hypopharynx (n = 5), andthe larynx with extension to the pharynx (n = 2).All patients underwent panendoscopy under gencmlanesthesia to assess for the presence or absenceof tumor fixation to the prevertebralcompartment. Patients thought to be surgical candidatesduring panendoscopy underwent openneck exploration and surgical resection.All examinations were performed with a Signal.5-T scanner (General Electric Medical Systems,Milwaukee, WI) using an anterior-posterior volumeneck coil (Medical Advances, Madison, WI).The MR imaging protocol consisted of standardspin-echo sagittal Il-weighted images (TRITErange, 600/I 1-17) followed by fat-suppressed axialfast spin-echo T2-weighted (‘FR rangelFE,3500-4000/90) and axial spin-echo TI-weightedimages (600/1 1-17). Images of the neck extendedfrom the level of the cavernous sinus to the thoracicinlet. After the administration of 0.1 mmoi/kg gadopentetate dimeglumine IV (Magnevist;Schering, Berlin, Germany) axial spin-echo TIweightedimaging was repeated using the same parametersas the unenhanced scans. Fast spin-echoand contrast-enhanced studies were obtained withthe application of frequency-selective fat-saturationtechniques. For the saginal Tl-weighted localizingMR images, a slice thickness of 5 mmwith a gap of 1 mm and a 30-cm field of view wereused. For all other sequences, a slice thickness of 5mm with interleaved images was used. Other imagingparameters included one or two excitations,24- to 26-cm field of view, a 256 x 128 matrix forsagittal and contrast-enhanced Tl-weighted images,and a 256 x 192 matrix for axial unenhancedTl- and T2-weighted images.Retrospective image analysis was perfonnedindependently by two head and neck radiologistswho were unaware of the surgical findings. AllMR images were evaluated for the presence or absenceof the following findings in the prevertebrallongus muscle complex: concavity of the prevertebralmuscles, irregular or serrated muscular bordersat the tumor-muscle interface, abnormal T2signal intensity of the muscle, and enhancement ofthe muscle.The MR findings were correlated with findingson panendoscopy, at which time fixation or mobilityof the tumor to the prevertebral musculature was determinedby digital palpation and manipulation ofthe mass. Tumors found to be fixed on panendoscopywere deemed inoperable. Those masses determinedto not be fixed by manual manipulationunderwent open neck exploration. Resection wasaborted in patients in whom the tumor was found tobe fixed to the prevertebral compartment during surgery.In those patients without evidence of fixation,the tumors were resected and compared with findingsof the final histologic examination. Specifically,the margins of the surgical specimens werestudied retrospectively by a head and neck pathologistto ensure that no tumor extended to the borderwith the prevertebral space.The data were analyzed to determine the sensitivity,specificity, accuracy, and positive and negativepredictive values of each criterion. Interobserveragreement regarding image interpretation was basedon kappa analysis.ResultsSurgicalFindingsIn six patients, tumors were fixed to the prevertebralstructures on manual manipulationduring panendoscopy and were considered inoperable.During open neck exploration in theremaining nine patients, two were found tohave tumor fixed to the prevertebral musculatureand surgery was aborted (one of these patientsalso had intraoperative biopsy-provenprevertebral muscle invasion). In the other patientwhose tumor was found to be fixed duringopen neck exploration, a 3-week delayoccurred between panendoscopy and surgery.This patient had a poorly differentiated carcinoma,and it is possible that the developmentoffixation might be explained by rapid intervalgrowth. In the remaining seven patients, extirpationof the tumors was performed, and themacro- and microscopic margins of the surgicalspecimens were free of tumor.MRFindingsFig. 1.-Normal anatomy in 46-year-old man.A, Off midline sagittal Ti-weighted MR image (600/17 hR/TEl; section thickness, 5 mm) shows prevertebral compartmentof perivertebral space demarcated by precervical retropharyngeal fat seen as hyperintense linearband (arrows). Note longus muscle complex (L).B, Axial Ti-weighted MR image (600/17; section thickness, 5 mm) obtained at level of oropharynx shows prevertebralcompartment demarcated by precervical retropharyngeal fat (arrows). Note longus muscle complex (LI,internal carotid artery (asterisk), and jugular vein lv).The MR images of 15 patients each hadfour imaging criteria assessed for a total of 60interpretations. The observers agreed in 57 of60 readings (ic = .88) and resolved the threediscrepant interpretations by consensus. Theindividual criteria for prevertebral fixation (ipsilateralmuscle concavity, irregular muscular1390 AJR:170, May 1998

MR Imaging of Squamous Cell Carcinoma of the Head and Neck‘revertebral Muscle Fixation: Comparison of Criteria Revealed by MRmaging In IS Patients,: ,. Criteria #{149}!SensitivitySpecificityPPV(%) NPV(%) Accuracy88 -14545053lrregularborders-’T2 hyerintensity ]Enha1’nement’ 4P’ ‘!.t ..62 L50 tt 4f-. 88 43432956505850 4367534760Note.-PPV = positive predictive value, NPV = negative predictive value.border at the tumor-muscle interface. muscleT2 hyperintensity, and muscle enhancement)suffered from both low specificity (range, 14-43%) and low accuracy (range. 53-60%) dueto a high false-positive rate (Tables I and 2).Although the presence of muscle concavityand enhancement each showed 88% sensitivityfor prevertebral fixation, high false-positiverates resulted in low specificities (14% and29%, respectively). No correlation existed betweenprevertebral muscle fixation and thepresence or absence of either irregular muscularborders at the tumor-muscle interface orT2 hyperintensity (Figs. 2 and 3). The presenceof enhancement of the muscle was themost likely predictor of tumor fixation (positivepredictive value, 58%) and was the mostaccurate criterion at just 60%. The correlationbetween the number of positive MR criteriaand the presence of fixation was poor. Somepatients with few positive criteria had fixation.Even in the seven patients with all fbur criteriapresent, only three had tumors that had prevertebralfixation on panendoscopy.Although the sample size of patients wastoo small to apply a grading system for eachof the MR criteria, we did note that in patientswith fixation of tumor to the prevertebral compartmentthe degree of T2 hyperintensity andenhancement within the prevertebral musclewas usually more prominent than in those patientswithout fixation.Discussion*Fig. 2.-49-year-old woman with primary carcinoma of oropharynx.A, Sagittal Ti-weighted MR image (600/17 ETA/TEl; section thickness, 5 mm) shows attenuation of right retropharyngealfat plane (arrows).B, Axial Ti-weighted MR image (600/17; section thickness, 5 mm) shows attenuation of right retropharyngeal fatplane (arrows) and mild enlargement of right longus muscle complex; compare with normal left side (LI. Note retropharyngealnodal mass (N).C, Axial T2-weighted MR image (3500/90; section thickness, 5 mm) reveals abnormally high signal intensity in Iongusmuscle complex (arrows).D, Contrast-enhanced axialTi-weighted MR image(600/i7; sectionthickness, 5 mm)shows enhancement of prevertebralmuscle (arrows). On intraoperative panendoscopy, tumor was found to be fixed to prevertebral musculature,making resection impossible.The prevertebral space is the anterior compartmentof the perivertebral space. It is locatedbehind the retropharynx. investedanteriorly by a layer of fat and the deep cervicalfascia. The prevertebral space. encapsulatedby the deep layer of the deep cervicalfascia, contains a fat plane that is located betweenthe two layers of the precervical fascia,the anterior prevertebral muscles (longus capitis,longus colli, rectus capitis anterior. andrectus capitis lateralis), the paraspinal musculature,and the vertebral bodies ( 14, 151 (Fig.I ). The musculus longus colli runs along theventral surface of the vertebral bodies, extendingfrom the atlas to the third or fourth vertebralbody. The musculus longus capitis arisesfrom the base of the occipital bone and cxtendsto the anterior tubercles of the transverseprocesses of the third through sixth vertebrae.The longus colli and capitis muscles are themost vulnerable of the prevertebral muscles tothe spread of disease processes by virtue oftheir proximity and contiguity to the pharyn-AJR:170, May 1998 1391

Loevner et al.Fig. 3-59-year-old woman with cancer of right oropharynx. Prevertebral invasion was suspected on basis of MR findings; however, intraoperatively, mass was not fixedto prevertebral structures and tumor was resected. Final histology revealed no evidence of tumor in surgical margins.A, Axial Ti-weighted MR image (600/17 ETRITEI; section thickness, 5 mm) shows large oropharyngeal mass (M) with obliteration offat between mass and prevertebral muscle.B, Axial contrast-enhanced Ti-weighted MR image (600/il; section thickness, 5 mm) reveals concavity of longus muscle complex (arrowhead) and muscle enhancement(arrows).C. Axial 12-weighted MR image (3500/90; section thickness, 5 mm) shows concavity of prevertebral muscle complex (arrowhead) and abnormal signal intensity (arrow).geal mucosal and retropharyngeal spaces. respectively[15, 16J. Although the deep cervicalfascia is a relatively resilient barrier to the cxtensionof disease processes from the pharyngealmucosal and the deep nonmucosal spacesof the anterior neck, spread of disease includinginfectious and neoplastic processes mayoccur [15-17].Spread of tumor to the prevertebral compartmentin the form of frank neoplastic invasionof the prevertebral musculature mayoccur. However, prevertebral extension mayalso be manifested by fixation of tumor to theprevertebral fascia without violation of thefascia or by tumor penetration through thisfascia but without direct extension into themuscle. In head and neck cancer, any form ofprevertebral extension (including only fixationto the prevertebral fascia) is significant in thatit often renders the tumor inoperable and thepatient incurable because surgeons are unableto obtain tumor-free surgical margins. Theprevertebral musculature is intimately associatedwith and interdigitates with the fascia ofthe prevertebral column. Hence, resection ofthe prevertebral muscle is difficult, dangerous,and unlikely to achieve complete resection ofthe gross tumor. In addition, partial surgicaldebulking of macroscopic tumor is associatedwith a poor clinical and functional outcome,In patients with squamous cell carcinoma ofthe pharynx at risk for prevertebral space invasionwho are otherwise surgical candidates (noencasement of the internal carotid artery andno intracranial perineural extension throughthe skull base foramina), determination of tumorfixation to the prevertebral compartmentis presently made by digital manipulation onpanendoscopy under general anesthesia, If unequivocalfixation of the tumor exists, open cxplorationis often not necessary. Otherwise,open neck exploration is usually performedthrough the side of the neck not involved bythe primary tumor, If both sides ofthe neck appearto be involved by tumor, the side with lessdisease is used for access. The technique involvesretraction of the carotid sheath and itscontents laterally and rotation of the larynxmedially. Then a finger is run superiorly to infenorlyin the plane anterior to the prevertebralmuscle to determine if the tumor is fixed, If thetumor appears adherent to the deep cervicalfascia, but not through it, some head and neckoncology surgeons will resect the fascia withthe tumor. In some cases, a biopsy of regionsof suspicion in the muscle may be performed.and the sample is evaluated by frozen sectionto determine if the muscle has been invaded bytumor [ 1 31. Iftumor extension through the prevertebralfascia to the muscle is found. surgeryis aborted and patients are treated with radiationtherapy or combined radiation and chemotherapy.If fl() direct evidence of tumorextension exists, extirpative surgery is performed.Although the possibility of microinvasioncannot he excluded until the finalhistology is reported. this is of less concern tothe surgeon because most patients are treatedwith radiation therapy after surgery.Imaging plays a critical role in the staging ofhead and neck cancer including detection oflymphadenopathy, cartilage invasion. and tumorspread into the submucosal spaces of theneck [5-I 2. 18-22 . The goal of the head andneck radiologist is not only to help direct theappropriate surgery for a patient with cancer butalso to determine which tumors are surgicallyunresectable. Assessment of the prevertebralspace is vital in this regard; however, little radiologicinvestigation has been done to determineif imaging findings exist that wouldindicate the presence or absence of neopla.sticextension to the prevertebral compartment. In astudy by Righi et al. [ 131. CT scans in 29 patientswith T3 and T4 pharyngeal carcinomaswere retrospectively reviewed by two neuroradiologistsand compared with operative findingsduring open neck exploration. In 1 7 patients,the CT scans were interpreted as negative forneoplastic spread to the prevertebral musclesusing the criterion of preservation of the fatplane between the tumor and the muscle. Intraoperatively.three of these I 7 patients werefound to have prevertebral invasion and surgerywas aborted. Hence, maintenance of the precervicalfat plane correctly predicted absence ofprevertebral involvement 82ck of the time. Thepreoperative CT scans of I 2 patients were interpretedas suggestive of prevertebral invasion onthe basis of the obliteration of the fat plane betweenthe tumor and the prevertebral muscleand asymmetric enlargement of the musclecomplex contiguous with the tumor. Three ofthese patients (25c4 ) had involvement of theprevertebral space on intraoperative assessment.The renlaining nine patients in this groupunderwent resection, and, in three, microscopictulilor along the deep margin of the surgical1392 AJR:ilO, May 1998

MR Imaging of Squamous Cell Carcinoma of the Head and NeckFig. 4-52-year-old man with cancer of right oropharynx (tumor also involves right superior alveolus and retromolartrigone).A, Axial Ti-weighted MR image (600/il ITRITEI; section thickness, 5 mm) shows large oropharyngeal mass (M)compressing prevertebral compartment with concavity of muscle complex and irregular tumor-muscle interface(arrows).B, Axial 12-weighted MR image (3500/85; section thickness, 5 mm) acquired at same axial level as A shows similarfindings along prevertebral compartment. No signal intensity abnormality is seen in longus muscles. Tumor wasfreely mobile during surgery with tumor-free margins on histologic examination of resected specimen.specimen was present on final histology; however,the prevertebral muscle fliscia was intactand uninvolved on direct inspection. Overall,this study suggests that CT suffers from lowsensitivity and low specificity in revealing prevertebralspace invasion.In the present study. MR findings were correlatedwith intraoperative assessment in 15patients with large pharyngeal or laryngeal primarytumors that obliterated the prevertebralfat such that the tumors appeared contiguouswith the prevertebral muscles (Figs. 4 and 5).The study by Righi et al. I 131 suggested thatmaintenance of the precervical fat plane on CTcorrectly predicted absence of macroscopicprevertebral involvement 82% of the time.With the improved soft-tissue resolution ofMR imaging and its multiplanar capabilities.the accuracy in predicting preservation of theprecervical flit could potentially be higher.Nonetheless, the surgeons at our institution believethat preservation of this fat plane on imagingin the absence of other indicators ofinoperability warrants evaluation by panendos-COf))’ or surgical exploration even in the eventthat occasionally a tumor may he found to beunresectable during surgery.In this study. MR images were analyzed forthe presence or absence of ipsilateral muscleconcavity. irregular tumor-muscle interface.abnormal T2 hyperintensity in the muscle. andmuscle enhancement. At least two ofthese imagingfindings were present in I I ofthe 15 patients,and none of’ these findings individually01’ together were consistently reliable in distinguishingthose patients with prevertebral cxtension(eight) from those without (seven)(Tables 1 and 2). Although the sample size ofpatients was too small to apply a grading systemfor each of the MR criteria. we did notethat in patients with fixation of tumor to theprevertebral compartment the degree of T2hyperintensity and enhancement within theprevertebral muscle was usually more prominentthan in those patients without fixation.The presence of muscle enhancement was themost sensitive (88%) and the most accurate(60%) criterion for tumor fixation, but it wasnot an accurate indicator of neoplastic spread.We speculate that a reactive inflammatory infiltrationproduced by the squamous cell carcinomaof the neck may account for the muscleT2 hyperintensity or enhancement. Some basisfor this hypothesis can be found in themusculoskeletal literature 1231. Musculoskeletalneoplasms, tumor invading muscle, andnonneopla.stic muscle edema may be hyperintenseon T2-weighted images due to increasedwater content and may show enhancement aftercontrast material administration [23, 24]. Astudy by Lang et al. 1241, who attempted todistinguish peritumoral edema from tumor,suggested that these entities may be differentiatedby dynamic scanning and spatial mappingof instantaneous enhancement rates.These authors found that viable tumor showedgreater and more rapid increases in T I -weighted signal intensity after contrast materialadministration than perineopla.stic edema,which showed lower and more gradual increasesin signal intensity. The applicability ofMR imaging in the head and neck remains tobe determined.In conclusion, using the current MR techniquesdescribed herein, MR imaging seemsunable to consistently distinguish neoplasticfixation or invasion of the prevertebral musculaturefrom benign reaction. because bothFig. 5-52-year-old man with pharyngealcancer.A, Axial Ti -weighted MR image (600/17 [TR/TEI; section thickness, 5 mm)shows large pharyngeal mass (m)obliterating retropharyngeal fat andmildly compressing prevertebralmuscle complex (arrowheads).B, Axial 12-weighted MR image(3500/85; section thickness, 5 mm)shows increased signal intensity inmuscle (arrows). On panendoscopy,fixation of mass was equivocal. Onopen neck exploration tumor was notfreely mobile, and intraoperative biopsyrevealed tumor invading prever.tebral muscle.AJR:170, May i998 1393

Loevner et al.processes can have similar imaging findings.Abnormal 12 signal intensity or enhancementshould not be taken as an absolute mdicationof fixation or invasion because it maybe seen in patients whose tumors are resectable,as in this study. Currently, determiningfixation or invasion of primary head and neckcarcinomas to the prevertebral compartmentmust be made intraoperatively. The numberof patients in our study was small (n = 15),and a study with a larger sample size isneeded for further evaluation of this observation.Other limitations include an imperfectgold standard for determining prevertebralmuscle invasion-namely, lack of pathologicproof of tumors determined to be fixed onpanendoscopy. The possibility of microscopicinvasion in patients with intact retropharyngeal-precervicalfat planes was alsonot addressed in this study.ReferencesI . Freeman DE, Mancuso AA, Parsons iT, MendenhallWM, Million RR. Irradiation alone for supraglotticlarynx carcinoma: can CT findings predicttreatment results? tnt J Radiat Oncol Biol Pin’s1990;l9:485-4902. Sanghvi V. The new combined surgical approachfor cancer involving the base of tongue-supraglotticcomplex. Lar’ngoscope 1994;l04:725-7303. Loveday EJ, Bleach NR, Van Hasselt CA, MetreweliC. Ultrasound imaging in laryngeal cancer:a preliminary study. Clin Radio! 1994;49:676-6824. Zeitels SM, Vaughn CW. Preepiglottic space invasionin “early” epiglottic cancer. Ann Oto! Rhino!Laryngo! 1991:100:789-7925. Ali YA, Saleh EM, Mancuso AA. Does conventionaltomography still have a place in glotticcancer evaluation? C/in Radio! 1992;45: I 14-I 196. Mafee MF, Schild JA, Valva.ssori GE, Capek V.Computed tomography of the larynx: correlationwith anatomic and pathologic studies in cases of Iaryngealcarcinoma. Radiology 1983;147: 123-1287. Hoover LA, Calcaterra IC, Walter GA, Larrson5G. Pre-operative CT scan evaluation for laryngealcarcinoma: correlation with pathologic findings.Lars’ngoscope 1984;94:3l0-3158. Gregory RT, Lloyd GAS, Michaels L. Computedtomography of the larynx: a clinical and pathologicstudy. Head Neck Surg 1981;3:284-2969. Tien RD, Hesselink JR. Chu PK, Szumowski J.Improved detection and delineation of head andneck lesions with fat-suppression spin-echo MRimaging. AJNR 1991:12:19-2410. van den Brekel MWM, Stel HV, Castelijns JA, etal. Cervical lymph node metastasis: assessment ofradiologic criteria. Radio!ogv 1990:177:379-384I I . Castelijns JA, Gemtsen GJ, Kaiser MC, et al. Invasionof laryngeal cartilage by cancer: comparisonof CT and MR imaging. Radio!ogv 1987:166:199-20612. Yousem DM, Som PM, Hackney DB, SchwaiboldF, Hendrix RA. Central nodal necrosis and extracapsularneoplastic spread in cervical lymphnodes: MR imaging versus CT. Radiology 1992;182:753-75913. Righi PD, Kelley DJ, Ernst R, Ct al. Evaluation ofprevertebral muscle invasion by squamous cellcarcinoma. Arch Oto!arvngo! Head Neck Surg1996:122:660-66314. Madison MT. Remley KB, Latchaw RE, MitchellSL. Radiologic diagnosis and staging of head andneck squamous cell carcinoma. Radio! C!in NorthA,n 1994:32:163-18115. Parker GD. Harnsberger HR. Radiologic evaluationof the normal and disea.sed posterior cervicalspace.AJR1991;157:l6l-l6516. Davis WL, Hamsberger HR. Smoker WR. et al.Retropharyngeal space: evaluation of normalanatomy and diseases with CT and MR imaging.Radiology 1990:174:59-6417. Paonessa DF. Goldstein JC. Anatomy and physiologyof head and neck infections (with emphasison the fascia of the face and neck). Oto!arvngolC!in North Am 1976:9:561-580I 8. Som PM. Lymph nodes of the neck. Radiology1987; 165:593-60019. Dooms GC. Hncak H, Crooks LE. et al. Magneticresonance imaging of the lymph nodes: comparisonwith CT. Radiology 1984:153:719-72420. Muraki AJ, Mancuso AA, Harnsberger HR. Metastaticcervical adenopathy from tumors of unknownorigin: role of CT. Radiology 1984:152:749-75321. Dooms GC. Hricak H. Radiologic imaging modalities.including magnetic resonance, for evaluatinglymph nodes. West J Med 1986:144:49-5722. Becker M, Zbaren P. Laeng H. Stoupis C. PorcelliniB, Vock P. Neoplastic invasion of the laryngealcartilage: comparison of MR imaging andCT with histopathologic correlation. Radiology1995; 194:66 1-66923. Seeger LL, Widoff BE, Bassett LW, Rosen G,Eckardt ii. Preoperative evaluation of osteosarcoma:value of gadopentetate dimeglumine-enhancedMR imaging. AiR 1991:157:347-35124. Lang P. Honda G, Roberts 1, et al. Musculoskeletalneoplasm: perineoplastic edema versus tumoron dynamic postcontrast MR images with spatialmapping of instantaneous enhancement rates. Radio!ogv1995:197:831-8391394 AJR:170, May 1998