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  • Economic Consequences of Diagnostic Imaging for Vocal Cord Paralysis 1

    Amon Y. Liu, MD, David M. Yousern, MD, Ara A. Chalian, MD, Curtis P. Langlotz, MD, PhD

    Rationale and Objectives. The purpose of this retrospective study was to estimate the economic consequences of evaluat- ing suspected vocal cord paralysis with magnetic resonance (MR) imaging and computed tomography (CT).

    Materials and Methods. Reports from MR imaging (n = 30) or CT (n = 19) studies of the neck in 49 patients were retrospectively reviewed for causes of vocal cord paralysis. The patients were divided into high-suspicion (n = 20) and low-suspicion (n = 29) groups, based on the presence or absence of a clinically detectable abnormality other than vocal cord immobility. Clinic and inpatient charts were examined to determine the work-up in all cases. The Medicare Re- source-based Relative Value Scale was u~ed to estimate the costs of most procedures.

    Results. The high-clinical-suspicion group included nine true-positive, four false-positive, seven true-negative, and no false-negative cases. Further work-up was performed in seven true-positive, three false-positive, and one true-negative cases. The total cost of immediate diagnostic work-up in these 20 patients, including MR imaging and/or CT, was $20,737 ($2,304 per true-positive case). The low-suspicion group included two true-positive, nine false-positive, 18 true- negative, and no f~/lse-negative cases. Further work-up was performed in both true-positive, four false-positive, and two true-negative cases. The total cost of immediate diagnostic work-up in these 29 patients was $21,698, (mean, $748; $10,849 per true-positive case).

    Conclusion. The average cost of finding space-occupying lesions in patients with vocal cord paralysis is more than 4.5 times higher in patients without suspicious antecedent clinical findings than in those with such a history. The benefits of obtaining negative findings and of detecting a small number of space-occupying lesions should be weighed against the costs of such examinations and of additional work-up for false-positive findings.

    Key Words. Cost-effectiveness; economics, medical; neck, CT; neck, MR; vocal cords, neoplasms.

    Vocal cord paralysis has numerous causes, including

    trauma, neoplasms, infection, inflammation, and congeni-

    tal or idiopathic conditions. Paralysis can be acute or

    chronic and can be caused by a recurrent laryngeal nerve,

    superior laryngeal nerve, or total vagal nerve deficit. Both

    Acad Radiol 2001; 8:137-148

    1 From the Department of Radiology, Virginia Commonwealth University, Richmond (A.Y.L.); the Department of Radiology, Division of Neuroradiol- ogy, The Johns Hopkins Hospital, 600 N Wolfe St, Houck B-112, Baltimore, MD 21287 (D.M.Y.); and the Departments of Otorhinolaryngology, Head and Neck Surgery (A.A.C.) and Biostatistics and Epidemiology (C.P.L.), Uni- versity of Pennsylvania Medical Center, Philadelphia. Received July 10, 2000; revision requested September 12; revision received Septerpber 25; accepted September 26. Address correspondence to D.M.Y.

    AUR, 2001

    central and peripheral lesions may result in vocal cord

    paralysis. Radiologic imaging is used in the evaluation of

    vocal cord paralysis, primarily to detect an underlying

    malignancy that may have vocal cord paralysis as its only

    manifestation.

    Although surgical trauma has long been recognized as

    the most common cause of unilateral (and bilateral) vocal

    cord paralysis (1,2), authors of other studies have con-

    cluded that malignant neoplasms are a more common

    cause, accounting for up to 40% of cases of unilateral

    vocal cord paralysis (3,4).

    A variety of imaging procedures have been advocated

    in the work-up of vocal cord paralysis, including neck

    ultrasonography, chest computed tomography (CT),

    137

  • esophagography, and chest radiography (5-7). The opti- mal role for CT or magnetic resonance (MR) imaging of the neck, frequently requested in the work-up, is uncer- tain. In this study, we sought to estimate the economic consequences of using neck MR imaging o1" CT in the

    evaluation of patients suspected of having vocal cord pa- ralysis.

    Between January 1992 and October 1997, 96 patients were referred to the ear, nose, and throat (ENT) clinic of the University of Pennsylvania for evaluation of suspected vocal cord paralysis. These patients underwent cross-sec- tional imaging of the neck (MR imaging or CT) at this institution. The decision to perform neck CT or MR im-

    aging was made after vocal cord immobility or hypomo- bility was detected, along with hoarseness at clinical ex- amination. The primary purpose of cross-sectional imag-

    ing was to exclude an underlying mass causing vocal cord paralysis rather than simply to find radiologic evidence of

    vocal cord paralysis. The presence of vocal cord paralysis was confirmed by means of outpatient nasopharyngolaryn- goscopy (NPL).

    Clinical records could be obtained for 49 of the 96 patients. The medical records of the remaining 47 patients could not be retrieved from the hospital film library, med- ical records, or ENT clinic. Many of these patients were referred by physicians outside the home institution. In

    practice patterns analyzed by an otorhinolaryngologist (A.A.C.), however, there were no patient differences noted between outside and inside refen-als.

    The 49 patients who form the basis of this study were examined with MR imaging (n = 30) or CT (n = 19) of the neck (from the skull base to the aortic arch) to deter- rnine the origin of the vocal cord paralysis. The cases of these patients were retrospectively divided into high-sus- picion (n = 20) and low-suspicion (n = 29) groups, based on the presence or absence of a clinically detected abnormality other than vocal cord immobility. These ab- normalities included a known history of head and neck cancer (including thyroid carcinoma) in 10 cases, other cancer in nine cases, and other space-occupying lesions (nodal enlargement) in one case.

    All enhanced CT examinations were performed with either an HSA or a 9800 Quick scanner (GE Medical Systems, Milwaukee, Wis). The patient was placed in the supine position with the neck extended in a modified coronal head holder and was asked to breathe quietly and

    resist swallowing during acquisitions. Axial images were

    obtained with 3-5-mm-thick contiguous sections from the cavernous sinuses to the aortic arch. The field of view was 22 x 22 cm. The total scanning time was 1-1 V2 minutes (HSA scanner) or 5-10 minutes (9800 Quick

    scanner), and the radiation dose was 280 mAs at 140 kV. Iothalamate meglumine (Conray; Mallinkrodt Medical, St Louis, Mo) was intravenously administered by an injector with an automated two-phase program: an initial 100-mL bolus injected at a rate of 2 rnL/sec fbllowed by 50 mL at

    1 mL/sec, for a total dose of 150 mL. Scanning was initi- ated after a 50-second delay.

    The MR images were obtained with a 1.5-T Signa im-

    ager (GE Medical Systems) and included 5-toni-thick contiguous T I-weighted images (500-700/11-17 [repeti- tion time msec/echo time msec]; number of signals aver-

    aged [NSA], 1-2), fat-suppressed fast-spin-echo T2- weighted images (3,000-5,000/80-102; NSA, 1-2), and fat-suppressed gadolinium-enhanced Tl-weighted images (either 600-750/11-30; NSA, 1; or spoiled gradient-echo sequences, 35/I.8-2.3: NSA, I, 30o-40 flip angle). Ga-

    dopentetate dimeglumine (Magnevist: Berlex, Fairfield, NJ) was injected at standard doses and rates (0.1 mmol/kg over 20 seconds).

    MR and CT imaging were performed from the skull base to the level of the aortic arch to cover the course of the vagus and recurrent laryngeal nerves bilaterally. When the upper mediastinum was not visualized on the initial images, the patient was asked to return for additional im- aging.

    All of the MR and CT studies were interpreted by board-certified neuroradiologists, and the radiology re- ports were retrospectively reviewed in all cases for signs of vocal cord impairment, including adduction or medial

    deviation of the vocal cord and aryepiglottic fold, rotation of the arytenoid cartilage, atrophy of the true vocal cord, or enlargement of the piriforna sinus, vallecula, or laryn- geal ventricle. Reports were further reviewed for the pres- ence of masses (medullary, skull base, carotid sheath, thyroid, esophageal, mediastinal, or laryngeal/tracheal) that may cause vocal cord paralysis. Clinic and inpatient charts were examined to deternfine the extent and nature of additional work-up after MR imaging o1" CT, as well as the clinical outcome (eg, results of direct laryngoscopy or biopsies).

    The cases were classified into four categories for both the high- and low-suspicion groups: true-positive, false- positive, true-negative, and false-negative. The classifica- tion was based on the presence of radiologic abnornlali-

    138

  • Table 1 Characteristics of Cases in High-Clinical-Suspicion Group

    Radiologic Evidence of Outcome of Patient Reason for High Suspicion Imaging Vocal Cord Paralysis Further Work-up Work-up

    1 Laryngeal carcinoma MR Yes Yes 2 Sarcoidosis MR Yes Yes 3 Supraclavicular spindle cell carcinoma MR Yes Yes 4 Neck squamous cell carcinoma MR No" Yes 5 Head and neck carcinoma MR Yes Yes 6 Thyroid carcinoma CT Yes Yes 7 Head and neck carcinoma MR Yes Yes 8 Laryngeal carcinoma MR No* Yes 9 Head and neck carcinoma CT Yes Yes

    10 Salivary gland cancer; brain stem astrocytoma MR Yes Yes 11 Breast carcinoma CT No Yes 12 Breast carcinoma CT Yes No 13 Hodgkin lymphoma MR Yes No 14 Lymphoma MR No No 15 Renal cell carcinoma CT No No 16 Thyroid ca