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Traumatic Neuroma and Recurrent Lymphadenopathy after Neck Dissection: Comparison of Radiologic Features¹

¹ From the Departments of Radiology (H.Y., T.K.), Head and Neck Surgery (K.T.), and Pathology (Y.H.), National Kyushu Cancer Center, Fukuoka, Japan; and Department of Radiology, National Oita Hospital, Oita, Japan (T.F.). From the 2002 RSNA scientific assembly. Received May 23, 2003; revision requested August 4; final revision received December 7; accepted February 16, 2004. Address correspondence to H.Y., Department of Radiology, Kyushu University, 3-1-1 Maidashi, Higashi-ku, Fukuoka 812-8582, Japan (e-mail: yabuuchi@radiol.med.kyushuu.ac.jp).

	ABSTRACT

TOP ABSTRACT INTRODUCTION MATERIALS AND METHODS RESULTS DISCUSSION REFERENCES

 
PURPOSE: To retrospectively evaluate the ultrasonographic (US), computed tomographic (CT), and magnetic resonance (MR) imaging features that differentiate traumatic neuroma from recurrent lymphadenopathy after neck dissection.

MATERIALS AND METHODS: Imaging findings of 10 patients with a traumatic neuroma and 17 with recurrent lymphadenopathy were reviewed. US and CT were performed in all patients; MR imaging was performed in 16 patients. Findings analyzed at US included the diameter of the long and short axes, the short-axis–to–long-axis ratio, and the presence of a central hyperechoic area. Findings analyzed at CT were contiguity with common or internal carotid artery, lesion location in correlation with carotid artery, and the presence of a hyperattenuating rim. Findings analyzed at MR imaging included signal intensity on T1- and T2-weighted images, the presence of ring enhancement, and the presence of a hypointense rim on T2-weighted images.

RESULTS: Statistically significant differences were found between traumatic neuroma and recurrent lymphadenopathy in the short-axis–to–long-axis ratio (mean, 0.47 vs 0.72; P < .001), the short-axis diameter (mean, 5.7 vs 12.2 mm; P < .001), the presence of a central hyperechoic area (five of 10 patients [50%] vs one of 17 patients [6%]; P < .05), the frequency of contact with carotid artery (two of 10 patients [20%] vs 13 of 17 patients [76%]; P < .01), and the presence of a hypointense rim on T2-weighted MR images (three of six patients [50%] vs zero of 10 patients [0%]; P < .05). Findings in other parameters were not statistically significant.

CONCLUSION: Several imaging findings can differentiate traumatic neuroma from recurrent lymphadenopathy after neck dissection.

© RSNA, 2004

Index terms: Head and neck neoplasms, CT, 276.1211, 997.129 • Head and neck neoplasms, MR, 276.121411, 276.12143, 997.12941, 997.12972 • Head and neck neoplasms, US, 276.1298, 997.1298 • Lymphatic system, diseases, 276.39, 276.33, 997.33 • Neuroma, 27.45

	INTRODUCTION

TOP ABSTRACT INTRODUCTION MATERIALS AND METHODS RESULTS DISCUSSION REFERENCES

 
Traumatic or amputation neuroma is a well-known disorder that occurs after trauma or surgery involving the peripheral nerve. Rather than representing a neoplasm, neuroma represents a reactive hyperplasia of nerve tissue and usually occurs at the proximal end of a severed nerve. In the head and neck region, neuromas have been reported to occur after the extraction of teeth (1), parotidectomy (2), mandibular osteotomy (3), and neck dissection (4). Traumatic neuromas were found to occur in 1.1%–2.7% of patients who underwent neck dissection (4,5). Such neuromas are usually painful, firm, subcutaneous nodules that are typically located posterior to the carotid artery near the second cervical nerve (6). Painful hypersensitivity or paresthesia is a characteristic symptom of traumatic neuroma, though asymptomatic patients are not rare (2). Treatment of this disorder is unnecessary unless the patient has severe pain (7).

Data on the radiologic features of traumatic neuroma after neck dissection have been limited. Huang et al (5) reported computed tomographic (CT) findings of traumatic neuroma after neck dissection in four patients. They found that traumatic neuromas were characteristically stable nodules that were located posterior and close to the carotid artery and that the nodules showed central hypoattenuation, a hyperattenuating rim, and intact overlying fat at CT. Ultrasonography (US) is used for the evaluation of superficial lesions, such as cervical lymphadenopathy, and magnetic resonance (MR) imaging is widely used for the initial and postoperative evaluation of head and neck malignancies. To our knowledge, US and MR features of traumatic neuroma, however, have not yet been reported. Because neck dissection is usually performed for malignancy of the head and neck, the differentiation of this disorder from recurrent lymphadenopathy is important.

The purpose of this study was to retrospectively evaluate if there are any US, CT, and MR features that would be useful in differentiating traumatic neuroma from recurrent lymphadenopathy after neck dissection.

	MATERIALS AND METHODS

TOP ABSTRACT INTRODUCTION MATERIALS AND METHODS RESULTS DISCUSSION REFERENCES

 
Patients
Medical records from 1995 through 2002 were obtained from the National Kyushu Cancer Center and were reviewed to find patients with traumatic neuroma or recurrent lymphadenopathy after neck dissection. Patients with more than two lymph node metastases were not included in this study because multiple lesions were less likely to be traumatic neuromas. The study sample consisted of 10 patients with traumatic neuroma and 17 patients with recurrent lymphadenopathy. All patients of both groups had previously undergone neck dissection. The study protocol was approved by the institutional review board of the National Kyushu Cancer Center. All patients gave written informed consent for review of their records, files, and images.

Patients with traumatic neuroma included five men and five women (age range, 25–70 years; median, 46.5 years). Those with recurrent lymphadenopathy included 11 men and six women (age range, 45–82 years; median, 56 years). Results of the Mann-Whitney U test produced no statistically significant difference between the age of patients with traumatic neuroma and the age of those with recurrent lymphadenopathy (P = .053). There was also no statistically significant difference between sex ratios of the two groups by using the Fisher exact probability test (P = .73).

In seven of 10 patients, traumatic neuroma was diagnosed by using specimens obtained during surgery; in the remaining three patients, traumatic neuroma was diagnosed by using aspiration cytology. In 12 of 17 patients, recurrent lymphadenopathy was diagnosed by using specimens obtained during surgery; in the remaining five patients, recurrent lymphadenopathy was diagnosed by using aspiration cytology.

The primary lesions in patients with traumatic neuroma were thyroid carcinoma in eight patients, tongue carcinoma in one patient, and parotid gland carcinoma in one patient. The primary lesions in patients with recurrent lymphadenopathy were laryngeal carcinoma in four patients, tongue carcinoma in three patients, thyroid carcinoma in two patients, oropharyngeal carcinoma in two patients, gingival carcinoma in two patients, nasopharyngeal carcinoma in one patient, parathyroid carcinoma in one patient, oral floor carcinoma in one patient, and submandibular gland carcinoma in one patient. In patients with traumatic neuroma, seven had previously undergone radical neck dissection, and three had previously undergone modified neck dissection. In patients with recurrent lymphadenopathy, 12 had previously undergone radical neck dissection, and five had previously undergone modified neck dissection. Information about the patients and their conditions is summarized in Table 1.

Imaging and Analysis
US was performed in all 27 patients (Power Vision 6000; Toshiba Medical, Tokyo, Japan). All examinations were performed with a linear probe with a 12-MHz transducer (Toshiba Medical). The diameters of the short and long axes of each lesion were measured. Thereafter, the short-axis–to–long-axis (S/L) ratio was calculated. The presence of a central hyperechoic area was recorded.

CT was performed in all patients by using one of three units (W-1000 or W-3000, Hitachi Medical, Tokyo, Japan; Aquillion, Toshiba Medical). In all patients, 100 mL of a nonionic contrast medium, either iopamidol (Iopamiron 300; Nihon Schering, Osaka, Japan) or iohexol (Omnipaque 300; Daiichi Pharmaceutical, Tokyo, Japan), was injected intravenously at a rate of 1 mL/sec by using a power injector. Both contrast media have an iodine content of 300 mg/mL.

For all 27 patients, transverse CT images were obtained from the base of the skull to the superior mediastinum by using a 5-mm section thickness at 5-mm intervals. The findings that were analyzed at CT were contiguity with common or internal carotid artery, the location of the lesion relative to the carotid artery, and the presence of hyperattenuating rim. A lesion was judged to be in contact with the carotid artery when there was no fat plane between the two structures. The location of the lesion relative to the carotid artery was categorized as either anterior, posterior, medial, lateral, anteromedial, anterolateral, posteromedial, and posterolateral.

MR imaging was performed on 16 patients—six with traumatic neuroma and 10 with recurrent lymphadenopathy. A 0.5-T imager was used for all studies (Vectra EX; GE-Yokogawa Medical Systems, Tokyo, Japan). Spin-echo images were obtained with an anterior neck coil in all cases. Transverse and coronal T1-weighted (repetition time msec/echo time msec, 500–650/12–30) and T2-weighted (2200–3500/70–100) images were obtained with a 5-mm section thickness at 6-mm intervals. In all patients, 0.2 mL/kg gadopentetate dimeglumine (Magnevist; Nihon Schering) was administered intravenously. The findings that were analyzed with MR images were the signal intensity on T1- and T2-weighted images, the presence of ring enhancement on contrast-enhanced T1-weighted images, and the presence of a hypointense rim on T2-weighted images. The signal intensity of the lesions on T1- and T2-weighted images was compared with that of muscle. The presence of a hypointense rim was recorded when a hypointense band was observed in the circumference of the lesions on T2-weighted images.

Measurements of diameters of the short and long axes of the lesions at US and the interpretation of CT and MR images were performed by two authors who had experience in head and neck radiology (H.Y., 10 years experience; T.K., 13 years experience). A consensus was established if there were any disagreements.

Histopathologic Analysis
Imaging findings were compared with the histopathologic findings of surgical specimens obtained from seven of 10 patients with traumatic neuroma and 12 of 17 patients with recurrent lymphadenopathy. Without prior knowledge of imaging findings, one pathologist (Y.H.) examined all of the histopathologic specimens while paying special attention to the presence of central collagenous tissue or necrosis and surrounding fibrous tissue.

Statistical Analysis
For differences between traumatic neuroma and recurrent lymphadenopathy, imaging findings (except for the diameters at US) were statistically analyzed by using the Fisher exact probability test. An unpaired t test was used to determine if any difference was observed between the two groups in terms of the diameter of the short and long axes and the S/L ratio. A P value of less than .05 was considered to indicate a statistically significant difference. Statistical software (SPSS 11.5 J for Windows; SPSS, Chicago, Ill) was used to analyze the raw data.

	RESULTS

TOP ABSTRACT INTRODUCTION MATERIALS AND METHODS RESULTS DISCUSSION REFERENCES

 
US Scanning
The long-axis diameters of traumatic neuroma and recurrent lymphadenopathy were 8–20 mm (mean, 13.0 mm; standard deviation, 4.5 mm) and 9–30 mm (mean, 17.4 mm; standard deviation, 5.9 mm), respectively. There was no statistically significant difference in the long-axis diameters between groups (P = .053). The short-axis diameters of traumatic neuroma and recurrent lymphadenopathy were 5–7 mm (mean, 5.7 mm; standard deviation, 0.82 mm) and 7–20 mm (mean, 12.2 mm; standard deviation, 3.9 mm), respectively, and the difference was statistically significant (P < .001). The S/L ratios of traumatic neuroma and recurrent lymphadenopathy were 0.32–0.72 (mean, 0.47; standard deviation, 0.14) (Figs 1a, 2a) and 0.4–1.0 (mean, 0.72; standard deviation, 0.16) (Fig 3a), respectively. This difference was statistically significant (P < .001). A central hyperechoic area was seen at US in five of 10 traumatic neuromas (50%) (Figs 1a, 2a) and in one of 17 recurrent lymphadenopathy (6%). A statistically significant difference was observed between the two groups with regard to the presence of a central hyperechoic area at US (P < .05).

View larger version (140K): [in this window] [in a new window] [Download PPT slide]   Figure 1a. Traumatic neuroma after right radical neck dissection for thyroid carcinoma in a 43-year-old man. (a) Longitudinal sonogram of the right side of the neck shows well-defined, hypoechoic nodule (small arrows) with central hyperechoic area (large arrow). S/L ratio is 0.53 (short-axis diameter, 6.0 mm; long-axis diameter, 11.4 mm). (b) Contrast material-enhanced transverse CT scan shows hypoattenuating nodule (arrowhead) posterolateral to right internal carotid artery (arrow). Nodule does not make contact with right internal carotid artery. (c) Transverse T1-weighted spin-echo MR image (600/20) before contrast material enhancement shows nodule (arrow) with signal intensity similar to that of muscle. (d) Transverse T1-weighted spin-echo MR image (600/20) after contrast material enhancement shows heterogeneously enhanced nodule (arrow). (e) Transverse T2-weighted fast spin-echo MR image (3000/80) shows an intermediate-signal-intensity nodule with hypointense rim (arrow). (f) Histopathologic image shows numerous distinct neural bundles (arrows) that are trapped within densely collagenous connective tissue. (Hematoxylin-eosin stain; original magnification, x200.) (g) Histopathologic image shows surrounding fibrous tissue (arrows) in periphery. (Hematoxylin-eosin stain; original magnification, x100.)

View larger version (142K): [in this window] [in a new window] [Download PPT slide]   Figure 1b. Traumatic neuroma after right radical neck dissection for thyroid carcinoma in a 43-year-old man. (a) Longitudinal sonogram of the right side of the neck shows well-defined, hypoechoic nodule (small arrows) with central hyperechoic area (large arrow). S/L ratio is 0.53 (short-axis diameter, 6.0 mm; long-axis diameter, 11.4 mm). (b) Contrast material-enhanced transverse CT scan shows hypoattenuating nodule (arrowhead) posterolateral to right internal carotid artery (arrow). Nodule does not make contact with right internal carotid artery. (c) Transverse T1-weighted spin-echo MR image (600/20) before contrast material enhancement shows nodule (arrow) with signal intensity similar to that of muscle. (d) Transverse T1-weighted spin-echo MR image (600/20) after contrast material enhancement shows heterogeneously enhanced nodule (arrow). (e) Transverse T2-weighted fast spin-echo MR image (3000/80) shows an intermediate-signal-intensity nodule with hypointense rim (arrow). (f) Histopathologic image shows numerous distinct neural bundles (arrows) that are trapped within densely collagenous connective tissue. (Hematoxylin-eosin stain; original magnification, x200.) (g) Histopathologic image shows surrounding fibrous tissue (arrows) in periphery. (Hematoxylin-eosin stain; original magnification, x100.)

View larger version (150K): [in this window] [in a new window] [Download PPT slide]   Figure 1c. Traumatic neuroma after right radical neck dissection for thyroid carcinoma in a 43-year-old man. (a) Longitudinal sonogram of the right side of the neck shows well-defined, hypoechoic nodule (small arrows) with central hyperechoic area (large arrow). S/L ratio is 0.53 (short-axis diameter, 6.0 mm; long-axis diameter, 11.4 mm). (b) Contrast material-enhanced transverse CT scan shows hypoattenuating nodule (arrowhead) posterolateral to right internal carotid artery (arrow). Nodule does not make contact with right internal carotid artery. (c) Transverse T1-weighted spin-echo MR image (600/20) before contrast material enhancement shows nodule (arrow) with signal intensity similar to that of muscle. (d) Transverse T1-weighted spin-echo MR image (600/20) after contrast material enhancement shows heterogeneously enhanced nodule (arrow). (e) Transverse T2-weighted fast spin-echo MR image (3000/80) shows an intermediate-signal-intensity nodule with hypointense rim (arrow). (f) Histopathologic image shows numerous distinct neural bundles (arrows) that are trapped within densely collagenous connective tissue. (Hematoxylin-eosin stain; original magnification, x200.) (g) Histopathologic image shows surrounding fibrous tissue (arrows) in periphery. (Hematoxylin-eosin stain; original magnification, x100.)

View larger version (150K): [in this window] [in a new window] [Download PPT slide]   Figure 1d. Traumatic neuroma after right radical neck dissection for thyroid carcinoma in a 43-year-old man. (a) Longitudinal sonogram of the right side of the neck shows well-defined, hypoechoic nodule (small arrows) with central hyperechoic area (large arrow). S/L ratio is 0.53 (short-axis diameter, 6.0 mm; long-axis diameter, 11.4 mm). (b) Contrast material-enhanced transverse CT scan shows hypoattenuating nodule (arrowhead) posterolateral to right internal carotid artery (arrow). Nodule does not make contact with right internal carotid artery. (c) Transverse T1-weighted spin-echo MR image (600/20) before contrast material enhancement shows nodule (arrow) with signal intensity similar to that of muscle. (d) Transverse T1-weighted spin-echo MR image (600/20) after contrast material enhancement shows heterogeneously enhanced nodule (arrow). (e) Transverse T2-weighted fast spin-echo MR image (3000/80) shows an intermediate-signal-intensity nodule with hypointense rim (arrow). (f) Histopathologic image shows numerous distinct neural bundles (arrows) that are trapped within densely collagenous connective tissue. (Hematoxylin-eosin stain; original magnification, x200.) (g) Histopathologic image shows surrounding fibrous tissue (arrows) in periphery. (Hematoxylin-eosin stain; original magnification, x100.)

View larger version (141K): [in this window] [in a new window] [Download PPT slide]   Figure 1e. Traumatic neuroma after right radical neck dissection for thyroid carcinoma in a 43-year-old man. (a) Longitudinal sonogram of the right side of the neck shows well-defined, hypoechoic nodule (small arrows) with central hyperechoic area (large arrow). S/L ratio is 0.53 (short-axis diameter, 6.0 mm; long-axis diameter, 11.4 mm). (b) Contrast material-enhanced transverse CT scan shows hypoattenuating nodule (arrowhead) posterolateral to right internal carotid artery (arrow). Nodule does not make contact with right internal carotid artery. (c) Transverse T1-weighted spin-echo MR image (600/20) before contrast material enhancement shows nodule (arrow) with signal intensity similar to that of muscle. (d) Transverse T1-weighted spin-echo MR image (600/20) after contrast material enhancement shows heterogeneously enhanced nodule (arrow). (e) Transverse T2-weighted fast spin-echo MR image (3000/80) shows an intermediate-signal-intensity nodule with hypointense rim (arrow). (f) Histopathologic image shows numerous distinct neural bundles (arrows) that are trapped within densely collagenous connective tissue. (Hematoxylin-eosin stain; original magnification, x200.) (g) Histopathologic image shows surrounding fibrous tissue (arrows) in periphery. (Hematoxylin-eosin stain; original magnification, x100.)

View larger version (166K): [in this window] [in a new window] [Download PPT slide]   Figure 1f. Traumatic neuroma after right radical neck dissection for thyroid carcinoma in a 43-year-old man. (a) Longitudinal sonogram of the right side of the neck shows well-defined, hypoechoic nodule (small arrows) with central hyperechoic area (large arrow). S/L ratio is 0.53 (short-axis diameter, 6.0 mm; long-axis diameter, 11.4 mm). (b) Contrast material-enhanced transverse CT scan shows hypoattenuating nodule (arrowhead) posterolateral to right internal carotid artery (arrow). Nodule does not make contact with right internal carotid artery. (c) Transverse T1-weighted spin-echo MR image (600/20) before contrast material enhancement shows nodule (arrow) with signal intensity similar to that of muscle. (d) Transverse T1-weighted spin-echo MR image (600/20) after contrast material enhancement shows heterogeneously enhanced nodule (arrow). (e) Transverse T2-weighted fast spin-echo MR image (3000/80) shows an intermediate-signal-intensity nodule with hypointense rim (arrow). (f) Histopathologic image shows numerous distinct neural bundles (arrows) that are trapped within densely collagenous connective tissue. (Hematoxylin-eosin stain; original magnification, x200.) (g) Histopathologic image shows surrounding fibrous tissue (arrows) in periphery. (Hematoxylin-eosin stain; original magnification, x100.)

View larger version (171K): [in this window] [in a new window] [Download PPT slide]   Figure 1g. Traumatic neuroma after right radical neck dissection for thyroid carcinoma in a 43-year-old man. (a) Longitudinal sonogram of the right side of the neck shows well-defined, hypoechoic nodule (small arrows) with central hyperechoic area (large arrow). S/L ratio is 0.53 (short-axis diameter, 6.0 mm; long-axis diameter, 11.4 mm). (b) Contrast material-enhanced transverse CT scan shows hypoattenuating nodule (arrowhead) posterolateral to right internal carotid artery (arrow). Nodule does not make contact with right internal carotid artery. (c) Transverse T1-weighted spin-echo MR image (600/20) before contrast material enhancement shows nodule (arrow) with signal intensity similar to that of muscle. (d) Transverse T1-weighted spin-echo MR image (600/20) after contrast material enhancement shows heterogeneously enhanced nodule (arrow). (e) Transverse T2-weighted fast spin-echo MR image (3000/80) shows an intermediate-signal-intensity nodule with hypointense rim (arrow). (f) Histopathologic image shows numerous distinct neural bundles (arrows) that are trapped within densely collagenous connective tissue. (Hematoxylin-eosin stain; original magnification, x200.) (g) Histopathologic image shows surrounding fibrous tissue (arrows) in periphery. (Hematoxylin-eosin stain; original magnification, x100.)

View larger version (103K): [in this window] [in a new window] [Download PPT slide]   Figure 2a. Traumatic neuroma after right radical neck dissection for thyroid carcinoma in a 25-year-old man. (a) Longitudinal sonogram of right side of the neck shows well-defined, hypoechoic nodule (small arrows) with central hyperechoic area (large arrow). S/L ratio is 0.36 (short-axis diameter, 4.8 mm; long-axis diameter, 13.4 mm). (b) Contrast-enhanced transverse CT scan shows heterogeneously enhanced nodule (arrowhead) posterolateral to right common carotid artery (arrow). Nodule does not make contact with right common carotid artery. (c) Transverse T1-weighted spin-echo MR image (600/20) before contrast material enhancement shows an intermediate-signal-intensity nodule (arrow). Signal intensity of lesion is similar to that of muscle. (d) Transverse T1-weighted spin-echo MR image (600/20) after contrast material enhancement shows a heterogeneously enhanced nodule (arrow). (e) Transverse T2-weighted fast spin-echo MR image (2500/70) shows high-signal-intensity nodule with hypointense rim (arrow).

View larger version (127K): [in this window] [in a new window] [Download PPT slide]   Figure 2b. Traumatic neuroma after right radical neck dissection for thyroid carcinoma in a 25-year-old man. (a) Longitudinal sonogram of right side of the neck shows well-defined, hypoechoic nodule (small arrows) with central hyperechoic area (large arrow). S/L ratio is 0.36 (short-axis diameter, 4.8 mm; long-axis diameter, 13.4 mm). (b) Contrast-enhanced transverse CT scan shows heterogeneously enhanced nodule (arrowhead) posterolateral to right common carotid artery (arrow). Nodule does not make contact with right common carotid artery. (c) Transverse T1-weighted spin-echo MR image (600/20) before contrast material enhancement shows an intermediate-signal-intensity nodule (arrow). Signal intensity of lesion is similar to that of muscle. (d) Transverse T1-weighted spin-echo MR image (600/20) after contrast material enhancement shows a heterogeneously enhanced nodule (arrow). (e) Transverse T2-weighted fast spin-echo MR image (2500/70) shows high-signal-intensity nodule with hypointense rim (arrow).

View larger version (153K): [in this window] [in a new window] [Download PPT slide]   Figure 2c. Traumatic neuroma after right radical neck dissection for thyroid carcinoma in a 25-year-old man. (a) Longitudinal sonogram of right side of the neck shows well-defined, hypoechoic nodule (small arrows) with central hyperechoic area (large arrow). S/L ratio is 0.36 (short-axis diameter, 4.8 mm; long-axis diameter, 13.4 mm). (b) Contrast-enhanced transverse CT scan shows heterogeneously enhanced nodule (arrowhead) posterolateral to right common carotid artery (arrow). Nodule does not make contact with right common carotid artery. (c) Transverse T1-weighted spin-echo MR image (600/20) before contrast material enhancement shows an intermediate-signal-intensity nodule (arrow). Signal intensity of lesion is similar to that of muscle. (d) Transverse T1-weighted spin-echo MR image (600/20) after contrast material enhancement shows a heterogeneously enhanced nodule (arrow). (e) Transverse T2-weighted fast spin-echo MR image (2500/70) shows high-signal-intensity nodule with hypointense rim (arrow).

View larger version (159K): [in this window] [in a new window] [Download PPT slide]   Figure 2d. Traumatic neuroma after right radical neck dissection for thyroid carcinoma in a 25-year-old man. (a) Longitudinal sonogram of right side of the neck shows well-defined, hypoechoic nodule (small arrows) with central hyperechoic area (large arrow). S/L ratio is 0.36 (short-axis diameter, 4.8 mm; long-axis diameter, 13.4 mm). (b) Contrast-enhanced transverse CT scan shows heterogeneously enhanced nodule (arrowhead) posterolateral to right common carotid artery (arrow). Nodule does not make contact with right common carotid artery. (c) Transverse T1-weighted spin-echo MR image (600/20) before contrast material enhancement shows an intermediate-signal-intensity nodule (arrow). Signal intensity of lesion is similar to that of muscle. (d) Transverse T1-weighted spin-echo MR image (600/20) after contrast material enhancement shows a heterogeneously enhanced nodule (arrow). (e) Transverse T2-weighted fast spin-echo MR image (2500/70) shows high-signal-intensity nodule with hypointense rim (arrow).

View larger version (151K): [in this window] [in a new window] [Download PPT slide]   Figure 2e. Traumatic neuroma after right radical neck dissection for thyroid carcinoma in a 25-year-old man. (a) Longitudinal sonogram of right side of the neck shows well-defined, hypoechoic nodule (small arrows) with central hyperechoic area (large arrow). S/L ratio is 0.36 (short-axis diameter, 4.8 mm; long-axis diameter, 13.4 mm). (b) Contrast-enhanced transverse CT scan shows heterogeneously enhanced nodule (arrowhead) posterolateral to right common carotid artery (arrow). Nodule does not make contact with right common carotid artery. (c) Transverse T1-weighted spin-echo MR image (600/20) before contrast material enhancement shows an intermediate-signal-intensity nodule (arrow). Signal intensity of lesion is similar to that of muscle. (d) Transverse T1-weighted spin-echo MR image (600/20) after contrast material enhancement shows a heterogeneously enhanced nodule (arrow). (e) Transverse T2-weighted fast spin-echo MR image (2500/70) shows high-signal-intensity nodule with hypointense rim (arrow).

View larger version (132K): [in this window] [in a new window] [Download PPT slide]   Figure 3a. Recurrent lymphadenopathy after left radical neck dissection for oropharyngeal carcinoma in a 69-year-old man. (a) Longitudinal sonogram of left side of the neck shows well-defined, hypoechoic nodule (arrows) without central hyperechoic area. S/L ratio is 0.83 (short-axis diameter, 10 mm; long-axis diameter, 12 mm). (b) Contrast-enhanced transverse CT scan shows ring-enhanced mass (arrows) anteromedial to left internal carotid artery (arrowhead). Mass is in contact with left internal carotid artery. (c) Transverse T1-weighted spin-echo MR image (600/20) before contrast enhancement shows a mass (arrow) with intensity similar to that of muscle. (d) Transverse T1-weighted spin-echo MR image (600/20) after contrast enhancement shows peripheral enhancement (thin arrows) and central nonenhancement (thick arrow). (e) Transverse T2-weighted fast spin-echo MR image (2500/70) shows peripheral high signal intensity (thin arrows) and central low signal intensity (thick arrow). (f) Histopathologic image shows central coagulation necrosis (*) and peripheral tumor cells. Coagulation necrosis in central portion of tumor was thought to result in central low signal intensity on T2-weighted MR image. (Hematoxylin-eosin stain; original magnification, x100.)

View larger version (122K): [in this window] [in a new window] [Download PPT slide]   Figure 3b. Recurrent lymphadenopathy after left radical neck dissection for oropharyngeal carcinoma in a 69-year-old man. (a) Longitudinal sonogram of left side of the neck shows well-defined, hypoechoic nodule (arrows) without central hyperechoic area. S/L ratio is 0.83 (short-axis diameter, 10 mm; long-axis diameter, 12 mm). (b) Contrast-enhanced transverse CT scan shows ring-enhanced mass (arrows) anteromedial to left internal carotid artery (arrowhead). Mass is in contact with left internal carotid artery. (c) Transverse T1-weighted spin-echo MR image (600/20) before contrast enhancement shows a mass (arrow) with intensity similar to that of muscle. (d) Transverse T1-weighted spin-echo MR image (600/20) after contrast enhancement shows peripheral enhancement (thin arrows) and central nonenhancement (thick arrow). (e) Transverse T2-weighted fast spin-echo MR image (2500/70) shows peripheral high signal intensity (thin arrows) and central low signal intensity (thick arrow). (f) Histopathologic image shows central coagulation necrosis (*) and peripheral tumor cells. Coagulation necrosis in central portion of tumor was thought to result in central low signal intensity on T2-weighted MR image. (Hematoxylin-eosin stain; original magnification, x100.)

View larger version (138K): [in this window] [in a new window] [Download PPT slide]   Figure 3c. Recurrent lymphadenopathy after left radical neck dissection for oropharyngeal carcinoma in a 69-year-old man. (a) Longitudinal sonogram of left side of the neck shows well-defined, hypoechoic nodule (arrows) without central hyperechoic area. S/L ratio is 0.83 (short-axis diameter, 10 mm; long-axis diameter, 12 mm). (b) Contrast-enhanced transverse CT scan shows ring-enhanced mass (arrows) anteromedial to left internal carotid artery (arrowhead). Mass is in contact with left internal carotid artery. (c) Transverse T1-weighted spin-echo MR image (600/20) before contrast enhancement shows a mass (arrow) with intensity similar to that of muscle. (d) Transverse T1-weighted spin-echo MR image (600/20) after contrast enhancement shows peripheral enhancement (thin arrows) and central nonenhancement (thick arrow). (e) Transverse T2-weighted fast spin-echo MR image (2500/70) shows peripheral high signal intensity (thin arrows) and central low signal intensity (thick arrow). (f) Histopathologic image shows central coagulation necrosis (*) and peripheral tumor cells. Coagulation necrosis in central portion of tumor was thought to result in central low signal intensity on T2-weighted MR image. (Hematoxylin-eosin stain; original magnification, x100.)

View larger version (140K): [in this window] [in a new window] [Download PPT slide]   Figure 3d. Recurrent lymphadenopathy after left radical neck dissection for oropharyngeal carcinoma in a 69-year-old man. (a) Longitudinal sonogram of left side of the neck shows well-defined, hypoechoic nodule (arrows) without central hyperechoic area. S/L ratio is 0.83 (short-axis diameter, 10 mm; long-axis diameter, 12 mm). (b) Contrast-enhanced transverse CT scan shows ring-enhanced mass (arrows) anteromedial to left internal carotid artery (arrowhead). Mass is in contact with left internal carotid artery. (c) Transverse T1-weighted spin-echo MR image (600/20) before contrast enhancement shows a mass (arrow) with intensity similar to that of muscle. (d) Transverse T1-weighted spin-echo MR image (600/20) after contrast enhancement shows peripheral enhancement (thin arrows) and central nonenhancement (thick arrow). (e) Transverse T2-weighted fast spin-echo MR image (2500/70) shows peripheral high signal intensity (thin arrows) and central low signal intensity (thick arrow). (f) Histopathologic image shows central coagulation necrosis (*) and peripheral tumor cells. Coagulation necrosis in central portion of tumor was thought to result in central low signal intensity on T2-weighted MR image. (Hematoxylin-eosin stain; original magnification, x100.)

View larger version (141K): [in this window] [in a new window] [Download PPT slide]   Figure 3e. Recurrent lymphadenopathy after left radical neck dissection for oropharyngeal carcinoma in a 69-year-old man. (a) Longitudinal sonogram of left side of the neck shows well-defined, hypoechoic nodule (arrows) without central hyperechoic area. S/L ratio is 0.83 (short-axis diameter, 10 mm; long-axis diameter, 12 mm). (b) Contrast-enhanced transverse CT scan shows ring-enhanced mass (arrows) anteromedial to left internal carotid artery (arrowhead). Mass is in contact with left internal carotid artery. (c) Transverse T1-weighted spin-echo MR image (600/20) before contrast enhancement shows a mass (arrow) with intensity similar to that of muscle. (d) Transverse T1-weighted spin-echo MR image (600/20) after contrast enhancement shows peripheral enhancement (thin arrows) and central nonenhancement (thick arrow). (e) Transverse T2-weighted fast spin-echo MR image (2500/70) shows peripheral high signal intensity (thin arrows) and central low signal intensity (thick arrow). (f) Histopathologic image shows central coagulation necrosis (*) and peripheral tumor cells. Coagulation necrosis in central portion of tumor was thought to result in central low signal intensity on T2-weighted MR image. (Hematoxylin-eosin stain; original magnification, x100.)

View larger version (170K): [in this window] [in a new window] [Download PPT slide]   Figure 3f. Recurrent lymphadenopathy after left radical neck dissection for oropharyngeal carcinoma in a 69-year-old man. (a) Longitudinal sonogram of left side of the neck shows well-defined, hypoechoic nodule (arrows) without central hyperechoic area. S/L ratio is 0.83 (short-axis diameter, 10 mm; long-axis diameter, 12 mm). (b) Contrast-enhanced transverse CT scan shows ring-enhanced mass (arrows) anteromedial to left internal carotid artery (arrowhead). Mass is in contact with left internal carotid artery. (c) Transverse T1-weighted spin-echo MR image (600/20) before contrast enhancement shows a mass (arrow) with intensity similar to that of muscle. (d) Transverse T1-weighted spin-echo MR image (600/20) after contrast enhancement shows peripheral enhancement (thin arrows) and central nonenhancement (thick arrow). (e) Transverse T2-weighted fast spin-echo MR image (2500/70) shows peripheral high signal intensity (thin arrows) and central low signal intensity (thick arrow). (f) Histopathologic image shows central coagulation necrosis (*) and peripheral tumor cells. Coagulation necrosis in central portion of tumor was thought to result in central low signal intensity on T2-weighted MR image. (Hematoxylin-eosin stain; original magnification, x100.)

MR Imaging
The signal intensity of the lesion was equal to that of the muscles on T1-weighted images in six of six cases of traumatic neuroma (100%) (Figs 1c, 2c) and in eight of 10 cases (80%) of recurrent lymphadenopathy (Fig 3c). On T2-weighted images, all cases of traumatic neuroma (Figs 1e, 2e) and recurrent lymphadenopathy (Fig 3e) were hyperintense. A hypointense rim on T2-weighted MR images was seen in three of six cases (50%) of traumatic neuroma (Figs 1e, 2e). This frequency was statistically significant (P < .05). Ring enhancement on contrast-enhanced T1-weighted images was seen in two of six cases (33%) of traumatic neuroma and in seven of 10 cases (70%) of recurrent lymphadenopathy (Fig 3d). This difference was not statistically significant. Results of all imaging findings are summarized in Table 2.

	DISCUSSION

TOP ABSTRACT INTRODUCTION MATERIALS AND METHODS RESULTS DISCUSSION REFERENCES

 
The goal of this study was to analyze the radiologic findings of traumatic neuroma and recurrent lymphadenopathy after neck dissection and to clarify the imaging features that differentiate the two entities. Results of the present study indicated five differential imaging features. First, the S/L ratio for traumatic neuroma was significantly smaller than that for recurrent lymphadenopathy. Second, the short-axis diameter of traumatic neuromas was significantly smaller than that of recurrent lymphadenopathy. Third, a central hyperechoic area was seen more frequently at US in traumatic neuromas than in recurrent lymphadenopathy. Fourth, traumatic neuromas were in contact with the carotid artery less frequently than recurrent lymphadenopathy. Fifth, a hypointense rim on T2-weighted MR images was seen only in traumatic neuromas. The location of the lesion relative to the carotid artery, the presence of a hyperattenuating rim on contrast-enhanced CT or MR images, and the signal intensity on T1- or T2-weighted MR images was not useful in differentiating the two entities.

Huang et al (5) reported CT findings of traumatic neuroma in four patients after neck dissection. In that report, traumatic neuromas were characteristically stable nodules that were located posterior and close to the carotid artery and that showed central hypoattenuation, a hyperattenuating rim, and intact overlying fat. We investigated US and MR, as well as CT, findings in an attempt to find imaging features that would differentiate traumatic neuroma from recurrent lymphadenopathy. We believe that our findings provide information that is particularly useful in asymptomatic patients with traumatic neuroma after neck dissection.

According to previous reports concerning US findings of traumatic neuroma of the knee, a well-defined hypoechoic mass in the line of the transected nerve and an echogenic nerve running into the mass are two characteristics of traumatic neuroma (8,9). In our investigation, we did not find a nerve running into traumatic neuromas. One possible explanation for the discrepancy between studies is that our study focused on traumatic neuroma of the neck, where the nerves are smaller than those in the knee.

The results of our present study indicated that a small S/L ratio, a small short-axis diameter, and the presence of a central hyperechoic area are important findings of traumatic neuroma at US. The small S/L ratio and small short-axis diameter of traumatic neuroma are probably attributable to reparative growth of the terminal end of the severed nerve along its long-axis. The short-axis diameter of traumatic neuroma was smaller than that of recurrent lymphadenopathy, but this finding did not seem to be clinically useful because there would be some overlap between the size of a traumatic neuroma and that of a recurrent lymphadenopathy as a metastatic node grows. Patients with symptomatic traumatic neuromas would likely undergo imaging earlier than those with metastatic nodes, because the former patients would have tenderness or hypersensitivity.

In our study, the centrally located dense collagenous tissue that was observed in the resected specimens of patients with traumatic neuroma was probably responsible for the central hyperechoic area visible at US. This finding mimics one feature of reactive lymphadenopathy that was described in a previous report (10). Reactive lymphadenopathy frequently shows a central hyperechoic area that corresponds to fat tissue in the hilum, but these fatty deposits are not diagnostically problematic because of their multiplicity and soft consistency at palpation. Our study revealed that US images showed a hypoechoic mass with a central hyperechoic area in five of 10 patients with traumatic neuroma. Fornage (8) reported that traumatic neuroma showed a hypoechoic mass at US, but their evaluation was only of two cases. This discrepancy could be attributed to the difference of spatial resolution of the US unit. We used a US probe with a 12-MHz transducer that was able to depict internal hyperechoic areas, whereas Fornage used a 5- or 7.5-MHz transducer.

A small S/L ratio and the disappearance of fat tissue in the central hilum has been reported to be a characteristic US finding of metastatic lymphadenopathy (11). In the present study, the disappearance of central fat was observed at US in 16 of 17 patients with recurrent lymphadenopathy. Also, central necrosis, which may explain the disappearance of a hyperechoic area at US, was observed in histopathologic findings in seven of 12 cases of metastatic lymphadenopathy.

With regard to CT findings, Huang et al (5) reported that a hyperattenuating rim is a characteristic of traumatic neuroma. In our study, this feature was observed in both traumatic neuroma and recurrent lymphadenopathy. A hyperattenuating rim at CT has also been reported in metastatic lymphadenopathy when there is central necrosis (12). We therefore believe that this CT finding cannot be used as a differentiating radiologic feature.

We found traumatic neuromas were located close to (but rarely in contact with) the carotid arteries, whereas recurrent lymphadenopathy was frequently found in contact with carotid arteries. We assume that recurrent lymphadenopathy arises from residual lymph nodes, which tend to be spared at surgery and are in contact with the carotid artery. A traumatic neuroma, on the other hand, usually arises from the cervical nerve that courses near the carotid artery but is not in contact with it. Seventy percent of traumatic neuromas were located posterolateral to the carotid artery in our patients. Additionally, no traumatic neuroma was medial to the carotid artery. This can be explained based on the fact that neuromas grow from the stump of a severed nerve, such as the cervical nerve, as is reported in previous articles (13). Our findings, however, indicated that recurrent lymphadenopathy can arise anywhere around the carotid artery; in 42% of cases, recurrent lymphadenopathy arose at the same location as traumatic neuroma. Therefore, the location of the lesions was not helpful in differentiating traumatic neuroma from recurrent lymphadenopathy.

There was no significant difference in the signal intensity on T1- or T2-weighted images of traumatic neuroma and recurrent lymphadenopathy. A hypointense rim on T2-weighted MR images, however, was seen only in traumatic neuroma. This difference was statistically significant. This hypointense rim corresponded to the surrounding fibrous scar tissue that was observed during the histopathologic analysis of the resected specimen. This correspondence has been reported already in the pathology literature (13). This finding agrees with those in a report by Singson et al (14) concerning MR images of postamputation neuromas at the knee. Singson et al reported that a low-signal-intensity, peripheral rim on T1- and T2- weighted MR images was recognized in all nine patients, and that focal fibrous tissue condensation might account for the dark rim.

According to the previous literature, tenderness or hypersensitivity that corresponds to the lesion is characteristic of traumatic neuroma because the sensory nerve is frequently involved (3,5); this, however, was seen in only 40% of the cases of traumatic neuroma in our present study. When a patient is encountered who, after neck dissection, has a neck mass with pathognomonic tenderness or hypersensitivity, differential diagnosis should not be difficult. If, however, the patient does not have these symptoms, then imaging should play an important role in decision making for treatment.

We therefore believe that clinical findings, such as tenderness or hypersensitivity after neck dissection, along with imaging findings could produce more accurate diagnosis in patients who previously underwent neck dissection. In addition to presenting the imaging findings, we also believe that it is important to increase the awareness of this rare entity to radiologists.

In conclusion, several radiologic findings can help differentiate traumatic neuroma from recurrent lymphadenopathy after neck dissection; therefore, such findings may be useful for avoiding surgery in patients with asymptomatic traumatic neuroma.

	FOOTNOTES

 
Abbreviation: S/L = short-axis–to–long-axis

Authors stated no financial relationship to disclose.

Author contributions: Guarantor of integrity of entire study, H.Y.; study concepts and design, H.Y.; literature research, H.Y.; clinical studies, H.Y., T.K.; data acquisition, H.Y.; data analysis/interpretation, H.Y., T.K.; statistical analysis, H.Y.; manuscript preparation and definition of intellectual content, H.Y.; manuscript editing, T.K., T.F.; manuscript revision/review, T.K., T.F., K.T., Y.H.; manuscript final version approval, all authors

	REFERENCES

TOP ABSTRACT INTRODUCTION MATERIALS AND METHODS RESULTS DISCUSSION REFERENCES

 

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