Cervicothoracic Lesions in Infants and Children

INTRODUCTION

Lymphangioma is the most common cervicothoracic mass in children; however, many other lesions involve both the cervical and thoracic compartments. These lesions may be classified as congenital lesions, inflammatory lesions, benign tumors, malignant tumors, and traumatic lesions. Several imaging modalities are used to study this area: plain radiography, ultrasonography (US), nuclear medicine, computed tomography (CT), and magnetic resonance (MR) imaging; the latter two are the most widely used. Nevertheless, MR imaging is the preferred cross-sectional tool for assessment of cervicothoracic lesions because of the following features: multiplanar capability, excellent soft-tissue contrast, absence of beam-hardening artifacts from the shoulders, and optimal visualization of vascular anatomy and the adjacent brachial plexus.

In this article, we review the anatomic pathways of spread through the thoracic inlet and discuss the differential diagnosis, clinical manifestations, and imaging features of cervicothoracic lesions in children.

IMAGING TECHNIQUE

We retrospectively studied the cervicothoracic lesions that occurred in children who were seen at our hospital during the past 15 years and who were evaluated with US, CT, or MR imaging. Plain radiography was performed in most of these patients; in some cases, scintigraphy and barium esophagography were also performed. Most of the diagnoses were surgically confirmed.

In most cases, US was performed with an Acuson model 128 (Mountain View, Calif) and 5.0- or 7.5-MHz real-time linear-array transducers. Duplex and color Doppler images were used to assess suspected vascular lesions. CT was performed with an Elscint model 2400 (Haifa, Israel) or an Elscint Twin II. Contiguous contrast material–enhanced axial images were obtained; the section thickness was 3–5 mm. In some cases, posterior processing was performed on overlapped sections from a spiral CT data set to produce secondary multiplanar and three-dimensional reconstruction images. MR imaging was performed with a 1.0-T unit (Impact; Siemens, Erlangen, Germany) or a 1.5-T unit (Magnetom or Vision; Siemens). Body, head, neck, or surface coils were used according to the size of the child and the structure to be studied. Axial, coronal, or sagittal spin-echo or fast spin-echo T1- and T2-weighted images were obtained; the section thickness was 3–6 mm. Occasionally, contrast-enhanced, fat saturation, and gradient-echo images were also obtained.

For sedation, we used orally administered chloral hydrate (children <12 months of age) or intravenously administered pentobarbital sodium when necessary.

ANATOMIC REVIEW

All cervicothoracic lesions except superficial lesions extend from the neck to the thorax through the thoracic inlet. The thoracic inlet is the junction between the neck and thorax and is delineated by the Sibson fascia, which extends bilaterally from the transverse process of C7 to the medial border of the first rib. Because the posterior attachment is more cranially located, the plane of the thoracic inlet is oblique, higher posteriorly than anteriorly (^,1).

There are two primary fascial layers in the neck: the superficial cervical fascia and the deep cervical fascia (DCF). The three layers of the DCF (superficial, middle, and deep) divide the neck into spaces (^,Figs 1, ^,2). These layers normally cannot be seen on CT or MR images but nonetheless define the spaces of this area, provide barriers to the spread of disease in this region, and determine the anatomic pathways of spread from the neck to the mediastinum (^,2–^,5). Solitary cervical lesions are primarily bound by compartmental fascial planes. Thus, knowledge of the cervical fascial planes, the contents of these planes, and displacement of surrounding structures permits accurate differential diagnosis (^,Table).

The visceral space is the only space that is exclusively within the infrahyoid portion of the neck. Thyroid and parathyroid disease, esophageal lesions, abscesses, and pathologic lymph nodes are seen in this space. Jugular vein thrombosis, paraganglioma, schwannoma, neurofibroma, atypical branchial cleft cyst, and inflammatory or metastatic lymph nodes can be seen in the carotid space. In the infrahyoid retropharyngeal space, inflammatory disease (cellulitis or abscesses) and malignant tumor (direct invasion or extranodal metastases) may be seen. Rarely, lipoma or hemangioma may be found in this space, although they are seen more frequently in the posterior cervical space. Lymphangioma is a common lesion in the posterior cervical space, but branchial cleft cyst, neurofibroma, schwannoma, pathologic lymph nodes, and abscesses can also be seen. Inflammatory or tumoral vertebral lesions are primarily confined to the prevertebral space. Lesions of the roots of the brachial plexus (traumatic or tumoral) may be partially seen in this space because they usually enter the posterior cervical space on the way to the axilla. The anterior cervical space has limited contents, and lipoma is the most common lesion arising in this space (^,2–^,4).

Many cervicothoracic lesions are extensive or multiple and may involve several spaces simultaneously. Multiple contiguous spaces (transspatial lesions) or noncontiguous spaces (multispatial lesions) may be involved (^,6). Nodal disease (inflammatory or neoplastic) and neurofibromatosis can be multispatial lesions. Lymphangioma, hemangioma, branchial cleft cyst, transspatial abscesses, lipoma, hematoma, nerve sheath tumors, fibromatosis, and malignant tumors are usually transspatial lesions (^,6,^,7).

CONGENITAL LESIONS

We found lymphangioma to be the most common congenital cervicothoracic lesion, but we have also seen hemangioma, abnormalities of the thymopharyngeal ducts, and vascular anomalies.

Lymphangioma

Lymphangiomas develop from congenital obstruction of lymphatic drainage. They can reside within vascular malformations and are considered to be a spectrum of manifestations of the same pathologic process. These tumors tend to surround and invade normal anatomic structures. Lymphangioma has been reported in abortuses and fetuses with the 45,X karyotype (Turner syndrome). Approximately 75% of lymphangiomas occur in the neck, generally in the posterior triangle, and 3%–10% extend into the mediastinum. Less than 1% of all lymphangiomas are purely mediastinal (^,8). Spontaneous regression occurs in 6% of cases. Most often, lymphangiomas are asymptomatic and manifest as painless masses. Ninety percent are detected by 2 years of age (^,9–^,11).

On CT and MR images, lymphangiomas appear as multilocular transspatial masses of fluid attenuation or signal intensity (^,Fig 3). After injection of contrast material, the walls of the septa may enhance, particularly if there is a history of surgery or infection. Occasionally, hemorrhagic areas and fluid-fluid levels can be seen (^,,,Fig 4) (^,12). MR imaging is the most accurate technique for evaluating the extent of the tumor, the relationship of the tumor to neurovascular structures, and the eventual associated venous anomalies, factors that may be important for surgical planning (^,8).

Hemangioma

Hemangiomas are benign masses composed of proliferating endothelial cells. These tumors characteristically increase in size and gradually involute. They occur most commonly in the 1st year of life and are often discovered at birth. On MR images, they usually demonstrate intermediate signal intensity on T1-weighted images, high signal intensity on T2-weighted images, diffuse contrast enhancement, and high-flow vessels. Areas of fatty replacement can be seen (^,,,Fig 5) (^,13–^,15).

Defective Pathways of Embryologic Descent of Thymic Primordia

Defective pathways of embryologic descent of thymic primordia may lead to a spectrum of migrational abnormalities. These abnormalities often manifest as solid or cystic masses. They are most frequently located along the pathway of thymic descent from the angle of the mandible to the superior mediastinum (^,16).

Cervical Extension of Mediastinal Thymus

Cervical extension of mediastinal thymus is due to incomplete mediastinal descent and manifests as a solid, midline thymus at the thoracic inlet (^,Fig 6) (^,16,^,17). Thymic tissue is found in the neck in 21%–42% of infants and occasionally simulates a cervical tumor in children. Cervical extension of mediastinal thymus has been related to innominate artery (brachiocephalic trunk) syndrome. The diagnosis of cervical mediastinal thymus can be made on the basis of homogeneous signal intensity similar to that of the thymus with all MR imaging sequences or the connection to the normally located thymus.

Thymic Cyst

Thymic cysts are caused by persistence or degeneration of the thymopharyngeal ducts. About 50% of cervical thymic cysts are continuous with mediastinal masses. Most of these anomalies are found on the left side of the neck. At CT, they are generally well marginated and uni- or multilocular; the attenuation is close to that of water. They have low signal intensity on T1-weighted MR images and intermediate or high signal intensity on T2-weighted MR images. The signal intensity on T1-weighted images may increase if the cyst contains blood or protein. Thin septa can be identified within the cyst. When these cysts occur in the neck, they are located at least partially within the carotid sheath. A histologic diagnosis can be made if the cyst wall contains Hassall corpuscles (^,,,,Fig 7) (^,16–^,18).

Most thymic cysts are congenital, but they have also been reported in association with infection, neoplasms, radiation therapy, trauma, and thoracotomy (^,19). The differential diagnosis includes other fluid-filled masses such as thymic tumors with cystic changes, cystic hygroma, cystic teratoma, and abscess. When a thymic cyst is located mainly in the neck, a third or fourth branchial cleft cyst should also be considered.

Vascular Anomalies

Vascular anomalies such as venous malformations or arteriovenous malformations are rarely seen in the neck. Jugular vein thrombosis often occurs after placement of a central catheter or in association with compressive lesions in the neck or mediastinum. The primary feature of jugular vein thrombosis on contrast-enhanced CT or MR images is luminal obliteration, which may be associated with a thin rim of enhancement of the vasa vasorum (^,7).

In cases of cervical aortic arch, there is a high-positioned, usually right-sided aortic arch (^,Fig 8), which is occasionally associated with other cardiac and vascular anomalies (^,20). Many cases are asymptomatic, whereas others manifest as respiratory problems or dysphagia. A pulsatile mass is often found in the neck.

INFLAMMATORY LESIONS

Inflammatory adenopathy reactive to tuberculosis, mononucleosis, tularemia, cat-scratch fever, infection with human immunodeficiency virus, or other upper respiratory tract infections can manifest as cervicothoracic lesions. Tuberculous abscesses and abscesses of other origins can also be seen in this region.

Cervical Abscess

Cervical abscesses have become rare in the era of antibiotics. Such abscesses seldom cross the thoracic inlet into the mediastinum. Infections in the visceral space may extend into the anterior mediastinum, whereas infections in the retropharyngeal and prevertebral spaces may extend into the posterior mediastinum (^,21).

Imaging is used to distinguish cellulitis and suppurative adenopathy from abscesses, which require surgical treatment. As suppuration occurs, a focal hypoattenuating mass with an enhancing rim is seen on contrast-enhanced CT scans and a complex hypoechoic to anechoic mass with a variably thick rim of solid tissue is seen on US scans. The appearance of the fluid collection varies on T1- and T2-weighted MR images according to the protein content. Skin thickening and reticulated fat planes may be seen adjacent to the abscess margins on both CT and MR images; nevertheless, MR images can be more challenging to interpret than CT scans (^,21,^,22).

Tuberculous Spondylitis with Abscess Formation

It is estimated that 2 billion people worldwide are infected with Mycobacterium tuberculosis. Approximately 80% of all tuberculosis cases are pulmonary tuberculosis. Tuberculous spondylitis accounts for 6% of new cases of extrapulmonary tuberculosis. The lower thoracic and lumbar spines are the most commonly affected locations. The cervical spine is an uncommon site (3%–6% of cases) (^,23).

The infection usually starts anteriorly in the vertebral body. In nearly 90% of cases, at least two vertebrae are affected. Skip lesions occur in up to 4% of cases (^,23). Paraspinal abscesses are present in 55%–90% of cases. Loss of disk height is commonly seen; occasionally, only one vertebra will be affected, thus sparing the intervertebral disk. Vertebral collapse may result in kyphosis, kyphoscoliosis, vertebral dislocation, or epidural cord compression.

The illness typically has an indolent course. Patients may be afebrile and free of systemic symptoms until the late stage of the infection. Neurologic deficits may be apparent, although they are relatively less severe than would be expected in other types of disease. Paralysis can occur in the active or healed stage of the disease. In the neck, dysphagia, hoarseness, and lymphadenopathy are accompanying features.

CT shows extensive bone destruction and a large, calcified paraspinal abscess (^,,,Fig 9) (^,23). MR imaging often shows infection spreading beneath the longitudinal ligament to involve adjacent vertebral bodies. The disks are sometimes relatively spared in relation to the degree of bone destruction. Gadopentetate dimeglumine has been shown to be useful in demonstrating the presence and extent of epidural and intradural disease and the presence of paraspinal abscesses.

Retropharyngeal Abscess with Mediastinal Extension

Retropharyngeal abscesses in children commonly result from tonsillar infection, although such abscesses may also result from iatrogenic or traumatic perforation of the pharynx. Retropharyngeal soft-tissue thickening and displacement of the airway can be seen on plain radiographs. The retropharyngeal space may serve as a conduit for infection between the neck and mediastinum (^,,,Figs 10, ^,,,11). The retropharyngeal space and danger space should be considered together because diseases affecting these spaces cannot be differentiated radiologically. The danger space is important because it terminates at the level of the diaphragm and thus represents a pathway for spread of retropharyngeal infection into the posterior mediastinum (^,2,^,24) (^,Table).

BENIGN TUMORS

We have seen lipoma, lipoblastoma, aggressive fibromatosis, and nerve sheath tumors as isolated masses or in association with neurofibromatosis.

Lipoma

Lipomas are fairly uncommon during the first 2 decades of life. These tumors are often an incidental finding at imaging. Benign fatty tumors are generally classified according to morphology and cell type. Simple lipomas are well-defined fatty tumors that usually arise in the subcutaneous tissue but can also occur in other regions (^,,,Fig 12). They manifest as well-encapsulated masses that may contain fibrous septa and have a characteristic signal intensity pattern that parallels that of subcutaneous fat (high on T1-weighted MR images, intermediate on T2-weighted MR images, and loss of signal intensity on fat-suppressed MR images). CT shows a hypoattenuating mass with low attenuation values (−10 to −100 HU) (^,7,^,25).

Lipoblastoma

Lipoblastomas are rare, usually encapsulated, benign neoplasms of the embryonal fat. They are composed of both mature and immature fat cells and occur almost exclusively in infants and children. Ninety percent arise before the age of 3 years. The male-female ratio is 3:1. Lipoblastomatosis represents the unencapsulated, diffuse form. Most lipoblastomas arise in the extremities, although some originate in the trunk, head, or neck.

At CT, lipoblastomas contain fat separated by septa of soft-tissue attenuation and do not enhance after administration of contrast material (^,Fig 13) (^,26). Unlike lipomas, which have a characteristic appearance on MR images (high signal intensity on T1-weighted images), lipoblastomas can be heterogeneous and have intermediate to high signal intensity on T1-weighted images according to the amount of immature lipoblasts. On fat-suppressed MR images, lipoblastomas usually demonstrate areas of high signal intensity, which can suggest the diagnosis (^,27).

Neurofibromatosis

Neurofibromas and schwannomas occur in neurofibromatosis but are also seen sporadically. Neurofibromas can be localized or diffuse and can occur singly or at multiple levels (^,,,Fig 14). Plexiform neurofibromas are pathognomonic of type 1 neurofibromatosis (^,Fig 15). Plexiform neurofibromatosis is the more diffuse form and consists of multiple masses or fusiform enlargement of the peripheral nerves.

The tumors are usually hypo- to isoattenuating at CT; contrast enhancement is more often seen with schwannomas than with conventional or plexiform neurofibromas. At MR imaging, the tumors usually have low to intermediate signal intensity on T1-weighted images and intermediate to high signal intensity on T2-weighted images and demonstrate nonuniform gadolinium enhancement. Malignant degeneration is seen in 15%–30% of cases. In plexiform neurofibromatosis, the tumors form a network that often involves the contiguous soft tissue (^,10).

Aggressive Fibromatosis

Aggressive fibromatosis is characterized by proliferation of fibrous tissue with locally aggressive behavior and a tendency toward recurrence after resection. The appearance of fibromatosis on MR images is often infiltrative and can suggest malignancy. The signal intensity pattern is greatly variable: Fibromatosis usually has low signal intensity on both T1- and T2-weighted images, which permits diagnosis (^,,,Fig 16); however, we have seen cases with intermediate or high signal intensity on T2-weighted images, a pattern similar to that of most other soft-tissue tumors. T2 shortening (decreased signal) in fibromatosis is attributed to low cellularity and high collagen content (^,7,^,27).

MALIGNANT TUMORS

Lymphoma was the most common malignant tumor involving the cervicothoracic area in our series. We also found thyroid carcinoma, neuroblastoma, and chest wall tumors (rhabdomyosarcoma, Ewing sarcoma, and neuroectodermal tumor).

Lymphoma

Lymphoma is the most common anterior mediastinal mass. Hodgkin and non-Hodgkin lymphoma are the two major cell types, although Hodgkin disease accounts for the majority of lymphomatous anterior mediastinal masses. The neoplastic cells typically infiltrate the thymus. Thymic involvement is almost always accompanied by involvement of mediastinal lymphnodes. Lymphoma of the neck involves the cervical lymph node chain, the Waldeyer tonsillar ring, and lymphoid tissue at the base of the tongue. Such lymphoma is most often of the non-Hodgkin type (^,Fig 17). Calcification and necrosis can be seen if the lymphoma was treated previously (^,10,^,14).

Thyroid Carcinoma

Thyroid carcinoma is the most frequent type of endocrine tumor and represents about 1% of all malignancies. Three major types of thyroid cancer occur in childhood: papillary (80% of cases), follicular (15%), and medullary (5%). Anaplastic carcinoma, lymphoma, and sarcoma are rarely found. The female-male ratio is 4:1. Lymph node metastases are more frequent than in adults (60% vs 30%) (^,,,Fig 18), and lung involvement is found in 5%–42% of cases (^,28,^,29). The frequency of thyroid malignancy is increased in patients with a history of cervical irradiation or multiple endocrine neoplasia.

Thyroid masses are usually evaluated with US and scintigraphy. CT or MR imaging is performed only when unanswered questions remain or to evaluate tumoral extent when malignant tumors are suspected. It is difficult to distinguish benign from malignant nodules because the findings are often nonspecific. Nevertheless, if a thyroid mass has infiltrating margins that obscure adjacent soft-tissue planes and there is associated adenopathy, carcinoma is the most likely possibility. Scintigraphy has an important role because “cold” nodules have a higher frequency of malignancy. MR imaging is the preferred cross-sectional tool for preoperative evaluation of thyroid malignancy because the iodine administered during CT can cause iodine-131 therapy to be postponed for up to 6 months after removal of the maximum tumor volume (^,3).

Neuroblastoma

Neuroblastoma is one of the most common malignancies seen in childhood. Neuroblastomas arise from neural crest blasts located in the adrenal gland or in the sympathetic chain from the cervical region to the pelvis. Ten percent to 15% of neuroblastomas are located in the posterior mediastinum. Origin in the neck is rare (<5% of cases) and is generally associated with a good prognosis. Patients with cervical neuroblastoma usually develop a firm mass in the lateral neck during the first 3 years of life and may have respiratory or feeding difficulties. Heterochromia iridis and ipsilateral Horner syndrome may be signs of a thoracic apical or cervical mass. Heterochromia iridis is a difference in color between the two irides, and Horner syndrome is related to lesions of the cervical sympathetic nerve (^,30,^,31).

Neuroblastomas are frequently apparent at plain radiography, and approximately 50% contain calcifications. CT demonstrates calcification in up to 90% of cases. However, MR imaging is the technique of choice for demonstrating the full extent of the mass, chest wall invasion, and extradural intraspinal involvement (^,Fig 19) (^,8,^,10,^,30).

Chest Wall Tumors

Most large intrathoracic tumors that arise from the chest wall are malignant. Such tumors include rhabdomyosarcoma, Ewing sarcoma, and malignant primitive neuroectodermal tumors (eg, Askin tumor). Recognition of destruction of the ribs or vertebrae and detection of soft-tissue extension into the chest wall are imaging clues that help one recognize a lesion as being of chest wall origin (^,,,Fig 20). MR images are better for identification of muscle invasion of the chest wall, although CT scans permit visualization of bone involvement and identification of pulmonary metastases (^,32).

TRAUMATIC LESIONS

Traumatic cervicothoracic lesions include pneumomediastinum of traumatic origin, traumatic pharyngeal pseudodiverticulum, esophageal foreign-body granuloma, and cervicothoracic hematoma.

Pneumomediastinum

Pneumomediastinum may pass into the cervical area (^,,,Fig 21). Air travels from the mediastinum along the fascial planes to the neck, subcutaneous tissues, and chest wall (^,7). The most common causes of pneumomediastinum in children are asthma, aspiration of a foreign body, and barotrauma or other trauma.

Traumatic Pharyngeal Pseudodiverticulum

Pharyngeal pseudodiverticulum is considered to be of traumatic origin (^,,,Fig 22). Perforation can be caused by endotracheal or nasogastric tubes but has also been related to digital manipulation during delivery, aggressive attempts at extraction of an impacted foreign body, and child abuse (^,33,^,34). Respiratory symptoms and evidence of an abnormal air collection are usually present, but in some clinically silent cases an aberrant position of a feeding catheter is the diagnostic clue. Most cases are treated conservatively, although surgery has been performed in cases in which an abscess has developed.

Esophageal Foreign-Body Granuloma

Esophageal foreign bodies are most commonly seen in infants but are found throughout childhood. The most common site of retention is the upper esophagus, particularly at the thoracic inlet. Long-standing foreign bodies produce a granulomatous tissue reaction that manifests as a mass (^,,,,Fig 23). Mediastinitis and abscess can be seen in this region as complications of perforation by a foreign body (^,35).

Cervicothoracic Hematoma

Cervicothoracic hematoma can occur with trauma or with perforation of a great vessel during placement of a central catheter. Venous access can be particularly problematic in the pediatric population, and complications are more commonly seen when catheters are not positioned correctly. Hematomas are usually transspatial lesions. On CT scans, hematoma is hyperattenuating in the acute phase. As the hematoma matures, the attenuation decreases and approaches that of serum (20–30 HU). On occasion, the periphery of a chronic hematoma may calcify. On MR images, the appearance of hematoma also varies with time. Most subacute components (weeks to months) have increased signal intensity on T1- and T2-weighted images owing to extracellular methemoglobin. More chronic collections have a rim of low signal intensity due to hemosiderin deposition (^,27).

CONCLUSIONS

Children have a higher frequency of congenital anomalies, inflammatory lesions, and benign neoplasms and a lower frequency of malignant neoplasms in the cervicothoracic region than do adults. In our experience, lymphangioma is the most common congenital cervicothoracic mass, reactive lymph node is the most common inflammatory mass, and lymphoma is the most common malignancy. CT or MR imaging can be used to evaluate cervicothoracic lesions. Nevertheless, MR imaging is the preferred cross-sectional tool for evaluating the full extents of cervicothoracic masses and the relationships to neurovascular structures. Our proposed algorithmic approach is shown in ^,Figure 24. Radiologists must choose between the two techniques according to the clinical diagnosis and status of the patient, the urgency of the study, and the availability of the apparatus.

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Abbreviation: DCF = deep cervical fascia