Non-neoplastic pathology at the crossroads between neck imaging and cardiothoracic imaging
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The thoracic inlet is located at the crossroads between imaging of the neck and chest. It represents an important anatomic landmark, serving as the central conducting pathway for many vital structures extending from the neck into the chest and vice versa. Many important body systems are located within this region, including the enteric, respiratory, vascular, lymphatic, neurologic, and endocrine systems. A detailed examination of this region is essential when reviewing neck and thoracic imaging. This article will discuss the normal anatomic boundaries of the thoracic inlet and present an image-rich systematic discussion of the non-neoplastic pathology that can occur in this region. The neoplastic pathology of the thoracic inlet will be covered in a companion article.
KeywordsThoracic inlet Head and neck imaging Thoracic imaging Radiology
Deep cervical fascia
Diffuse idiopathic skeletal hyperostosis
Deep layer of the deep cervical fascia
Internal jugular vein
Middle layer of the deep cervical fascia
Partial anomalous pulmonary venous return
Posterior cervical space
Superficial cervical fascia
Superficial layer of the deep cervical fascia
Superior vena cava
The thoracic inlet is an important anatomic region from which various non-neoplastic pathologies can arise.
It contains many vital body systems such as the enteric, respiratory, lymphatic, neurologic, musculoskeletal, and endocrine structures/systems, allowing for the development of a systematic approach to the review of the thoracic inlet.
Many of these findings can be subtle and easily overlooked as the thoracic inlet is located at the crossroad between different imaging specialties.
The thoracic inlet is at the crossroads of imaging, often captured as the first or last set of images obtained during cross-sectional studies of the chest or neck respectively. This ultimately increases the chance this region is overlooked during the interpretation of the study, especially if both regions are imaged, as the neck radiologist may feel that it is part of the chest territory and the chest radiologist may feel that it is part of the neck territory. In addition, confident interpretation of this region can be difficult as many radiologists are fellowship trained in either neuroradiology or cardiothoracic imaging, but not both specialties.
Representative non-neoplastic pathology of the thoracic inlet based on the mnemonic “VINDICATE”
Aberrant right subclavian artery, partial anomalous pulmonary venous return (PAPVR), internal jugular venous thrombosis, vasculitis
Lemierre’s syndrome, mediastinitis, esophagitis
Traction injury of the brachial plexus/brachial plexopathy, perineural cyst/Tarlov cyst, laryngeal nerve injury
Esophageal diverticulum (Zenker’s, Killian-Jamieson), tracheal diverticulum, musculoskeletal degenerative changes (cervical osteophytosis, diffuse idiopathic skeletal hyperostosis (DISH), disc herniation
Tracheoesophageal fistula, radiation therapy, esophageal tear
Tracheobronchomegaly, dilated thoracic duct, branchial cleft cyst, narrowed thoracic inlet, fibromatosis colli, aberrant right subclavian artery, PAPVR
Hashimoto’s thyroiditis, systemic sclerosis causing esophageal dilatation, antiphospholipid syndrome causing thrombosis, thymic hyperplasia
Blunt or penetrating trauma causing injuries to the esophagus, trachea, vasculature, nerves, muscles, bones, and soft tissues. Examples include pneumomediastinum, sternocleidomastoid muscle hematoma
Thyroid goiter, parathyroid hyperplasia, Madelung disease
Multiple imaging modalities can be utilized to assess the thoracic inlet, including radiography, fluoroscopy, CT, MRI, and ultrasound. In general, radiography is limited in providing spatial details, however is an important screening tool in a trauma setting. Pneumomediastinum and subcutaneous emphysema are well detected by radiographs, as well as osseous abnormalities including conditions such as cervical osteophytes and diffuse idiopathic skeletal hyperostosis (DISH). Fluoroscopy is the workhorse in dynamic visualization of the esophagus. It is a helpful screening tool for esophageal abnormalities such as diverticula, ulcers, stenosis, dysmotility, and cancer. CT provides extensive spatial resolution and is the “gold standard” for evaluating most vascular pathology, cancer staging, and as a quick evaluation tool in the setting of trauma. Evaluation of superficial structures such as the thyroid gland, cervical lymph nodes, and cervical vascular structures can be easily performed with ultrasound, which has the added benefit of portability and lack of radiation exposure. MRI is an advanced modality, with superior soft tissue resolution, critical in the assessment of neural and lymphatic structures such as the brachial plexus and thoracic duct, which cannot be as reliably assessed with CT.
Anatomy of the thoracic inlet
Above the level of the first rib, familiarity with the cervical fasciae and infrahyoid neck spaces can help a radiologist construct a comprehensive differential diagnosis of pathology involving the thoracic inlet. The cervical fasciae define the spaces of the neck from which specific diseases can arise. They form important barriers which can limit the spread of infection and certain tumors .
Normal blood vessels in anomalous location and configuration can mimic a mass and be challenging to interpret. Familiarity with the more common vascular anomalies can increase confidence in interpretation. Alternatively, pathology involving the vasculature in the thoracic inlet can be easily overlooked.
Aberrant right subclavian artery
Partial anomalous pulmonary venous return
Internal jugular vein thrombus
Infection of the thoracic inlet region may arise spontaneously, as a result of traumatic injury, surgical complication, or extension from another space such as osteomyelitis or diskitis.
The spectrum and symptoms from neurologic pathology of the thoracic inlet can be highly variable as many important nerves traverse this region, including the brachial plexus, vagus nerve, recurrent laryngeal nerves, phrenic nerve, and sympathetic chain. Some examples of non-neoplastic pathology are nerve sheath cysts, laryngeal nerve injury, brachial plexopathy, and post-radiation injury.
Traction injury to the brachial plexus
Perineural cyst of the brachial plexus
Degeneration is a gradual deterioration of specific tissues, cells, or organs with impairment or loss of function due to injury, disease, or aging. This process occurs in all organ systems and in the thoracic inlet; this condition is most evident in the musculoskeletal, vascular, and digestive systems.
Diffuse idiopathic skeletal hyperostosis
Iatrogenic complications are a broad category of conditions that directly result from healthcare treatment or intervention. Common causes at the level of the thoracic inlet include complications following surgical procedures and post-radiation changes leading to fibrosis and scarring of the region.
Some frequently encountered congenital anomalies of the thoracic inlet are tracheobronchomegaly, dilated thoracic duct, branchial cleft cysts, narrowed thoracic inlet, and fibromatosis colli, as well as the previously discussed tracheoesophageal fistula and vascular anomalies including the aberrant right subclavian artery and partial anomalous pulmonary venous return.
Dilated thoracic duct
Autoimmune conditions are generally systemic, with some demonstrating propensity for specific organs, including those traversing the thoracic inlet. For example, systemic sclerosis can affect the esophagus causing esophageal dilatation . Autoimmune thyroiditis such as Hashimoto’s thyroiditis causes thyroid enlargement with nodules and can have an association with lymphoma . Antiphospholipid syndrome is associated with venous and arterial thrombosis .
The thymus has a variable appearance, typically soft tissue density at birth through adolescence, reaching a maximal size by the late teens, then gradually becoming fatty replaced through adulthood. The gland can extend from the lower border of the thoracic inlet through the fourth costal cartilage anteriorly.
There are many causes of traumatic injury to the thoracic inlet, each with unique features depending on the method of trauma and the structures involved. Importantly, trauma to the neck accounts for 5–10% of all serious traumatic injuries . The two most common forms of trauma are blunt force trauma and penetrating trauma.
Sternocleidomastoid muscle hematoma
Endocrinological organs to consider in the region of the thoracic inlet include the parathyroid and thyroid glands. The thyroid isthmus lies just above the level of the thoracic inlet in the midline. The parathyroid glands are normally paired bilaterally, typically located posterior to the thyroid gland. However, their location can be variable, occurring anywhere along the thyrothymic tract, extending from the angle of the mandible to the lower aspect of the superior mediastinum . Abnormalities and variants of these organs are commonly reported, including thyroid nodules, thyroid pyramid, and parathyroid hyperplasia. Thyroid nodules are incidental findings in 4–8% of adults [30, 31].
As seen, the thoracic inlet is a critical landmark in radiology, as it is a central conduit for many organ systems, and thus allowing itself to a vast array of non-neoplastic pathology. It is therefore important to critically evaluate this region and be aware that it may be overlooked on imaging of the neck or chest. The thoracic inlet marks a critical junction between the neck and chest imaging. A detailed examination of this region is essential when reviewing both neck and thoracic studies. The mnemonic VINDICATE is a helpful guide to methodically create differential diagnoses for non-neoplastic pathology encountered in this region.
The authors would like to acknowledge the following individuals for their contributions: Nadezhda Kiriyak for illustrated figures and Sarah Klingenberger for preparing the figures for submission.
TN drafted the manuscript. PEM, KKJ, and AAB participated in its design and editing. All authors read and approved the final manuscript.
Ethics approval and consent to participate
Consent for publication
The authors declare that they have no competing interests.
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