LATERAL COMPARTMENT: NONNODAL MASSES
- Magnetic resonance imaging and computed tomography provide the critical and usually definitive data needed in the diagnosis and management of lateral compartment masses.
- Prompt and accurate imaging can help to avoid potentially severe complications in some lateral compartment pathology.
- Imaging-guided tissue sampling may be useful in the management of these masses.
The lateral compartment of the neck is discussed in this chapter as the site of origin of nonnodal mass lesions of the infrahyoid neck. Nodal masses are discussed in Chapters 157 through 159. The lateral compartment is commonly secondarily involved by masses that originate in the visceral compartment, posterior compartment, and contiguous retropharyngeal space; this is discussed in Chapters 150, 161, and 162. The lateral compartment may also be secondarily involved with inflammatory conditions, such as suppurative adenitis, thrombophlebitis, arteritis, and the less common deep neck abscess, which occasionally mimic other masses; these are discussed in Chapter 155. Other sources of masses include acquired vascular conditions, discussed in Chapter 154, and developmental branchial abnormalities, discussed in Chapter 153 (Fig. 156.1). The spectrum of disease that might present as a mass and that arises in the lateral compartment is outlined in Table 156.1.
The primary presentation may be that of a neck mass of uncertain etiology without associated signs, symptoms, or other physical findings. There may be associated pain, dysphagia, odynophagia, or dysphonia (Fig. 156.2). Airway compression is possible. There is often a history of progressive enlargement of the mass.
Tenderness, fever, and associated generalized swelling may be present and are much more likely in the inflammatory conditions discussed in Chapter 155. Vascular malformations may be compressible and/or pulsatile, and masses may feel obviously cystic to palpation (Chapter 154).
Neurologic dysfunction may be due to involvement of the cervical sympathetics, vagus nerve, recurrent laryngeal nerve, and phrenic nerve. Signs of cervical spinal cord compromise or rapid enlargement, when present, suggest that a very urgent problem might be at hand.
The anatomy of the lateral compartment is essentially that of the carotid sheath and its relationship to the anterior and posterior triangles, the sternocleidomastoid muscle, and the core visceral and posterior compartments. All of these elements, together with knowledge of neck development, predict the possible source of a nonnodal mass. The relationship of the lateral compartment to the retropharyngeal space medially and the thoracic inlet and suprahyoid neck space must be understood. Essentially, there is relatively free communication within the lateral compartment between the anterior and posterior triangles and the retropharyngeal space. The relationship of those spaces to the superficial fascia (platysma) and investing and prevertebral layers of the cervical fascia should be reviewed, if necessary, in Chapter 149.
Structures of Interest
The analysis of a nonnodal mass of the lateral compartment depends on a thorough understanding of its relationship to the carotid sheath and the following boundaries:
- Superiorly: Hyoid bone as the arbitrary boundary
- Inferiorly: Thoracic inlet
- Anteriorly: Anterior triangle
- Posteriorly: Posterior triangle
- Medially: Visceral compartment, retropharyngeal space, and posterior compartment
- Laterally: Sternocleidomastoid muscle and/or the superficial fascia and subcutaneous fat
Computed Tomography and Magnetic Resonance Imaging
The infrahyoid neck is mainly evaluated with computed tomography (CT) and magnetic resonance imaging (MRI). The specifics and relative value of using these studies in this anatomic region are reviewed in Chapter 149. Problem-driven protocols for CT and MRI are presented in Appendixes A and B. MRI is preferable when the known or suspected diagnosis is a venolymphatic malformation or if there is neurologic compromise.
Ultrasound has a potential triage role to play in the evaluation of a pulsatile mass but is most often cost additive and unlikely to contribute to definitive medical decision making (Fig. 156.3). It may actually delay a more timely use of a likely more definitive CT or magnetic resonance (MR) study.
Catheter angiography is used very selectively and most often as a prelude to endovascular intervention once the diagnosis has been established by imaging and related computed tomographic angiography or MR angiography.