Neck dissection is performed to diagnose and/or remove at risk and/or diseased lymph nodes and, in some cases, surrounding structures. The main types of neck dissection include selective, modified, radical, and extended neck dissection (Table 10.2). Features of each of these can be appreciated on CT (Figs. 10.16, 10.17, 10.18, 10.19, and 10.20).

Postoperative imaging is usually performed with contrast-enhanced CT and serves to identify clinically occult disease, which occurs in 7.5–28% of cases. Per NCCN guidelines, a baseline study is usually obtained within about 6 months of surgery for comparison with subsequent studies, which are usually obtained depending on symptoms, physical exam, and findings from previous imaging. During the early postoperative period, local hemorrhage and edema are common findings for all types of neck dissection. These changes usually resolve by 6 weeks after surgery and have a reticular appearance on CT. Over time, there may be persistence of edema and development of fibrosis, particularly if radiotherapy is administered. The degree of retropharyngeal edema can be exacerbated by resection of the internal jugular vein. A stable postoperative appearance may not be attained until 12–18 months after surgery.

Following selective and modified radical neck dissection, atrophy of the sternocleidomastoid and strap muscles is also common. In addition, removal of the adipose tissue and lymph nodes around the carotid sheath decreases the space between the sternocleidomastoid and internal jugular veins. The presence of scarring may accentuate the degree of asymmetry and effacement of the fat planes. Nonvisualization of the ipsilateral internal jugular vein occurs in about 20% of cases of selective neck dissection and may be attributable to thrombosis and should be reported. Following removal of the ipsilateral submandibular gland with level I dissection, the remaining contralateral submandibular gland should not be misinterpreted as a lesion itself. Radical neck dissection results in more conspicuous flattening of the neck contour and blurring of the tissue planes than modified radical neck dissection. There may also be reduced flow in the carotid artery due to surgical manipulation and radiation therapy. Rarely, the common carotid artery is sacrificed during extended neck dissection. Myocutaneous flaps are usually required to reconstruct large defects resulting from radical and extended neck dissection. Tissue flaps are also sometimes used to provide coverage of the external carotid artery after modified radical neck dissection.

Potential pitfalls in the interpretation of imaging after neck dissection has been performed are cauterized adipose tissue and suture granulomas, which can be mistaken for lymphadenopathy. Cauterized adipose tissue can appear as nodular foci of soft tissue attenuation, but often conserve some degree of fat attenuation centrally (Fig. 10.21). Suture granulomas can also appear as soft tissue nodules, but the occasional presence of hyperattenuation centrally associated with the suture is a help clue (Fig. 10.22). In either case, these conditions tend to remain static on serial imaging, as opposed to recurrent neoplasm.

Complications depend on the extent of neck dissection. Denervation injury results in high T2 signal and enhancement within the first few months and fatty atrophy and laxity on a chronic basis. The more frequently encountered sites for denervation injury after neck dissection include the trapezius muscle and the tongue (Fig. 10.23). Extensive neck dissection can potentially impair lymphatic drainage and lead to cervicofacial edema, which appears as diffuse swelling and fat stranding (Fig. 10.24) and can be exacerbated by radiation therapy. Leakage of chyle from the lymphatic system can result in lymphoceles, which typically appear as unilocular fluid collections with thin walls (Fig. 10.25). Infections can occur in the skin and subcutaneous tissue as cellulitis and abscesses (Fig. 10.26). In addition, osteomyelitis of the clavicle can result from lower central compartment or supraclavicular lymph node dissection (Fig. 10.27). This should not be confused with degenerative changes and effusions of the sternoclavicular joint due to altered biomechanics and neuropathic joint (Fig. 10.28).

Parotidectomy is most commonly performed for primary salivary neoplasm resection, but is also performed for oncologic management of skin cancers. Several types of parotidectomy can be implemented, including superficial parotidectomy and total parotidectomy with or without facial nerve preservation, depending on the type, size, and location of the tumor (Figs. 10.29, 10.30, and 10.31). The defects created by more extensive resections can be reconstructed using tissue flaps or synthetic materials. Furthermore, when the facial nerve is compromised, eyelid weights are often used to aid eye closure.

In general, complications and expected consequences related to parotidectomy may include cosmetic deformity, facial nerve deficits, sialocele, wound infection, hematoma, and tumor recurrence. In particular, recurrence of parotid pleomorphic adenoma has an incidence of 1–5% and most commonly occurs within the first 10 years following surgical resection. Recurrent lesions have fairly characteristic imaging features. On T2-weighted MRI, the majority of recurrent tumors have very high signal intensity due to myxoid contents. The presence of multiple subcentimeter nodules is a strong indicator of recurrence and is observed in about two-thirds of cases. This feature results in a “bunch of grapes” appearance (Fig. 10.32). Recurrent pleomorphic adenomas are sometimes located in the subcutaneous tissues or adjacent neck spaces perhaps due to spillage during surgery. The enhancement pattern is variable, depending upon the extent of cystic components, fibrosis, and necrosis.

Salivary duct stones can be managed by sialendoscopic extraction. Sometimes, plastic stents are inserted after stone removal in order to reduce the risk of subsequent stenosis (Fig. 10.33). These appear as tubular hyperattenuating structures on CT and should not be misinterpreted as residual sialolithiasis. Occasionally, stone extraction can be complicated by sialocele or even cutaneous fistula formation due to the friability of the inflamed tissues in the setting of acute sialadenitis and sialodacryoadenitis. In such cases, imaging can be performed to assess for the extent of associated fluid collections and sinus tracts (Fig. 10.34).

Facial reanimation can be performed for treating the effects of chronic facial nerve paralysis. This can be accomplished with techniques, such as functioning free muscle transfer or temporalis muscle transposition and suspension combined with suborbicularis oculi fat (SOOF) lift. Overall, these techniques successfully restore smiles and provide improvement in mouth function in most patients.

Functioning free gracilis microneurovascular muscle transfer is a form of dynamic facial reanimation that can help restore facial tone and movement. The free muscle flap is buried in the subcutaneous tissues of the face extending from the temporal fossa to the oral commissure region. CT and MRI can demonstrate the intact muscle fibers in the healthy grafts (Fig. 10.35). In addition, Doppler ultrasound is useful for evaluating the patency of the feeding artery and draining vein. Transfer of compound flaps containing muscle and other tissue, such as the skin, can be performed for cases of complex facial paralysis that involve skin or soft tissue deficits after tumor excision. Alternatively, tensor fascia lata and AlloDerm grafts can be used and also appear as soft tissue bands on imaging, but these do not offer dynamic facial animation (Figs. 10.36 and 10.37).

Temporoparietal fascia and temporalis muscle transposition and suspension procedures consist of detaching and repositioning the flap approximately 180° inferiorly toward the oral commissure and/or nasolabial folds via a tunnel through subcutaneous tissues (Figs. 10.38 and 10.39). The tissues superficial to the plane of dissection can be translated superomedially and sutured to the fascia of the temporalis muscle. If necessary, the procedure can be augmented using Silastic prostheses to fill the defect. Alternatively, the muscle can be extended using polytetrafluoroethylene.

The suborbicularis oculi fat (SOOF) lift involves superior mobilization of midface structures, which are fastened to the orbital rim using a variety of approaches (Fig. 10.40). Often, the intraorbital fat pads are also released and sutured to the SOOF.

Depending on the stage of oral tongue malignancies, such as squamous cell carcinomas, variable degrees of glossectomy may be performed, ranging from partial, subtotal, or total, with or without floor of the mouth resection, mandibulectomy, and laryngectomy (Figs. 10.41, 10.42, 10.43, 10.44, and 10.45). Of note, composite tumor resection consisting of glossectomy, mandibulectomy, and neck dissection known as “Commando,” an acronym for combined mandibulectomy and neck dissection operation, can be performed for advanced cancers of the oral cavity. Furthermore, the submandibular gland may be removed with rerouting of the duct as part of the approach or as part of the combined suprahyoid neck dissection. Alternatively, the submandibular gland may be the main target of surgery when it is involved by primary salivary gland neoplasms. There are a variety of options for reconstructing surgical defects in the oral cavity region, including myocutaneous flaps, such as single or double bilobed radial forearm flaps, FAMM flaps, submental island flaps, and acellular dermal matrix, or a combination of these.

The role of imaging after glossectomy is to evaluate complications, such as infection, sialocele, and tumor recurrence (Figs. 10.46, 10.47, and 10.48). Of note, one must be particularly vigilant for the presence of perineural tumor spread on imaging before and after surgery, especially following resection of salivary gland malignancies, which is often along the maxillary division branches of the trigeminal nerve for oral cavity tumors. Furthermore, since radiation often accompanies surgical treatment of oral cancers, the mandible is at risk for osteonecrosis. This complication tends to occur at least 1 year after radiation therapy and appears as areas of cortical irregularity and lucency (Fig. 10.49). There can be superimposed infection and pathological fracture.

Tonsillectomy and adenoidectomy are two of the most commonly performed pediatric surgical procedures. The main indications for tonsillectomy and adenoidectomy include adenotonsillar hyperplasia with obstructive sleep apnea, failure to thrive, or abnormal dentofacial growth; malignant neoplasms; and adenotonsillar hyperplasia with upper airway obstruction, dysphagia, or speech impairment and halitosis. Furthermore, otitis media and recurrent or chronic rhinosinusitis or adenoiditis are indications for adenoidectomy, but not tonsillectomy, while recurrent or chronic pharyngotonsillitis, peritonsillar abscess, and streptococcal carriage are indications for tonsillectomy, but not adenoidectomy. Frequently, the appearance on postoperative imaging is that of asymmetric absence of Waldeyer ring tissue, whereby the residual normal tissue can hypertrophy and should not be mistaken for a lesion (Fig. 10.50). Sometimes, the trace amounts of residual Waldeyer ring tissues can regrow over the course of years after tonsillectomy/adenoidectomy, such that the effects of surgery are not noticeable. As in many other parts of the head and neck, when more extensive surgeries are performed for tumor resection, the resulting defects may be reconstructed using soft tissue flaps (Fig. 10.51).

Among patients who underwent tonsillectomy for obstructive apnea, cine MRI is a useful modality for evaluating anatomy and function when there are recurrent symptoms. Potential causes include glossoptosis, hypopharyngeal collapse, recurrent and enlarged adenoids and lingual tonsils, and macroglossia. If lingual tonsils were greater than 10 mm in diameter and abutted both the posterior border of the tongue and the posterior pharyngeal wall, they can be considered markedly enlarged (Fig. 10.52). On the other hand, patients can develop velopharyngeal insufficiency following excessive removal of adenoid tissues. This can manifest as a gap between the pharynx and soft palate on cine MRI, which can be treated via palatoplasty or pharyngeal augmentation with substances, such as hydroxyapatite filler (Fig. 10.53).

Among patients who underwent tonsillectomy/adenoidectomy for neoplasm, 18FDG-PET/CT is useful for evaluating recurrent tumor. However, infection at the site of surgery can manifest as focal hypermetabolism (Fig. 10.54). Noninfectious inflammation and granulation tissue at the surgical site can also yield false-positive results on 18FDG-PET/CT. However, as opposed to tumor recurrence, activity on 18FDG-PET/CT should decrease over time with infection and inflammation.

Transoral robotic surgery (TORS) is a minimally invasive technique that involves the use of endoscopic visualization and dexterous robotic arms and has been mainly implemented for resecting T1 and T2 squamous cell carcinomas of the oropharynx, although various other applications have been explored. TORS offers a high rate of preserved postoperative swallowing function, but low incidence of complications. The postoperative imaging findings to TORS generally differ from those related to open surgery. Tongue base tumor TORS resection typically includes approximately the half of the tongue base on the side of the tumor, with dissection to the circumvallate papillae and glossotonsillar sulcus. Consequently, during the first weeks to months after surgery, retraction of the tongue base bed is apparent on postoperative imaging (Fig. 10.55), without evidence of solid enhancement. A radical tonsillectomy using a TORS approach involves the tonsil, anterior and posterior tonsillar pillars, portions of the soft palate, tongue base, to encompass the superior constrictor muscle as the depth of resection and the posterior pharyngeal wall are resected. Imaging during the first several postoperative weeks typically demonstrates distortion of the fat planes around the medial pterygoid muscle and retropharyngeal edema (Fig. 10.56), which can result from retraction or thermal injury during the surgery. Over the ensuing months, scar tissue formation leads to gradual retraction of the lateral oropharyngeal wall, with “tilting” of the soft palate toward the surgical bed.

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