Acs0207 Neck Dissection

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  • 1. © 2004 WebMD, Inc. All rights reserved. ACS Surgery: Principles and Practice 2 HEAD AND NECK 7 NECK DISSECTION — 1 7 NECK DISSECTION Miriam N. Lango, M.D., Bert W O’Malley, Jr., M.D., F.A.C.S., and Ara A. Chalian, M.D. . Preoperative Evaluation rent; are deeper than 6 mm; involve the ear, the temple, or the In the majority of cases, cancer in the neck is a metastasis from classic H zone; occur in an immunocompromised patient; or are a primary lesion in the upper aerodigestive tract, though me- poorly differentiated—have a significant occult metastatic rate, tastases from skin, thyroid, and salivary gland neoplasms are ranging from 20% to 60%. The presence of cervical metastases also encountered. Lymphomas often present as cervical reduces 5-year survival to about 32%,3 which suggests that early lymphadenopathy. intervention for high-risk cutaneous lesions, involving regional When a patient presents with a suspicious lesion in the neck, a lymphadenectomy, sentinel lymph node (SLN) biopsy, or irradi- careful history and physical examination should be performed, ation of at-risk lymph node basins, may be warranted. along with a thorough evaluation of the aerodigestive tract aimed at locating the source of possible metastatic disease. Fine-needle Salivary Gland Neoplasms aspiration (FNA) of the neck mass should then be done to deter- With salivary gland neoplasms [see 2:1 Oral Cavity Lesions], mine whether the mass is malignant. FNA can often differentiate the incidence of cervical metastases is related to the histopathol- between epithelial and lymphoid malignancies, and this differen- ogy as well as the size of the tumor. The most aggressive salivary tiation will guide subsequent workup. The reported sensitivity of gland lesions are squamous cell carcinoma, carcinoma ex pleo- FNA ranges from 92% to 98%; the reported specificity, from morphic adenoma, adenocarcinoma, and salivary ductal carcino- 94% to 100%.1,2 ma. Patients with these lesions often have cervical metastases at If FNA reveals the presence of atypical lymphoid cells, an exci- presentation that warrant a therapeutic neck dissection [see Table sional lymph node biopsy should be performed to supply the 1]. How best to manage occult cervical salivary gland metastatic pathologist with a large enough sample to allow full typing of the disease is controversial. The occult metastatic rate for aggressive tissue. An excisional biopsy may also be performed if the FNA is lesions ranges from 25% to 45%. For such lesions, a selective negative or indeterminate, the surgeon suspects a malignancy, neck dissection is typically incorporated into the surgical and the rest of the physical examination yields negative results. approach.4 Routine excisional biopsy of neck masses for diagnostic purposes is not recommended, however, because it may result in tumor Metastatic Well-Differentiated Thyroid Cancer spillage into the wound and complicate subsequent definitive Cervical lymph node metastases are present in 10% to 15% of resection. patients with well-differentiated thyroid carcinoma. The impact Once the presence of an epithelial malignancy is established, of nodal metastases on local recurrence and survival has not been the primary site of the lesion must be determined if it is not established. Other factors (e.g., age, sex, tumor extent, and dis- apparent on initial physical examination. Imaging studies (e.g., tant metastases) appear to have a greater effect on prognosis. computed tomography and magnetic resonance imaging) may be Nevertheless, in the presence of clinically apparent nodal disease, helpful in locating the source of a cervical metastasis. Positron a formal neck dissection is advised: so-called cherry-picking oper- emission tomography (PET) detects lesions with increased meta- ations or limited lymph node excisions result in higher rates of bolic activity but has the limitation of being unable to detect recurrence.5 lesions smaller than 1 cm in diameter. Primary lesions greater than 1 cm in diameter usually are easily identified on physical Squamous Cell Carcinoma of the Upper Aerodigestive Tract examination and other imaging studies; thus, PET scans are of With upper aerodigestive tract squamous cell carcinomas, the limited value in this setting. In any patient with metastatic cervi- incidence of cervical metastases is related to the site of the pri- cal adenopathy thought to originate in the upper aerodigestive mary lesion, the size of the tumor, the degree of differentiation, tract, panendoscopy and biopsy with general anesthesia are the depth of invasion, and a number of other factors. A signifi- mandatory for locating and characterizing the primary source of cant proportion of head and neck cancer patients who harbor the tumor and ruling out the presence of synchronous lesions. clinically silent primary tumors of the base of the tongue, the The most common occult primary sites are the base of the tonsils, or the nasopharynx initially present with cervical tongue, the tonsils, and the nasopharynx. In 5% to 10% of adenopathy [see Table 1]. These sites lack anatomic barriers that patients who present with a metastatic node, the primary lesion is limit tumor spread and are supplied by rich lymphatic networks never found despite extensive workup. that facilitate metastasis. In contrast, patients with glottic and lip cancers are more likely to present early, without clinical INCIDENCE AND IMPACT OF NECK METASTASES adenopathy. The presence of cervical metastases negatively affects progno- Cutaneous Squamous Cell Carcinoma sis and has been associated with increased recurrence rates and The incidence of cervical metastases is governed by many fac- reduced disease-free and overall survival.The presence of clinical tors. Cervical metastases from cutaneous squamous cell carcino- adenopathy decreases survival by 50%. Metastatic tumors that mas are rare, occurring in 2% to 10% of cases. However, certain rupture the lymph node capsule—a process known as extracap- lesions—those that are greater than 2 cm in diameter; are recur- sular spread (ECS)—are biologically more aggressive. Patients
  • 2. © 2004 WebMD, Inc. All rights reserved. ACS Surgery: Principles and Practice 2 HEAD AND NECK 7 NECK DISSECTION — 2 Table 1 Incidence of Cervical Metastases in the nasopharynx; it also applies to metastases from major salivary Selected Head and Neck Cancers gland and sinonasal malignancies but not to metastases from cutaneous or thyroid malignancies, which use an alternate staging system. Tumor Incidence of Cervical Adenopathy The purpose of staging is to characterize the tumor burden of Cutaneous squamous cell carcinoma 2%–10% an individual patient. Accordingly, an effective staging system should incorporate factors known to have prognostic and thera- Salivary gland malignancies peutic significance, thereby facilitating planning of therapy and Mucoepidermoid carcinoma (high- 30%–70% appropriate patient counseling. In addition, it should attempt to grade) 8% standardize reporting so that meaningful cross-institutional com- Adenoid cystic carcinoma 25% parisons can be obtained. A staging system ideally should also be Malignant mixed tumor 46% Squamous cell carcinoma simple to apply while still incorporating biologically important 50% Salivary duct carcinoma factors that permit accurate patient stratification in prospective 40% Acinic cell carcinoma clinical trials. Precise characterization and differentiation of tu- Metastatic well-differentiated thyroid mors facilitate identification of those patients who are most like- 10%–15% cancer ly to benefit from treatment. Squamous cell carcinoma of upper The TNM staging system does not include a number of fac- aerodigestive tract tors that are known to have an impact on prognosis, such as the Alveolar ridge 30% presence or absence of ECS and the pattern of lymphatic spread. Hard palate 10% Nonanatomic factors (e.g., comorbidity, immune status, and nu- Oral tongue 30% tritional status) have a strong impact on survival as well but are Anterior pillar/retromolar trigone 45% also not incorporated in the current staging system. In general, Floor of mouth 30% TNM staging has been found inadequate for use in clinical Soft palate 44% trials.12 Tonsillar fossa 76% Tongue base 78% The limitations of clinical staging of the neck are well de- Bilateral 20% scribed.The addition of imaging to clinical examination improves diagnostic sensitivity but not specificity. Imaging is particularly useful after chemoradiation because of the difficulty of clinical who have palpable cervical lymphadenopathy with ECS manifest examination in this setting. Pathologic review of neck specimens a 50% decrease in survival compared with those who have pal- remains the gold standard for anatomic staging. The addition of pable cervical lymphadenopathy without ECS.6 In addition, ultrasound-guided FNA of neck nodes yields enhanced diagnos- about 50% of clinically negative, pathologically positive neck tic accuracy in cases where the neck is clinically negative but the specimens exhibit ECS. Clinically negative, pathologically posi- radiologic findings are positive. This approach is employed to tive, and ECS-positive specimens are associated with a high risk select patients for neck dissection in a number of centers, partic- of regional recurrence and distant metastases.7-9 The presence of ularly in Europe; whether it provides more accurate staging than ECS in lymph node metastases may in fact be the single most alternative methods, such as SLN biopsy, remains to be deter- important prognostic factor in patients with head and neck can- mined. Results from the First International Conference on cer. Identification of this patient subset may be the most impor- Sentinel Node Biopsy in Mucosal Head and Neck Cancer tant benefit of elective neck dissection, in that it allows these revealed that SLN biopsy of the clinically negative neck has a sen- patients to be offered adjuvant therapy. Nonrandomized studies sitivity comparable to that of a staging neck dissection.13 In gen- have found that both disease-specific and overall survival are sig- eral, imaging modalities appear to be neither sufficiently sensitive nificantly improved when these high-risk patients are treated nor sufficiently specific in the evaluation of the clinically negative with adjuvant postoperative chemoradiation.10 However, ran- neck. Uptake of 2-deoxy-3 [18F] fluoro-D-glucose, as measured domized clinical trials are needed to confirm the clinical benefits by PET scans, is undetectable in small foci of cancer in the clin- of adjuvant chemoradiation in this setting. ically negative neck.14 Whereas anatomic and pathologic factors (e.g., ECS) have Proper staging is important for stratification of patients into long been known to predict tumor behavior, it is only compara- risk categories on the basis of tumor biology, so that high-risk tively recently that the impact of comorbidity has been well char- patients may be appropriately selected for clinical trials or offered acterized.When patients are stratified by tumor stage, those with adjuvant therapy and other patients may be spared unnecessary comorbidities fare worse. In fact, the impact of comorbidity on treatment. Until accurate methods of assessing the clinically neg- overall survival is greater than that of tumor stage or treatment ative neck are developed, selective neck dissection will be per- type.10,11 In addition, comorbidity is associated with both formed to treat the neck when the occult metastatic rate is increased frequency and increased severity of surgical complica- expected to be higher than 20%. tions.These factors may be important in treatment selection and patient counseling. To date, comorbidity has not been incorpo- INDICATIONS FOR NECK DISSECTION rated into clinical staging of head and neck cancer patients. The classic indication for neck dissection is for treatment of metastatic carcinoma in the neck, most frequently deriving from STAGING OF NECK CANCER a mucosal site in the upper aerodigestive tract. Over time, the Staging of the neck for metastatic squamous cell carcinomas of indications for neck dissection have changed. With wider use of the head and neck is based on the TNM classification formulated chemoradiation therapy for head and neck cancer, treatment of by the American Joint Committee on Cancer (AJCC) [see 2:1 metastatic disease in the neck has become increasingly nonsurgi- Oral Cavity Lesions]. The N classification applies to cervical cal. Currently, neck dissections are considered either therapeutic metastases from all upper aerodigestive tract mucosal sites except (performed to treat palpable disease in the neck) or elective (per-
  • 3. © 2004 WebMD, Inc. All rights reserved. ACS Surgery: Principles and Practice 2 HEAD AND NECK 7 NECK DISSECTION — 3 Operative Planning CHOICE OF PROCEDURE Comprehensive Dissection: Radical and Modified Radical Neck Dissection The radical neck dissection was first described in 1906 by George Crile, who based his approach on the Halstedian princi- ple of en bloc resection. The procedure was subsequently stan- dardized by Hayes Martin at Memorial Hospital in New York in II the 1930s and 1940s. In this latter version of the procedure, lym- phatic structures from the strap muscles anteriorly, the trapezius I posteriorly, the mandible superiorly, and the clavicle inferiorly are removed. Nonlymphatic structures in this space are also sacri- ficed, including the spinal accessory nerve, the sternocleidomas- toid muscle, the internal and external jugular veins, the sub- III VI mandibular gland, and sensory nerve roots. The routine sacrifice of the spinal accessory nerve, the internal jugular vein, and the V sternocleidomastoid muscle contributes to the significant mor- bidity associated with radical neck dissection. IV Since the 1970s, the necessity of en bloc resection for onco- logic cure has been reexamined. Structures once routinely sacri- ficed are now routinely preserved unless they are grossly involved with cancer.The various functional, or modified, radical neck dis- sections are classified according to which structures are pre- Figure 1 Cervical lymph nodes are divided into six levels served. Type I dissections preserve the spinal accessory nerve; on the basis of their location in the neck. type II, the spinal accessory nerve and the internal jugular vein; type III, both of these structures along with the sternocleidomas- toid muscle. Modified radical neck dissections have proved to be formed when the expected incidence of occult metastases from a as effective in controlling metastatic disease to the neck as the lesion exceeds 20%).Technically, neck dissections are classified as classic radical neck dissection.17 comprehensive dissections, which incorporate five levels of the neck, or selective dissections, in which only selected lymph node Selective Neck Dissection levels are removed according to predicted drainage patterns from In a selective neck dissection, at-risk lymph node drainage specific primary sites.There is also a third technical classification, basins are selectively removed on the basis of the location of the extended neck dissections, which can be combined with selective primary tumor in a patient with no clinical evidence of cervical or comprehensive neck dissections for removal of additional lymphadenopathy. Cancers in the oral cavity, for example, typical- nodal basins [see Operative Planning, Choice of Procedure, ly metastasize to levels I through III and, occasionally, IV; laryn- below]. Six lymph node drainage basins in the neck are recognized geal cancers typically metastasize to levels II through IV.The ratio- [see Figure 1]. nale for selective neck dissection is based on retrospective patho- logic reviews of radical neck dissection specimens from patients CONTRAINDICATIONS TO NECK DISSECTION without palpable lymphadenopathy. These reviews revealed that The only absolute contraindication to neck dissection is surgi- lymph node micrometastases were confined to specific neck levels cal unresectability. The determination of unresectability is made for a given aerodigestive tract site.18 by the operating surgeon either preoperatively, on the basis of The advantages of selective neck dissection over radical and imaging studies, or in the operating room.Typically, the presence modified radical neck dissection are both cosmetic and function- of Horner syndrome, paralysis of the vagus nerve or the phrenic al. A selective neck dissection involves less manipulation (and nerve, or invasion of the brachial plexus or the prevertebral mus- thus less risk of devascularization) of the spinal accessory nerve, cles indicates that the tumor is unresectable. The involvement of thereby decreasing the incidence of postoperative shoulder dys- the carotid artery may be predicted on the basis of imaging stud- function. Preservation of the sternocleidomastoid muscle allevi- ies. Encasement of the carotid artery by tumor suggests direct ates the cosmetic deformity seen with a radical neck dissection invasion of the vessel; however, studies correlating imaging char- and provides some protection for the carotid artery. acteristics and pathologic invasion of the carotid have shown that Preservation of the internal jugular vein decreases venous con- tumors surrounding 180° or more of the carotid’s circumference gestion of the head and neck and is necessary if the contralateral have a higher incidence of carotid invasion than tumors sur- internal jugular vein is sacrificed.With primary lesions located in rounding less than 180° (75% versus 50%). In the absence of the midline in the base of the tongue, the supraglottic larynx, or direct invasion of the vessel wall, tumor may be peeled off by the medial wall of the piriform sinus, bilateral regional metastases means of subadventitial surgical dissection. Tumors surrounding are common, and bilateral neck dissections are therefore indicat- 270° of the vessel have an 83% incidence of carotid invasion, ed. Sacrifice of both internal jugular veins is associated with sig- necessitating sacrifice of the artery.15 However, sacrifice of the nificant morbidity, including increased intracranial pressure, syn- carotid artery, with or without reconstruction with a vein graft, drome of inappropriate antidiuretic hormone secretion, airway has been associated with significant morbidity and confers no edema, and death. Bilateral internal jugular sacrifice is managed survival benefit.16 by staging the neck dissections or by carrying out vascular repair.
  • 4. © 2004 WebMD, Inc. All rights reserved. ACS Surgery: Principles and Practice 2 HEAD AND NECK 7 NECK DISSECTION — 4 In the presence of multiple pathologically positive lymph nodes went a planned neck dissection. Tumor cells were present in the or evidence of ECS, adjuvant therapy is indicated.19 Accordingly, neck specimens of 25% of patients with complete and 39% of selective neck dissection may be viewed as a diagnostic as well as patients with incomplete clinical responses. No patients with a therapeutic procedure. To date, however, no randomized clini- complete pathologic responses experienced regional recurrence, cal trials have demonstrated that selective neck dissection with whereas 20% of patients with pathologically positive neck dis- adjuvant treatment as needed is better than so-called watchful section specimens experienced nonsalvageable regional recur- waiting with regard to prolonging survival in patients who present rences. In addition, planned neck dissection led to reduced rates without evidence of cervical metastatic disease. Therefore, it of regional recurrence in patients treated with chemoradiation. is not yet possible to justify the added cost and morbidity of elec- The authors suggested that all patients presenting with N2 or tive neck dissection in patients without evidence of metastatic dis- N3 cervical lymphadenopathy should undergo planned neck ease. SLN mapping may facilitate pathologic staging in this set- dissection, regardless of clinical response to chemoradiation ting and spare low-risk patients from unnecessary interventions; therapy. however, its sensitivity and specificity for this purpose are still The required extent of planned neck dissection after chemora- under investigation. diation is still under investigation. Neck dissection after chemora- The growing focus on preservation of function and limitation diation carries significant morbidity in the form of severe soft tis- of morbidity has led some surgeons to promote the use of selec- sue fibrosis and increased spinal accessory nerve injury. Pathologic tive neck dissection to treat node-positive neck tumors. review of comprehensive neck specimens after chemoradiation Although retrospective studies have suggested that a selective reveals that in patients with oropharyngeal cancer, levels I and V neck dissection may be adequate in carefully selected node-pos- are rarely involved in the absence of radiographic abnormalities,23 itive patients,20 the effectiveness of this approach is still which suggests that a planned selective dissection involving levels unproven, and its application remains subject to individual sur- II through IV may be sufficient for cases of oropharyngeal cancer gical judgment. treated with chemoradiation. This more limited approach un- doubtedly causes less morbidity, but additional data are required Extended Neck Dissection to assess its oncologic efficacy. Extended neck dissections can be combined with selective Typically, management of the neck is determined in part by or comprehensive neck dissections to remove additional nodal management of the primary tumor. Early neck dissection for basins, such as the suboccipital and retroauricular nodes. These bulky nodal disease before nonsurgical treatment of the primary groups of nodes, which are located in the upper posterior neck, lesion is a controversial practice. Bulky cervical adenopathy is are the first-echelon nodal basins for posterior scalp skin can- unlikely to exhibit a complete pathologic response to nonsurgical cers. The retroauricular nodes lie just posterior to the mastoid treatment. A patient who requires dental extractions before radi- process, and the suboccipital nodes lie near the insertion of the ation therapy may undergo a neck dissection at the same time, trapezius muscle into the inferior nuchal line. Cancers of the proceeding to radiation therapy 7 to 10 days after operation. anterior scalp, the temple, and the preauricular skin drain to peri- Early neck dissection decreases the tumor burden, thereby allow- parotid lymph nodes; these lymph nodes are removed in con- ing lower adjunctive doses of radiation to be delivered to the neck. junction with a parotidectomy [see 2:6 Parotidectomy]. Retro- Thus, it is possible that early neck dissection for bulky resectable pharyngeal nodes may be removed in the treatment of selected cervical adenopathy can reduce the expected morbidity of cancers originating in the posterior pharynx, the soft palate, or planned postchemoradiation neck dissection.There is limited evi- the nasopharynx. A mediastinal lymph node dissection may be dence in the literature that such an approach is feasible in certain combined with a neck dissection in the treatment of metastatic circumstances24; however, it is recommended that significant thyroid carcinomas. delays in initiating treatment to the primary site be avoided because such delays may ultimately have a negative impact on NECK DISSECTION AFTER CHEMORADIATION survival. The indications for neck dissection have been significantly RECONSTRUCTION AND RECURRENCE AFTER NECK affected by the increasing use of organ preservation protocols for DISSECTION the treatment of head and neck cancer. Nasopharyngeal carcino- mas, which are uniquely radiosensitive, are generally treated with The use of microvascular free tissue transfer to reconstruct irradiation, with or without chemotherapy; neck dissection is surgical defects in the head has allowed surgeons to resect large reserved for patients who experience an incomplete response and tumors with large margins while simultaneously achieving for patients with bulky cervical lesions. Similarly, patients with improved functional results. Preservation of vascular—and, early nodal disease (N0 or N1) treated according to organ preser- occasionally, neural—structures during neck dissection may vation protocols may undergo nonsurgical therapy. For patients facilitate the reconstructive process. Typically, several vessels, who have advanced neck disease (N2 or N3) or who respond including an artery and one or two veins, are required for inflow incompletely to therapy, a planned posttreatment neck dissection and outflow into a free flap. The facial artery, the retro- is recommended because surgical salvage of so-called neck fail- mandibular vein, and the external jugular vein, which are pre- ures is rarely successful.21 As a rule, the planned neck dissection served during level I and level II dissection, are the vessels that should be done within 6 weeks of the completion of chemoradi- are most frequently used for flap revascularization. If these ves- ation therapy: if it is delayed past the 6-week point, progressive sels are unavailable as a consequence of high-volume neck dis- soft tissue fibrosis may develop, resulting in difficult surgical dis- ease, the superior thyroid artery and the transverse artery, with section, increased postoperative morbidity, and, potentially, companion veins, are suitable substitutes. To date, there is no tumor progression. evidence in the literature that preservation of vascular structures A 2003 study highlighted the need for planned neck dissection in the neck predisposes patients to regional recurrence. Cau- after definitive chemoradiation for N2 or N3 nodal disease.22 In tion must, however, be exercised in the setting of pathologic this study, 76 patients presenting with N2 or N3 disease under- lymphadenopathy.
  • 5. © 2004 WebMD, Inc. All rights reserved. ACS Surgery: Principles and Practice 2 HEAD AND NECK 7 NECK DISSECTION — 5 a b c d e f Figure 2 Illustrated are incisions used for neck dissections. Incision design is a critical element of operative plan- ning. Incisions are chosen with the aims of optimizing exposure of relevant neck levels and minimizing morbidity. The incisions depicted in (a) and (b) are useful for selective neck dissections. For the more extensive exposure required in a radical or modified radical neck dissection, a deeper half-apron style incision (c) may be used, or a vertical limb may be dropped from a mastoid-submental incision (d); the latter incision is less reliable and may break down, expos- ing vital structures such as the carotid. The incision depicted in (e) is also useful for selective neck dissections. The Macfee incision (f) provides limited exposure and results in persisent lymphedema in the bipedicled skin flap. Operative Technique Step 2: Dissection of Anterior Compartment Embedded within the fascia overlying the submandibular RADICAL NECK DISSECTION gland is the marginal mandibular branch of the facial nerve, Step 1: Incision and Flap Elevation which must be elevated and retracted to prevent lower-lip weak- ness. The submental fat pad is then grasped, retracted posterior- When a radical or modified radical neck dissection is indicated, ly and laterally, and mobilized away from the floor of the sub- appropriate neck incisions must be designed so as to facilitate expo- mental triangle.The omohyoid muscle is identified inferior to the sure while preserving blood flow to the skin flaps [see Figure 2]. The digastric tendon and skeletonized to its intersection with the ster- incision provides access to the relevant levels of the neck, affects nocleidomastoid muscle posteriorly.The omohyoid muscle forms cosmesis, and determines the extent of lymphedema and postoper- the anteroinferior limit of the dissection. ative fibrosis (“woody” neck), especially in previously irradiated Fat and lymphatic structures are dissected away from the areas. If a biopsy was previously performed, the tract should be excised and incorporated into the new incision.When a total laryn- digastric muscle and the mylohyoid muscle. The hypoglossal and gectomy is done, the stoma is fashioned separately from the neck lingual nerves lie just deep to the mylohyoid muscle and are pro- incision; in the event of a pharyngocutaneous fistula, the salivary tected by it [see Figure 3]. In this region, the distal end of the facial flow will be diverted away from the stoma. artery can be identified and preserved as needed for reconstruc- Once the incision is made, subplatysmal flaps are raised. If tive purposes. Once the posterior edge of the mylohyoid muscle there is extensive lymphadenopathy or extension of tumor into is visualized, an Army-Navy retractor is inserted beneath the the soft tissues of the neck, skin flaps may be raised in a muscle to expose the submandibular duct, the lingual nerve with supraplatysmal plane to ensure negative surgical margins. Such its attachment to the submandibular gland, and the hypoglossal flaps, however, are not as reliably vascularized as subplatysmal nerve.The submandibular duct and the submandibular ganglion, flaps. Clinical judgment must be exercised in these situations.The with its contributions to the gland, are ligated, and the sub- flaps are raised to the mandible superiorly, the clavicle inferiorly, mandibular gland is retracted out of the submandibular triangle. the omohyoid muscle and the submental region anteriorly, and The posterior belly of the digastric muscle is then identified the trapezius posteriorly. Typically, radical neck dissections are inferior to the submandibular gland and skeletonized to the ster- performed in patients with clinically positive lymphadenopathy, nocleidomastoid muscle posteriorly, where it inserts on the mas- and adequate exposure of levels I through V is required. If a ver- toid tip.The specimen must be mobilized off structures just infe- tical limb is used, it must not be centered over the carotid artery, rior to the digastric muscle. To prevent inadvertent injury, it is because of the risk of potentially catastrophic dehiscence. Deep essential to understand the relationships among these structures utility-type incisions yield more limited exposure of level I but [see Figure 3]. The hypoglossal nerve emerges from beneath the provide reliable vascular inflow to skin flaps. mylohyoid muscle and passes into the neck under the digastric
  • 6. © 2004 WebMD, Inc. All rights reserved. ACS Surgery: Principles and Practice 2 HEAD AND NECK 7 NECK DISSECTION — 6 Internal Carotid Artery External Carotid Artery Facial Artery Digastric Muscle Spinal Lingual Accessory Artery Nerve Hypoglossal Nerve Occipital Artery Mylohyoid Internal Jugular Muscle Vein Hyoid Bone Ansa Hypoglossi Superior Thyroid Hyoglossal Artery Muscle Carotid Sheath Common Carotid Artery Vagus Nerve Figure 3 Depicted are the key anatomic relationships in levels I and II that must be kept in mind in performing a neck dissection. View is of the right neck. muscle. It then loops around the external carotid artery at the ori- placed along the lymphatic pedicle until there is no evidence of gin of the occipital artery and ascends to the skull base between clear or turbid fluid on the Valsalva maneuver. Care is taken to the external carotid artery and the internal jugular vein. Often, avoid inadvertent injury to the vagus nerve or the phrenic nerve, the hypoglossal nerve is surrounded by a plexus of small veins, which course through this region. branching off the common facial vein. Bleeding in this region places the hypoglossal nerve at risk.The jugular vein, located just Step 4: Mobilization of Supraclavicular Fat Pad (“Bloody posterior to the external carotid artery and the hypoglossal nerve, Gulch”) may be isolated and doubly suture-ligated at this point. The fascia overlying the supraclavicular fat pad is incised, and Frequently, the spinal accessory nerve is identified just lateral and the supraclavicular fat pad is bluntly retracted superiorly so as to posterior to the internal jugular vein, proceeding posteriorly into free the tissues from the supraclavicular fossa. If transverse cervi- the sternocleidomastoid muscle. cal vessels are encountered, they are clamped and ligated as nec- In a radical neck dissection, the sternocleidomastoid muscle essary. Fascia is left on the deep muscles of the neck, which also and the spinal accessory nerve are transected at this point and ele- envelop the brachial plexus and the phrenic nerve. vated off the splenius capitis and the levator scapulae to the trapezius posteriorly. The anterior edge of the trapezius is skele- Step 5: Dissection and Removal of Specimen tonized from the occiput to the clavicle. The accessory nerve is Attention is then turned to the posterior aspect of the neck. Fat again transected where it penetrates the trapezius. and lymphatic tissues are retracted anteriorly with Allis clamps, and the specimen is dissected off the deep muscles of the neck Step 3: Control of Internal Jugular Vein Inferiorly; Ligation of with a blade. Again, a layer of fascia is left on the deep cervical Lymphatic Pedicle musculature: stripping fascia off the deep cervical musculature The sternal and clavicular heads of the sternocleidomastoid results in denervation of these muscles, which adds to the mor- muscle are transected and elevated to expose the anterior belly of bidity associated with accessory nerve sacrifice. Once the speci- the omohyoid muscle.The soft tissue overlying the posterior belly men is mobilized beyond the phrenic nerve, the cervical nerves of the omohyoid muscle is dissected, clamped, and ligated as nec- (C1–C4) may be divided. The specimen is peeled off the carotid essary. The omohyoid muscle is then transected, and the jugular artery and removed. vein, the carotid artery, and the vagus nerve are exposed. The jugular vein is isolated and doubly suture-ligated. Care is taken Step 6: Closure not to transect the adjacent vagus nerve and carotid artery. The The neck incision is closed in layers over suction drains. lymphatic tissues in the base of the neck adjacent to the internal MODIFIED RADICAL NECK DISSECTION jugular vein are clamped and suture-ligated 1 cm superior to the clavicle. If a chyle leak is encountered, a figure-eight stitch is The incision is made and flaps elevated as in a radical neck dis-
  • 7. © 2004 WebMD, Inc. All rights reserved. ACS Surgery: Principles and Practice 2 HEAD AND NECK 7 NECK DISSECTION — 7 section. Care must be exercised in elevating the posterior skin External flap.Typically, the platysma is deficient in this area, and often, no Digastric Muscle Mylohyoid Carotid Occipital natural plane exists. Dissection deep in the posterior triangle may (Posterior Belly) Muscle 12th Nerve Artery Artery result in inadvertent injury to the spinal accessory nerve, which travels inferiorly and posteriorly across the posterior triangle in a relatively superficial plane to innervate the trapezius. A type I modified radical neck dissection begins with dissec- tions of levels I and II, as described for a radical neck dissection (see above). The spinal accessory nerve is identified just superfi- cial or posterior to the internal jugular vein and preserved; the distal spinal accessory nerve is then identified in the posterior tri- angle.Typically, the spinal accessory nerve can be identified 1 cm superior to the cervical plexus along the posterior border of the sternocleidomastoid muscle. Provided that the patient is not fully paralyzed, the surgeon can distinguish this nerve from adjacent sensory branches by using a nerve stimulator. Once the spinal accessory nerve is identified, it is dissected and mobilized distally to the point at which it penetrates the trapez- ius. Proximally, the nerve is dissected through the sternocleido- mastoid muscle, which is transected over the nerve. The branch to the sternocleidomastoid muscle is divided with Metz scissors, and the nerve is fully mobilized from the trapezius posteroinferi- orly to the posterior belly of the digastric muscle anterosuperior- ly, then gently retracted out of the way. Omohyoid Common Internal Sternocleido- 11th Nerve The rest of the neck dissection proceeds as described for a rad- Muscle Carotid Jugular mastoid ical neck dissection. If the tumor does not involve the internal Artery Vein Muscle jugular vein, it may also be preserved; this constitutes a type II modified radical neck dissection. If the spinal accessory nerve, the Figure 4 Selective neck dissection. The posterior belly of the internal jugular vein, and the sternocleidomastoid muscle are all digastric muscle is identified inferior to the submandibular gland. preserved, the procedure is a type III modified radical neck dis- This muscle protects several critical structures just deep to it (the hypoglossal nerve, the carotid artery, the internal jugular vein, section. In a type III dissection, the sternocleidomastoid muscle and the spinal accessory nerve). View is of a left neck dissection. is fully mobilized and retracted with two broad Penrose drains, and the contents of the neck are exposed. The spinal accessory nerve is preserved thoughout its entire course, including the ed. Because the artery curves around the submandibular gland, branch to the sternocleidomastoid muscle. The remainder of the the facial artery, if not preserved, must be ligated twice (proxi- neck dissection proceeds as previously described (see above). mally and distally). If the neck dissection is part of a large extir- pative procedure involving free-flap reconstruction, the facial SELECTIVE NECK DISSECTION artery is preserved for use in microvascular anastomosis. The posterior belly of the digastric muscle is then identified Levels I to IV inferior to the submandibular gland. This muscle has been In a selective neck dissection, the posterior triangle is not referred to as one of several “resident’s friends” in the neck removed; thus, there is no need to elevate skin flaps posterior to because it serves to protect several critical structures that lie just the sternocleidomastoid muscle. Limited elevation of skin flaps is deep to it, including the hypoglossal nerve, the external carotid beneficial, particularly for patients who have previously under- artery, the internal jugular vein, and the spinal accessory nerve gone chemoradiation therapy, in whom extensive flap elevation [see Figure 4]. The posterior belly of the digastric muscle is skele- may contribute to significant persistent lymphedema after opera- tonized to the sternocleidomastoid muscle, where it inserts on the tion. Subplatysmal skin flaps are raised sufficiently to expose the mastoid tip.The specimen is then mobilized away from structures neck levels to be dissected, with the central compartment left just inferior to the digastric muscle. The hypoglossal nerve undisturbed. If level I dissection is planned, the fascia overlying emerges from beneath the mylohyoid muscle and passes into the the submandibular gland is raised and retracted so as to preserve neck just below the digastric muscle, looping around the external the marginal nerve. The submental fat pad is grasped and mobi- carotid artery at the origin of the occipital artery and ascending lized away from the floor of the submental triangle (composed of to the skull base between the external carotid artery and the inter- the anterior belly of the digastric muscle and the mylohyoid mus- nal jugular vein. Bleeding from small branches of the common cle). Inferiorly, the lymphatic tissues are mobilized off the poste- facial vein that envelop the hypoglossal nerve place this structure rior aspect of the omohyoid muscle, which forms the anteroinfe- at risk for injury. The spinal accessory nerve is often visualized rior limit of the neck dissection. just superficial or posterior to the internal jugular vein, extending Once the digastric tendon and the posterior edge of the mylo- posteriorly to innervate the sternocleidomastoid muscle. hyoid muscle are visualized, the mylohyoid is retracted with an Next, the fascia overlying the sternocleidomastoid muscle is Army-Navy retractor so that the submandibular duct, the lingual grasped and unrolled medially throughout its length, starting at nerve with its attachment to the submandibular gland, and the the anterior edge of the muscle. The fascia is removed until the hypoglossal nerve are visualized. The submandibular duct and spinal accessory nerve is identified at the point where it pene- ganglion are ligated, and the submandibular gland is retracted out trates the muscle.This nerve is dissected and mobilized superior- of the submandibular triangle. ly through fat and lymphatic tissues to the digastric muscle. Care At this point, the facial artery is encountered and suture-ligat- must be taken not to inadvertently injure the internal jugular
  • 8. © 2004 WebMD, Inc. All rights reserved. ACS Surgery: Principles and Practice 2 HEAD AND NECK 7 NECK DISSECTION — 8 vein, which lies in close proximity to the nerve superiorly. Tissue include the presence of a sucking sound in the neck, a mill-wheel posterior to the accessory nerve is grasped and freed from the murmur over the precordium, ECG changes, and hypotension. deep muscles of the neck, the digastric muscle superiorly, and the Predisposing factors include elevation of the head of the bed and sternocleidomastoid muscle posteriorly.The tissue included in so- spontaneous breathing, which increase negative intrathoracic called level IIb is passed beneath the spinal accessory nerve and pressure and thus promote entry of air into the venous system. incorporated into the main specimen. Injury to the internal jugular vein is more difficult to control when The sternocleidomastoid muscle is retracted, and the fascia it occurs distally in the neck or chest at the junction with the sub- posterior to the internal jugular vein is incised. Dissection is car- clavian vein. For this reason, ligation of the internal jugular vein in ried down to the deep cervical musculature and cervical nerves, radical and modified radical neck dissections is typically per- which form the floor of the dissection. The specimen is retracted formed 1 cm superior to the clavicle. anteriorly. A layer of fascia is left on the deep cervical musculature Opalescent or clear fluid in the inferior neck suggests the pres- and the cervical nerves to preserve innervation of the deep mus- ence of a chyle fistula. Chyle fistulas generally can be prevented cles of the neck and protect the phrenic nerve as it courses over by clamping and ligating the lymphatic pedicle at the base of the the anterior scalene muscle. neck.Those fistulas that occur are repaired at the time of the neck The specimen is peeled off the internal jugular vein and dissection.There is no benefit in isolating individual lymphatic ves- removed. Dissection too far posteriorly behind the vein may result sels, because these structures are fragile, do not hold stitches, and in injury to the vagus nerve or the sympathetic trunk and predis- are prone to tearing. A figure-eight stitch is placed along the lym- poses to postoperative thrombosis of the vein. Ligation of internal phatic pedicle until there is no evidence of clear or turbid fluid jugular vein branches should be done without affecting the caliber on the Valsalva maneuver. Care must be taken not to inadvertently of the vein or giving the vessel a “sausage link” appearance, which injure the vagus nerve or the phrenic nerve during repair of a chyle would create turbulent flow patterns predisposing to thrombosis. leak. Overall, gentle dissection around all vessels, with care taken to POSTOPERATIVE avoid pulling-related trauma, minimizes the risk of endothelial injury. Dissection behind the internal jugular vein may result in The best treatment of postoperative complications such as injury to the vagus nerve or the sympathetic trunk. hematoma and chyle leak is prevention. Hematomas, once pre- A level IV dissection may be facilitated by retracting the omo- sent, are best managed by promptly returning the patient to the hyoid muscle inferiorly or by dividing it for additional exposure. OR for evacuation. Management of postoperative leakage of chyle The tissue inferior to the omohyoid is mobilized and delivered depends on the volume of the leak. Low-volume leaks may be with the main specimen. The lymphatic pedicle is clamped and managed with packing, wound care, and nutritional supplemen- ligated. Care is taken to look for leakage of chyle, particularly tation with medium-chain triglycerides. when a level IV dissection is performed on the left. Wound complications (e.g., infection, flap necrosis, and carotid artery exposure or rupture) share certain interrelated causative Levels II to IV factors. Poor nutritional status, advanced tumor stage at presen- When level I is spared, a smaller incision suffices for exposure. tation, hypothyroidism, and preoperative radiation therapy have Subplatysmal flaps are raised superiorly to the level of the sub- all been associated with wound complications. After chemoradia- mandibular gland. The inferior flap is raised, exposing the anteri- tion therapy, the use of smaller incisions and more limited dissec- or edge of the sternocleidomastoid muscle. Dissection proceeds tion of soft tissues may lower the incidence of postoperative just inferior to the submandibular gland until the posterior belly of wound problems, including persistent lymphedema and soft tis- the digastric muscle is identified. The digastric muscle is skele- sue fibrosis. Conversely, poor planning of skin incisions may tonized posteriorly to the sternocleidomastoid muscle and anteri- increase the likelihood of wound complications such as wound orly to the omohyoid muscle, which forms the anterior limit of the breakdown, skin flap loss, and exposure of vital structures.Wound dissection. The rest of the neck dissection proceeds as described complications predispose to carotid artery rupture, the most cat- for a selective neck dissection involving levels I through IV. astrophic complication of neck dissection. In some case, severe edema after planned neck dissections in patients previously treated with chemoradiation may cause respi- Complications ratory decompensation that necessitates tracheotomy. Postopera- tive internal jugular vein thrombosis is not uncommon despite INTRAOPERATIVE preservation at the time of surgery,25 and it may exacerbate Most intraoperative complications may be prevented by means edema. Impaired venous outflow predisposes to increased of careful surgical technique, coupled with a thorough under- intracranial pressure.26 This may be a greater concern in patients standing of head and neck anatomy. Injury to the internal jugular who require bilateral neck dissections. If a radical neck dissection vein may occur either proximally or distally. Uncontrolled proxi- is performed on one side, the internal jugular vein must be pre- mal bleeding endangers adjacent critical structures, such as the served on the other, or else the neck dissections must be staged. carotid artery and the hypoglossal nerve.The bleeding may be ini- These problems are further exacerbated when the patient has tially controlled with pressure, followed by a methodical search for undergone chemoradiation therapy before operation. the bleeding source. Internal jugular vein lacerations can often be Most neck dissections result in some degree of temporary repaired with 5-0 nylon sutures; if a laceration cannot be repaired, shoulder dysfunction. Patients in whom nerve-sparing procedures the vein must be ligated. Occasionally, a laceration extends up to are performed can expect function to return within 3 weeks to 1 the skull base, and the vessel cannot be controlled with clamping year, depending on the procedure performed. Shoulder dysfunc- and ligation. In these cases, it is acceptable to pack the jugular tion and pain are exacerbated when nerves supplying the deep foramen for hemostasis. muscles of the neck are also sacrificed. All patients benefit from It is important to gain distal control of the internal jugular vein physical therapy, which preserves full range of motion in the before repair to prevent air embolism. Harbingers of air embolism shoulder while function returns.
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