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Imaging the treated oral cavity and oropharynx
European Journal of Radiology 44 (2002) 96 – 107 www.elsevier.com/locate/ejrad
Imaging the treated oral cavity and oropharynx, Franz J. Wippold II a,b,c,* a
Mallinckrodt Institute of Radiology, Washington Uni6ersity Medical Center, 510 South Kingshighway Boule6ard, St. Louis, MO 63110, USA b Department of Radiology, Barnes-Jewish Hospital, St. Louis, MO 63110, USA c Department of Radiology/Nuclear Medicine, F. Edward He´bert School of Medicine, Uniformed Ser6ices Uni6ersity of the Health Sciences, Bethesda, MD 20814, USA Received 20 February 2002; received in revised form 22 February 2002; accepted 25 February 2002
Abstract Cross-sectional imaging has become essential in the evaluation of the treated oral cavity and oropharynx. The purpose of this paper is to review the imaging guidelines for the evaluation of this region and to detail the typical changes encountered on imaging following surgical and radiation treatment for cancer. © 2002 Elsevier Science Ireland Ltd. All rights reserved. Keywords: MR; CT; Oral cavity; Oropharynx
1. Introduction The evaluation of the treated oral cavity and oropharynx with cross-sectional imaging can be daunting for the radiologist unfamiliar with treatment options or typical post-therapy anatomic alterations. The purpose of this article is to provide guidelines for the evaluation of the treated oral cavity and oropharynx and for the recognition of typical changes encountered following treatment.
2. Imaging techniques Bolus-drip injection contrast-enhanced computed tomography (CT) remains a popular initial imaging study in many medical centers. Special care must be taken in angling the gantry in the oral cavity and oropharynx patient, however, due to dental restoration and appliance artifacts. Three- to 5-mm-thick axial slices should extend from the skull base to the hyoid bone. Five-mil-
limeter-thick slices from the hyoid bone to the thoracic inlet provide useful information about the lymph node chains. Direct coronal slices supplement the conventional axial slices because the tongue lies in the axial plane. Bone window settings assist in determination of skull base and mandible involvement. Helical imaging, which has gained support for larynx and neck regions, is also useful in the oral cavity and oropharynx [1]. Magnetic resonance (MR) imaging has emerged as a powerful tool in the evaluation of the treated oral cavity and oropharynx. A standard head coil can produce excellent coronal and axial images in most patients. Cervical lymph node assessment requires a neck coil. Useful techniques include T1-weighted sequences (for general anatomy), enhanced T1-weighted sequences with fat saturation (for perineural spread, skull base involvement, and identification of recurrent tumor margins) [2], and T2-weighted sequences (for tissue characterization and edema).
3. Anatomy
Presented at the XV International Congress of Head and Neck Radiology, Kumamoto, Japan, October 2000. The opinions and assertions contained herein are the private views of the authors and are not to be construed as official or as reflecting the views of the Department of Defense. * Tel.: +1-314-362-5949; fax: + 1-314-362-4886. E-mail address: [email protected] (F.J. Wippold, II).
Appreciation of the imaging findings of the treated oral cavity and oropharynx begins with reviewing the normal anatomic borders and contents of these regions. The oral cavity extends from the vermillion border of the lips to the junction of the hard and soft palates
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superiorly and the junction of the anterior two-thirds of the tongue and posterior one-third of the tongue inferiorly. For purposes of cancer staging and treatment, the major head and neck regions are further subdivided into subsites. Within the oral cavity, the following subsites are defined: lip, buccal mucosa, lower alveolar ridge, upper alveolar ridge, retromolar trigone, floor of mouth, hard palate, and anterior tongue (oral tongue) [3– 5]. The oropharynx borders the oral cavity posteriorly. Separating the oropharynx from the oral cavity are the anterior tonsillar pillars, circumvallate papillae, and the anterior margin of the soft palate. Inferiorly the epiglottis, glossoepiglottic folds, and pharyngoepiglottic folds separate the oropharynx from the larynx and hypopharynx. The soft palate forms the roof of the oropharynx. The superior and middle constrictors define the posterior margins. Regions within the oropharynx include: anterior wall (posterior one-third of the tongue and vallecula), lateral wall (faucial tonsil, tonsillar fossa, and glossotonsillar sulci), posterior wall, and superior wall (inferior surface of the soft palate and uvula) [5].
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4. Pathology Cancer is the most common lesion of the oral cavity and oropharynx requiring treatment. Squamous cell carcinomas account for 90% of oral malignancies and usually begin as surface epithelial lesions. These carcinomas may then superficially spread or deeply infiltrate. Ulcerations commonly occur in superficial lesions. Infiltrating neoplasms follow anatomic tissue planes, nerves and lymphatic pathways as they track deeply into submucosal tissues. Adenocarcinomas typically arise in submucosal epithelial appendages and smoothly elevate the overlying mucosal surface. Ulcerations are uncommon unless the lesion is traumatized. Less common tumors include lymphoma and sarcomas [6,7]. 5. Therapies Therapies directed at lesions of the oral cavity and oropharynx are designed to cure or control with as much preservation of function and cosmesis as possible. Specifically recommended therapy depends on the histology and behavior of the tumor, the primary tumorregional lymph node-distant metastasis (TNM) classification at time of presentation, the anatomic site of origin, and the comorbidities and desires of the patient. Therapeutic tools include surgery, radiation, chemotherapy, or any combination of these modalities. Surgery can be considered primary (in which the lesion is resected), adjunctive (in which distant spread is arrested), and reconstructive (in which function is restored). Radiation may be primary as a definitive treatment or adjunctive when used in concert with other therapies. Imaging evaluation of the treated oral cavity and oropharynx is challenging because the usual imaging landmarks are distorted or absent.
5.1. Primary surgery
Fig. 1. Diagrams illustrating types of glossectomy: (a) partial lateral glossectomy, (b) partial anterior glossectomy, (c) hemiglossectomy of anterior two-thirds of tongue, (d) glossectomy of anterior two-thirds of tongue, (e) hemiglossectomy extending into base of tongue, (f) total glossectomy. Lesion (black area), surgical bed (shaded area). Adapted from Ref. [4], with permission.
The glossectomy may be used as a primary procedure for tongue lesions. Glossectomies include partial glossectomy (removal of a portion of the tongue), hemiglossectomy (removal of half of the anterior tongue with or without extension to the tongue base), and total glossectomy (removal of anterior and base of tongue) [4] (Fig. 1). Successful partial glossectomy requires preservation of one lingual artery and companion hypoglossal nerve [8,9]. Recognition of partial glossectomy may be difficult on imaging. Superficial resections may have few recognizable changes on scans. With more extensive resections, imaging reveals the expected distortion of the involved anatomy (Figs. 2 and 3). The tongue and adjacent tissues are typically reduced in bulk and asymmetrically distorted.
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Fig. 2. Glossectomy and flap reconstruction. Elderly male patient with carcinoma of the tongue treated with total glossectomy, left mandibular resection, and myocutaneous graft. Sagittal T1-weighted MR image demonstrates an enlarged oral cavity and oropharynx due to the glossectomy (white asterisk). The fat-containing graft (black asterisk) fills the floor of the mouth.
labiomandibuloglossotomy, in which the lips, mandible and tongue are split and retracted [10] (Fig. 4). Evidence of this procedure on imaging is minimal and usually consists of mandible fixation wires and plates following closure. Floor of mouth tumors adherent to the lingual cortex of the mandible but without marrow invasion may be treated with a marginal mandibulectomy [8,11–13] (Fig. 5). This procedure shaves a limited portion of the superior and lingual cortex of the mandible and underlying marrow cavity. The continuity of the mandible is preserved [14]. Marrow involvement may require a segmental mandibulectomy in which a block of mandible is resected (Fig. 5). This procedure results in mandibular discontinuity and requires extensive reconstruction for cosmetic and functional reasons [10–12,14]. Marginal mandibulectomies may be difficult to appreciate on axial images. Segmental resections are recognized on imaging by the discontinuity of the mandible and the reconstruction material (Figs. 6 and 7). Injury to the hypoglossal nerve may cause hemiatrophy and fatty infiltration of the tongue, which may be difficult to differentiate from recurrent tumor involvement of the nerve (Fig. 8).
Fig. 3. Partial glossectomy. Elderly man with cancer of the tongue treated with partial glossectomy. The diminished bulk of the resected tongue is emphasized by the vacuous oropharynx (asterisk).
Tumors involving other sites within the oral cavity and oropharynx may be treated by primary excision tailored to subsite and extent of disease. Access to deeply situated tumors may require variations of
Fig. 4. Labiomandibulotomy with paralingual extension for approach to deep lesions within the tonsillar fossa, retromolar region, soft palate, and base of tongue. The lower lip, mandible and floor of mouth are split and retracted to approach the lesion (arrow). For midline lesions, the tongue may split by glossotomy. Adapted from Ref. [10], with permission.
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Fig. 5. (a) Marginal mandibulectomy. Limited portion of superior and lingual cortex of mandible and marrow is removed, preserving continuity of mandible. (b) Segmental mandibulectomy. Block of mandible is resected, requiring reconstruction. Adapted from Ref. [4], with permission.
Fig. 6. Segmental mandibulectomy and fibular graft. A 69-year-old patient with alveolar ridge carcinoma treated with segmental mandibulectomy and fibular graft reconstruction. CT demonstrating edges of the resection (arrowheads) and the graft (arrow), which has not yet healed.
Fig. 7. Hemimandibulectomy and flap reconstruction. CT of elderly patient with carcinoma of alveolar ridge treated with hemimandibulectomy, radial forearm flap, and mandibular reconstruction. The right hemimandible is absent except for the condyle. The fat-containing flap (arrows) adds soft tissue support to the resection site and reconstruction (not shown).
Hard palate and alveolar ridge resections are recognizable by characteristic absence of the resected bone. Tonsillar and soft palate resections cause soft tissue asymmetries. Appreciation of the extent of surgery through consultation with the primary physician can be helpful in avoiding misinterpreting the normal contralateral side as a mass. Additionally, primary surgeries may be complemented with adjunctive laryngectomy to minimize aspiration or reconstructive flaps to restore tissue bulk.
5.2. Adjuncti6e surgery The radical neck dissection is one of the most commonly encountered adjunctive surgical procedures (Fig. 9). It is indicated for clinically palpable lymphadenopathy at time of presentation of a primary lesion and for clinically N0 necks in patients with primary tumors that
Fig. 8. Partial mandibulectomy and hemiatrophy of the tongue. CT image of an elderly man with a right partial mandibulectomy and right hemiatrophy of the tongue (arrows), manifested by fatty infiltration of the intrinsic muscles, presumably due to hypoglossal injury. No recurrent tumor was found.
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Fig. 9. (a) Diagram of the left neck with skin and fascia removed. The level staging system localizing cervical lymph nodes is outlined. (b) Radical neck dissection with limits of resection outlined. The sternocleidomastoid muscle, internal jugular vein, spinal accessory nerve, skin, superficial fascia, and outlined nodal regions are typically removed.
have a high likelihood for lymph node spread. The dissection removes all ipsilateral lymph nodes from levels I through V, the submandibular gland, the internal jugular vein, the sternocleidomastoid muscle, and the spinal accessory nerve. Removal of the sternohyoid muscle, sternothyroid muscle, anterior and posterior bellies of the digastric muscle, and the ipsilateral thyroid gland may also be necessary [15– 18] (Fig. 10). Sacrifice of the spinal accessory nerve causes atrophy of the trapezius muscle. The ipsilateral levator scapulae muscle hypertrophies as it assumes the functional role for these muscles. This hypertrophy should not be mistaken for tumor recurrence [19]. Several modified radical neck dissections have been developed in order to preserve specific non-nodal structures such as the internal jugular vein, sternocleidomastoid muscle and spinal accessory nerve, and to lessen postoperative morbidity [15,16]. Selective neck dissections leave certain low-risk nodal groups intact. More extensive disease warrants extended radical neck dissections that remove nodal groups in addition to groups I– V and any non-nodal structures deemed at risk. Systematic identification of all neck structures as a means of recognizing missing elements is more helpful than attempting to merely label the surgery. Accurate identification of the specific procedure on imaging is greatly facilitated by consulting the surgeon.
5.3. Reconstructi6e surgery Oral cavity and neck reconstructions following major dissections attempt to restore cosmetic and functional
utility. Skin grafts and more substantial flaps are used to fill surgically created anatomic defects and cover vital structures such as exposed carotid arteries, and create structures such as neopharyngeal tubes and neotongues. Skin and subcutaneous tissues (cutaneous flaps), muscle (myocutaneous flaps) and occasionally bone (osteocutaneous or osteomyocutaneous flaps) provide material for flap reconstructions [20,21]. Flaps may be donated from local tissues and rotated into place preserving a vascular pedicle or derived from a distant site (free flaps) with surgical anastomoses of
Fig. 10. Radical neck dissection. Elderly man with tonsillar carcinoma and metastatic lymphadenopathy treated with a right radical neck dissection. Enhanced CT reveals the surgical absence of the right jugular vein and sternocleidomastoid muscle. The right common carotid artery (large arrow) is preserved. Note the left sternocleidomastoid muscle (M), left common carotid artery (small arrow) and left internal jugular vein (arrowhead) on the non-operated side.
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On imaging, the reconstructed region is usually grossly distorted and may display a prominent fatty mass (Figs. 2 and 12). The vascular pedicle or incorporated breast tissue may appear as a soft tissue density and should not be mistaken for recurrent cancer. Postsurgical hematomas, seromas, lymphoceles, and abscesses may also present as masses [21] (Fig. 13). Potential mimics of myocutaneous flaps on CT include normal fatty tissue in a massively obese patient (especially in the patient scanned with the head poorly positioned causing asymmetry of anatomic structures) and lipomas. Recognition of obturator prostheses and surgical appliances may prevent potential confusion at the time of image interpretation (Fig. 14).
5.4. Radiation therapy
Fig. 11. Prosthetic mandibular reconstruction. CT scout image identifies the extensive metallic mandibular reconstruction prosthesis (arrowheads).
Radiation therapy is often used in treating oral cavity and oropharyngeal cancers [22]. On CT, the skin and platysma are thickened (Fig. 15). Interstitial edema causes stranding and hyperintensity of the subcutaneous fat. As doses approach 7000 cGy, skin ulceration may occur [23]. Doses of 1000–2000 cGy may cause mucositis [23]. On CT, the major salivary glands enhance and then eventually atrophy (Figs. 15 and 16). Three-dimensional radiation port planning shields the parotid glands and may ameliorate post-therapy xerostomia [24].
Fig. 12. Flap reconstruction. Middle-aged woman treated with a right radial neck dissection and myocutaneous flap. The flap (asterisk) appears as a large fat-containing structure on T1-weighted MR axial image.
vascular pedicles [18,20] (Fig. 2). Bony grafts may originate from fibular or iliac crest free flaps [4] (Fig. 6). The scout image may be very valuable in identifying the operative reconstruction (Fig. 11). Metallic artifact may obscure small recurrent tumors on both CT and MR imaging.
Fig. 13. Seroma in flap reconstruction. A 44-year-old patient with flap reconstruction for mandibulectomy. Enhanced CT demonstrates fluid beneath the flap (arrowheads). Drainage confirmed serosanguinous fluid.
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unfortunately high rate of fatal tumor recurrence, sarcomas are not usually seen.
6. Recurrent tumor Recurrent tumors usually present as enlarging soft tissue masses within the resected bed and may invade a flap reconstruction (Figs. 18–20). Submucosal spread can involve the pharyngeal constrictors and adjacent spaces. Therapy failures usually manifest as locore-
Fig. 14. Recurrent tonsillar and palate carcinoma. A 50-year-old man with right tonsillar carcinoma invading the palate, treated with resection and complicated by several recurrences including spread into the right masticator space. Enhanced CT shows a barely detectable mass invading the remnant of the right masseter muscle (arrows). Note the dense prosthetic obturator (asterisk).
The mucosal surfaces may enhance due to mucositis (Fig. 16). The adjacent skeleton may demonstrate hyperintense marrow signal on T1-weighted images due to post-therapy marrow fat infiltration. The mandible may develop osteoradionecrosis due to vascular damage and direct injury to osteoblasts [23]. The bone becomes devitalized. Injury is further compounded by xerostomia and resultant dental caries. The necrotic bone exhibits focal demineralization, disorganized trabeculae, cortical thickening, patchy sclerosis, and occasionally pathological fractures. The marrow of the involved mandible demonstrates hypointensity on T1-weighted and hyperintensity on T2-weighted MR images as normal fat is replaced; enhancement may be vigorous [25] (Fig. 17). Periosteal reaction is unusual and should prompt consideration of infection. Associated soft tissue mass suggests tumor recurrence. Post-radiation sarcomas are rare and usually appear after a latent period measured in decades. Because of the age of the typical oral cavity and oropharyngeal cancer patient, the associated medical debilities from chronic smoking, and the
Fig. 15. Radiation-induced soft tissue changes. CT in a patient receiving radiation shows enhancement of the submandibular salivary glands (large arrows), swelling of the epiglottis (arrowheads), and thickening of the skin and platysma with edema and stranding of the subcutaneous fat (small arrows).
Fig. 16. Radiation-induced soft tissue changes. CT in a patient receiving radiation demonstrates enhancement of the mucosal surface (large arrowheads) and both submandibular salivary glands (asterisks). The skin is thickened and subcutaneous fat is edematous and stranded (arrows). Note the enhancing submandibular ducts (small arrowheads).
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On CT, bone algorithm images may reveal cortical erosions and replacement of normal medullary fat with soft tissue [4,14]. Neural foramina may be enlarged [28]. Because invasion by tumor often occurs on the occlusive surface of the jaw, axial slice CT oriented parallel to the pathological involvement may not accurately identify invasion [29]. Coexistent periodontal disease, dental reconstructive hardware from the patient’s original surgery, and prior radiation may also confound accurate diagnosis [30]. Marrow involvement may be suggested by the replacement of the normal marrow signal on T1-weighted and T2-weighted MR images [4,31,32] (Figs. 22 and 23). Tumor recurrence within a flap bed presents as a focal, dense mass, often with necrosis on CT (Figs. 19 and 20). Soft tissue planes may be diffusely distorted by recurrent tumor. Early detection may be confounded by superimposed tissue changes caused by radiation [33]. Post-surgical growth of residual lymph nodes is an ominous sign. The retropharyngeal nodes and contralateral neck nodes must be carefully surveyed for recurrent disease. Consultation with the surgeon is extremely important in verifying the treatment and in
Fig. 17. Osteoradionecrosis. A 43-year-old man with floor of mouth cancer treated with marginal mandibulectomy and radiation. The covering flap broke down, leaving chronically exposed bone and surrounding soft tissue swelling. Subsequent segmental resection revealed devitalized necrotic bone without tumor. On T1-weighted MR image, the normal hyperintense fatty marrow has been replaced by isointense soft tissue (arrowheads).
gional recurrences or lymph node metastases [26]. When recurrent tumors involve adjacent spaces such as the masticator space, defining borders such as the medial pterygoid fascia are obscured (Fig. 14). The fascicles of the medial pterygoid muscles appear disrupted with increased signal on T2-weighted images. Large recurrent tumors may encase the carotid artery. Circumferential attachment of tumor covering 270° or more of the carotid implies carotid involvement [27]. Perineural spread of tumor and intracranial involvement with skull base invasion can be studied using T1-weighted fat-suppressed images [2] (Fig. 21). Enhanced nerves or meninges suggest tumor spread. Recurrent tumors may also invade the mandible. Erosive changes manifest as scalloped and resorbed bone margins at the interface of an advancing contiguous tumor. Infiltrative changes as tumor penetrates marrow through perivascular spaces manifest as diffusely replaced marrow due to destruction of cancellous bone [28] (Figs. 22 and 23). Tumor may track along the inferior alveolar nerve resulting in a numb chin.
Fig. 18. Recurrent tongue carcinoma. Elderly patient with carcinoma of the tongue, treated with glossectomy and reconstruction, presents with expanding mass in floor of mouth. Coronal T1-weighted image demonstrates large soft tissue mass (arrowheads) subjacent to flap.
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radiation changes form recurrent tumor; however, results in the head and neck have been somewhat disappointing.
7. Recommendations Edema and hemorrhage usually persist on imaging during the early postoperative period and for up to 4–6 weeks. A baseline study is therefore best delayed for at least a month. Scanning at intervals of 4– 6 months for the first 1–3 years after surgery is recommended [16,39]. Yearly examinations are then performed unless a change in clinical status prompts a more timely scan. Eventually, fat within the flap will atrophy. Definition of tissue planes will improve but remain somewhat obscured compared with the preoperative scans. Appearance of a dense soft tissue mass usually indicates recurrent tumor, whereas scar tends to be less dense on CT. Differentiation may require biopsy. MR imaging Fig. 19. Recurrent carcinoma. An 84-year-old man with alveolar ridge carcinoma treated with hemimandibulectomy and flap reconstruction who now presents with a new mass. T1-weighted MR image demonstrates a soft tissue mass (asterisk) within the fat-containing flap (arrowheads). The mass had extended from tissues adjacent to flap.
communicating any clinically suspicious imaging findings. Differentiating post-radiation changes from recurrent tumor is difficult on CT and MR imaging. Although fibrosis tends to be hypointense on T1-weighted and T2-weighted images compared with tumor recurrence, which typically has higher signal, hemorrhage and edema may obscure these findings [34]. One of the best criterion for a successful radiation response is the complete or nearly complete resolution of the primary lesion on imaging. The appearance of new focal masses denotes a recurrence. Care must be taken when interpreting intracranial spread in patients who have undergone radiation to the skull base. Intra-axial enhancing lesions in the temporal lobe may actually represent radiation necrosis rather than tumor, especially if the lesion remains stable over an extended time period [35]. Intracranial tumor penetration usually begins as an extradural meningeal process (Fig. 21). Other modalities, such as 18F-fluorodeoxyglucose (FDG), positron emission tomography (PET) or single-photon-emissioncomputed tomography (SPECT), may ultimately prove more useful than conventional cross-sectional imaging (Fig. 24). On FDG-PET, recurrent tumors usually demonstrate intense uptake despite previous radiation [36 –38]. Proton magnetic resonance spectroscopy has been another new development in differentiating post-
Fig. 20. Recurrent carcinoma. A 39-year-old woman with carcinoma of the tongue treated with glossectomy and flap reconstruction. Enhanced CT reveals the fat-containing floor of mouth flap (asterisk). Adjacent to the flap is a densely enhancing mass (arrows) indicating local recurrence of tumor.
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Fig. 21. Adenoid cystic carcinoma with perineural spread. A 63-year-old woman with recurrent adenoid cystic carcinoma manifested by perineural spread involving the cisternal portion of the fifth cranial nerve (arrow) and Meckel’s cave (asterisk) on enhanced T1-weighted fat-suppressed MR image. Tumor spreads along the meninges adjacent to the sphenoid bone (small arrowheads). A nodule of tumor extends into the left temporal lobe (large arrowheads).
Fig. 22. Mandibular invasion. T1-weighted MR image of elderly man with alveolar ridge carcinoma invading mandible. A soft tissue mass (arrowheads) has engulfed the mandible causing destruction of the lingual cortex and replacement of the normally hyperintense fatty marrow with isointense tumor tissue.
Fig. 23. Recurrent carcinoma invading masticator space and mandible. T1-weighted MR image in a 70-year-old man with recurrent carcinoma demonstrates a mass within the right masticator space (arrows). The normally hyperintense marrow of the mandible has been replaced by tumor (arrowhead).
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rence, whereas scar remains stable or diminishes with time [16]. SPECT and FDG-PET may complement CT and MR imaging [40]. Timing of FDG-PET is critical, however. A negative FDG-PET scan performed within 1 month of radiation therapy may not detect disease, although a positive scan should be viewed as a likely treatment failure. Therefore, some authors advise waiting at least 4 months after radiation therapy before scanning, and keeping in mind that FDG-PET may be positive at sites of inflammation and muscular activity [38]. Biopsy may be necessary for confirmation of diagnosis.
8. Conclusion CT and MR imaging are invaluable in the assessment of the post-therapy patient with oral cavity or oropharyngeal cancer. Primary surgeries address the lesion and are often accompanied by adjunctive procedures, such as the radical neck dissection, to arrest distant spread. Reconstructive surgeries attempt to restore cosmesis and function. Radiation also provides a tool for local and regional disease control. Familiarity with the typical imaging changes encountered with these procedures greatly facilitates patient care. References
Fig. 24. Recurrent carcinoma. A 66-year-old man with presumed recurrent carcinoma in the right parapharyngeal space. T1-weighted MR image demonstrates loss of the right parapharyngeal fat due to fibrosis or recurrent tumor (arrowheads). Axial FDG-PET image reveals intense hyperactivity in the right parapharyngeal region and skull base confirming recurrent tumor.
may fail to reliably distinguish recurrent tumor from edema, radiation necrosis or inflammatory lesions. Recurrent tumor is hyperintense on T2-weighted images, whereas fibrosis tends to be hypointense. Expansion of any soft tissue density on imaging usually signals recur-
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evaluation and treatment of the neck in carcinoma of the oral cavity. Acta Otolaryngol 1997;529(Suppl.):223 –5. Yousem DM, Hatabu H, Hurst RW, Seigerman HM, Montone KT, Weinstein GS, Hayden RE, Goldberg AN, Bigelow DC, Kotapka MJ. Carotid artery invasion by head and neck masses: prediction with MR imaging. Radiology 1995;195:715 –20. Totsuka Y, Usui Y, Tei K, Fukuda H, Shindo M, Iizuka T, Amemiya A. Mandibular involvement by squamous cell carcinoma of the lower alveolus: analysis and comparative study of histologic and radiologic features. Head Neck 1991;13:40 –50. Brown JS, Griffeth JF, Phelps PD, Browne RM. A comparison of different imaging modalities and direct inspection after periosteal stripping in predicting the invasion of the mandible by oral squamous cell carcinoma. Br J Oral Maxillofac Surg 1994;32:347 – 59. Close LG, Merkel M, Burns DK, Schaeffer SD. Computed tomography in the assessment of mandibular invasion by intraoral carcinoma. Ann Otol Rhinol Laryngol 1986;95:383 –8. Chung TS, Yousem DM, Seigerman HM, Schlakman BN, Weinstein GS, Hayden RE. MR of mandibular invasion in patients with oral and oropharyngeal malignant neoplasms. Am J Neuroradiol 1994;15:1949 – 55. Ator GA, Abemayor E, Lufkin RB, Hanafee WN, Ward PH. Evaluation of mandibular tumor invasion with magnetic resonance imaging. Arch Otolaryngol Head Neck Surg 1990;116:454 – 9. Hudgins PA, Burson JG, Gussack GS, Grist WJ. CT and MR appearance of recurrent malignant head and neck neoplasms after resection and flap reconstruction. Am J Neuroradiol 1994;15:1689 – 94. Sugimura K, Kuroda S, Furukawa T, Matsuda S, Yoshimura Y, Ishida T. Tongue cancer treated with irradiation: assessment with MR imaging. Clin Radiol 1992;46:243 – 7. Chong VF-H, Fan Y-F, Mukherji SK. Radiation-induced temporal lobe changes; CT and MR imaging characteristics. Am J Roentgenol 2000;175:431 – 6. Keyes JW Jr, Watson NE Jr, Williams DW III, Greven KM, McGuirt WF. FDG PET in head and neck cancer. Am J Roentgenol 1997;169:1663 – 9. Anzai Y, Carroll WR, Quint DJ, Bradford CR, Minoshima S, Wolf GT, Wahl RL. Recurrence of head and neck cancer after surgery or irradiation: prospective comparison of 2-deoxy-2-[F18]fluoro-D-glucose PET and MR imaging diagnoses. Radiology 1996;200:135 – 41. Fischbein N, Anzai Y, Mukherji K. Application of new imaging techniques for the evaluation of squamous cell carcinoma of the head and neck. Semin US CT MRI 1999;20:187 – 212. Dillon WP, Harnsberger HR. The impact of radiologic imaging on staging of cancer of the head and neck. Semin Oncol 1991;18:64 – 79. Curran AJ, Toner M, Quinn A, Wilson G, Timon C. Mandibular invasion diagnosed by SPECT. Clin Otolaryngol 1996;21:542 – 5.
Imaging the treated oral cavity and oropharynx, Franz J. Wippold II a,b,c,* a
Mallinckrodt Institute of Radiology, Washington Uni6ersity Medical Center, 510 South Kingshighway Boule6ard, St. Louis, MO 63110, USA b Department of Radiology, Barnes-Jewish Hospital, St. Louis, MO 63110, USA c Department of Radiology/Nuclear Medicine, F. Edward He´bert School of Medicine, Uniformed Ser6ices Uni6ersity of the Health Sciences, Bethesda, MD 20814, USA Received 20 February 2002; received in revised form 22 February 2002; accepted 25 February 2002
Abstract Cross-sectional imaging has become essential in the evaluation of the treated oral cavity and oropharynx. The purpose of this paper is to review the imaging guidelines for the evaluation of this region and to detail the typical changes encountered on imaging following surgical and radiation treatment for cancer. © 2002 Elsevier Science Ireland Ltd. All rights reserved. Keywords: MR; CT; Oral cavity; Oropharynx
1. Introduction The evaluation of the treated oral cavity and oropharynx with cross-sectional imaging can be daunting for the radiologist unfamiliar with treatment options or typical post-therapy anatomic alterations. The purpose of this article is to provide guidelines for the evaluation of the treated oral cavity and oropharynx and for the recognition of typical changes encountered following treatment.
2. Imaging techniques Bolus-drip injection contrast-enhanced computed tomography (CT) remains a popular initial imaging study in many medical centers. Special care must be taken in angling the gantry in the oral cavity and oropharynx patient, however, due to dental restoration and appliance artifacts. Three- to 5-mm-thick axial slices should extend from the skull base to the hyoid bone. Five-mil-
limeter-thick slices from the hyoid bone to the thoracic inlet provide useful information about the lymph node chains. Direct coronal slices supplement the conventional axial slices because the tongue lies in the axial plane. Bone window settings assist in determination of skull base and mandible involvement. Helical imaging, which has gained support for larynx and neck regions, is also useful in the oral cavity and oropharynx [1]. Magnetic resonance (MR) imaging has emerged as a powerful tool in the evaluation of the treated oral cavity and oropharynx. A standard head coil can produce excellent coronal and axial images in most patients. Cervical lymph node assessment requires a neck coil. Useful techniques include T1-weighted sequences (for general anatomy), enhanced T1-weighted sequences with fat saturation (for perineural spread, skull base involvement, and identification of recurrent tumor margins) [2], and T2-weighted sequences (for tissue characterization and edema).
3. Anatomy
Presented at the XV International Congress of Head and Neck Radiology, Kumamoto, Japan, October 2000. The opinions and assertions contained herein are the private views of the authors and are not to be construed as official or as reflecting the views of the Department of Defense. * Tel.: +1-314-362-5949; fax: + 1-314-362-4886. E-mail address: [email protected] (F.J. Wippold, II).
Appreciation of the imaging findings of the treated oral cavity and oropharynx begins with reviewing the normal anatomic borders and contents of these regions. The oral cavity extends from the vermillion border of the lips to the junction of the hard and soft palates
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superiorly and the junction of the anterior two-thirds of the tongue and posterior one-third of the tongue inferiorly. For purposes of cancer staging and treatment, the major head and neck regions are further subdivided into subsites. Within the oral cavity, the following subsites are defined: lip, buccal mucosa, lower alveolar ridge, upper alveolar ridge, retromolar trigone, floor of mouth, hard palate, and anterior tongue (oral tongue) [3– 5]. The oropharynx borders the oral cavity posteriorly. Separating the oropharynx from the oral cavity are the anterior tonsillar pillars, circumvallate papillae, and the anterior margin of the soft palate. Inferiorly the epiglottis, glossoepiglottic folds, and pharyngoepiglottic folds separate the oropharynx from the larynx and hypopharynx. The soft palate forms the roof of the oropharynx. The superior and middle constrictors define the posterior margins. Regions within the oropharynx include: anterior wall (posterior one-third of the tongue and vallecula), lateral wall (faucial tonsil, tonsillar fossa, and glossotonsillar sulci), posterior wall, and superior wall (inferior surface of the soft palate and uvula) [5].
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4. Pathology Cancer is the most common lesion of the oral cavity and oropharynx requiring treatment. Squamous cell carcinomas account for 90% of oral malignancies and usually begin as surface epithelial lesions. These carcinomas may then superficially spread or deeply infiltrate. Ulcerations commonly occur in superficial lesions. Infiltrating neoplasms follow anatomic tissue planes, nerves and lymphatic pathways as they track deeply into submucosal tissues. Adenocarcinomas typically arise in submucosal epithelial appendages and smoothly elevate the overlying mucosal surface. Ulcerations are uncommon unless the lesion is traumatized. Less common tumors include lymphoma and sarcomas [6,7]. 5. Therapies Therapies directed at lesions of the oral cavity and oropharynx are designed to cure or control with as much preservation of function and cosmesis as possible. Specifically recommended therapy depends on the histology and behavior of the tumor, the primary tumorregional lymph node-distant metastasis (TNM) classification at time of presentation, the anatomic site of origin, and the comorbidities and desires of the patient. Therapeutic tools include surgery, radiation, chemotherapy, or any combination of these modalities. Surgery can be considered primary (in which the lesion is resected), adjunctive (in which distant spread is arrested), and reconstructive (in which function is restored). Radiation may be primary as a definitive treatment or adjunctive when used in concert with other therapies. Imaging evaluation of the treated oral cavity and oropharynx is challenging because the usual imaging landmarks are distorted or absent.
5.1. Primary surgery
Fig. 1. Diagrams illustrating types of glossectomy: (a) partial lateral glossectomy, (b) partial anterior glossectomy, (c) hemiglossectomy of anterior two-thirds of tongue, (d) glossectomy of anterior two-thirds of tongue, (e) hemiglossectomy extending into base of tongue, (f) total glossectomy. Lesion (black area), surgical bed (shaded area). Adapted from Ref. [4], with permission.
The glossectomy may be used as a primary procedure for tongue lesions. Glossectomies include partial glossectomy (removal of a portion of the tongue), hemiglossectomy (removal of half of the anterior tongue with or without extension to the tongue base), and total glossectomy (removal of anterior and base of tongue) [4] (Fig. 1). Successful partial glossectomy requires preservation of one lingual artery and companion hypoglossal nerve [8,9]. Recognition of partial glossectomy may be difficult on imaging. Superficial resections may have few recognizable changes on scans. With more extensive resections, imaging reveals the expected distortion of the involved anatomy (Figs. 2 and 3). The tongue and adjacent tissues are typically reduced in bulk and asymmetrically distorted.
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Fig. 2. Glossectomy and flap reconstruction. Elderly male patient with carcinoma of the tongue treated with total glossectomy, left mandibular resection, and myocutaneous graft. Sagittal T1-weighted MR image demonstrates an enlarged oral cavity and oropharynx due to the glossectomy (white asterisk). The fat-containing graft (black asterisk) fills the floor of the mouth.
labiomandibuloglossotomy, in which the lips, mandible and tongue are split and retracted [10] (Fig. 4). Evidence of this procedure on imaging is minimal and usually consists of mandible fixation wires and plates following closure. Floor of mouth tumors adherent to the lingual cortex of the mandible but without marrow invasion may be treated with a marginal mandibulectomy [8,11–13] (Fig. 5). This procedure shaves a limited portion of the superior and lingual cortex of the mandible and underlying marrow cavity. The continuity of the mandible is preserved [14]. Marrow involvement may require a segmental mandibulectomy in which a block of mandible is resected (Fig. 5). This procedure results in mandibular discontinuity and requires extensive reconstruction for cosmetic and functional reasons [10–12,14]. Marginal mandibulectomies may be difficult to appreciate on axial images. Segmental resections are recognized on imaging by the discontinuity of the mandible and the reconstruction material (Figs. 6 and 7). Injury to the hypoglossal nerve may cause hemiatrophy and fatty infiltration of the tongue, which may be difficult to differentiate from recurrent tumor involvement of the nerve (Fig. 8).
Fig. 3. Partial glossectomy. Elderly man with cancer of the tongue treated with partial glossectomy. The diminished bulk of the resected tongue is emphasized by the vacuous oropharynx (asterisk).
Tumors involving other sites within the oral cavity and oropharynx may be treated by primary excision tailored to subsite and extent of disease. Access to deeply situated tumors may require variations of
Fig. 4. Labiomandibulotomy with paralingual extension for approach to deep lesions within the tonsillar fossa, retromolar region, soft palate, and base of tongue. The lower lip, mandible and floor of mouth are split and retracted to approach the lesion (arrow). For midline lesions, the tongue may split by glossotomy. Adapted from Ref. [10], with permission.
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Fig. 5. (a) Marginal mandibulectomy. Limited portion of superior and lingual cortex of mandible and marrow is removed, preserving continuity of mandible. (b) Segmental mandibulectomy. Block of mandible is resected, requiring reconstruction. Adapted from Ref. [4], with permission.
Fig. 6. Segmental mandibulectomy and fibular graft. A 69-year-old patient with alveolar ridge carcinoma treated with segmental mandibulectomy and fibular graft reconstruction. CT demonstrating edges of the resection (arrowheads) and the graft (arrow), which has not yet healed.
Fig. 7. Hemimandibulectomy and flap reconstruction. CT of elderly patient with carcinoma of alveolar ridge treated with hemimandibulectomy, radial forearm flap, and mandibular reconstruction. The right hemimandible is absent except for the condyle. The fat-containing flap (arrows) adds soft tissue support to the resection site and reconstruction (not shown).
Hard palate and alveolar ridge resections are recognizable by characteristic absence of the resected bone. Tonsillar and soft palate resections cause soft tissue asymmetries. Appreciation of the extent of surgery through consultation with the primary physician can be helpful in avoiding misinterpreting the normal contralateral side as a mass. Additionally, primary surgeries may be complemented with adjunctive laryngectomy to minimize aspiration or reconstructive flaps to restore tissue bulk.
5.2. Adjuncti6e surgery The radical neck dissection is one of the most commonly encountered adjunctive surgical procedures (Fig. 9). It is indicated for clinically palpable lymphadenopathy at time of presentation of a primary lesion and for clinically N0 necks in patients with primary tumors that
Fig. 8. Partial mandibulectomy and hemiatrophy of the tongue. CT image of an elderly man with a right partial mandibulectomy and right hemiatrophy of the tongue (arrows), manifested by fatty infiltration of the intrinsic muscles, presumably due to hypoglossal injury. No recurrent tumor was found.
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Fig. 9. (a) Diagram of the left neck with skin and fascia removed. The level staging system localizing cervical lymph nodes is outlined. (b) Radical neck dissection with limits of resection outlined. The sternocleidomastoid muscle, internal jugular vein, spinal accessory nerve, skin, superficial fascia, and outlined nodal regions are typically removed.
have a high likelihood for lymph node spread. The dissection removes all ipsilateral lymph nodes from levels I through V, the submandibular gland, the internal jugular vein, the sternocleidomastoid muscle, and the spinal accessory nerve. Removal of the sternohyoid muscle, sternothyroid muscle, anterior and posterior bellies of the digastric muscle, and the ipsilateral thyroid gland may also be necessary [15– 18] (Fig. 10). Sacrifice of the spinal accessory nerve causes atrophy of the trapezius muscle. The ipsilateral levator scapulae muscle hypertrophies as it assumes the functional role for these muscles. This hypertrophy should not be mistaken for tumor recurrence [19]. Several modified radical neck dissections have been developed in order to preserve specific non-nodal structures such as the internal jugular vein, sternocleidomastoid muscle and spinal accessory nerve, and to lessen postoperative morbidity [15,16]. Selective neck dissections leave certain low-risk nodal groups intact. More extensive disease warrants extended radical neck dissections that remove nodal groups in addition to groups I– V and any non-nodal structures deemed at risk. Systematic identification of all neck structures as a means of recognizing missing elements is more helpful than attempting to merely label the surgery. Accurate identification of the specific procedure on imaging is greatly facilitated by consulting the surgeon.
5.3. Reconstructi6e surgery Oral cavity and neck reconstructions following major dissections attempt to restore cosmetic and functional
utility. Skin grafts and more substantial flaps are used to fill surgically created anatomic defects and cover vital structures such as exposed carotid arteries, and create structures such as neopharyngeal tubes and neotongues. Skin and subcutaneous tissues (cutaneous flaps), muscle (myocutaneous flaps) and occasionally bone (osteocutaneous or osteomyocutaneous flaps) provide material for flap reconstructions [20,21]. Flaps may be donated from local tissues and rotated into place preserving a vascular pedicle or derived from a distant site (free flaps) with surgical anastomoses of
Fig. 10. Radical neck dissection. Elderly man with tonsillar carcinoma and metastatic lymphadenopathy treated with a right radical neck dissection. Enhanced CT reveals the surgical absence of the right jugular vein and sternocleidomastoid muscle. The right common carotid artery (large arrow) is preserved. Note the left sternocleidomastoid muscle (M), left common carotid artery (small arrow) and left internal jugular vein (arrowhead) on the non-operated side.
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On imaging, the reconstructed region is usually grossly distorted and may display a prominent fatty mass (Figs. 2 and 12). The vascular pedicle or incorporated breast tissue may appear as a soft tissue density and should not be mistaken for recurrent cancer. Postsurgical hematomas, seromas, lymphoceles, and abscesses may also present as masses [21] (Fig. 13). Potential mimics of myocutaneous flaps on CT include normal fatty tissue in a massively obese patient (especially in the patient scanned with the head poorly positioned causing asymmetry of anatomic structures) and lipomas. Recognition of obturator prostheses and surgical appliances may prevent potential confusion at the time of image interpretation (Fig. 14).
5.4. Radiation therapy
Fig. 11. Prosthetic mandibular reconstruction. CT scout image identifies the extensive metallic mandibular reconstruction prosthesis (arrowheads).
Radiation therapy is often used in treating oral cavity and oropharyngeal cancers [22]. On CT, the skin and platysma are thickened (Fig. 15). Interstitial edema causes stranding and hyperintensity of the subcutaneous fat. As doses approach 7000 cGy, skin ulceration may occur [23]. Doses of 1000–2000 cGy may cause mucositis [23]. On CT, the major salivary glands enhance and then eventually atrophy (Figs. 15 and 16). Three-dimensional radiation port planning shields the parotid glands and may ameliorate post-therapy xerostomia [24].
Fig. 12. Flap reconstruction. Middle-aged woman treated with a right radial neck dissection and myocutaneous flap. The flap (asterisk) appears as a large fat-containing structure on T1-weighted MR axial image.
vascular pedicles [18,20] (Fig. 2). Bony grafts may originate from fibular or iliac crest free flaps [4] (Fig. 6). The scout image may be very valuable in identifying the operative reconstruction (Fig. 11). Metallic artifact may obscure small recurrent tumors on both CT and MR imaging.
Fig. 13. Seroma in flap reconstruction. A 44-year-old patient with flap reconstruction for mandibulectomy. Enhanced CT demonstrates fluid beneath the flap (arrowheads). Drainage confirmed serosanguinous fluid.
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unfortunately high rate of fatal tumor recurrence, sarcomas are not usually seen.
6. Recurrent tumor Recurrent tumors usually present as enlarging soft tissue masses within the resected bed and may invade a flap reconstruction (Figs. 18–20). Submucosal spread can involve the pharyngeal constrictors and adjacent spaces. Therapy failures usually manifest as locore-
Fig. 14. Recurrent tonsillar and palate carcinoma. A 50-year-old man with right tonsillar carcinoma invading the palate, treated with resection and complicated by several recurrences including spread into the right masticator space. Enhanced CT shows a barely detectable mass invading the remnant of the right masseter muscle (arrows). Note the dense prosthetic obturator (asterisk).
The mucosal surfaces may enhance due to mucositis (Fig. 16). The adjacent skeleton may demonstrate hyperintense marrow signal on T1-weighted images due to post-therapy marrow fat infiltration. The mandible may develop osteoradionecrosis due to vascular damage and direct injury to osteoblasts [23]. The bone becomes devitalized. Injury is further compounded by xerostomia and resultant dental caries. The necrotic bone exhibits focal demineralization, disorganized trabeculae, cortical thickening, patchy sclerosis, and occasionally pathological fractures. The marrow of the involved mandible demonstrates hypointensity on T1-weighted and hyperintensity on T2-weighted MR images as normal fat is replaced; enhancement may be vigorous [25] (Fig. 17). Periosteal reaction is unusual and should prompt consideration of infection. Associated soft tissue mass suggests tumor recurrence. Post-radiation sarcomas are rare and usually appear after a latent period measured in decades. Because of the age of the typical oral cavity and oropharyngeal cancer patient, the associated medical debilities from chronic smoking, and the
Fig. 15. Radiation-induced soft tissue changes. CT in a patient receiving radiation shows enhancement of the submandibular salivary glands (large arrows), swelling of the epiglottis (arrowheads), and thickening of the skin and platysma with edema and stranding of the subcutaneous fat (small arrows).
Fig. 16. Radiation-induced soft tissue changes. CT in a patient receiving radiation demonstrates enhancement of the mucosal surface (large arrowheads) and both submandibular salivary glands (asterisks). The skin is thickened and subcutaneous fat is edematous and stranded (arrows). Note the enhancing submandibular ducts (small arrowheads).
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On CT, bone algorithm images may reveal cortical erosions and replacement of normal medullary fat with soft tissue [4,14]. Neural foramina may be enlarged [28]. Because invasion by tumor often occurs on the occlusive surface of the jaw, axial slice CT oriented parallel to the pathological involvement may not accurately identify invasion [29]. Coexistent periodontal disease, dental reconstructive hardware from the patient’s original surgery, and prior radiation may also confound accurate diagnosis [30]. Marrow involvement may be suggested by the replacement of the normal marrow signal on T1-weighted and T2-weighted MR images [4,31,32] (Figs. 22 and 23). Tumor recurrence within a flap bed presents as a focal, dense mass, often with necrosis on CT (Figs. 19 and 20). Soft tissue planes may be diffusely distorted by recurrent tumor. Early detection may be confounded by superimposed tissue changes caused by radiation [33]. Post-surgical growth of residual lymph nodes is an ominous sign. The retropharyngeal nodes and contralateral neck nodes must be carefully surveyed for recurrent disease. Consultation with the surgeon is extremely important in verifying the treatment and in
Fig. 17. Osteoradionecrosis. A 43-year-old man with floor of mouth cancer treated with marginal mandibulectomy and radiation. The covering flap broke down, leaving chronically exposed bone and surrounding soft tissue swelling. Subsequent segmental resection revealed devitalized necrotic bone without tumor. On T1-weighted MR image, the normal hyperintense fatty marrow has been replaced by isointense soft tissue (arrowheads).
gional recurrences or lymph node metastases [26]. When recurrent tumors involve adjacent spaces such as the masticator space, defining borders such as the medial pterygoid fascia are obscured (Fig. 14). The fascicles of the medial pterygoid muscles appear disrupted with increased signal on T2-weighted images. Large recurrent tumors may encase the carotid artery. Circumferential attachment of tumor covering 270° or more of the carotid implies carotid involvement [27]. Perineural spread of tumor and intracranial involvement with skull base invasion can be studied using T1-weighted fat-suppressed images [2] (Fig. 21). Enhanced nerves or meninges suggest tumor spread. Recurrent tumors may also invade the mandible. Erosive changes manifest as scalloped and resorbed bone margins at the interface of an advancing contiguous tumor. Infiltrative changes as tumor penetrates marrow through perivascular spaces manifest as diffusely replaced marrow due to destruction of cancellous bone [28] (Figs. 22 and 23). Tumor may track along the inferior alveolar nerve resulting in a numb chin.
Fig. 18. Recurrent tongue carcinoma. Elderly patient with carcinoma of the tongue, treated with glossectomy and reconstruction, presents with expanding mass in floor of mouth. Coronal T1-weighted image demonstrates large soft tissue mass (arrowheads) subjacent to flap.
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radiation changes form recurrent tumor; however, results in the head and neck have been somewhat disappointing.
7. Recommendations Edema and hemorrhage usually persist on imaging during the early postoperative period and for up to 4–6 weeks. A baseline study is therefore best delayed for at least a month. Scanning at intervals of 4– 6 months for the first 1–3 years after surgery is recommended [16,39]. Yearly examinations are then performed unless a change in clinical status prompts a more timely scan. Eventually, fat within the flap will atrophy. Definition of tissue planes will improve but remain somewhat obscured compared with the preoperative scans. Appearance of a dense soft tissue mass usually indicates recurrent tumor, whereas scar tends to be less dense on CT. Differentiation may require biopsy. MR imaging Fig. 19. Recurrent carcinoma. An 84-year-old man with alveolar ridge carcinoma treated with hemimandibulectomy and flap reconstruction who now presents with a new mass. T1-weighted MR image demonstrates a soft tissue mass (asterisk) within the fat-containing flap (arrowheads). The mass had extended from tissues adjacent to flap.
communicating any clinically suspicious imaging findings. Differentiating post-radiation changes from recurrent tumor is difficult on CT and MR imaging. Although fibrosis tends to be hypointense on T1-weighted and T2-weighted images compared with tumor recurrence, which typically has higher signal, hemorrhage and edema may obscure these findings [34]. One of the best criterion for a successful radiation response is the complete or nearly complete resolution of the primary lesion on imaging. The appearance of new focal masses denotes a recurrence. Care must be taken when interpreting intracranial spread in patients who have undergone radiation to the skull base. Intra-axial enhancing lesions in the temporal lobe may actually represent radiation necrosis rather than tumor, especially if the lesion remains stable over an extended time period [35]. Intracranial tumor penetration usually begins as an extradural meningeal process (Fig. 21). Other modalities, such as 18F-fluorodeoxyglucose (FDG), positron emission tomography (PET) or single-photon-emissioncomputed tomography (SPECT), may ultimately prove more useful than conventional cross-sectional imaging (Fig. 24). On FDG-PET, recurrent tumors usually demonstrate intense uptake despite previous radiation [36 –38]. Proton magnetic resonance spectroscopy has been another new development in differentiating post-
Fig. 20. Recurrent carcinoma. A 39-year-old woman with carcinoma of the tongue treated with glossectomy and flap reconstruction. Enhanced CT reveals the fat-containing floor of mouth flap (asterisk). Adjacent to the flap is a densely enhancing mass (arrows) indicating local recurrence of tumor.
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Fig. 21. Adenoid cystic carcinoma with perineural spread. A 63-year-old woman with recurrent adenoid cystic carcinoma manifested by perineural spread involving the cisternal portion of the fifth cranial nerve (arrow) and Meckel’s cave (asterisk) on enhanced T1-weighted fat-suppressed MR image. Tumor spreads along the meninges adjacent to the sphenoid bone (small arrowheads). A nodule of tumor extends into the left temporal lobe (large arrowheads).
Fig. 22. Mandibular invasion. T1-weighted MR image of elderly man with alveolar ridge carcinoma invading mandible. A soft tissue mass (arrowheads) has engulfed the mandible causing destruction of the lingual cortex and replacement of the normally hyperintense fatty marrow with isointense tumor tissue.
Fig. 23. Recurrent carcinoma invading masticator space and mandible. T1-weighted MR image in a 70-year-old man with recurrent carcinoma demonstrates a mass within the right masticator space (arrows). The normally hyperintense marrow of the mandible has been replaced by tumor (arrowhead).
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rence, whereas scar remains stable or diminishes with time [16]. SPECT and FDG-PET may complement CT and MR imaging [40]. Timing of FDG-PET is critical, however. A negative FDG-PET scan performed within 1 month of radiation therapy may not detect disease, although a positive scan should be viewed as a likely treatment failure. Therefore, some authors advise waiting at least 4 months after radiation therapy before scanning, and keeping in mind that FDG-PET may be positive at sites of inflammation and muscular activity [38]. Biopsy may be necessary for confirmation of diagnosis.
8. Conclusion CT and MR imaging are invaluable in the assessment of the post-therapy patient with oral cavity or oropharyngeal cancer. Primary surgeries address the lesion and are often accompanied by adjunctive procedures, such as the radical neck dissection, to arrest distant spread. Reconstructive surgeries attempt to restore cosmesis and function. Radiation also provides a tool for local and regional disease control. Familiarity with the typical imaging changes encountered with these procedures greatly facilitates patient care. References
Fig. 24. Recurrent carcinoma. A 66-year-old man with presumed recurrent carcinoma in the right parapharyngeal space. T1-weighted MR image demonstrates loss of the right parapharyngeal fat due to fibrosis or recurrent tumor (arrowheads). Axial FDG-PET image reveals intense hyperactivity in the right parapharyngeal region and skull base confirming recurrent tumor.
may fail to reliably distinguish recurrent tumor from edema, radiation necrosis or inflammatory lesions. Recurrent tumor is hyperintense on T2-weighted images, whereas fibrosis tends to be hypointense. Expansion of any soft tissue density on imaging usually signals recur-
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