Oropharynx and Oral Cavity

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455 17 Oropharynx and Oral Cavity Th. Vogl 17.1 Anatomy, Imaging Techniques and Imaging Findings 456 17.1.1 Normal Anatomy 456 17.1.2 Imaging Techniques 456 17.1.3 Imaging Findings 456 17.

1 Oropharynx and Oral Cavity Th. Vogl 17.1 Anatomy, Imaging Techniques and Imaging Findings Normal Anatomy Imaging Techniques Imaging Findings Congenital Anomalies and Malformations Trauma Inflammatory Diseases Tumours Malignant Tumours Benign Tumours Summary 460 T. J. Vogl, W. Reith, E. J. Rummeny (Eds.), Diagnostic and Interventional Radiology, DOI / _17, SpringerVerlag Berlin Heidelberg 2016

2 456 Chapter 17 Oropharynx and Oral Cavity Anatomy, Imaging Techniques and Imaging Findings Normal Anatomy The oral cavity includes the hard palate superiorly, the mucosa of the lips laterally, the alveolar ridges of the upper and lower jaws, and contains the anterior twothirds of the tongue. Inferiorly, the floor of the mouth is also a part of the oral cavity. The mandible provides the bony framework of the floor of the mouth. The paired mylohyoid muscle slings are stretched as a diaphragm between the mandible and hyoid bone supporting the structure of the floor of the mouth. Complex muscle groups such as the genioglossus and hyoglossus muscles form an anatomical barrier to the spread of pathological disorders. The oropharynx is the part of the pharynx posterior to the oral cavity and extends from the soft palate superiorly to the level of the valleculae caudally. Magnetic resonance imaging provides the best spatial resolution for the examination of the three complex intercommunicating spaces (oropharynx, oral cavity, floor of the mouth), with accurate delineation of the fascia, muscles and other softtissue structures Imaging Techniques General The mucosal surface of the oral cavity, oropharynx and floor of the mouth are easily accessible for clinical assessment. Imaging, mainly contrastenhanced CT and MRI, is usually used for the assessment of the deeper structures. Important imaging findings include invasion of the deep structures and infiltration of the surroundings by a malignant lesion and the differentiation between malignant and benign or inflammatory lesions. In the oral cavity, the specified imaging modalities are applied for the evaluation of dental problem. Ultrasonography Ultrasonography is usually performed as a first step before proceeding to crosssectional imaging modalities, CT and MRI. The main application for ultrasonography is the diagnosis of salivary gland diseases ( Chap. 16). Computed Tomography In patients with a bad general condition or those who lack cooperation, CT represents the primary modality for the imaging of diseases of the oropharynx, oral cavity and floor of the mouth. CT should be performed before and after IV contrast medium administration. CT provides highresolution images of the bone and softtissue structures of this complex anatomical region. The scan length of CT performed for tumour staging should start from the skull base down to the upper mediastinum, to evaluate the primary tumour as well as any lymph node metastases. Artefacts caused by the patient s swallowing and motion often cause image degradation, but can be reduced by having the patient bite on a mouthpiece. Data acquisition is primarily in the axial plane. Sagittal and coronal images are secondarily reformatted. Contrast medium administration is mandatory, particularly for differentiating the lymph nodes from blood vessels and muscles. This involves the injection of ml of contrast medium, followed by ml of NaCl. Dynamic contrastenhanced examination is outmoded; MRI plays more a more significant role. Images should be evaluated in soft and then bone window settings to detect possible osseous infiltration, particularly with tumours of the floor of the mouth. Magnetic Resonance Imaging Magnetic resonance imaging with field strengths between 1.0 and 3.0 Tesla is best suited for imaging of the head and neck region. The data acquisition is optimised with the use of a circularly polarised head coil and sometimes with specially designed surface coils. The minimum matrix display should be pixels, with section thickness of 4 mm or even less. The sequences used include spinecho sequences (SE), inversionrecovery (STIR), gradientrecalled echo (GRE) and turbo spinecho (TSE) sequences. Fat suppression may be used with GRE and TSE sequences. The signal intensity of individual structures depends on the tissue contrast and includes various parameters (proton density, relaxation times T1 and T2, flow velocity in blood vessels, susceptibility effects). The anatomical relations of oral cavity, oropharynx and floor of the mouth lesions can be best depicted by T1weighted sequences because of the low signal intensity of most lesions, unlike anatomical fat planes. After administration of contrast medium, there is often contrast uptake by tumours with an increase in signal intensity. Contrast enhancement is helpful for the evaluation of tumour size and vascularity and for the delineation of adjacent structures Imaging Findings Neoplastic diseases represent the main indication for crosssectional imaging of the oral cavity, oropharynx and floor of the mouth. The first imaging sign is alteration of the usual symmetry of the oropharynx, oral cavity and floor of the mouth. kkloss of Symmetry Asymmetry can be caused by a decrease in muscle mass as with partial muscle atrophy or muscle denervation as well as by neoplastic lesions. With hypoglossal nerve palsy, MRI characteristically shows asymmetry of the affected hemitongue with increased signal intensity on T1weighted spinecho sequence. The affected hemitongue appears hypodense on CT. Overlapping asymmetric structures may be confused with the imaging appearance of inflammatory and neoplastic processes. Detection of other signs such as displacement of fat tissue septa, for example, the sublingual and parapharyngeal spaces, allows reliable diagnoses of denervation muscle atrophy.

17.5 Tumours 457 17 kkcontrast Enhancement Tumours of the oropharynx, oral cavity and floor of the mouth usually enhance with contrast media.

17.2 Congenital Anomalies and Malformations Primary congenital anomalies of this region are uncommon. Important malformations include lingual thyroid at the base of the tongue (. Fig. 17.

3 17.5 Tumours kkcontrast Enhancement Tumours of the oropharynx, oral cavity and floor of the mouth usually enhance with contrast media. The enhancement is interstitial, so that it is most pronounced s after IV injection of contrast medium. About 85% of all tumours of this region will show such enhancement, either with CT or MRI Congenital Anomalies and Malformations Primary congenital anomalies of this region are uncommon. Important malformations include lingual thyroid at the base of the tongue (. Fig. 17.1) Trauma See Chap. 15 (Mandible, Teeth and Temporomandibular Joints) Inflammatory Diseases Crosssectional imaging of inflammations of the oropharynx and oral cavity is indicated in exceptional cases only (. Figs. 17.2, 17.3). Only complications of tonsillitis, such as a pharyngeal abscess, septic venous thrombosis or necrotising fasciitis, and rarely dentogenic infections, require imaging. With specific infections such as tuberculosis, imaging becomes necessary for the assessment of lymph nodes. Of particular importance is the imaging diagnosis of osteomyelitis of the mandible. Fig Lingual thyroid in the base of tongue. Contrastenhanced fatsuppressed T1weighted SE sequences, TR/TE = 500 / 17. Markedly enhancing soft tissue in the inferior base of the tongue (arrows), anterior to the hypopharynx 17.5 Tumours Malignant Tumours Basics Tumours of the oropharynx, oral cavity and floor of the mouth represent about 2% of all malignant tumours, about 90% of those are squamous cell carcinomas. Other histological entities are uncommon such as adenoid cystic carcinoma with a high incidence of recurrence. Other uncommon tumours include lymphoma and, in the paediatric age, rhabdomyosarcoma. Staging of tumours in the oropharynx, oral cavity and floor of the mouth is based on the TNM staging. Clinical staging is crucial for the choice of the appropriate primary treatment strategy, to monitor outcome and followup under ongoing oncological treatment. Direct imaging signs of malignant tumours include: Mass lesion with obliteration of fatconnective tissue spaces Bone destruction Infiltration of muscle and softtissue structures Fig Parapharyngeal abscess due to staphylococcal infection (arrows). Contrastenhanced axial CT image shows illdefined swelling of the tonsil on the right side (arrow); with a small hypodense zone of necrosis, oedema of the surrounding structures and displacement of the pharyngeal lumen (P)

458 Chapter 17 Oropharynx and Oral Cavity 1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 Suspected complication MRI (A) Acute Clinical evaluation Inflammation Chronic Exclusion of tumour

3 Diagnostic flowchart for the diagnostic evaluation of suspected inflammatory diseases of the oropharynx, oral cavity and floor of the mouth Indirect signs of malignant tumours are: Contrast

4 458 Chapter 17 Oropharynx and Oral Cavity Suspected complication MRI (A) Acute Clinical evaluation Inflammation Chronic Exclusion of tumour s.ll neoplasm Fig Diagnostic flowchart for the diagnostic evaluation of suspected inflammatory diseases of the oropharynx, oral cavity and floor of the mouth Indirect signs of malignant tumours are: Contrast enhancement of the tumour after contrast agent administration (. Fig. 17.4) Internal heterogeneities with necrosis Lymph node metastases with contrast enhancement and central necrosis a b Tumours are usually isointense to muscles on unenhanced CT and MRI, and can be detected only by their mass effect. After administration of contrast agent there is often solid or marginal contrast enhancement of the tumours. T1/T2 Tumours Small tumours (< 4 cm), stage T1 or T2, are usually delineated by the intense contrast enhancement, both on CT and MRI. The differential diagnosis is hyperplastic lymphoid tissue, especially in the region of the tonsils. CT examination is sometimes limited by beamhardening artefacts caused by dense bone, teeth or dental fillings in the mandible or maxilla. These artefacts are significantly reduced with the use of MRI. In particular, tumour growth in the region of the tonsils, as well as the soft palate, is often difficult to detect by CT. T3 Tumours T3 tumours are, by definition, > 4 cm. Tumours usually show evident contrast enhancement. CT and MRI allow accurate determination of tumour size, infiltration of neighbouring structures, and crossing the midline (. Figs ). The best diagnostic results can be achieved by MRI because of its excellent tissue contrast and fewer artefacts. The ability of the patient to cooperate and remain motionless throughout the MRI examination is necessary to obtain highresolution T1 and T2weighted spinecho images. Besides primary diagnosis, diagnostic imaging is crucial for followup after chemotherapy, radiation therapy, combination therapy or locoregional chemotherapy. Fig. 17.4a,b Oropharyngeal carcinoma stage T4 with infiltration of the soft palate, parapharyngeal spaces, tonsillar fossae on both sides with extension into the nasopharynx. a Contrastenhanced, fatsuppressed, T1 weighted spinecho sequence, TR/TE 500 / 17. Markedly enhanced tumour infiltrating the entire oropharynx (arrows); with infiltration of the parapharyngeal and retropharyngeal spaces (arrowheads). b Coronal contrastenhanced T1weighted sequence, 500 / 17 shows extensive infiltration of the entire oropharynx, tonsils and parapharyngeal spread. Pathologically enlarged jugulodigastric lymph nodes at levels 2, 3 (arrowheads). MRI staging T4, N2. Infiltration of the prevertebral fascia upgrades the tumour to T4 stage

17.5 Tumours 459 17 Fig. 17.5 Base of tongue carcinoma. Fatsuppressed T2weighted sequence, TR/TE = 2,000 / 90.

contacting the mandible (arrows) Fig. 17.6a,b Anterior tongue carcinoma. MRI and MR proton spectroscopy.

b MR spectrum showing choline spectrum at 3.2 ppm, creatine at 3.0 ppm.

5 17.5 Tumours Fig Base of tongue carcinoma. Fatsuppressed T2weighted sequence, TR/TE = 2,000 / 90. Large leftsided high signal intensity tumour in the tongue base crossing the midline, extending to the lateral pharyngeal wall and contacting the mandible (arrows) Fig. 17.6a,b Anterior tongue carcinoma. MRI and MR proton spectroscopy. a Proton densityweighted MR sequence for localisation of the tumour for spectroscopy (white square). b MR spectrum showing choline spectrum at 3.2 ppm, creatine at 3.0 ppm. Note the significant increase in the choline peak as a criterion for malignancy. This examination is especially helpful for followup after therapy Fig Tongue carcinoma. Sagittal contrastenhanced T1weighted image showing the tumour (1) with marginal enhancement, central necrosis and tumoursupplying vessels (arrows)

6 460 Chapter 17 Oropharynx and Oral Cavity T4 Tumours. T4 tumours are characterised by infiltration of the surrounding structures such as bones, blood vessels and prevertebral fascia. Differential Diagnosis of Squamous Cell Carcinoma Differential diagnoses include other malignant tumours, for example: Adenoid cystic carcinoma (formerly known as cylindromas) Hodgkin s disease/nonhodgkin s lymphoma from other primary tumours Aggressive fibromatosis A diagnostic flow chart for initial and followup diagnosis is shown in (. Fig. 17.8). Sarcomas Metastases Benign Tumours The characteristic findings of benign tumours include the following: Haemangiomas: Intra or subcutaneous (. Fig. 17.9) High signal intensity on T2weighted sequences Low signal intensity in T1weighted sequences Marked contrast enhancement Lipomas: CT: hypodense with negative density values ( 100 HU) MRI: high signal intensity on T1weighted sequences Discrete calcifications Clinical evaluation Suspected neoplasm > > Signs of malignancy: infiltrative growth pattern and detection of nonfatty components with contrast enhancement. Cysts: Odontogenic aetiology, follicular, radicular Neurinoma: Located in the parapharyngeal space CT: wellcircumscribed, softtissue density masses, with cystic areas and variable contrast enhancement Cavernous lymphangioma, cystic hygroma: Multiseptation is characteristic, 80% in the lateral cervical region Cystic masses MRI: T1weighted sequence: low signal, gadolinium DTPA, enhanced wall and septations T2weighted imaging: high signal 17.6 Summary Diagnostic imaging of the oropharynx, oral cavity and floor of the mouth is essentially based on the use of CT and MRI. Crosssectional imaging should always be preceded by clinical examination. Imaging is indicated in the presence of malignant tumours for precise anatomical delineation for staging, therapy monitoring or followup. In rare cases, crosssectional imaging may be requested for the primary evaluation of inflammatory diseases, abscess or inflammatory phlegmons Nasopharynx, soft palate, oral cavity Larynx, hypopharynx, other parts of the oropharynx Uncooperative patient MRI (P) MRI (P) Vascular neoplasm Angiography, possibly embolization Fig Diagnostic flow chart for the diagnostic evaluation of suspected neoplastic diseases of the oropharynx, oral cavity and floor of the mouth. *Lymph node evaluation

17.6 Summary 461 17 a b Fig. 17.9a,b Haemangioma of the oropharynx.

Lobulated high signal intensity mass in the region of the oropharynx with displacement of the

7 17.6 Summary a b Fig. 17.9a,b Haemangioma of the oropharynx. a Axial unenhanced T1 weighted spinecho sequence, TR/TE 500 / 17. Lobulated high signal intensity mass in the region of the oropharynx with displacement of the lumen (arrows), b Coronal unenhanced T2weighted sequence 2,000 / 90. High signal intensity cystic mass (arrows). No infiltration of the surrounding structures

Head & Neck Clinical Sub Group. Network Agreed Imaging Guidelines for UAT and Thyroid Cancer. Measure Nos: 11-1C-105i & 11-1C-106i

Greater Manchester, Lancashire & South Cumbria Strategic Clinical Network & Senate Head & Neck Clinical Sub Group Network Agreed Imaging Guidelines for UAT and Thyroid Cancer Measure Nos: 11-1C-105i &