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Introductory Cases in Head and Neck Imaging

July 2001

Ted Mau, Harvard Medical School Year IVGillian Lieberman, MD

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IntroductionWith its complex anatomy, the head and neck area can present a challenge for the radiology student. This incipient teaching file contains several cases that may serve as a simplified introduction to head and neck imaging.

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ContentsInfectiousPatient 1: Lingual tonsillitisPatient 2: Peritonsillar abscessNeoplasticPatient 3: Parotid tumor 1Patient 4: Parotid tumor 2

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Patient 1

46 yo male with 1-wk h/o severe throat pain, odynophagia, and swollen lingual tonsil on exam

A CT of the neck with contrast was obtained. One axial section is shown on the next slide.

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Question 1:

Which part of the head and neck is this?

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Approach to Head and Neck Axial Images: LANDMARKS

The key to reading head and neck axial images is to first identify landmarks. On this CT image, several bony and soft tissue landmarks tell us which section of the anatomy we are looking at.

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mandible

geniohyoid muscles and the lingual septum between them

(The lingual septum is hypodense in CT due to its high fat content)

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Can you now identify the geniohyoid without the labels?

You can also see the mylohyoid muscles lateral to the geniohyoid.

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These landmarks place this axial section at the level of the floor of the mouth.

Now for Question 2:

Where is the abnormality?

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Approach to Head and Neck Axial Images: SYMMETRY

Abnormalities in the head and neck often present as asymmetric lesions. Can you identify the asymmetry here?

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Note the prominence of the right posterior pharyngeal wall compared to the left, with slight impingement of the airway. This prominence extends inferiorly to the supraglottic larynx (next slide).

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The hyoid bone identifies this section as the supraglottic larynx. You can also see the calcified superior horns of the thyroid cartilage. Note the prominence of the right posterior pharyngeal wall.

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Patient 1: Radiologic Diagnosis and Clinical Course

Note that the pharyngeal wall prominence was of the same density as the surrounding soft tissue in this contrast CT study. There was no evidence of a fluid collection or abscess. This study was read as right-sided pharyngeal soft tissue swelling with slight airway impingement. The patient was diagnosed with lingual tonsillitis and treated with IV antibiotics, with eventual resolution of his symptoms.

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Patient 1: Lingual Tonsillitis

• Causative organisms: Group A -hemolytic streptococci, staphylococci, pneumococci, H. influenzae, anaerobes, viruses

• Antibiotics: Penicillin has been the standard initial treatment. However, the involvement of penicillinase- producing anaerobes and the rise in other penicillin- resistant organisms have prompted a switch to clindamycin as the initial treatment of choice.

• Complications: Peritonsillar abscess (quinsy), epiglottitis, otitis, laryngitis. The most severe complication is airway compromise.

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Patient 1: Summary

The teaching points of this first case are to: • Know anatomical landmarks• Take advantage of symmetry• Distinguish between soft tissue density and

fluid collection in an infectious or inflammatory process.

We will revisit the last point in Patient 2.

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Patient 2

22 yo male with 2-wk h/o worsening dysphagia, odynophagia, trismus, and left neck pain. Exam revealed mild left peritonsillar fullness with no erythema or exudate.

A CT of the neck with contrast was obtained. One axial section is shown on the next slide.

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Which part of the head and neck is this ?

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The mandibular rami, the alveolar ridge, and the styloid processes (projecting antero- medio-inferiorly) identify this section as at the level of the oral cavity.

What is the abnormality?

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There is a large parapharyngeal low attenuation heterogeneous mass with slight heterogeneous enhancement.

This is in contrast to the pharyngeal prominence seen in Case 1, which was homogeneous with similar attenuation as surround soft tissue.

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This mass extends down to the level of the supraglottic larynx. Landmarks here are the hyoid bone, the epiglottis, and the aryepiglottic folds.

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Patient 2: Radiologic Diagnosis

The differential for this large left parapharyngeal low attenuation heterogeneous mass includes inflammatory etiologies and possible malignancy. Given the clinical presentation, however, the mass was most likely an abscess.

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Patient 2: Clinical Course

The patient was given the diagnosis of left peritonsillar abscess. He was started on IV clindamycin (recall Case 1) and taken to the OR. The abscess was opened, but no pus was drained, consistent with the lack of a well-defined fluid collection seen on CT. The patient improved clinically on POD1 and had an uncomplicated course of recovery.

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Patient 2: Summary

We have now:• learned more head and neck landmarks, • compared two cases with similar clinical

presentations but distinct radiographic findings: the first with only tissue swelling, the second more severe with abscess formation.

The next two cases involve neoplasm in the parotid gland.

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Patient 3

69 yo female presented with new onset headaches. T1 and T2 weighted MR images of the head were obtained. No contrast was used. An incidental finding is shown on the next slide.

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T1 weighted T2 weighted

Question 1: Which part of the head and neck is this?

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Several structures are identifiable on this T1 weighted image:1. Outline of the nose and the palate just posterior to it2. Mandibular rami (cortical bone produces little signal in MR)3. Masseter muscles, just lateral to mandible4. Medial pterygoid muscles5. Parotid glands, postero-lateral to the mandibular rami

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Now that we’ve oriented ourselves, we can ask Question 2: What is the abnormality?

There is a well- circumscribed, 1.3cm lesion in the left parotid gland with high T2 signal and low T1 signal. Specifically, it is in the deep lobe of the gland.

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Parotid Tumors• 80% of salivary gland tumors occur in the parotids,

and 80% of parotid tumors are benign. The facial nerve, which courses between the two lobes of the parotid, is rarely involved with benign tumors.

• Pleomorphic adenomas are the most common salivary gland tumors. They are so named because they consist of epithelial, myoepithelial, and mesenchymal tissue. Of the ones in the parotid:- 90% arise in the superficial lobe- 10% arise in the deep lobe and may present as a parapharyngeal space mass or intraoral swelling- usually present in the fourth or fifth decades as painless, slow-growing masses

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Parotid Tumors (cont’d)

• Mucoepidermoid carcinoma is the most common malignant parotid tumor. Its growth behavior is similar to that of pleomorphic adenomas.

• In general, CT and MRI cannot differentiate between benign and malignant parotid tumors unless frank involvement of adjacent tissue is seen (this point will be illustrated in Case 4). Fine-needle aspiration (FNA) of the tumor is commonly used to make a diagnosis.

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Patient 3: Clinical Course

Subsequent ultrasound of the left parotid failed to detect the lesion seen in the MR study. Fine-needle aspiration was therefore deferred, and the decision was made to follow the lesion radiologically. A follow-up MR scan at 6 months showed a decrease in one dimension of the lesion (next slide).

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T2 weighted STIR (T2 weighted)6 months later

Comparison shows decrease in the size of the lesion

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Patient 3: Summary

This case:• illustrates the use of MR in the evaluation of a head and neck tumor

• Ilustrates clinical management of a benign head and neck neoplasm

Patient 4 involves a much rarer tumor.

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Patient 4

A 61 yo man was found to have a palpable, mobile lesion in the left parotid region. A CT scan with contrast was done to evaluate the lesion.

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Before looking at the lesion, try to identify the following structures (Recall Case 2): • mandibular rami• styloid processes• masseter muscles

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There is a well- circumscribed, 1.7cm lesion in the superficial lobe of the left parotid gland. It is hyperdense on this image with contrast, although no pre- contrast image was available for comparison.

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Patient 4: Clinical Course

This patient actually had a known history of metastatic renal cell carcinoma with involvement of the left ear. After the above scan was taken, he underwent a partial parotidectomy to remove the tumor. Pathology showed metastatic renal cell carcinoma.

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Patient 3 and 4: Summary

These cases ilustrated:• the evaluation of parotid tumors by CT vs. MR• parotid tumor in the superficial vs. deep lobes• a benign vs. malignant tumor• an intrinsic parotid tumor vs. a metastasis

Note the two tumors had very similar radiologic appearances, emphasizing the need for tissue diagnosis.

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Acknowledgement

People I worked with in neuroradiology:Dr. Jonathan KleefieldDr. Joseph MakrisDr. Ravi Thakur

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ReferencesGood introductory books on head and neck imaging:

•Lenz, Martin. CT and MRI of Head and Neck Tumors. 1993.

•Harnsberger, H.R. Head and Neck Imaging, in the Handbooks in Radiology series. 1990