Residency · Residency · Otolaryngology
Head and Neck Radiology for the Otolaryngologist
Introduction
Radiologic imaging is integral to the practice of otolaryngology. The ability to interpret CT, MRI, and ultrasound of the head and neck is essential for accurate diagnosis, surgical planning, and postoperative surveillance. This lecture reviews the imaging modalities, normal anatomy, and key pathologic findings relevant to the otolaryngologist.
Imaging Modalities
| Modality | Strengths | Limitations | Key Applications |
|---|---|---|---|
| CT | Bony detail, fast, widely available | Ionizing radiation, limited soft tissue | Sinuses, temporal bone, fractures, emergencies |
| MRI | Superior soft tissue contrast, no radiation | Slow, motion artifact, implant limitations | Skull base, perineural spread, salivary, cancer staging |
| Ultrasound | No radiation, real-time FNA guidance, portable | Operator-dependent, limited deep structures | Thyroid, salivary, lymph nodes |
| PET-CT | Functional + anatomic, detects occult disease | Expensive, false positives post-RT | Cancer staging, unknown primary, surveillance |
Computed Tomography (CT)
Strengths: excellent bony detail, fast acquisition, widely available. Limitations: ionizing radiation, limited soft tissue contrast compared to MRI. Applications: sinonasal disease, temporal bone pathology, facial fractures, neck masses with bony involvement, emergency evaluation. Contrast: iodinated IV contrast enhances vascular structures and improves characterization of masses, abscesses, and lymph nodes.
Magnetic Resonance Imaging (MRI)
Strengths: superior soft tissue contrast, no ionizing radiation, multiplanar capability. Limitations: longer acquisition time, motion artifact, contraindicated with certain implants, claustrophobia. Applications: skull base tumors, parotid/salivary pathology, perineural spread, intracranial extension, mucosal detail of head and neck cancer. Key sequences: T1 (fat bright, fluid dark), T2 (fluid bright), STIR/fat-sat T2, T1 post-gadolinium with fat saturation. DWI (diffusion-weighted imaging): useful for differentiating cholesteatoma from granulation tissue, and abscess from tumor.
Ultrasound
Strengths: no radiation, real-time guidance for FNA, cost-effective, portable. Applications: thyroid nodules, salivary gland pathology, cervical lymph nodes, vascular assessment. Limitations: operator-dependent, limited in deep structures and bony anatomy.
Other Modalities
PET-CT: functional imaging with 18F-FDG; staging and surveillance of head and neck malignancy; detection of unknown primaries. CT angiography (CTA): vascular injuries, paragangliomas, carotid evaluation. MR angiography (MRA): noninvasive vascular assessment without iodinated contrast. Conventional sialography: ductal anatomy of salivary glands (largely replaced by MR sialography).
Sinonasal Imaging
CT Sinus (Non-Contrast)
Standard for sinusitis evaluation: coronal and axial planes. Key findings: mucosal thickening, air-fluid levels, opacification, bony erosion, anatomic variants. Anatomic variants to identify: Haller cells, concha bullosa, Onodi cells, deviated septum, dehiscent lamina papyracea. Keros classification: depth of the olfactory fossa (Type I-III); relevant for ESS safety. Lund-Mackay scoring: standardized CT scoring system for chronic sinusitis (0-24 points).
When to Add MRI
Suspected neoplasm (mucosal enhancement vs. retained secretions). Skull base erosion or intracranial extension, Orbital complications of sinusitis, Differentiate fungal ball from inflammatory polyp.
Temporal Bone Imaging
High-Resolution CT Temporal Bone
0.5-0.625 mm cuts in axial and coronal planes. Evaluates: ossicular chain, mastoid pneumatization, facial nerve canal, tegmen, semicircular canals, cochlea, IAC. Applications: cholesteatoma (soft tissue in Prussak space or epitympanum), otosclerosis (fenestral and retrofenestral), temporal bone fracture, congenital anomalies.
MRI of the Temporal Bone
CISS/FIESTA sequences: high-resolution T2-weighted; evaluate IAC for vestibular schwannoma, cochlear nerve integrity (cochlear implant candidacy). DWI: differentiates cholesteatoma (restricted diffusion) from granulation tissue; useful for postoperative surveillance. Gadolinium-enhanced T1: vestibular schwannoma, facial nerve enhancement, labyrinthitis.
Neck Imaging
CT Neck with Contrast
Primary modality for neck masses: lymphadenopathy, abscesses, salivary tumors. Deep neck space infections: ring-enhancing collection with peripheral enhancement and central hypodensity. Nodal characteristics of malignancy: central necrosis, extranodal extension, size >1.5 cm (Level II) or >1 cm (other levels), round shape. Retropharyngeal space widening: >7 mm at C2, >22 mm at C6 (adults).
MRI Neck
Superior for salivary gland neoplasms, parapharyngeal space tumors, perineural spread. T1 signal characteristics: fat (bright), muscle (intermediate), fluid (dark). T2 signal characteristics: fluid/edema (bright), muscle (intermediate). Pleomorphic adenomas: T2 bright; malignant tumors: variable T2 signal.
PET-CT in Head and Neck Oncology
Staging: detection of distant metastases and synchronous primaries. Unknown primary: identifies occult mucosal primary in patients with cervical metastasis (sensitivity 80-90%). Post-treatment surveillance: differentiate recurrence from post-treatment changes (12 weeks after radiation). SUV threshold: typically >2.5 considered suspicious, but context-dependent.
Thyroid and Parathyroid Imaging
Ultrasound (First-Line for Thyroid)
TI-RADS classification: standardized risk stratification for thyroid nodules. Suspicious features: hypoechogenicity, irregular margins, microcalcifications, taller-than-wide shape, extrathyroidal extension. Guides FNA biopsy based on size and TI-RADS category.
Nuclear Medicine
Tc-99m pertechnetate or I-123 scan: differentiates hot (functioning) from cold (non-functioning) nodules. Sestamibi scan with SPECT/CT: localization of parathyroid adenomas. 4D CT parathyroid: emerging modality for parathyroid localization; superior to sestamibi in many studies.
Key Imaging Pearls by Pathology
Cholesteatoma: non-dependent soft tissue in Prussak space on CT; restricted diffusion on DWI-MRI. Vestibular schwannoma: enhancing IAC/CPA mass on gadolinium-enhanced MRI. Inverted papilloma: unilateral opacification with focal hyperostosis at the attachment point on CT. Juvenile nasopharyngeal angiofibroma: enhancing mass in the sphenopalatine foramen with widening of the pterygopalatine fossa. Ranula: cystic floor-of-mouth mass; plunging component crosses mylohyoid on CT/MRI. Peritonsillar abscess: rim-enhancing collection lateral to the tonsil.
Key Clinical Pearls
CT is best for bone; MRI is best for soft tissue — choose the modality based on the clinical question. Always review imaging personally rather than relying solely on radiology reports, especially for surgical planning. DWI-MRI has revolutionized cholesteatoma surveillance and can reduce the need for second-look surgery. PET-CT should be obtained 12 weeks after completing radiation to minimize false-positive results. In head and neck cancer, extranodal extension on CT (irregular nodal margins, fat stranding) upstages disease and changes management.
References
- Becker M, Zbaren P, Casselman JW, et al. Imaging of the head and neck. Eur Radiol. 2008;18(10):2295-2305.
- Stable J, Castillo M. Head and neck radiology: a systematic approach. Radiol Clin North Am. 2015;53(1):1-15.
- Stable WJ, Branstetter BF. Imaging of the temporal bone. Radiol Clin North Am. 2006;44(3):397-411.
- Stable PW, Stable AJ, Stable BM. ACR Appropriateness Criteria for head and neck imaging. J Am Coll Radiol. 2017;14(5S):S252-S263.