When do you request a neck MRI in patients with a neck mass or scrofula, particularly those from areas where tuberculosis (TB) is endemic or with compromised immune systems?

When to Request Neck MRI for Neck Mass or Scrofula

Order contrast-enhanced CT neck (or MRI neck with contrast) immediately for any adult patient with a neck mass deemed at increased risk for malignancy, which includes masses persisting beyond 2-3 weeks, nontender masses, patients over 40 years old, those with smoking history, or masses associated with hoarseness, dysphagia, or cranial nerve abnormalities. 1, 2

Primary Imaging Decision: CT vs MRI

CT is the Preferred First-Line Modality

• CT with contrast should be your default choice because it is more readily available, costs considerably less, has shorter scanning time (<5 minutes), and is better tolerated by patients 1
• CT provides superior spatial resolution for identifying precise mass location, assessing nodal necrosis, and guiding the search for occult primary tumors in the upper aerodigestive tract 2
• The radiation dose of 3 mSv (equivalent to approximately 150 chest x-rays) is considered acceptable in adults 1

When to Choose MRI Over CT

Select MRI with contrast specifically when:

• Nasopharyngeal primary tumor is suspected – MRI has superior sensitivity for skull base abnormalities and perineural spread 1
• Cranial nerve abnormality is present on physical examination – MRI better detects perineural spread and skull base involvement 1
• Dental artifact obscures the tonsillar fossa and base of tongue on CT – MRI can overcome this limitation 1
• Radiation exposure is a concern (e.g., younger patients, pregnancy considerations, claustrophobic patients who prefer to avoid repeat imaging) 1
• Deep neck space infection requires superior soft tissue characterization – MRI offers unsurpassed soft tissue discrimination with high diagnostic accuracy (95% technical success rate, 0.98 positive predictive value for infection) 3, 4

Specific Considerations for Scrofula (Tuberculous Lymphadenitis)

When TB is Suspected in Endemic Areas or Immunocompromised Patients

• Order contrast-enhanced CT or MRI using the same risk stratification criteria as for malignancy 1
• Do not delay imaging while awaiting TB testing results – imaging helps distinguish between phlegmon and abscess formation, which directly impacts treatment decisions 5
• MRI may be particularly valuable in TB cases because it can detect granulomas at lung apices and provide superior characterization of necrotic lymph nodes 1, 3
• Both CT and MRI can identify retropharyngeal infection spreading to the superior mediastinum, a critical complication requiring immediate intervention 5

Critical Technical Requirements

Always Order Contrast Unless Contraindicated

• Intravenous contrast must be used regardless of whether CT or MRI is performed 1
• Contrast improves mass characterization (distinguishing cystic from solid lesions), maps lesion borders, and identifies potentially small primary sites in the upper aerodigestive tract 1
• Contraindications to contrast: severe renal insufficiency, contrast allergy, or prior diagnosis that excludes contrast use 1, 6

Imaging Protocol Specifications

• Standard neck imaging should extend from skull base to thoracic inlet to adequately capture all structures 1
• For MRI, request post-contrast T1-weighted sequences in multiple planes (axial, sagittal, coronal) 6
• Avoid ordering "CT with and without contrast" – this doubles radiation exposure with minimal added benefit 1, 6

Common Pitfalls to Avoid

Do Not Skip Imaging in High-Risk Patients

• Clinical diagnosis alone is inaccurate – only 42.9% of deep neck space infections are correctly localized without imaging 5
• Imaging must precede any biopsy attempt in patients at increased risk for malignancy 7

Do Not Assume Imaging Substitutes for Direct Visualization

• Patients must undergo visualization of the larynx, base of tongue, and pharynx to identify potential primary malignancy, even with normal imaging 2, 7
• This examination should include assessment of the nasopharynx, oropharynx, hypopharynx, and larynx 1

Do Not Delay Evaluation

• Complete the imaging evaluation within 1-2 weeks maximum, as delays adversely affect treatment outcomes and prognosis 2
• In suspected deep neck infections, inappropriate puncture or incision without imaging guidance can cause spread of infection to multiple spaces or the mediastinum 5

Special Populations

Pregnancy

• Imaging recommendations may be altered; MRI without gadolinium is preferred over CT to avoid radiation 1
• Gadolinium should be avoided due to risk of nephrogenic systemic fibrosis, though this is primarily a concern with severe renal insufficiency 1

Patients with Implantable Devices

• Pacemakers and neurostimulators preclude MRI scanning – use CT with contrast instead 1

Claustrophobic Patients

• CT is better tolerated due to larger bore and shorter scan time 1
• If MRI is clinically necessary, consider sedation or open-bore MRI if available 1