How to read a Head and Neck CT

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Search for unexpected findings within the brain:

• Masses/metastases
• Hemorrhages
• Mass effect
• Aneurysms
• Etc.

Any contributory findings? 

• Globes
• Extra-occular muscles
• Cranial nerves: 2, 3, 4, V1/V2, 6
• Supraorbital/Infraorbital foramen
• Conjunctiva
• Lacrimal glands/ducts 

• Known primary tumor: are you expecting to see pathologic lymph nodes?

• Does your lymph node have "volume" in all 3 imaging planes?
• Are the suspicious lymph nodes in the expected drainage pattern fro underlying pathology?

Homogeneous density:

• Size--axial plane measures only (don't focus on size):

                        -- 1.0 cm long axis for all, EXCEPT: 

                        -- Level 1B and Jugulodigastric = 1.5 cm

                        -- Retropharyngeal - 0.8 cm

• Shape/Contour--should have 'volume' in all 3 planes (round, oval)

Heterogeneous density:

• Necrosis
• Cystic change 

                        -- Level 2, think HPV+ oropharyngeal SCCa

                        -- Can be present in papillary thyroid carcinoma nodal mets

• Calcification
• Extra-nodal extension of tumor (ENE)

                        -- Look for irregular nodal margins 

                        -- Peri-nodal fat must be otherwise clear--no inflammatory change or edema

• Abnormal contrast enhancement

Key to Level 2 = the posterior belly of the digastric muscle (especially when there is no IV contrast)

• Attaches along the medial aspect of the mastoid tip
• Courses anteriorly and inferiorly through level 2
• The lateral margin of the muscle abuts the deep lobe of the parotid gland
• The medial margin of the muscle abuts the internal jugular vein
• Jugulodigastric lymph nodes (special Level 2) must touch the posterior belly of the digastric muscle to qualify

• Ipsilateral drainage exceptions: tongue base, lips, midline structures
• Lateral oral tongue: drainage can be direct levels 3+4, skip 1+2
• Parotid gland: only major salivary gland with entire complement of lymphatics