Clival and Paraclival Lesions: Imaging Features and Differential Diagnosis

A practical radiology review of Clival and Paraclival Lesions: Imaging Features and Differential Diagnosis, focused on imaging findings, differential diagnosis, reporting points, and high-yield teaching pearls.

Anatomy & Physiology Pearls

• Spheno-occipital synchondrosis → fuses late teens–mid-20s ⏳ → incomplete fusion in young = don’t confuse with lytic lesion

Normal clival marrow

• T1 ≥ pons = normal
• T1 < pons = suspect pathology (marrow replacement, edema, tumor)

Marrow grading

• Grade 1: >50% low T1 signal
• Grade 2: 20–50%
• Grade 3: <20% (fatty)
• Useful for early infiltration detection in myeloma/metastases

Sequences

• FIESTA/CISS = tiny lesion detector
• Great for Ecchordosis physaliphora (EP) or small cystic lesions near brainstem
• Can show communication with prepontine cistern → diagnostic for EP

DWI/ADC

• Chordoma: ADC ↓ (restricted)
• Chondrosarcoma: ADC ↑ (more free diffusion)
• Skull Base Ostemyelitis: ADC ↑↑ (infection/inflammation = not restricted )
• NPC/Lymphoma: ADC ↓ (cellularity)
• ADC = secret diagnostic weapon for skull base differentiation

Benign Lesions

• Fibrous dysplasia
• Ground-glass CT texture = pathognomonic
• T1 ↓, T2 variable (depending on fibrous vs cystic)
• Can mimic meningioma hyperostosis — meningioma enhances dural-based; FD is intramedullary
• Only 44 clival cases ever reported → extreme rarity clue
• Benign-appearing notochordal lesion (BNL)
• Ecchordosis physaliphora (EP) ≠ Chordoma
• EP: non-enhancing, CSF-like signal, often on posterior clival surface, stalk-like attachment to dura
• Chordoma: enhancing, expansile, bone destruction
• Stable over time → 6-month MRI follow-up recommended

Malignant Lesions— Subtle Differentiation

Chordoma

• Classic “honeycomb” enhancement pattern
• May show hemorrhagic foci → T1 bright spots
• High recurrence even if low grade
• Pitfall: low-T2 chordoma = mimic metastasis or lymphoma

Chondrosarcoma

• Off-midline (petro-occipital synchondrosis)
• Popcorn / ring-and-arc calcification = chondroid matrix clue
• ADC higher than chordoma
• Tends to remodel bone (vs destructive)

Myeloma

• 5 marrow patterns: normal / focal / diffuse / salt-pepper / mixed
• “Normal marrow” pattern can still mean active disease — rely on clinical + lab correlation

Metastasis

• Mixed lytic–sclerotic (esp. breast, prostate )
• Multifocality + different lesion stages = metastatic clue
• ADC ↓ in high-cellular types; ↑ in necrotic ones

Infectious / Inflammatory — Diagnostic Traps

• Central Skull Base Osteomyelitis (SBO)
• Often starts as sinus infection → spreads to clivus
• MRI: T1 ↓, T2 variable, contrast ↑ diffuse
• ADC ↑ (helps distinguish from tumor)
• Common bug: Pseudomonas (esp. diabetics)
• Bone changes lag clinical response → follow-up based on CRP/ESR, not imaging
• FDG-PET may stay positive even after MRI normalization — persistent metabolic activity ≠ relapse

Secondary / Adjacent Spread Lesions

NPC

• Iso–hyper T2, diffusion restriction, strong enhancement
• Clival involvement = T3 disease per AJCC
• Often shows perineural spread → follow CN V2–V3 course
• Sinonasal malignancy
• Mucinous → T2 bright
• Non-mucinous → T2 dark
• Enhancement pattern > signal intensity for tumor typing
• Lymphoma vs carcinoma → Lymphoma enhances homogeneously, shows restricted diffusion, no necrosis

PitNET (macroadenoma)

• Now officially malignant (“3” code in WHO 5th ed)
• Extrasellar ones can arise from clivus = ectopic PitNET
• Hypointense/isointense T1, variable T2, mild enhancement

Intraosseous meningioma

• Osteoblastic type = hyperostosis
• Osteolytic type = can mimic metastasis
• Homogeneous enhancement helps ID