Meckel Cave Lesion

Anne G. Osborn, MD, FACR

DIFFERENTIAL DIAGNOSIS

Common

Less Common

Rare but Important

ESSENTIAL INFORMATION

Key Differential Diagnosis Issues

Helpful Clues for Common Diagnoses

Schwannoma, Trigeminal, Intracranial
- Variable configuration
  - “Dumbbell” tumor with CPA component, constriction of tumor at entrance to Meckel cave, Meckel cave mass
  - May involve MC only
  - ± Extracranial extension along V1, V2, &/or V3
- Unilateral unless NF2
- Hyperintense on T2WI, strong enhancement on T1 C+
- May result in atrophy of muscles of mastication
Meningioma
- Uni- > bilateral involvement
- Dural thickening along cavernous sinus, tentorium (dural “tail sign”)
- ± Ipsilateral denervation, atrophy of muscles of mastication
Metastasis, Skull Base
- Metastases to Meckel cave can be hematogenous, direct geographic extension, perineural, or CSF spread
  - Hematogenous spread to central skull base (BOS) with secondary involvement of cavernous sinus
  - Direct extension from extracranial primary (e.g., nasopharyngeal squamous cell carcinoma) into central BOS
  - Uni- > bilateral involvement
- Sagittal T1WI helpful
  - Look for replacement of normal fatty clival marrow ± cortical destruction

Helpful Clues for Less Common Diagnoses

Metastasis, CSF/Meningeal
- Pia-arachnoid tumor spread may extend into MCs
- ± Enhancement along cisternal CN5
Metastasis, Perineural CNV3
- Retrograde tumor spread along mandibular nerve
- Look for mass in retromolar trigone, masticator space
- Adenoid cystic carcinoma, squamous cell carcinoma most common
- CNV3 appears thick, enhancing ± erosion of foramen ovale
Meningitis
- Any etiology (e.g., pyogenic, TB)
- Dura-arachnoid disease can extend into MC
- Look for basal cistern enhancement
Neurosarcoid
- Pituitary gland, infundibular stalk, dural masses common
- Can be uni- or bilateral
Neurofibroma
- Orbit/scalp/lid plexiform in NF1
- May extend posteriorly through SOF, infiltrate V1 branches → MC
Pseudotumor, Intracranial
- Typically originates in/around orbit
- Extends through SOF into CS, MC
- Variable dura-arachnoid thickening, enhancement
- Idiopathic invasive subtype
  - May erode bone, mimic aggressive infection, neoplasm
Pituitary Macroadenoma
- Can extend into one or both CSs, MCs
- Pituitary gland generally cannot be distinguished from mass
- Gland IS mass
- Aggressive invasive type may destroy central skull base, clivus
  - Pituitary adenoma > > > > carcinoma
  - Can mimic malignant disease, so do endocrine workup

Helpful Clues for Rare Diagnoses

Metastasis, Perineural CNV2
- Often skin carcinomas (basal, squamous cell)
- Infiltrates along inferior orbital canal
- May enlarge/erode foramen rotundum
- Thickened, enhancing maxillary nerve
Trigeminal Herpetic Neuritis
- Herpes zoster oticus > trigeminal neuritis
- Edematous, enhancing CN5
  - Ophthalmic division most commonly involved
Lipoma
- MC is rare site
- Uni- > bilateral
Epidermoid Cyst
- May originate in MC or as extension from CPA epidermoid
- Does not suppress on FLAIR; restricts on DWI
Dermoid Cyst
- Looks like fat in MC, not CSF
- May occur with or without rupture, CSF fatty droplets
Neurocysticercosis
- Cysts in basal cisterns may extend into one or both MCs
Chronic Thrombosis, Dural Sinus
- Chronically occluded dural sinus(es)
- Dural thickening, enhancement secondary to collateral venous drainage
- May involve one or both MCs