Key points
-
The skull vault has its own limited spectrum of disease.
-
Pseudolesions should be known and easily recognized.
-
Some benign entities may mimic malignancy if analyzed using classical signs.
-
Recognition of key findings may assist in the differential diagnosis.
-
MR spectroscopy, MR diffusion, and MR perfusion curve analysis may be useful for specific scenarios.
Background
Pseudolesions | Lytic | Sclerotic/mixed | Transdiploic |
---|---|---|---|
Arachnoid granulation Meningo-/encephalocele Dilated vascular canals Internal hyperostosis Biparietal thinning Enlarged parietal foramina Sinus pericrani | Fibrous dysplasia Epidermal inclusion cyst Eosinophilic granuloma Intraosseous hemangioma Plasma-cell myeloma Giant-cell tumor Aneurysmal bone cyst Meningioma* Lymphoma* Metastasis* | Osteoma Osteosarcoma Meningioma* Lymphoma* Metastasis* | Meningioma* Hemangiopericytoma Lymphoma* Plasmacytoma* Metastasis* |
Pseudolesions
Arachnoid (pacchionian) granulations
Meningeal herniations
Dilated vascular canals and lacunae
Hyperostosis frontalis interna
Bilateral thinning of the parietal bones
Enlarged parietal foramina
Sinus pericranii
Predominantly lytic lesions
Young patient | Fibrous dysplasia (ground-glass matrix) Eosinophilic granuloma (“button sequestrum”) |
Elderly and multiple | Metastasis Plasma-cell myeloma |
Bone-expanding | Fibrous dysplasia (ground-glass matrix) Hemangioma (“spoke wheel”) Giant cell tumor (hypervascular, flow-voids) Aneurysmal bone cyst (hemosiderin levels) |
Diffusion-restricting | Epidermal inclusion cyst (previous trauma) Dermoid cyst (fatty content) |
Fibrous dysplasia
Epidermoid and dermoid cysts
Eosinophilic granuloma
Intraosseous hemangioma
Aneurysmal bone cysts
Giant cell tumor
Metastases
Myeloma
Predominantly sclerotic lesions
Osteoma
Blastic metastases
Osteosarcoma
Transdiploic lesions
Meningioma
Hemangiopericytoma
Lymphoma
Metastases and plasmacytoma
Summary of functional imaging techniques that may provide a clue when facing aggressive transdiploic lesions with soft tissue component
MR spectroscopy | MR perfusion | |
---|---|---|
Meningioma | Alanine (1.47 ppm): specific ↑Glutamate+Glutamine ↑Cho/Cr ratio | ↑↑↑ rCBV (hipervascular) Slow-progressive return to baseline |
Hemangiopericytoma | Myoinositol: Specific No alanine ↑ Cho/Cr ratio | Similar to Meningioma (hypervascular) |
Lymphoma/small-blue round-cell | ↑↑↑ Choline +/− Lipids or lactate | Recovery curve ABOVE baseline Slightly ↑ CBV (ratio 1–1.5) |
Metastasis | ↑↑ Lipids (tumor necrosis) | Recovery curve BELOW baseline |
Miscellany: metabolic, inflammatory infectious, and systemic disease
Paget’s disease of bone
Renal osteodystrophy
Sarcoidosis
Thalassemia
Osteopetrosis
Osteitis and osteomyelitis
Amyloidosis
Pseudolesions: Very common. Know-them to recognize them | |
Meningioma and hemangioma can simulate aggressive periosteal reaction | |
Meningioma: Calcification, dural tail, intense enhancement, hyperostosis. Beware of variable bone involvement. 1H-MRS: Alanine (specific) | |
Hemangioma: Expansile, trabeculated, spoke-wheel pattern, fatty content. | |
Epidermal inclusion cyst: Previous injury, DWI restriction | |
Dermoid cyst: DWI restriction, fatty content | |
Fibrous dysplasia: Young patient. “Ground-glass” matrix virtually pathognomonic. Possible predominant lytic-cystic component in calvarium | |
Eosinophilic granuloma: Young patient with focal lytic lesion with “button sequestrum” | |
Giant-cell tumor: Hypervascular bone expansion lesion with flow-voids | |
Aneurysmal bone-cyst: Bone-expanding lesion with fluid hemosiderin levels. May be secondary if prominent solid components | |
Myeloma/metastastasis: Elderly patients with multiple lesions | |
Blastic metastasis: Prostate, breast, transitional cell, neuroendocrine, PNET, lymphoma | |
Hypervascular metastasis: thyroid, renal, hepatocarcinoma, neuroendocrine and melanoma | |
Transdiploic or aggressive single lesion: Differential of plasmacytoma, metastasis, lymphoma or meningeal lesion (meningioma/ SFT). Functional imaging can be useful in narrowing differential |