Skull Normal Variants
Miral D. Jhaveri, MD
DIFFERENTIAL DIAGNOSIS
Common
Skull Normal Variants
Arachnoid Granulations, Calvarium
Vascular Grooves
Venous Lakes
Emissary Veins
Parietal Thinning
Asymmetric Marrow, Petrous Apex
Asymmetric Foramina (Jugular, Ovale)
Aerated Clinoids
Accessory Sutures (e.g., Mendosal)
Hyperostosis Frontalis Interna
Less Common
Prominent Convolutional Markings
Rare but Important
Wormian Bones
ESSENTIAL INFORMATION
Key Differential Diagnosis Issues
Important to recognize normal anatomic variations
These are “leave me alone” lesions
Should not be mistaken for real disease (e.g., metastases)
Helpful Clues for Common Diagnoses
Skull Normal Variants
Arachnoid Granulations, Calvarium
Sharply demarcated defect in inner table
Adjacent to/within dural venous sinuses
CSF density/intensity
Vascular Grooves
Usually inner table
Caused by meningeal arteries, veins
Outer table produced by superficial temporal artery branches
Venous Lakes
Round or oval configuration
Diploic venous channel can usually be traced into venous lakes
Emissary Veins
Connect meningeal veins/dural venous sinuses with pericranial (scalp) veins
Chiefly in frontal, parietal bones
Parietal Thinning
Elongated oval-shaped thinness
Upper part of parietal bone involved
Asymmetric Marrow, Petrous Apex
Non-pneumatized marrow hyperintense on T1WI
Opposite side pneumatized
Hyperostosis Frontalis Interna
Predominately inner table overgrowth
Usually bilateral, symmetrical
Frontal; usually stops at coronal suture
± Orbital roofs, parietal bones
Helpful Clues for Less Common Diagnoses
Prominent Convolutional Markings
Brain pulsations → inner table depressions
Children > > adults
Helpful Clues for Rare Diagnoses
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