Topics

Topic

design image
Diploic veins

Diploic veins are a network of large, thin-walled valveless venous channels located within the diploë, the spongy cancellous bone of the cranial vault. These veins play a key role in draining the bones of the skull and connect extracranial veins with the intracranial dural venous sinuses. Because of their unique location, diploic veins are clinically important, especially in the context of cranial trauma, infection, and various neurosurgical procedures. Their variable anatomy can pose challenges and opportunities in diagnostic imaging.

Synonyms

  • Cranial diploic veins

  • Skull diploic veins

  • Intraosseous cranial veins

Function

  • Drain venous blood from the spongy diploë of the cranial bones.

  • Serve as communicating channels between the extracranial veins (especially scalp veins) and intracranial dural venous sinuses (e.g., superior sagittal sinus, transverse sinus).

  • Act as a potential route for the spread of infection or metastases between extracranial and intracranial compartments.

  • Play a role in the regulation of intracranial pressure and venous outflow, especially in children.

MRI Appearance

  • T2-weighted Imaging:

    • Diploic veins appear as well-defined, tubular or oval flow voids within the diploic space of cranial bones.

    • High signal of surrounding marrow accentuates the low signal (void) of the veins due to flowing blood.

  • T1-weighted Imaging:

    • Seen as tubular or round low-signal-intensity structures within the high-signal diploic bone marrow.

    • More difficult to differentiate unless surrounded by fat-rich marrow.

  • Phase Contrast 3D (PC 3D):

    • Diploic veins demonstrate as flow-sensitive linear or curvilinear structures within the calvarium.

    • Enhanced visualization of flow direction and patency.

  • Post-Contrast T1-weighted Imaging:

    • Diploic veins enhance due to the intravascular contrast, making them more conspicuous as enhancing tubular structures within the diploic space.

CT Appearance

  • Appear as well-circumscribed, linear or oval lucencies within the diploic space of the skull vault.

  • May be confused with lytic lesions if not recognized as veins.

  • Larger veins may have thin sclerotic margins, distinguishing them from pathological lytic lesions.

CT Venography (CTV) Appearance

  • Diploic veins enhance following intravenous contrast, appearing as enhancing channels within the diploic bone.

  • Clear visualization of their course and connections to dural venous sinuses and extracranial veins.

  • CTV is helpful for pre-surgical planning or in the evaluation of venous anomalies.

MRI images

Diploic veins MRI 3T axial image