General Considerations

• Variant seen in parietal bones in which there is thinning of the bones bilaterally
• About 0.4% of normal skulls
• More common in women
• Mean age 72
• Can be progressive
• May be familial
• No emissary vein is transmitted
• Some consider it developmental, some secondary to osteoporosis and others a dysplasia
• Stress produced by chewing has been implicated

Clinical Findings

• None

Imaging Findings

• Oval-shaped lucency seen at upper portion of parietal bone on lateral (sagittal) view
• Loss of diploic space in this region
• Usually bilaterally symmetrical
• Resorption of the outer table
• Inner table is usually intact

Differential Diagnosis

• Parietal foramina
  • Two symmetrical openings
• Posterior portion of parietal bone at upper margin
• If small, they may carry an emissary vein
• When large (several centimeters), they may not carry a vein

 

 

Parietal thinning. Axial CT scan of the skull on the left shows bilaterally symmetrical thinning of the parietal bones (white arrows). The outer table is resorbed and the diploic space is narrowed. The lateral radiograph on the right demonstrates and oval lucency at the vertex of the skull. Again, the outer table is involved while the inner table is intact.
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