Pachymeningeal enhancement, also known as dura-arachnoid enhancement 4 refers to visible enhancement seen following contrast administration of the pachymenges. Excessive enhancement is seen in a variety of pathological conditions that can represent changes in intracranial pressure, changes in perfusion of the meninges or infiltration by tumor or inflammatory cells.
Terminology
It is important to note that the very thin arachnoid membrane is attached to the inner surface of the dura mater. Thus, the term pachymeningeal enhancement can also be described as a dura-arachnoid enhancement 3.
On the other hand, the enhancement of the surface of the brain, usually referred to as leptomeningeal enhancement or pial enhancement, also sometimes referred to as pial-arachnoid enhancement as pathology is usually contained within the subarachnoid space bounded by the pia and arachnoid layers 3.
Causes
Normal enhancement
The periosteal layer and thecal layer of the dura are supplied by vessels that do not have a blood-brain barrier and, as such, enhance readily following administration of intravascular contrast agents. However, they are usually very thin and difficult to identify on routine imaging when up against the inner surface of the bone 7. Dural reflections, such as the falx, are visible but some of this enhancement is vascular rather than meningeal.
As a general rule, if complete enhancement of the pachymeninges is visible abutting the inner surface of the skull on both CT and MRI, excessive enhancement is likely to be present.
Excessive enhancement
Excessive pachymeningeal enhancement may occur in numerous disease states, including:
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idiopathic
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infective
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inflammatory
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other
haemodialysis
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tumors
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changes in perfusion/pressure