Dura mater (posterior fossa)

What it is

The dura mater is the tough, outermost of the three membranes (meninges) covering the brain and spinal cord. In the posterior fossa and at the craniocervical junction, it lines the bony compartment, and it is the membrane opened and patched during Chiari decompression with duraplasty.

Understanding Dura mater (posterior fossa)

The dura forms a tough envelope around the brain and spinal cord. At the craniocervical junction, a thickened or tight band of dura (sometimes a constricting band at the foramen magnum) can contribute to crowding and compression in Chiari. In posterior fossa decompression surgery, after removing bone, the surgeon may open the dura and sew in a patch (a duraplasty) to expand the space and improve CSF flow — this is the "with duraplasty" step that distinguishes the more extensive version of the surgery. Alternatively, some procedures leave the dura intact (bony-only decompression) or only split its outer layer. Understanding the dura clarifies a membrane central to both the crowding in Chiari and the surgery used to treat it.

Why it matters

Understanding the dura mater helps families see how a tight dural band can contribute to crowding at the foramen magnum, and why opening and patching the dura (duraplasty) is a key step in the more extensive version of decompression surgery.