L5/S1Herniation of Nucleus Pulposus (HNP) Large Extrusion of L5/S1 Disc

After describing the structure of a spinal disc in the previous blog, here are MRI scans showing a small and a large herniation of the L5/S1 nucleus pulpous. The disc doesn’t slip (a lay term) – the end plates stay attached. The disc annulus (capsule) may stretch or even tear open at a spot (the medical term is rupture) and the NP protrude (medical term is herniation). So these are all commonly referred to as ruptured discs or more succinctly as an HNPs, as shown above left. If the nucleus pulposus has torn through the annulus, above right, it is sub-classified as an extruded disc.

A large HNP does not necessarily require operative treatment. Sometimes, even an extruded fragment (which cannot go back into place) will get much smaller with time, probably by drying and shrinking like fried bacon does. Surgical indications depend on the symptoms and neurological damage being caused. As the saying goes, “we treat patients, not MRI scans.” Imaging studies are to confirm the diagnosis and locate the herniation for surgical planning when needed.

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