MRI Lumbar Spine
Herniated Nucleus Pulposus (HNP)
L: There are vertebral disc changes seen at the levels of L3–4, L4–5, and L5–S1. The
L3–4 change is located centrally and laterally to the right. The L5–S1 change is best seen
in the center of the disc
CAT: There are no remarkable changes in the paravertebral adjacent tissue.
CSB: The anterior portion of the nucleus pulposus of L5–S1 is well defined with a high
signal. The posterior border becomes poorly defined and has an irregular shape.
DC: The degenerative disc desiccation of L3–4, L4–5, and L5–S1 can be a general term
used to refer to a broad range of changes that occur in the disc with normal aging. The
loss of signal on a T2 image is characteristic of disc desiccation. This is due to the loss of
water in the disc. Herniated nucleus pulposus (HNP) occurs when the annulus fibrosis is
torn and the gelatinous nucleus pulposus squeezes through the tear. This is seen at levels
L3–4, L4–5 and L5–S1. HNPs can be classified as central (direct midline protrusion),
paracentral (eccentric herniation), lateral (along side of the spine and beyond the margin
of the spinal canal), or anterior (anterior margin of the vertebral body). At the level of
L3–4, the HNP is central and toward the right. The HNP at the level of L4–5 is
subligamentous, and the HNP at L5–S1 is centrally located.
C: Several factors influence the occurrence of HNP. Smoking is one risk factor.
Increased coughing can also cause a disc herniation. Sitting for long periods of time has
caused herniations due to the increase in disc pressures when sitting without lumbar
support. Disc herniations occur most commonly between the ages of 30 and 50 years. The
symptoms of a herniated disc are predominantly severe low back pain with radiculopathy
into the buttocks, legs, and feet. The pain is generally made worse with coughing,
straining, or laughing. Patients also complain of tingling or numbness in the legs and feet.
Depending on the specific nerve involved, there may be associated numbness or
weakness due to compression of that nerve. There are several tests that may help
diagnose an HNP. Those include, x-ray, MRI, CT, myelogram, and EMG. For the
majority of patients, a period of rest with anti-inflammatory medications followed by
physical therapy is a sufficient treatment. For those who need further treatment, steroid
injections or surgery may be the next options.