Spontaneous regression of herniated lumbar discs.

The spontaneous regression of a lumbar herniated disc is a common occurrence. Studies using imaging techniques as well as immunohistologic analyses have attempted to explain the mechanism for regression. However, the exact mechanism remains elusive. Understanding the process by which herniated discs disappear in the absence of surgery may better guide treatment. Recent case reports, radiographic and immunohistologic studies show that the extent of extrusion of the nucleus pulposus is related to a higher likelihood of regression. To our knowledge, Patient 3 is the first report of spontaneous regression occurring within 2 months. This occurrence was discovered intraoperatively. We present three illustrative patients. Patient 1, a 53-year-old man, presented with a large L2-L3 disc herniation. His 2 year follow-up MRI revealed a complete regression of the extruded fragment. Patient 2, a 58-year-old man, presented with an L3-L4 disc herniation with cephalad migration of a free fragment. MRI 9 months later showed no free fragment but progression of a disc bulge. Intraoperative exploration during the L3-L4 microdiscectomy confirmed the absence of the free fragment. Patient 3, a 58-year-old woman, presented with a large L2-L3 disc extrusion with cephalad migration. An imaging study performed 2 months after the initial study revealed an absence of the free fragment. Our case reports demonstrate the temporal variance in disc regression. While the time course and extent of regression vary widely, the rapid time in which regression can occur should caution surgeons contemplating discectomy based on an MRI performed a significant period prior to surgery.