Lumbar disc herniation is a common and highly treatable cause of leg pain and weakness as well as low back pain.
Discs are rubbery cushions between the spinal bones (vertebrae) that act as shock absorbers and provide the normal flexibility of the spinal column. Each disc’s normal location is directly adjacent to the spinal nerves. When the discs deteriorate with age, they become prone to herniation.
A disc herniation occurs when a piece of the disc moves out of place and squeezes a spinal nerve, which may cause leg pain, leg weakness, leg numbness, cauda equina syndrome, and/or low back pain.
Unlike most other parts of the body, lumbar discs begin to deteriorate (degenerate) at a young age. Many patients in their twenties will have disc degeneration on x-rays or MRI and virtually 100% of elderly people have multiple degenerated discs.
Figure 1: Sagittal (side view) MRI of an L3-4 herniated disc (marked by *) impinging on the spinal nerves.
As discs degenerate they lose their water content and elasticity, and the retaining wall around the disc (annulus) begins to fissure or tear. Pieces of the deteriorating disc can then protrude out (herniate) through the leaking annulus. As the disc degenerates, low back pain may result. If herniated disc fragments compress a spinal nerve, it may result in leg pain, weakness, and/or numbness.
Discs often herniate without any unusual traumatic event, but in some cases there may be contributing factors such as excessive weight, poor posture, heavy lifting, or trauma.
The most typical symptom of a disc herniation is pain that radiates from the low back down into the leg (sciatica). In addition to leg pain, the leg may also be weak or numb. One or both legs may be affected. Rarely, bowel or bladder function may be affected. Most patients with disc herniation also experience low back pain.
Only a medical professional can diagnose a disc herniation. A thorough medical history and physical examination can point to the possibility of a disc herniation. The diagnosis can be confirmed by special tests such as MRI and/or CT myelography (myelogram).
The majority of lumbar disc herniations get better on their own without any specific medical treatment. For those herniations that are persistently painful, treatment begins with the least invasive modalities such as anti-inflammatory medications and physical therapy. If symptoms continue, epidural steroid injections may be recommended. For those patients who have persistent symptoms despite nonsurgical treatments, lumbar microdiscectomy surgery typically provides excellent relief.
One notable exception to the use of surgery as the last treatment in lumbar disc herniation is in those patients who have significant weakness in leg muscles, in which case early surgery may be recommended in order to minimize the possibility of permanent nerve damage and persistent leg weakness.