As a disc degenerates, the inner core of the disc can extrude—or herniate—back into the spinal canal. The herniated disc material can irritate the nerve, which can cause pain to radiate down the path of the nerve - from the lower back through the buttocks and into the leg or even into the foot.

Spinal Disc Anatomy
Discs are positioned in between each vertebra (the bony building blocks of the spine) along the front of the spine. Each disc is composed of a tough outer ring and a soft inner core, which is the part that extrudes, or “herniates” out.

A disc herniation typically occurs toward the back of the spine where there is a thinner boundary in the outer ring. This weak spot in the disc can be directly under the nerve root.

Symptoms
A lumbar (lower back) herniated disc will typically cause one or a combination of the following symptoms:

• Dull or sharp pain that travels into the buttocks and back of the leg (sciatica)
• Numbness or tingling in different areas of the leg
• Muscle weakness in certain muscles of one or both legs
• Loss of some reflexes in the leg

Sitting or bending forward, and sneezing or coughing, will usually make the pain worse. If symptoms include any loss of bowel or bladder control, or there is progressive weakness in the legs, immediate medical attention should be sought.

The specific symptoms of a herniated disc depend primarily on the location and degree of the herniation. Approximately 90% of lumbar disc herniations will occur at the following segments of the lower spine:

• L4-L5 herniation (between lumbar segment 4 and 5)—Can cause weakness in extension of the big toe and potentially in the ankle (foot drop). Numbness and pain may be felt on top of the foot, and the pain may also radiate into the buttocks.
• L5-S1 herniation (between lumbar segment 5 and sacral segment 1)—May cause loss of the ankle reflex and/or weakness with ankle push off (e.g. patients cannot do toe rises). Numbness and pain can radiate down to the sole or outside of the foot.

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Diagnosis
A detailed medical history and physical examination can usually differentiate a herniated disc from other possible causes of similar symptoms. An MRI scan is usually needed to confirm the diagnosis and understand the location and degree of the herniation, and additional diagnostic tests may be needed to rule out other possible causes of the symptoms.

An MRI scan that shows a herniated disc does not necessarily mean that the herniation is causing the pain, as many disc herniations do not actually cause any symptoms. Therefore, it is important to get a diagnosis from a doctor to correlate the patient’s medical history and physical exam with the imaging test findings. (Continued on next page.)