Lumbar disks, plates of cartilage that cushion the movements of the vertebrae of the spine, can rupture and herniate, putting pressure on nerves. The common symptoms of a herniated disk in the lumbar spine vary depending on which vertebrae and lumbar nerves are affected by the herniation. The lower back has five sets of nerves that leave the spinal cord to emerge through the vertebrae of the lumbar spine.
Pain Management
Lumbar disk herniation may not produce any back pain at all. But it usually causes pain in one or both legs, according to the National Institutes of Health. Dr. John P. Revord, a pain medicine and management physician at NeuroSpine Centers of Wisconsin, reports that the last lumbar and first sacral nerves, known as L5 and S1, are most frequently involved in lumbar disk herniation. Damage to these particular nerves can cause sciatic pain, which radiates down the back of the leg.
When the disk between the L4 and L5 vertebrae herniates, the pain can pass down the back of the leg and also be felt in the top of the foot. Below the lumbar spine, a triangular-shaped bone called the sacrum, or S1, ends the spinal column. A disk herniation between the last lumbar vertebrae and the sacrum can cause pain to radiate into the sole and outer edge of the foot.
Muscle Weakness
The nerves of the lumbar spine carry instructions from the brain to the leg muscles. When these impulses are interrupted, muscle weakness can ensue. Specifically, Revord says, impingement of the fifth lumbar nerve can disrupt the flow of information to the muscles that lift the big toe and ankle. The condition caused by weakness of these muscles is known as “foot drop.” Herniation of the disk beneath the last lumbar vertebra can weaken muscles that make it possible for people to walk on their toes.
Diminished Reflexes
Reflexes test the path of nerve impulses. When a doctor taps a muscle’s ligament with a mallet, a sensory impulse is sent to the spinal cord, and an involuntary motor response is immediately sent back to the muscle, making it twitch. This phenomena is helpful in evaluating lumbar nerve damage. Nerve damage due to herniated disks in the lumbar spine may result in diminished reflex reactions in the ankle and knee.
