Signs of a trapped nerve in the back (sciatica)

In younger patients (aged between 18-60) by far the commonest cause of nerve root entrapment or irritation in the spinal canal is damage to an adjacent intervertebral disc.

The disc is a soft tissue in a hard place with an equally hard job to do. It forms flexible joints between the vertebrae (back bones) and acts as the main load-bearing and shock-absorbing structure. But when a slipped disc occurs it presses on the nerves and causes pain in the lower back, numbness and tingling, and problems when trying to bend or stand up straight.

Dr Anthony Hammond is a consultant rheumatologist who specialises in back pain and sciatica. Here he explains the signs you should watch out for and the potential risk factors for a slipped disc.

What happens when the disc slips?

In many instances, the load is just too much and the disc tear's along the back wall (the edge adjacent to the spinal nerves) and leads to bulges and inflammation. In the worst case, the back of the disc can tear through and a portion of the central disc nucleus is ejected into the spinal canal, which hits or compresses the nearest nerve root. This is called a slipped disc.

This, in turn, irritates the nerves that they contact and this results in various combinations of back pain and sciatica. This is a nerve root pain referred along the nerve and experienced in the buttock or the leg.

Which symptoms should I be concerned about?

Pain is obvious and will drive most patients to seek help. Loss of function, with numbness (loss or severe blunting of skin sensation) or weakness, however, is more serious in the sense that it may require operative-release to ensure the function is restored.

The most severe problem results from a large slipped disc in the centre of the canal producing numbness and loss of function of the bladder or bowel. This is called cauda equina syndrome and has to be released by surgery immediately or within a few hours to ensure full restoration of bladder or bowel function. Such an event should be treated as a medical emergency with immediate attendance at an emergency department.

What are risks factors for a trapped nerve?

Bending, twisting and lifting (especially all together) are designed to stress the rear edge of the disc and to induce these problems. A new mum, bending into the back seat of a car to lift a heavy toddler is a good example. Childbirth is also a frequent provoking event for spinal problems.

Heavy lifting with poor posture and poor core muscle control will do the same. Prolonged sitting with poor posture is also a contributor. However, very often patients report: “I didn’t do anything” or “I just bent to pick up a piece of paper” or “I simply woke up with…”

In short, the disc can tear and cause trouble simply under body weight and normal function.

Do not hesitate to book an appointment with Dr Hammond if you're concerned about your back pain.