Intervertebral Disc Protrusion: What It Is and How It Differs from a Hernia

An MRI report says "disc protrusion" — and this needs translating from medical language into plain language. It refers to bulging of the intervertebral disc in which its outer ring remains intact. Below — the mechanics of the process, the difference from a hernia, and the signs for which a doctor's visit should not be delayed.

Disc protrusion: what it is

The intervertebral disc is a cartilaginous pad between the vertebral bodies. It works like a shock-absorbing washer: it maintains the distance between the bones, cushions the load, and allows the spine to bend. Inside is a soft nucleus, outside is a fibrous ring of fibers.

The disc loses water, becomes less elastic, its height decreases, and cracks appear in the fibrous ring. Fixation of the vertebrae to each other worsens, and instability arises in the affected segment. The disc bulges into the spinal canal, but the ring does not rupture. The size of the bulge is 1 to 5 mm. While the ring is intact, irritation of the nerve roots is intermittent: the pain comes and goes rather than persisting constantly. Protrusions are most often found in the lumbar spine, less often in the cervical; the process is based mainly on hereditary causes.

Protrusion, extrusion, and hernia: what the difference is

The difference lies in the condition of the fibrous ring. In protrusion, the fibrous ring remains intact. A hernia (slipped, prolapsed, herniated disc) is the exit of the disc or part of it through a weakened area; pressure may fall on the nerves or spinal cord. Extrusion is encountered in clinical practice far less often than protrusion.

Lumbar protrusion and the L4–L5 disc

A disc is named after the vertebrae between which it lies: L4–L5 is the pad between the fourth and fifth lumbar vertebrae. The lumbar spine is the most common location of bulging, the cervical is second in frequency, and the thoracic is rarely involved. At the lumbar level, protrusion causes back pain and numbness in the groin area and legs. If the bulge presses on the sciatic nerve, the pain radiates to the buttock, thigh, and lower leg.

Symptoms and pain in lumbar protrusion

Not every protrusion hurts: many people are unaware of it. When the bulge irritates a nerve, the pain is more often one-sided and worsens:

• after prolonged standing or sitting;
• at night;
• when coughing, sneezing, laughing;
• when extending backward or walking a long distance;
• when straining.

Typical are sharp pain in one part of the leg, thigh, or buttock and numbness in other areas, pain or numbness along the posterior surface of the lower leg and in the sole, and weakness in the same leg. Reduced reflexes and muscle strength are seen by the doctor on examination earlier than the person notices the problem themselves.

How protrusion is detected and when a doctor is needed

The diagnosis is most often made from complaints and examination: sensitivity, reflexes, muscle strength, posture, and range of motion are checked, and the patient is asked to walk on tiptoes and heels and to bend over. Leg pain when raising a straightened leg on the couch usually points to the lumbar spine. Among the investigations used are MRI or CT of the spine, electromyography, myelography, nerve conduction velocity testing, X-ray, and densitometry. An X-ray by itself does not show a hernia: it provides a picture of the bone and the space for nerves to pass.

People go to the doctor if the pain does not respond to pain relief, does not ease over several weeks, if there is a high temperature, unexplained weight loss, swelling on the back, or if the pain worsens at night.

Call an ambulance immediately
A protrusion by itself is not a reason to call 103 or 112. An ambulance is called if, against a background of back pain, numbness has appeared around the anus or genitals, urination is impossible, sensation has been lost in one or both legs, control of urination and defecation is impaired, and also if the pain began after a serious accident.

This material is for reference: it helps to understand the entry in a report but does not replace a doctor's consultation.

This content is for reference and does not replace a doctor's consultation. Medical disclaimer