What are the different types of back pain? How does pain work?  

Pain is a complex concept. It arises through different mechanisms and routes. Low back pain can take several routes: it is a ‘mixed’ pain. There are three types of pain: nociceptive pain, neuropathic pain and so-called ‘mixed’ pain, which combines the first two. All have different causes, functions and pathways. And each requires its own specific treatment. Back pain is most often caused by nociceptive pain. But it can also be neuropathic, or even mixed.

1st type of back pain: inflammatory lumbago, pain caused by excess nociception

Low back pain is known as ‘nociceptive’, ‘excess nociceptive’ or ‘inflammatory’ pain. This means that it is caused by damage to a muscle, joint or bone in the spinal column. This injury (or inflammation) stimulates pain sensors called nociceptors, which are found throughout the body (skin, muscles, joints, viscera, etc.).

When their stimulation exceeds a certain threshold, the nociceptors react by sending a pain message to the brain. The information travels up the peripheral nerves and then through the spinal cord (ascending pain pathways) to reach the various brain structures (somatosensory cortex), which are responsible for interpreting the location and intensity of the pain (see diagram below). Excessive nociception is the body's alarm signal: it alerts the brain to the presence of an injury, a blow, a burn, etc.

It is the most common pain mechanism in the body. Nociceptive pain reacts positively to analgesics. This is why analgesics are recommended as the first line of treatment to relieve the painful symptoms of low back pain. If the lesion responsible for the excess nociception is repaired, the pain disappears. In the case of low back pain, the aim is to identify the cause of the injury (poor posture, inappropriate reactions to pain, strenuous work, etc.) in order to avoid its recurrence.

2nd type of back pain: neuropathic pain

Neuropathic pain is unusual in that it is felt without any stimulation and occurs spontaneously. Patients report sensations of burning, electric shocks or ‘stabbing’, itching, numbness, tingling, etc. There may also be disturbances of tactile sensitivity, with intense pain on touching (called ‘allodynia’) and exaggerated pain sensitivity (called ‘hyperalgesia’).

This pain is induced by a change in the transmission and control of nerve impulses. This is the case when a nerve or nerve root is damaged. For example, sciatica or a herniated disc can cause neuropathic pain if the compression is prolonged.

Diagnosing such pain can be extremely difficult, which is why specific assessment tools have been developed. In addition, this type of pain generally does not respond to analgesics and requires special medical treatment.

3rd type of back pain: Mixed pain

What does this have to do with low back pain? It would appear that neuropathic pain is not entirely unrelated to low back pain. According to a study published in 2017 in the Swiss Medical Journal, between 16% and 55% of patients suffering from chronic low back pain have a neuropathic component ⁽¹⁾.

This is why low back pain is known as ‘mixed’ pain. However, treatments for nociceptive pain and neuropathic pain are completely different, and are devised on a case-by-case basis. That's why it's vital to precisely identify the source and mechanism of the pain in order to adopt an appropriate treatment when suffering from low back pain.