Pain, the brain and the spine
Why is my spinal condition painful?
Pain is a complex unpleasant experience imagined to result from imagined or real tissue damage. Acute spinal pain is classically thought to be linked to a biological process such as inflammation, pressure or blood flow changes. In the acute phase it is the body's 'alarm system' and warns us of danger. This process lasts approximately 3-4 months.
Chronic pain often can be a biological process (but as the acute danger phase subsides this tends to become less) with a degree of 'central sensitisation' impacted upon by bio-psycho-social components variable with each individual sufferer. This refers to a wound up and upregulated central nervous system with abnormal or disproportionate production of pain sensitivity. Of patients undergoing spinal surgery and orthopaedic surgery such as hip and knee replacements, estimates vary that 25-40% of patients have some degree of central sensitisation.
Watch this video where Central Sensitisation is well explained by A/Prof Andrea Furlan of Toronto, Canada:
About 1 in 5 Australians experience chronic pain to some extent. A common example in about 2-4% of Australians is a probable diagnosis of 'fibromyalgia' where there are abnormal widespread pain responses and experiences across the spine, extremities, trunk and abdomen in addition to changes in sleep, mood and memory due to upregulated and sensitive nerves - there is a large overlap of these patients having what is thought to be spinal related pain. A classic example of the power of the pain pathway is in phantom limb pain with amputees, where their brain interprets painful signals in the imagined leg or arm even when it is no longer present. In the same way, some patients after surgery continue to feel unpleasant numbness despite a good relief of pressure off their nerves and a good technical performance of surgery which can be a recovering nerve that may take many months to normalise. The way individuals experience pain varies dramatically and even the same medications can be effective or ineffective comparing two different individuals due to different pain receptors. Where possible, this should be screened for and appreciated as it can affect patient expectations and outcomes.
For specific explanations and more details about why spinal conditions may cause symptoms you are having please visit the section "Spinal Anatomy and Disorders." While it is unfortunate that most spinal pain that persists for more than a year tends to remain over time (Chen et al. Trajectories and natural history of low back pain, Pain Journal 2018; Peng et al. Natural History of Disocgenic Pain - Pain Physician 2012), it is important to note that most causes of low back pain are not 'dangerous' and that it is important to manage the pain and try different coping strategies rather than adopt passive strategies or rely on medications. Degenerative spinal conditions are often asymptomatic and almost universal, increasing with age mainly according to genetic tendencies moreso than lifestyle or occupational factors. Below is an example of how modern imaging technology often can increase and heighten our fear and anxiety that something is wrong or there is a structural cause to blame for our pain when it is not necessarily the case - A male, approximately 40 years old has an MRI for research purposes - He does not have any pain, can lift, sprint and play sports for 1-2 hours with no issues. However, the MRI reports many concerning sounding abnormalities - he has 3 level degenerative disc disease with annular tears of L34 & L45, Moderate stenosis of L45, Retrolisthesis with biforaminal stenosis of L5S1 and facet arthritis, modic changes and possible interspinous impingement. To reiterate, however, he has no pain or symptoms. Also, importantly, his muscle in his back and around the spine is very large - this may be another the reason he does not have significant pain or dysfunction despite noted structural abnormalities..
In reality, pain is extremely complex and impacted upon by different parts of the mind and nerve body wiring from the brain all the way to the nerves in the limb or skin. Please see the diagram below. The best spinal treatments diagnose the likely cause and target the whole person, mind and body, for therapy in improving quality of life and lessening the distress from pain on each of the targets. Spinal pain is notoriously difficult to diagnose as it often does not follow the classic textbook descriptions and patients present with variations on a theme - some patterns make a spinal cause of the pain more likely but there is no 'pain scan' or test that can confirm with 100% certainty that a particular disc or nerve is causing the pain. The idea of a precision diagnosis and improve the odds of an accurately defined origin responsible for the patient's pain can involve multiple tests (in addition to an important history and examination) like MRI, spectroscopy, bone scan, discography, injections and EMG. This is another reason why surgery for spinal pain can be hit and miss, particularly when performed off non-reliable testing and precision diagnosis is not achieved. When one takes the neck (cervical) as an example there are dozens of pain generators and each can have 'classic' and atypical presentations where our understanding continues to evolve - for example, headaches and facial pains (usually due to migraines) were historically thought to be only rarely from the spine where our understanding of cervical related headaches is evolving (example: https://www.physio-pedia.com/Cervicogenic_Headache) and shoulderblade (scapula) pain was often thought to be local musculoskeletal or shoulder problems but is often referred from the neck.
Many patients come to see a spine surgeon for chronic spinal pain that have tried and failed multiple different treatment types along their pain journey - a large proportion of these patients may have central sensitisation which is a condition where more surgery targeting bio-structural issues around bone, nerves and discs are unlikely to help and may make things worse. Please take a minute to read through a good summary of "central sensitisation" if this is of interest to you (https://www.painscience.com/articles/sensitization.php). Where the pain is generated not just from a tissue (abnormal disc or joint) but involves a large and complicated network of fibres where the problem may be upstream of that painful tissue, surgery (e.g. fusion or discectomy) or injections just directed at that tissue will unlikely yield lasting significant results. Often, the unpleasant 'nerve' symptoms are not related to the spine with a common example being peripheral neuropathy. There is still much mystery on why certain patients have such sensitivity & research on understanding pain pathways & sensory receptors continues - the 'homunculus' or brain-motor-sensory mapping gives one an idea of these complexities. Having a team around you to guide you in being realistic with your pain journey, establishing a routine (e.g daily walking), pacing yourself & support appropriate thinking and re-framing about the pain (Cognitive Behavioral Therapy and psychoneuroeducation) combined with certain medications (e.g. Duloxetine, Gabapentin) has been shown to be beneficial for spinal pain.While opioids and strong pain-killers may be appropriate in the acute phase and for operative pain / fractures / cancers / infections, over time when taken for chronic pain they actually become counter productive - larger and larger doses are required to maintain an effect and pain receptors actually become upregulated making the sufferer 'feel pain even more'. As seen in the diagrams at the bottom of the page, trying to turn on your brain's natural pain suppression is possible with regular gentle exercise such as walking and swimming and utilising natural methods of producing endorphins.
Sometimes, when multiple spinal operations have been trialled, it is necessary to try to interfere with the pain signals travelling to and from the brain. This is an emerging and evolving area of pain science called neuromodulation - it can range from spinal cord stimulators that aim to 'turn down the volume' on pain signals all the way to transcranial magnetic stimulation which stimulation particular areas of the brain to dampen the pain response. Often a trial of the stimulator leads is undertaken with the leads being left external to the body initially. Only if this is useful and produces benefits does the definitive implantation of the impulse generator occur within the body. Below left is a temporary trial with the impulse generator external to the body while on the right is a final implantation of the pacemaker buried under skin.
The psychology of pain is very complex and discussed in depth by the references in the Spinal Health section - it is well acknowledged that unresolved emotional trauma, grief, conflict, catastrophic thinking and unhelpful beliefs can all affect outcomes. To summarise, pain is often a complex interplay between your mind, beliefs, fears, activity and biology (see diagrams below). This is the reason that to simply consider that surgery can be a 'magic bullet' for pain without the best possible conditions being present in the mind and body of the patient before surgery is often bound to lead to failure.