DISCOGENIC BACK PAIN

 

Discogenic low back pain is the most common cause of chronic back pain in young adults. It is the pain in low back occurring as a result of degenerated intervertebral disc in the spine. The intervertebral disc, the main joint between two consecutive vertebrae in vertebral column, has three structures – outer annulus fibrosus surrounding the inner gelatinous nucleus pulposus and two cartilage endplates that cover the upper and lower surfaces of vertebral bodies.

 

A healthy disc is like a water bed, with high water content of nucleus and inner annulus, acting like a fluid. The outermost annulus acts like a tensile skin restraining the nucleus. When zones of vascularized granulation tissue forms, along with extensive innervation in annular fissures, it causes painful discs. The discogenic pain can be caused by disc degeneration and non-nerve root referred pain at the back commonly called as Internal disc disruption (IDD). The low back pain can also be caused by disc herniation in lumbar region, lumbar segment instability and degenerative disc disease (DDD).

 

Genetic predisposition, mechanical load, nutritional factors can all lead to disc degeneration and thus, pain. It appears in MRI as a declined signal intensity – as the “black disc”. MRI can identify a pathology in disc, but it will not help differentiate a pathological painful disc from physiological aging disc.

 

Clinical features:

 

Patients may have back pain which may be burning or dull aching. It may be associated with numbness, tingling sensation and sometimes muscle weakness. It depends on the nerve root and the location of disc involved. Sciatica, the pain starting in low back and radiating towards legs can also be caused by disc herniation. Sometimes, patients may have audible pop with the onset of pain. Loading of spine as in sitting position and maintenance of posture increases pain.

 

Large disc herniation can cause compression of neural structures leading to cauda equine syndrome acutely or significant spinal canal stenosis with neurological compromise.

 

 

 

 

 

 

 

 

 

 

Diagnosis:

 

A proper clinical history with physical examination of the nervous and muscular system will help diagnose the pathology clinically. An X-ray may not show the pathology while MRI can identify a pathology in the disc. Disc prolapse, tear of annulus, buckling of ligamentum flavum (called hypertrophy) can all be the findings in MRI.

Internal disruption of disc can be diagnosed by provocative discography where a dye is injected inside the disc and the pathology of IDD can be confirmed with the characteristic morphological and biophysical features.

Electro diagnostic studies such as nerve conduction studies and Electromyography may help delineate the etiology, if there are multiple nerve root involvement.

 

Management:

 

There are many treatment modalities for discogenic low back pain. Physical therapy, exercises, manipulation along with pharmacotherapy may have some effects for relief of back pain. Exercise therapy by McKenzie method is slightly more effective than manipulation or is equal to strengthening training for patients with chronic low back pain.

 

Pharmacotherapy involves use of simple analgesics like paracetamol, non-steroidal anti-inflammatory drugs, tramadol, muscle relaxants and co-analgesics like pregabalin, gabapentin etc., The choice of analgesics depend on the type of pain with nociceptive pain ( aching, pressing) responding to paracetamol, NSAIDS or weak opioids like Tramadol while if the pain is neuropathic(tingling, numbness, burning, shooting, shock like), it might respond better to anti-neuropathic drugs like pregabalin, gabapentin or amitriptyline in appropriate doses.

 

Chronic discogenic pain is associated with psychological disturbances. Appropriate psychological counselling, treatment of associated anxiety and depression will help recover faster in patients in the long run.

 

 

 

 

 

 

 

 

 

Patient education and reassurance along with exercise therapy to strengthen back, flexibility exercises, proper lifting techniques, ergonomic advice, remaining active, manual mobilization or manipulation, massage, complimentary movement therapies like yoga, Pilates, physical therapy for gain training, core stability will help patients to lead a near normal life style.

 

If conservative treatment fails or there is worsening of pain, interventional therapies are indicated. Interventions include epidural injections of steroids by interlaminar, caudal or transforaminal routes, percutaneous discectomy or surgical fusion of lumbar vertebra. Epidural injection of steroids and local anesthetics act by interrupting nociceptive input, the reflex mechanism of the afferent fibers, reduce inflammation by inhibiting synthesis or release of pro inflammatory mediators and by causing a reversible local anesthetic effect.

Percutaneous treatments are directed at altering the internal mechanics or innervation of the disc by heat (Intradiscal electrothermal annuloplasty), disc dehydration (nucleolysis by ozone, laser or endoscopic discectomy).

 

 

Large disc herniation with cauda equine syndrome or spinal canal stenosis with neurological compromise may need urgent surgical decompression to avoid permanent neurological sequelae. Also the presence of red flags such as neurological deficits, bladder and bowel disturbances etc., warrant urgent radiological assessment and surgical intervention.

 

Since acute episodes of pain improve usually over several weeks, with frequent recurrences and there are chances of pain becoming chronic, patients with discogenic pain will benefit from multi-pronged approach aimed at symptom control and patient education to prevent recurrences.

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

References:

 

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