The "Unethical" Discovery of Sciatica
A common diagnosis with questionable roots..
Sciatica is really common.
I see it daily and that’s within GP land AND A&E. We often worry about cauda equina syndrome but for the patient, sciatica of any degree can cause troublesome symptoms. The pain, sensory loss and motor weakness can be unbearable and patients are desperate for some sort of treatment.
I recently came across an old paper, published by some clinicians from Leeds - doctors Smyth and Wright to be exact. These were two chaps who discovered the exact pathophysiology of sciatica and how disc herniations actually caused sciatica.
They took a sample of 40 patients with sciatica whom they operated on in order to remove the herniated disc. Instead of re-stitching them normally, they instead wrapped some nylon threat around the affected nerve roots and brought the ends of the thread to the surface
They then sewed the patients up but left the threads hanging out. They then decided to pull on the threads, “gently” apparently, in order to bring the nylon in contact with the root to exert some pressure. This resulted in the following observation,
“The patient jumped and exclaimed that a severe pain shot into the right buttock.”
They also observed that pulling on the nylon thread resulted in sensory symptoms. They repeated this on different patients with herniated discs at different levels and further defined the concept of dermatomes which we refer to today.
The idea of referred pain came from here too. Smyth and Wright noticed that depending on the extent of pull (or pressure), pain could radiate upwards or downwards.
It gets more interesting by the way. In 6 patients, they also wrapped some nylon around the neighbouring, uninjured nerve root but found that the pain on tugging was a lot less than the nerve that was compressed by a disc. This caused them to arrive at the concept of “hypersensitivity” which occurs after prolonged irritation of a nerve by a disc.
Of course, they needed to be sure that the pain in patients with sciatica actually came from the nerves. They tied nylon around the ligaments flavour, interspinous ligament and other aspects of the spine and found that pulling on these structures produced no pain.
So how does this impact our practice?
Putting ethics aside, Smyth and Wright discovered some really vital information. Not only did they confirm that it is indeed nerve irritation that causes the symptoms of sciatica, but also that not all sciatica is caused by disc herniation. It may be that due to repeated trauma, a nerve may have become hypersensitive hence causing the symptoms faced by the patient. This should encourage patients to feel that they don’t need to keep “nudging” the disc back into place as it may not be a disc protrusion in origin. It could just be simple hypersensitivity of the nerve due to long term inflammation which requires some light movement and may result in a quick recovery.
This laid the foundation of our current practice of using neuropathic medication that helps to act directly on the nerves and reduce their sensitivity to pain.
There you have it. Another short article on the history of medicine.
Until next time!
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