This month, Iona Collins MBBS, BMedSci(Hons), MRCS, FRC(Orth), Consultant Spinal Surgeon and founder of the website www.fixmyspine.co.uk looks at the painful condition of Sciatica
Sciatica was… “a problem related to a diseased hip joint”, according to the ancient Greeks, who noted that the pain would last around forty days in young men and for over a year in the elderly. Ischios is the Greek word for hip joint and is the origin of the word sciatica.
By the 18th Century, doctors began to realise that sciatica was not necessaryily a hip joint-related pain, but may be due to nerve pain and by the 20th Century, the spine was recognised as the source of the sciatica pain. Operations on the spine began at the turn of the 20th Century, with material removed described as tumours, but in 1931, two American surgeons saw striking similarities bet-ween the tumours removed and material found in the shock-absorbing discs. These two surgeons, Mixter and Barr, were the first people who publicised that “slipped discs” cause sciatica.
Sciatica is… pain, usually coming from the spine. Sciatic pain usually begins in the buttocks and travels down the leg along the thigh and below the knee. It is usually due to a trapped nerve in the spine, and the commonest cause of trapped nerves is a bulging disc in the spine. The pain tends to ease when lying in a certain position and tends to flare up with a cough or a sneeze. It often starts shortly after we “tweak” our backs, doing something fairly innocuous, such as bending forward to pick something up. While bulging discs may cause sciatica and sciatica may be due to a bulging disc, the two associations are not mutually exclusive.
Although 40% of us will experience sciatica to some degree during our lives, there are times when this pain can be alarmingly severe. The pain appears to reflect the degree of nerve irritation, rather than nerve compression, because there isn’t a strong association between the severity of pain and the size of a disc protrusion, or slipped disc compressing a nerve.
The first ever MRI was performed in Nottingham in 1974. MRI, or Magnetic Resonance Imaging, involves a giant magnet and radio waves, so some metallic devices like a pacemaker are not compatible with having an MRI. It’s also noisy and can feel slightly claustrophobic, but there are no X Rays or other radiation involved, which makes the MRI safe, as far we are aware. The best way currently of finding out where sciatica is coming from, is by getting an MRI of the spine.
Disc bulges mostly get better by themselves
The good news is that the body identifies loose disc material which has been squeezed out of its usual place inside a disc, causing a localised inflammation which dissolves the disc fragment. Unfortunately for us, though, the inflammation which dissolves the disc fragment also causes inflammation of the nerves nearby, which may cause sciatica pain.
A Japanese study of 42 people with MRI-proven disc bulges and sciatica had an MRI scan repeated every 3 months to see what happened over time. They found that by twelve months, 88% of the disc bulges had reduc-ed by at least 50%, with the sciatica symptoms improved to “good” or “excellent” in 90% of the people studied. This means that with time, the back tends to heal itself and the sciatica improves or goes away altogether.
So, sciatica is mostly caused by a disc bulge, which mostly settles without any specific intervention. There’s a good reason to avoid investigating sciatica with a safe but costly MRI when the pain first develops – we can as-sume that we have a disc bulge and focus on ways to help the pain and concentrate on good spinal posture instead. Our backs are not designed to automatically fail and an MRI survey of yoga instructors in 2011 demon-strated that it’s possible to have nearly perfect spines when we use our spines appropriately. It can’t be coinci-dence that our shock-absorbing discs usually fail backwards where the nerves are, rather than forwards. If the discs are compressed at the front of the spine, then the soft contents of the disc get squeezed out backwards over time, with recurring episodes of sciatica as small fragments of disc tissue leave the disc at intervals.
Spinal Posture and Flexibility
A favourite yoga quote is that “you are as young as your spine”. A supple spine, held upright and moved constantly is a healthy spine, in contrast to a stiff spine, which is kept in a flexed, sitting position for several hours a day. An American study in 2014 demonstrated that sitting for at least four hours a day causes the L4/5 disc (a shock-absorbing disc toward the bottom of the spine) to flatten, giving the MRI appearance of
early wear and tear. We already know from earlier studies by Alf Nachemson, an exceptional pioneer in spine care, that sitting causes the discs to work harder since greater forces are exerted on them in the sitting position compar-ed with standing upright.
Robin McKenzie was a physiotherapist from New Zealand who sadly passed away in 2013, but lived long enough to see his original book from the 1980s called Treat Your Own Back, help many thousands of people who suffer with sciatica. His small and simple book outlines the importance of good posture and working on spinal flexibility, especially with spinal extension, which we tend to neglect, with excellent results. The book is safe to use, although it can be pretty uncomfortable when a stiff, painful back is put through its paces. It’s worth persevering, though, since thousands of people who have placed online reviews of the book say how much these exercises have helped them.
When Sciatica needs an MRI
This is not an exhaustive list; these are a few of the important situations when an early MRI is a good idea:
- If the sciatica is causing any issues with going to the toilet, then it’s worth seeing a doctor urgently to be checked for a rare condition called Cauda Equina Syndrome (CES). Symptoms such as difficulty passing water, poor flow, incomplete bladder emptying and altered feeling where you wipe are all worrying symptoms which need to be assessed by a medical professional straight away. CES is a condition where the slipped disc or disc protrusion is compressing the nerves which supply the bladder and bowel – these nerves are delicate and if the pressure isn’t removed from them promptly, they can scar, causing permanent bladder and bowel problems.
- If the sciatica is causing weakness in a leg, then an MRI should be organised promptly to see whether a compressed nerve needs to be treated to prevent permanent leg weakness. The weakness can be relatively subtle at first e.g. an ankle giving way when walking. This can go on to become a condition called “foot-drop”, as well as other types of leg weakness.
- If you are feeling generally unwell, the sciatica may not be due to the common cause of a slipped disc and an MRI would be useful to look into this more closely. Spinal infections can cause sciatica, which can occur in people whose immune system isn’t 100%, or people who have recently had an infection elsewhere e.g. a tooth abscess. Spinal infections need to be treated promptly to avoid potentially-permanent spinal problems.
- If you’re being treated for cancer, then a prompt MRI would be very useful to make sure that the sciatica isn’t related to the cancer being treated.
References for further reading. Most of these are free downloads
This article gives more information about historical literature relating to sciatica.
This article from the British Association of Spinal Surgeons gives an overview of what treatment options are available for sciatica
This homepage introduces sciatica and has links to related sites.
472 adults were compared with respect to their treatment for lumbar disc protrusions in a study called the SPORT study. The study concluded that most people improved significantly over two years, but people who underwent surgery might have done marginally better, but they could not prove this observation.
Another study trying to establish whether surgery offers an advantage when people have sciatica due to
lumbar disc protrusions/“slipped discs”. They con-
cluded that surgery may help the pain more quickly, but in the end, they could not find evidence to con-clusively demonstrate that surgery provided better help than no surgery over time.
A great article which measures the number of people with slipped discs on MRI when they have an MRI for many different spinal reasons, including sciatica.
This small study looks at how many MRIs show slip-ped discs in normal, pain-free volunteers.
Sitting causes discs to squash at end of day one on MRI.
9 Takeda and Takahashi, Journal of Orthopaedic Surgery 2001, 9(1): 1–7 Natural history of lumbar disc hernia with radicular leg pain: Spontaneous MRI changes of the herniated mass and correlation with clinical outcome.
10 Pressure changes in the discs according to spinal position.
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