DEFINITION OF SCIATICA
Sciatica is pain within the pathway and distribution of the
sciatic nerve. The sciatic nerve is formed by nerves from the spine
at the junction of the lumbar and sacral regions. The nerve passes
from the spine into the pelvis then into the buttock, posterior (back
of) thigh and down below the knee.
Below the knee the nerve divides into two branches, one going
through the posterior (back) calf down the inner side of the ankle,
and a second division goes through the outer side of the calf around
the top of the ankle and foot to the toes. The important features of
sciatic pain are that it goes below the knee, and it is associated
with neurological symptoms. The neurological symptoms include a sharp
or burning character to the pain; changes in sensation such as
tingling, pins and needles or numbness; and association with
weakness.
The branches of nerves from the spine that make up the sciatic
nerve are the low lumbar and upper sacral nerves. These branches give
sensation to the front, the outside and the posterior (back) part of
the leg below the knee. They also give strength to the muscles that
pull up the ankle and the toes, turn the foot to the outside and give
strength to the calf muscles.
The nerve roots involved also supply the ankle reflex. The most
common nerve roots that are involved in sciatica are the L5 (Fifth
Lumbar) nerve root and the S1 (First Sacral) nerve root. These
differing nerve distributions result in differing areas of numbness
and weakness. The L5 nerve root (so named because its origin is from
the lower part of the 5th lumbar vertebra) is often associated with
numbness that goes through the top of the foot to the great toe.
The S1 nerve root (named because it exits the spine below the
first sacral vertebral segment) is associated with sensation that
goes through the outer aspect of the foot to the little toe. Loss of
function of the S1 root will be associated with numbness in this
area.
It is important to understand that sciatica is pain that goes
through the course of the sciatic nerve and this means that it should
go below the knee. Many people mistake buttock pain for sciatica. It
is true that the sciatic nerve goes through the buttock but many
other causes of pain from the spine may be referred to the buttock
and the presence of pain in the buttock alone does not imply
irritation, inflammation or compression of the sciatic nerve.
CAUSES OF SCIATICA
Pain that occurs within the distribution and path of the sciatic
nerve is most frequently due to compression of the nerve within the
spinal canal. This most commonly occurs secondary to disc herniation
in the middle years from 20 through to 60. In older age groups it may
occur secondary to narrowing of the path for the nerve ways (spinal
stenosis).
There are many other causes of sciatica. Potentially any injury or
abnormal process that involves the sciatic nerve may cause sciatica.
In practice the commonest cause of sciatica is disc herniation.
DISC HERNIATION
The discs in the lumbar spine are the soft tissue structures that
lie between the vertebrae. A disc consists of an outer casing or
annulus, and an inner jelly-like substance or nucleus. The healthy
disc has a jelly-like nucleus, but as discs age or have been subject
to damage and/or prolapse, the healthy jelly dries out to have more
of a consistency of crab meat. A disc herniation occurs when the wall
of the disc or annulus develops a tear or weakness and disc material
comprising nucleus and annulus is pushed out through the weakening in
the outer annulus. This may be associated with local back pain
related to the damage to the annulus.
When the disc herniates or ruptures it frequently puts pressure on
the nerve root that passes in close to the disc in the spinal canal.
This is where the symptoms of sciatica may occur. Most discs that
rupture develop changes in the disc material consistent with
degeneration or wear and tear. It is not entirely clear whether this
occurs before the disc ruptures or after it. It seems likely that a
variety of possibilities exist. The disc annulus may weaken and
develop tears with age, but it also seems likely that injury may have
a role.
Newer evidence suggests that some groups of patients may have
abnormalities in the tissue makeup of the disc that predispose them
to rupture or weakening of the outer annulus or casing.
When the nerve passing the disc is exposed to a rupture, the nerve
can either be affected by direct pressure of the prolapse or by
chemical inflammation caused by the tissue from the disc. Direct
pressure occurs when the nerve is trapped by a prolapse within the
nerve canal. This probably accounts for changes in nerve conduction
which the patient feels as altered feeling or muscle weakness. The
other effect that the disc prolapse can have is to inflame the nerve.
There is now good evidence that the chemicals from the nucleus can
leak out of the prolapse onto the nerve root resulting in
inflammation of the nerve, pain within its distribution (sciatica)
and also changes of nerve function (again manifest by numbness, pins
and needles or weakness).
INCIDENCE
As most patients with back problems find, these are exceptionally
common. It is often stated that 80% of adults will experience severe
back problems at some stage of their life. It is also stated that 20%
people may have significant back symptoms in the current year. Back
pain is much more common than sciatica, but bouts of sciatica are
also exceptionally common and many people experience these. It has
also been discovered, with the use of new scanning techniques, that
many disc herniations occur without giving the patient pain or indeed
any awareness of the problem. Scans on people with no symptoms at all
have shown that many will have disc herniations. It is unclear why
some patients are extremely troubled by disc herniation causing
sciatica, and other patients do not have symptoms.
NATURAL HISTORY OF SCIATICA
As stated above, disc herniation and sciatica are very common.
Patients may have disc prolapse without symptoms of sciatica. When
sciatica does occur, it tends to be associated with an early, intense
phase of severe pain which is probably due to both pressure and
inflammation secondary to disc herniation. The pain often settles
after the first few weeks. It may resolve completely or plateau at a
level less severe than when it was most intense, but still giving
ongoing pain. Some have suggested that the early intense pain
correlates with inflammation and the latter pain with ongoing
pressure. The natural history of any condition is the description of
events that occur if no treatment is instituted. We believe that many
bouts of sciatica resolve without treatment. Treatment may hasten
resolution or ameliorate symptoms at the time. If sciatica occurs and
has been present for a short duration of time it is more likely to
spontaneously resolve. If it has been present for a long period of
time it becomes much less likely to resolve. If it has resolved and
recurs particularly more than once, then it is more likely that
further recurrences will occur and treatment will eventually be
necessary.
As a guideline, if the sciatica has been present for less than
four weeks there is still a reasonable chance that it may resolve. If
it has been present for more than six weeks the likelihood of rapid
resolution becomes much less.
EVALUATION OF SCIATICA
When a patient sees the doctor for symptoms of sciatica, detailed
evaluation is required. This normally consists of a detailed history
of symptoms and events that led to the onset of them. It should also
include a systemic questioning to exclude other potential causes of
problems.
History is then followed by an examination which aims to exclude
other causes of leg pain and document any evidence of tension on the
nerve, tenderness to the spine and neurological change in the sciatic
nerve distribution.
This will include a neurological examination of the legs checking
for sensation, strength and any change in reflexes. It is very common
for the doctor to ask about symptoms relating to abnormal function of
the bladder or bowel.
This inquiry relates to symptoms of loss of control of the bladder
or bowel rather than change in regularity. If there are symptoms
related to loss of bladder or bowel control the doctor may have to
perform a rectal examination where the back passage is checked for
any loss of sensation or anal muscle strength.
It is not uncommon for patients who have pain or who are taking
pain relieving medication to become constipated or find that they are
inhibited from straining on the toilet. It is also not uncommon for
patients with back pain to go to the toilet more frequently. The
doctor asks about symptoms of control loss because there are very
rare cases where large disc herniations put pressure on the nerves
supplying the bladder and bowel. If this should happen and there were
permanent damage to these nerves, it might result in permanent loss
of control of bladder and bowel function. This has very important
social as well as medical consequences.
Most often the diagnosis of sciatica is based on the history and
examination findings. X-rays may be performed. Most often an x-ray
will not give an obvious clue as to the cause of the sciatica. It is
performed to exclude some of the rarer causes including infection or
tumour. Many researchers have found that the routine use of x-rays
for early symptoms is unwarranted.
They have suggested that x-rays should be withheld until the six
week stage if symptoms have not resolved. If there is any suspicion
of other possible cause of sciatica, such as a past history of
cancer, the doctor will tend to move to x-rays earlier.
The newer investigations include CT and MRI scan. These scans
demonstrate the disc in detail, and the MRI scan will also
demonstrate the nerves.
They show the disc herniation. The use of such scans has become
much more common. Normally it is a final step before considering
surgical intervention.
TREATMENT OPTIONS - NON SURGICAL CARE
Most patients desire relief from pain when they have severe
sciatica. This can be achieved using a number of medications. Simple
pain killers and anti-inflammatory medications are most commonly
prescribed. These can be used together. Anti-inflammatories can be
very useful although care must be taken if there is a history of
peptic ulcer disease or other gastrointestinal upset, or any history
of poor kidney function.
Stronger pain relievers, some with an opioid base, may be used for
more severe and persistent pain. Patients with intense neuralgic or
nerve type pain may also respond to medications that specifically act
to reduce the sensitivity of the nerves. These include low-dose
antidepressants (tricyclics) and other drugs of a sedative nature.
During the very severe phase of sciatica rest may be necessary. There
is a growing trend to avoid prolonged periods of rest unless
absolutely essential. Many find that it is the only way that the very
severest of symptoms can be controlled.
Physiotherapy may have a role, although with severe sciatica it
can sometimes upset symptoms. Simple interventions such as massage
and heat may help relieve symptoms but have not been proven to effect
the outcome.
Other physical therapy interventions such as the McKenzie
technique may have a role when provided by experienced
practitioners.
Epidural injections of steroid may also be used. This is a
technique where cortisone/steroid preparations are injected around
the nerves in the spinal canal. The aim of the injection is to reduce
the inflammation around the nerve root. This technique may be very
effective but is somewhat unpredictable. In some patients it is not
beneficial. The risks are relatively low. It remains controversial as
to whether or not this option has a role.
All patients who are being cared for with sciatica should be
encouraged to maintain activity. This represents part of the swing
away from bed rest mentioned before. It is clearly better if patients
can maintain function and employment if possible even when symptoms
persist. Many patients take the view that they should rest and should
not overdo it at this stage.
The medical evidence does not support extreme activity
restriction. The role of other physical therapy such as chiropractic
or osteopathic manipulation for sciatica remains unclear.
Sometimes patients get relief from this but there is also the risk
that pressure on a nerve may be exacerbated by manipulation. It is
not unknown to see patients who develop sciatica after manipulation
of the spine.
SURGICAL OPTIONS FOR SCIATICA
If sciatica has been present for a prolonged period of time (over
six weeks) and has failed to respond to conservative care, surgical
treatment may have a role. It is imperative that in this situation
the patient is investigated with a CT or MRI scan to demonstrate the
disc herniation. At this point surgical treatment may be offered. The
commonest and most effective treatment is partial excision of the
disc and is normally referred to as "discectomy". This should only be
considered for prolonged pain (greater than six weeks), pain within a
sciatic distribution below the knee, pain associated with some form
of neurological symptom and pain that is exacerbated by stretching
the nerve. In these situations pain can most often be relieved with
partial discectomy.
DISCECTOMY - THE PROCEDURE
Discectomy involves an operation on the low part of the spine done
from a posterior surgical approach. Under anaesthetic the patient is
placed prone and a longitudinal incision made over the relevant area
of the spine. The muscles are separated so that the vertebra can be
seen and then the soft linings on the back of the spinal canal are
removed between the bony vertebrae. The nerves are inspected and
moved to the side to allow the disc herniation pushing on them to be
visualised. When the disc herniation is seen, it is removed, leaving
the nerves free of pressure.
Many patients are concerned that the disc will be removed
completely. This does not happen. The bulging portion of the annulus
or outer casing of the disc is incised and it is removed. Free
fragments of the disc core are also removed, but the remainder of the
outer casing of the disc is left intact. This normally allows the
nerve to lie freely without pressure and is associated with relief of
sciatica. The incision that is made into the disc through its casing
wall then scars over in the weeks subsequent to surgery.
All patients who have a discectomy are left with an abnormal disc,
yet few suffer significant back pain.
The operation of discectomy in its various forms has been around
for 70 years. The main features of the operation have not changed
although many surgical modifications have been performed to make the
incision smaller.
Along with this, the hospital stay has been reduced and an
increased speed of rehabilitation has been observed. Many patients
can get back to work within a couple of weeks from surgery although
often with some restriction of activities.
RECOVERY FROM SURGERY
When standard discectomy is performed, most patients leave
hospital 24-48 hours after surgery. The expectation is of relief of
sciatica although there will be pain in the back from the surgical
procedure.
Patients are encouraged to remain active at home and only rest for
short periods as necessary. A walking programme is often useful.
Theoretically sitting can be disadvantageous but in practical terms
it must be achieved. Many patients find sitting the least comfortable
position, yet despite this many are able to return to work and
driving at 2-3 weeks.
Most patients are advised to limit activity to a walking programme
through that period of time. This allows a return of general fitness
along with improved movement of the trunk without stressing it. After
the six week period patients are encouraged to increase activity.
Increasing walking along with a swimming programme can be useful.
At the 12 week post-operative stage patients can further increase
their activity. A programme at the gymnasium working on upper and
lower body strength may be useful. Cycling can also be beneficial at
this stage.
Return to other more aggressive activities is programmed in
conjunction with the surgeon.
ALTERNATIVE SURGICAL TREATMENT
There has been much discussion in the media of alternative
surgery.
There is always enthusiasm for percutaneous discectomy or laser
assisted procedures. Many such procedures have been tried in the
spine. There has been a wide expansion of equipment for such
operations in the last few years. Unfortunately there is little doubt
that most of these procedures are inferior to the traditional
operation of discectomy. Part of the reason for this is that although
the operation is called a discectomy, the focus is not so much on the
disc, but on protection and decompression of the spinal nerve in the
spinal canal. The modified operations mentioned above have focused on
resection of tissue within the centre of the disc. This does not
allow access to the nerve, yet it is the nerve that must be seen,
protected and released.
There is good evidence that these newer procedures are inferior to
traditional partial discectomy. The discectomy operation remains the
gold standard.
Other alternatives to surgery have included injection of chemicals
to shrink the centre of the disc so as to reduce the effects of the
prolapse on the nerves. This treatment (chymopapain injection /
chemonucleolysis) is not practised in New Zealand. It has been
popular in other parts of the world, but has now faded from
prominence. The treatment of chemonucleolysis is clearly better than
no treatment, however it has not been able to match the success rates
of standard discectomy.
REQUIREMENT FOR URGENT TREATMENT
As noted above, the situation where a large disc herniation puts
pressure on the nerves to the bladder and bowel is an emergency. The
consequences of this situation left untreated can be severely
disabling.
All doctors are on the look out for this situation, and should
this occur it requires urgent assessment and treatment. It is the
sort of situation that is attended to acutely with urgent surgery.
Delays of days can be very serious and result in permanent loss of
function. Apart from this situation, most other cases of sciatica
should be treated cautiously with an attempt to manage them non
operatively. In some situations major muscle weakness may result in
clinical syndromes of foot drop and severe limp. These are often
treated more urgently although it is somewhat questionable whether
early or urgent treatment is of great benefit.
COMPARISON OF SURGICAL OR NON SURGICAL TREATMENT FOR
SCIATICA
Because sciatica presents with a variety of syndromes (in terms of
intensity and duration of pain) the outcome and appropriate treatment
options can be varied. Most authors would agree that short term
sciatica without major neurological loss should be treated without
operation. This involves activity modification and treatment of
symptoms with analgesics. It is likely that many cases will settle
down and if symptoms are resolving after 3-6 weeks, surgical
treatment may not be required.
When symptoms have been present for a longer period of time, the
likelihood of spontaneous resolution is less. It is clear that in
this latter situation surgery offers a significant chance of rapidly
improving symptoms. If surgery is not performed at this stage it is
likely that gradual resolution will occur in the majority of
patients. Unfortunately without surgery this resolution tends to be
slow. Proponents of non operative treatment will argue that at time
periods several years after the onset of sciatica, the pain relief
will be the same in those who have had surgery as those who have not
had surgery. It is clear that patients who have surgery have much
earlier relief from pain, normally soon after the operation. Most
patients far prefer the rapid resolution of pain particularly if it
is severe.
It is also clear that the optimum time for surgical treatment
includes a "golden window." Most patients who have marked sciatica
secondary to disc herniation benefit from operation between six weeks
and six months from onset. If pain is prolonged, it is likely that
disability will also increase dramatically. In this situation, where
a patient has had sciatica for perhaps years, the nerve probably
undergoes changes which cannot be reversed. There is evidence of
complex changes in the pathways of the nerve and spinal cord when
there has been long term compression or stimulation of the nerve
causing pain. In these situations late operation for sciatica is
often associated with inferior outcomes. The dilemma for the patient
is often whether or not to wait and see if the sciatica will resolve
on its own without surgical treatment. A practical approach to this
problem would be that if the pain is continuing to improve after the
six weeks period then it seems that a wait and see approach is
justified.
If, however, pain resolution is incomplete with significant
residual symptoms, or if there are recurrences of severe pain, then
it is much less likely that pain will resolve spontaneously. In that
situation the history of surgical treatment would suggest that this
may be a better option.
COMPLICATIONS OF SURGERY
In experienced surgical hands the risks of complications secondary
to discectomy are low. As with all operations, discectomy is
associated with the risk of infection, clots in the legs (DVT), and
allergic reactions or anaesthetic complications. The risk of
infection is less than 1% but when it occurs can be associated with
infection in the disc space and this can be a serious complication.
Treatment involves prolonged antibiotics. More commonly a superficial
wound infection may occur and this resolves with a short course of
antibiotics.
Because the disc is abnormal at the time of herniation and is not
made normal by the operation of discectomy, residual back pain may
occur. The incidence of severe back pain following discectomy is
probably less than 10% and is most often managed conservatively. A
small proportion of patients may come for further surgical treatment
if severe back pain persists. This treatment may include spinal
fusion although a detailed discussion of this is beyond the scope of
this article.
A further complication that patients should be aware of is that of
recurrence of disc herniation. In most articles the recurrence rate
is about 5%. A further piece of disc material may escape through the
area of previous disc rupture. This can occasionally occur soon after
an operation and perhaps more commonly occurs some years later. The
treatment for this is consideration of repeat discectomy if symptoms
warrant, and if there is failure to respond to non operative
care.
Repeat discectomy is a technically more difficult operation
because of scar tissue. Expectation of outcome is somewhat more
guarded than primary or first time discectomy.
Complications such as nerve damage are uncommon. Occasionally the
lining to the nerve (the dura) can be torn. This can generally be
repaired or patched and, apart from a short period of increased bed
rest after operation, does not normally result in other
complications. Major complications such as nerve damage resulting in
major muscle weakness or paralysis are very uncommon. It is however
not uncommon for patients to be left with persistent patchy
numbness.
Once the nerve has been inflamed or compressed, the most sensitive
function is that of sensation and this may not recover. Residual
numbness is not uncommon. After surgery often the relief of pain is
associated with more appreciation of numbness. This generally
recovers and may do so for up to two years from surgery. Persistent
numbness is not uncommon and seldom disabling if good pain relief has
been achieved.
OUTCOMES FROM SURGERY
The majority of articles following up patients who have undergone
discectomy for sciatica demonstrate major improvement in leg pain in
80%-90% cases. This normally occurs rapidly after surgery and is
sustained. This is a considerable improvement upon the natural
history of sciatica when patients have had prolonged symptoms.
ONGOING BACK CARE
When sciatica has resolved, whether or not surgery has been
required, the patient should maintain optimum conditions for their
spine. The fact that the spine has had a prolapse, and is not normal,
does not preclude a relatively normal lifestyle.
General recommendations include avoidance of smoking (which is
associated with increased back pain and poorer outcomes from spinal
surgery), and avoidance of obesity (which is associated with greater
loads across the spine and other joints).
An exercise programme to maintain aerobic fitness is to be
encouraged. This may include regular brisk walking, swimming or
cycling. Specific exercises to maintain flexibility and strengthen
the abdominal and spinal muscles are important. These can be obtained
from physical therapists with an interest in home based exercise
programmes.
Finally, the patient who has had major spinal problems or surgery
should be cautious with heavy lifting and prolonged manual work which
may expose them to recurrence of prolapse or other back injury. This
latter comment should not be interpreted as an instruction to "wrap
themselves in cotton wool!" as too little activity is more of a
danger than too much activity.
TOP
