Sciatica and lumbar disc prolapse

LUMBAR DISC PROLAPSE

SCIATICA:back related lower limb pain
1.2 Epidemiology
. Back pain is an extremely common phenomenon. Nachemson estimated that 80 percent of individuals experience back pain at some time in their lives.(5) Horal noted that 35 percent of patients with low back pain will at sometime develop sciatica.(6)
The prevalence of the problem is demonstrated in Nachemson's review, which indicates that 4.8 percent of the male population and 2.5 percent of the female population beyond the age of 35 will at some time in their life experience sciatica.(5) Risk factors for the disease include pregnancy, and certain occupations that require heavy repetitive lifting or the operation of vehicles. (7) Each lumbar disc consists of two components, an internal semi fluid mass, the nucleus pulposus, and a laminar fibrous container, the annulus fibrosus. Teleologically, the function of the nucleus is to resist compressive forces within the spine, whereas the main function of the annulus is to withstand horizontal and torsional tension.(4) The annulus is closely attached to the adjacent vertebral bodies, it is stronger anteriorly than posteriorly, and it is not as well attached to the posterior ligament as to the anterior. This arrangement may partly explain the propensity of discs to herniate posteriorly rather than anteriory). Because the lumbar vertebrae are subjected to the greatest loads in the spinal column, they are relatively massive structures.


Biomechanics of intervertebral disc

Contrary to popular belief, the intervertebral disc is relatively resistant to failure under compressive loads. The vertebral end plate usually fails first in both normal and degenerative discs. However, in torsion the disc is the part that fails first. Another loading situation that causes disc herniation is the sudden application of axial compression force while the spine is laterally bent and hyperflexed.
The load on the spine has been shown to vary considerably with posture and external loads and is much larger than generally believed.
At the L3 L4 inter space, a person sitting has a higher intradisc pressure than when standing and the lowest pressures are obtained when the person is lying on the back .
Because the spine acts as a flexion boom to the high wire actions of the paraspinous muscles, it is the fulcrum of a lever system in which loading has a considerable mechanical advantages.





. Symtoms

The initial symptom is most commonly backache that may be acute or gradual in onset. There may be history of prior episodes of focal back pain without sciatica which resolved spontaneously.
Back pain may persist for several days or weeks and then it may be followed by incapacitating radiating pain into the leg.
This may be accompanied by parasthesia or numbness in the affected dermatome .
It also may be followed by weakness in selected muscle groups. Occasionally, the clinical picture is one of severe leg pain and cramping which occurs very soon after the onset of symptoms. In either case, the pain is often aggravated by sitting, standing and walking as well as by coughing, sneezing, or straining. In some patients, it may be increased by sitting but relieved by lying down, particularly with the hip and knee flexed.

Back and leg pain may persist together, but it often happens that the back pain is decreased with the onset of sciatica. Apparently, this phenomenon is due to reduction in the stretch of pain fibers in the annulus, and posterior ligament that occurs with extrusion of the disc. Similarly, on rare occasions, severe sciatica may be suddenly relieved; however this is usually associated with motor weakness and sensory loss because of physiological interruption of function in a severely compressed nerve root.
In older patients, there may be little or no antecedent back pain, and leg pain dominates the clinical picture from onset.
In the presence of a narrow canal and a large midline protruded disc, the patient may complain principally of back pain and vague leg pain that alternates in intensity from side to side.
It is not unusual to see irritative symptoms including urinary urgency, frequency (including nocturia), and increase post void residual. Less commonly enuresis, and dribbling incontinence is repeated in radiculopathy. Occasionally a herniated lumbar disc may present only with bladder symptoms which may improve after surgery.


2 Signs
The back of the patient with a herniated disc may be normal-appearing, or it may be flattened with a slight forward tilting of the trunk and flexion of the hip and knee on the affected side. Scoliosis, directed toward or away from the affected side, may be present. Percussion of the back may produce focal pain over the affected vertebrae. Patient stand and change position in a slow, deliberate manner.Forward bending is limited to a variable degree because of splinting of the spine. Passive movement of the lumbar spine may produce pain.

The following tests may be elicited on the patient:

1. Lasegue's sign. (Straight Leg Raising Test ,SLR )
Helps differentiate sciatica from pain due to hip pathology. With patient supine, raise affected limb by ankle until pain is elicited (should occur at < 60, tension above this angle increases little in nerve). A positive test consists of leg pain or parasthesias in the distribution of pain (back pain alone does not qualify). The patient may also extend the hip (by lifting it off table) to reduce the angle.

2. Cram Test

With patient supine, raise the symptomatic leg with the knee slightly flexed, then extend the knee. Results similar to SLR test.

3. Crossed SLR (Fajersztajn's Sign)

SLR on the painless leg causes contralateral limb pain (a greater degree of elevation is usually required than the painful side).May correlate with a more central disc herniation.

4. Femoral Stretch Test (Reverse SLR)

Patient prone, examiner's palm at popliteal fossa, knee is maximally dorsiflexed. Often positive with L2, 3, or 4 nerve root compression or with extreme lateral lumbar disc herniation.

5. Bowstring Sign

Once pain occurs with SLR, lower the foot to the bed by flexing knee, keeping the hip flexed. Sciatica pain ceases with this maneuver, but hip pain persists.

6. Sitting Knee Extension Test

With patient seated and both hips and knees flexed 90, slowly extend one knee. Stretches nerve roots as moderate degree of SLR.


7. Naffziger's Test
When the patient is standing, jugular compression for 1 or 2 minutes accentuate pain and parasthesia in the affected area of the leg.

Weakness in the muscles is variable according to the level of the herniated disc. This is shown in table.

Table : Muscle weakness at different HLD levels
Muscle Level of HLDQuadriceps Usually L3-L4Ankle dorsiflexionUsually L4-L5Ankle plantarflexionUsually L5-S1Big toeL5-S1 60% and L4-L5 30%
Cauda Equina Syndrome (CES)
May be due to compression from massive ruptured disc, usually midline, most common at L4 5, often superimposed on a pre-existing condition (spinal stenosis, tethered cord).

Possible findings:-

Sphincter disturbance.
a- Urinary retention:- the most consistent finding at some point in time during course.
b- Urinary and / or fecal incontinence:- some patients with urinary retention will present with overflow incontinence.
Anal sphincter tone:- diminished in 60-80%.
Saddle anesthesia:- the most common sensory deficit. Distribution:- region of the anus, lower genitals, perineum, over the buttocks, posterior-superior thighs. Once total perineal anesthesia develops, patients tend to have permanent bladder paralysis.
Significant motor weakness:- usually involves more than a single nerve root (if untreated, may progress to paraplegia).
Low back pain and/or sciatica: sciatica is usually bilateral but may be unilateral or entirely absent.
Bilateral absence of achilles reflex has been noted.
Sexual dysfunction:- usually not detected until a later time.


Investigations
1. Conventional Radiographs of the Lumbosacral Spines
Routinely obtained in the study of lumbar disc disease, but they usually offer guidance rather than specific diagnostic information .
These films may reveal:-
some straightening of the lordotic curve.
Scoliosis.
Non specific degenerative changes.
Narrowing of one or more disc spaces The main reasons for obtaining radiographs in a patient with back pain or radiculopathy are:
a- For exclusion of the other conditions,such as spondylolisthesis, fracture, primary and secondary tumors of bone, pyogenic and tuberculous infection, congenital malformations, ankylosing spondylitis, fibrous dysplasia and hemangiomas of the verterbral body.
In preparation for surgery because these films may alert the surgeon to transitional vertebrae, which, if not recognized, may lead a surgeon to operate on a wrong disc. Also they reveal the presence of spina bifida or other anomalies that may affect the surgical exposure.
c- In patients with previous operation, spine films are the best way to appreciate the extent of the earlier bone removal and to help plan the second operation

2- MRI

This technique has become the procedure of choice for the diagnosis of spinal disorders. It is useful and accurate for the diagnosis of herniated discs and spinal stenosis and for the exclusion of other lesions, such as spinal tumors.It should be performed with a high quality including T1-and T2- weighted images and in patients with previous operation it should include the administration of gadolinium.










3.C.T.

Also a useful screening test for disc herniation. It should be done on late-generation scanners with high-contrast resolution. The test is less accurate than modern MRI for diagnosing most herniated discs. It has a number of disadvantages:-
It provides axial scan of the spine.
It usually only images lower portion of the lumbar spine.
It may miss an intradural tumor or a very large central disc herniation.
It is less useful in patients who have undergone prior surgery.
Even with the administration of intravenous contrast material, it may not clearly differentiate scar from recurrent herniated disc.

For these reasons, plain C.T. is no longer performed, as the procedure of choice for the diagnosis of disc herniation and the surgeon does not operate on patients solely on the basis of C.T. findings.

4- Myelography

Because of MRI, this test used much less often. In few cases myelography remains very helpful, particularly when it is combined with post myelographic C.T. It is believed that myelography is most useful in:-

Evaluating patients who have ambiguous or non diagnostic findings on MRI.

For patients who are unable to undergo MRI.
For certain patients in whom very specific information is needed which may be required in patients with lateral recess syndrome or borderline disc herniation, when a decision to operate may be based on whether filling or nonfilling of a nerve root is present.
It remains especially useful in cases where there is no neurological deficit.
When more than one nerve root is involved.
Where an apparently central disc herniation affect just one root.


5-Discography
This test is of highly controversial nature. Centers that treat large numbers of patients with back and leg pain usually do not use lumbar discography because of difficulty of the test, a high percentage of false positive results, uncertainty as to the value of the patient's responses, and lack of universal acceptance of the results.
It may have very limited use in combination with C.T. for evaluation of lateral disc herniation but even this has been overcomed by MRI which continues to be more accurate .

6- Epidural venography.

Interosseous vertebral venography was once recommended as a valuable screening procedure but with the advent of newer imaging techniques (especially MRI) venography has become largely obsolete.

7- Electrodiagnostic evaluation.

It is rare that an electrodiagnostic study such as EMG, nerve conduction velocity, or evoked response measurement can significantly help the surgeon to decide weather or not a lumbar disc operation is indicated.
When the radiographic appearance is normal, a positive EMG, should not force a surgeon to proceed with an operation.
The presence of electomyographic abnormalities does not make the diagnosis of nerve root compression secondary to lumbar disc disease.
There are occasional instances when lumbar disc disease mimics a peripheral neuropathy, motor neuron disease, lumbar plexitis, or similar condition, and in these instances, the electromyogram may be useful in the diagnosis of an entity other than lumbar disc herniation.
Also, when the radiographic studies show multiple levels of involvement, in the absence of discrete neurological abnormalities, the electromyogram could conceivably help the surgeon determine the root to be inspected.
It is a subjective test, there may be significant variability among operators and when there are clear- cut symptoms and signs in the absence of radiographic findings, an electromyogram can narrow the examiner's differential diagnosis.
Differential Diagnosis
Chronic degenerative disc disease associated with osteoarthritis.
Tumor of the cauda equinq.
Vascular insufficiency.

Disease of the hip.
Peripheral nerve tumors.
.
Diabetic neuropathy and sciatic neuropathy due to entrapment or injection. Electromyography may be a particularly useful tool in the diagnosis of such lesions.
Other spinal causes of back and leg pain like spondylolisthesis, and anomalies of the lumbar nerve roots causing pain secondary to compression of the nerve root in the lateral recess.


Non-operative Management
This may include one or more of the following:-
1. Bed rest, traction, manipulation
Hospitalization is required only when home care is impossible. A firm resting surface is important. Any comfortable position can be assumed, but resting prone, because of the associated hyperextension, is discouraged. Trips to the bathroom and very short intervals of sitting for meals are allowed.The duration of treatment should be restricted. For patients with back pain the optimal duration is as short as two days. For patients with sciatica seven days appears optimal.
Traction adds nothing to the treatment except in patients whose psychological makeup requires this form of immobilization.

2. Drug therapy

Drug therapy may be directed to relief of nerve root inflammation, to analgesia, or to muscle relaxation. The anti-inflammatory effects of salicylates and steroids are well known. In fact, steroids are so effective that they may produce an artificial sense of improvement, which leads to disappointment when the steroids are discontinued in the face of a frank disc herniation. Salicylates may offer a better alternative. Acetaminophen is less effective because of its weaker anti-inflammatory properties, and it should be reserved for patients with prominent aspirin intolerance.
Individuals vary in their response to the newer generations of non steroidal anti-inflammatory drugs. Effectiveness and patient tolerance vary a great deal, and there is no easy recipe to indicate which drug will offer the least gastric irritation and the most pain relief. Surgeons, and subsequently their patients, will often find their favorite drug.

3. Other forms of non operative therapy.

Gravity traction, specific exercise programs, shoe lifts for unequal leg length, and so forth, have enjoyed periodic enthusiasm. A brace may provide relief for the ambulatory patient with an acute herniated disc.
A form of non operative treatment that has gained favor among experienced clinicians is the injection of long- acting steroids into the epidural space.
Transcutaneous electrical nerve stimulation (TENS) has been used to relieve low back and leg pain.
Operative Management
. Indications for Surgery

Generally, four indications for operative intervention are generally accepted:-
1- A massive midline protrusion that causes compression of the cauda equina, resulting in motor and sensory paresis and loss of sphincter control.
2- Nerve root compression associated with significant quadriceps weakness or a foot drop (although some studies do suggest that early operation does not improve the ultimate prognosis for recovery).
3- Sciatica, with or without neurological deficit, that does not improve on a period of non-operative management.
4- The recurrence of incapacitating episodes of back pain and sciatica that prevent the patient from living a reasonably normal life.


Contraindications to Surgery
Five important contraindications to surgery exist:-
A first episode of low back and sciatica pain without an adequate trial of conservative management.
Intermitten low back pain associated with occasional pains of an equivocal nature, extending into one or the other lower extremity, and equivocal results on myelography.
A prolonged history of intermittent low back pain and equivocal results on myelography.
Low back and intermittent sciatica pain with a myelogram demonstrating a lesion on the wrong, or pain-free side.
5- Improvement of the patient.
In the presence of significant motor weakness, if some slight improvement in the pain occurs, it may be justifiable to proceed with surgery. If pain is the primary symptom, however, improvement is an indication to cancel surgery.