1. What

The constriction of the lumbar spinal canal, like constriction of the cervical spinal canal, is not uncommon and can then give rise to symptoms.

2. Cause

The spinal column can show signs of wear, particularly in the elderly. Wear is a normal ageing phenomenon that occurs in everyone, even if the degree to which it occurs varies individually. This wear, also called osteoarthritis, is found in various joints such as the hip or the knee. As a reaction to osteoarthritis, the vertebral bone proliferates and it becomes thicker, mainly in the vertebral joints where thick ridges develop. This may occur at one level, for example C5/6, but often does so at multiple levels, from C2 to TH1. Obviously, the ridges narrow the spinal canal and can compress the spinal cord because of this. They can also constrict the openings where the nerve roots emerge from the spinal canal. Because these openings in the cervical spinal column are not very wide, pinching of the emerging nerve roots can quickly occur. Moreover, the yellow ligaments are also thickened, which results in even less room in the constricted spinal column for the spinal cord and the nerve roots. However, how much room eventually remains is further determined by the degree of wear and the width of the canal, which may both vary from person to person. Other less common causes of constriction of the cervical spinal canal are swelling of inflamed tissue with rheumatism of the cervical vertebral joints and the condition after an injury of cervical vertebrae where displacement of bone fragments has occurred.

Figure: Constriction of the cervical spinal canal due to the development of bone ridges on the vertebral bodies. A ridge at the C4/C5 level causes pinching of the C5 root that emerges there, but not of the spinal cord yet. Branches of the motor and sensory pathways occur in the emerging nerve roots, meaning that impingement of a root can give rise to pain, paralysis and sensory disorders. A ridge at the C6/C7 level can cause impingement with indentation of the spinal cord (myelopathy) with the motor and sensory pathways that run through this, thus threatening the motor and sensory functions.

3. Clinical picture

The symptoms and phenomena of cervical canal stenosis are the consequence of pressure on (compression of) the spinal cord, and/or of the nerve roots.

One can imagine that the pressure on the spinal cord could cause direct mechanical damage there, particularly if this occurs repeatedly with movement, but it is more likely that the blood circulation in the spinal cord will be disrupted by the feeding blood vessels being blocked. The spinal cord can be damaged by this, which is called myelopathy (myelum means spinal cord). The long motor pathways run through the cervical spinal cord; these are bundles of nerve fibres that pass on the instructions from the cerebrum to the cells in the spinal cord that control the muscles. The spinal cord also contains the long sensory pathways, which are bundles of nerve fibres that pass on the incoming sensory stimuli that arrive at the spinal cord to the brain. Therefore, compressing the spinal cord will result in motor and sensory disorders, which manifest themselves in the form of patients no longer having control over the movements of their legs and walking with a lurching gait. On the one hand, this occurs because they have less strength in their legs, (this is called paralysis or paresis of the leg muscles); on the other hand, this also occurs because they can no longer properly feel the position and the movement of their legs. Aside from a reduced sense of position, there is also decreased feeling to touch. Because of reduced sensation in the feet, it may appear as if they are walking in stocking feet when they are not wearing stockings. Additionally, the reduction in strength or paresis is of a spastic nature, which is to say that the legs, despite the reduced strength, are not limp but rather stiffer than normal, which makes it look as if they are stuck to the ground. In addition to disrupting the motor function and sensation in the legs, urine incontinence may also exist, which is to say that the patients cannot control their urinary bladder and can lose urine at inopportune moments. Another phenomenon that sometimes occurs is the sensation of an electric current passing through the spinal column when the neck is bent. These are all signs of compression of the spinal cord. In most instances, I communicate these symptoms to your general practitioner in the form of a Nurick scale. This ranges from I to IV, with the latter indicating that there is very little that you can do and the first indicating that you mainly have tingling feelings in the finger tips.

If the myelopathy persists and the impingement of the spinal cord is not relieved, it can result in the total disruption of the spinal cord, a so-called spinal cord injury that is characterised by general paralysis and a lack of feeling in the body parts below the level of the damage.

The signs of impingement of the cervical nerve roots, also called radiculopathy (radix means root), consist of shooting or radiating pain in the shoulder or the arm, possibly accompanied by a dull or tingling sensation, which can be exacerbated or induced by bending or turning the neck or by extending the arm.

Accordingly, the phenomena of cervical canal stenosis are very similar in appearance to that of a neck hernia, which is not entirely surprising, because both conditions can give rise to impingement of the spinal cord and the nerve roots. For stenosis, the accent lies more on impingement of the spinal cord and for the neck hernia, more on impingement of the routes. Another difference is that with stenosis, the symptoms occur more gradually, while with a neck hernia the symptoms can arise acutely, out of the blue. Obviously, cervical canal stenosis and a neck hernia can also occur as a combination, which is uncommon.

To the uninitiated, the symptoms of a cervical canal stenosis look similar to other spinal cord disorders, such as multiple sclerosis. Therefore, neurological examination and imaging diagnostics are necessary to arrive at the correct diagnosis and to be able to implement the correct treatment.

4. Diagnostic Imaging

Even an ordinary lateral X-ray scan of the cervical spinal column can reveal the narrowing of the spinal canal and the presence of the bone ridges that are causing the constriction.

An MRI of the cervical spinal column is also important. Not only can the bone ridges be recognised on a lateral MRI, but the relationship of the spinal canal to the spinal cord can also be assessed. Normally, a layer of spinal fluid can be seen at the front and back of the spinal cord that separates it from the front and back of the spinal canal, respectively. This means that there is sufficient space around the spinal cord. In cases of severe stenosis the bone ridges on the front may extend to the spinal cord and even cause indentations. On the MRI, one may also be able to determine whether the spinal cord has been damaged by the impingement (myelopathy). On transverse MRI scans of the cervical spinal column one can recognise whether this involves actual bone ridges or alternatively a hernia; one may also be able to see impingement of the roots.

Figure 1:MRI in longitudinal section.

The spinal cord is pinched at the C5 and C6 level.
The white flecks in the otherwise dark spinal cord indicate myelopathy (see text).

Figure 2: MRI cross section.

The spinal canal is severely narrowed; there is hardly any room for the spinal cord, which has been completely flattened.

5. Treatment

Wear of the spinal column is in itself not a reason for neurosurgical intervention, because many elderly people exhibit signs of wear to the cervical spinal column which are revealed by accident on X-ray scans, while the majority of them do not have any symptoms or phenomena of myelopathy. The presence of symptoms is not regarded as a reason to intervene, either, as long as the clinical picture remains stable. However, should the symptoms deteriorate, or if the scans also show signs of myelopathy in addition to the impingement, or if there is an episode of acute deterioration, then neurosurgical intervention is required. For instance, patients my experience a fall, after which they temporarily exhibit a full or partial spinal cord injury. If the photographs or scans show that this is based on a constriction of the cervical spinal column, the question of whether there is reason for surgical intervention must be answered in the affirmative, because the damage may become permanent in the event of another incident.

Results show that halting the deterioration of the clinical picture is a satisfactory outcome. After surgery most patients see an improvement (60%), while others experience no change despite the surgery (35%) or the clinical picture may even continue to deteriorate (5%). In the cases where there is no improvement the key factor may be the disruption of the blood supply to the spinal cord, which is not affected by the surgery.

In principle, the operation involves creating more space for the spinal cord. As with a neck hernia, this can be done from the back or from the front.

We recommend that the rear approach be used if the spinal cord has to be exposed over more than three vertebrae. This commonly occurs over multiple levels, from C2 through C7. The vertebrae are exposed by pushing down the rear neck muscles. The relevant vertebral arches are removed (this is called a laminectomy), followed by the yellow ligaments. Once the dural sac has been freed, one can clearly see it has expanded. The neck muscles that were pushed down are then reattached to each other over the dural sac, which provides the dural sac and its contents with adequate protection, despite there no longer being a covering layer of bone. If, aside from the channel stenosis, this also involves a hernia, this can be repaired during the same operation. Because the removal of the vertebral arches may increase the risk of instability, there are certain neurosurgeons who replace the pieces of bone that were removed and secure them with screws and plates, obviously in a position that provides more space in the spinal canal (a so-called laminoplasty).

For the frontal approach, the patient lies on his back on the operating table, with the face pointing straight up. An incision is made on the left side of the neck. Then the muscles and other structures that occur in the neck (such as the blood vessels, the airway, the oesophagus and the vocal cord nerves) are held apart to eventually locate the front of the cervical spinal column precisely. Thereafter, an X-ray is taken to check the precise location of the operation. After this, the intervertebral disc is removed at the level of the bone ridge until one reaches the front of the spinal canal at the back of the disc, after which the bone ridges above and below the intervertebral disc are removed (see film). Where necessary, the ridges that occur on other levels are also removed, after the corresponding intervertebral discs have first been removed. The space that is created after the removal of an intervertebral disc can be filled with a piece of bone (most often the patient’s own bone from an iliac crest, donor bone, bone cement, or a “small cage” made of plastic or the metal titanium). Others find that it is not necessary to fill up the created space. In rare cases it is necessary to remove the vertebral body itself if this is contributing to the constriction, and to replace it with the materials mention above. Still others, after surgery on multiple levels, prefer to secure the vertebral bodies to each other with plates and screws on the various levels concerned.

6. Risks of surgery

As with any operation there are also risks attached to surgery for cervical spinal column stenosis. However, the chances of this occurring are very slight. The clinical picture is common and the operation is classified as “routine surgery”. An inflammation of the surgical wound or of the intervertebral space has occurred on a few occasions, and post-surgery bleeding at the operation site can occur. With the frontal approach, there are often some short-term symptoms related to speech (hoarse voice) and swallowing (pain when swallowing and the sensation of “a frog in the throat”). Damage to a vocal cord nerve with hoarseness (whether or not transitory) is a rare complication. Even more rare, but nevertheless serious, is damage to the oesophagus or to the spinal cord.

7. After the operation

After an operation, the symptoms do not always improve. In quite a few cases, stopping further deterioration is the best achievable result. Evidently, the damage that has been done to the spinal cord, often over a long time, can no longer be repaired.

During the first few days there is often a painful wound on the back of the neck. Other than that, the patient can soon get out of bed to reduce the danger of thrombosis occurring in the legs, and in general he is mobile enough to return home in a few days. Rehabilitation is only necessary in cases with persisting, severe gait disorders.