Dr. Charles Tator, Neurosurgeon, at the
Canadian Syringomyelia Conference.
September 1997.

By Darlene Long RN, MHSc.

Dr. Charles Tator, Chairman, Department of Neurosurgery University of Toronto - Western Division. Dr. Tator started practise in Neurosurgery in 1969. He is a world renowned expert in the field of spinal cord injury and congenital neural defects. He is on the board of the Canadian Syringomyelia (SM) Network. In addition to his presentation at the conference he also answered questions from the group and I also had the opportunity to speak with him about issues that concern our World Arnold-Chiari Malformation (ACM) Association. What follows is a brief summary of the major points of his presentation.

Our understanding of ACM/SM has dramatically increased over the past five years with the advent of MR technology our ability to visualise this disorder and therefore diagnose and treat it has dramatically increased. MR technology itself is contantly changing and the newer equipment is far more accurate and detailed than the original models.

ACM can be congenital or acquired. The congenital form occurs during the first month of gestation. Many theories of the cause of ACM were discussed but Dr. Tator favors the idea that it is a type of neuro tube defect combined with bony malformation of the skull. He considers the cause still unknown.

Acquired ACM: this can happen as a result of trauma, even a seemingly minor trauma can alter fluid dynamics or cause a slight bleed that can set up a chain of events that can cause a herniation. ACM can also be aquired by sudden loss of cranial fluid, as in shunting or CSF leak. Dr. Tator went on to give details of a patient who severly herniated his brain after having a shunt inserted for hydrocephalus.

Syringomyelia (Syrinx, cord cavitation) can also be congenital (associated with an ACM) or aquired. Congenital Syringomyelia is always associated with Chiari Malformation and can remain silent or asypmtomatic for some time.

Acquired Syringomyelia can be as a result of trauma (whiplash injury is common), infection (meningitis) or a arachnoiditis. It can take months or years after the causitive event for the post traumatic Syringomyelia to develop. It can develop either above or below the level of original injury. When Syringomyelia is aquired in this fashion it is almost always progressive and will require surgical treatment.

ACM/Syringomyelia is often associated with other defects including abnormalities of the bones in the skull, hydrocephalis, spina-bifida, scoliosis, basiliar invagination, and abnormalities of odontoid and clivus.

At Toronto-Western hospital ACM is broken into three main groups:

ACM I - Displacement of cerebellar tonsils outside of the foramen magnum - may include Syringomyelia up to 75% and hyrdocephalus and bony abnormalities of the skull and spine.

ACM II - Includes displacement of not only cerebellar tissue but also the brainstem outside of the foramen magnum. May include Syringomyelia, hydrocephalus, bony abnormalities.

ACM III - In addition to the feature found in 1 and 2, this classification also includes bulging of the cord, ie. meningeocele, or myelomeningeocele.

ACM IV - now considered a different although related condition.

A study has been conducted at Toronto-Western hospital concerning the classification of ACM. Cases diagnosed as ACM Type 1 by an MR were followed into surgery and during surgery measurements were taken and investigations made. It was found that over a two year period 100% of cases considered to be ACM Type 1 when surgically investigated were found to actually be ACM Type 2. That is, they were found to have considerable herniation of the brainstem as well as the cerebellar tissue and the obex of the fourth ventricle was found to be caudal to the foramen magnum. This has led to a revised classification system at this hospital.

Symptoms:
Although symptoms differ widely some of the most common are headache, visual blurring, dysphagia (swallowing problems), limb weakness, numbness, ataxia, pain, burning, dizziness.

Some of the neurological signs found include: nystagmus, lower cranial nerve palsys (V-XII), cerebellar defecits, spastic quadraparesis, muscle atrophy, weakness and sensory loss.

Treatment:
Non operative: Non operative measures should be taken if the symptoms are mild and if they do not progress over time. Occassionally this condition can be arrested for lengthy periods of time. Due to the risks of surgery, if the symptoms don't get worse over time, then it's best to leave it alone.

Operative treatment: This can vary from region to region. Standard procedure for ACM with or without syringomyelia is to do a posterior fossa decompression sub craniectomy laminectomy and possibly duraplasty.

The duraplasty phase of the surgery is now controversial with variations and several groups that think the total opening of the dura is not required and can create more difficulty. These groups are advocating a procedure where only the topmost layer of the dura is opened.

Possible variations:
Durotomy without duraplasty (patch or graft), durtomy without closure of the dura and arachnoidal dissection. In the case of duraplasty a variety of materials are used for the graft or patch. The patients own fascialata (leg) or pericardial tissue. Cadaver dural tissue. Synthetic materials (goretex, dacron etc.).

These procedures are not without risks which include the following mechanical injury, shock, blood clots, stroke, meningitis, leakage of CSF, and air embolism. The determining factor for whether to have or not have the surgery for both patient and surgeon should be the following question:
Are your symptoms getting worse?  The syrinx or syringomyelia of patients with ACM will often eventually diminish after the decompression. If the syringomyelia is not satisfactorally treated after decompression then a shunt procedure is considered (Dr. Tator's personal preference is to decompress first then shunt if/when required).

Other procedures used in the past and proven useless for syringomyelia include radiotherapy, and needle aspiration of the syringomyelia. Shunting has become the procedeure of choice.  Unfortunately shunt technology has lagged the last twenty five years and we are still using the same material
to make the shunt. Silastic is still used because they have not found a material that performs better. This material can cause reactions and scarring in some people.

Once you have this condition (ACM/Syringomyelia) you have it for life and continued vigilance is required to monitor symptoms and changes.

Following the resentation with Dr. Tator there was an opportunity to present questions. This session is summarised below.

How many cases are there of syringomyelia/ACM in Canada?
We know there are about 200 diagnosed cases, which when calculated by population would mean at least 2000 cases in the US.

If decompression surgery did not collapse a syrinx is a shunt a good idea?
The question you have to ask here is *Is the condition getting worse?*  If there is no change in the size of the syrinx (ie it is not getting bigger) and there is no worsening of the symptoms then I would leave it alone. If the symptoms are getting worse then I would do a shunt procedure.

What are the chances of a shunt blocking?
Well shunts are made from silastic and all shunts have the potential for blocking.  The longer the shunt tubing the more of it here is to block. A tendency toward heavy scarring can make someone more likely to have a blockage, but it really is quite variable.

Does MRI show scar tissue?
No, it doesn't.  This is one of the unfortunate limitations of the technology.  It does not show the sar tissue unless it obstructs or fills up an area....and then you see the area as appearing abnormal you may not see the scar tissue which can be very thin...like a  membrane.  Scarring is usually seen at surgery.  Structures less than 1mm thick are usually not visualised.  Gadlinium contrast will show up some types of dense scarring.

Will my pain improve after surgery?
We can never guarantee the surgery will reduce or eliminate the pain associated with this condition.  This is one of the great unsolved problems of the disease. Post operative improvement of pain is variable for unknown reasons.  Some patients show an improvement of neurological function, and
related symptoms, others don't.  A good result is defined by an arrest of the condition..no further deterioration in a previously progressive case. We don't necessarily look for restoration of function.  Tissue becomes irreveribly damaged under pressure...the longer and more severe the pressure the more the damage.  Relieving pressure will sometimes help, but cells that have been destroyed can not be restored.

Are there any precautions for patients with ACM/syringo that become pregnant?
I would think that there would be some special things to do at the time of delivery involving minimilizing the effort involved.  We do recognise  that straining, forced bowel movements, and heavy lifting of weight can cause a syringomyelia to expand and create pressure problems for ACM  patients as
well.  Straining during labour or at any time isnot a good idea.   It is the excessive maximal effort that can cause a worsening of the condition or symptoms. So it is important for you people to keep yourselves regular!

It seems to be a common pattern, and it has been written in the literature, that symptoms can return or worsen around the 18 month to 3 year post op
mark.  Why is this, and what do we do about it?
Unfortunately this can be a problem.  The pathways and restricted areas we open up are prone to develop scarring.  We have cleaned up a compressed area and made lots of room...only to have seen the patient several years later with massive scarring to the point of obstruction again.  When scarring occurs around the arachnoid, we call it arachnoiditis, and this is a common problem seen with this condition.  It is another of those great unsolved mysteries of this disease I spoke about.  This type of scarring is often not seen on MRI until it reaches the point of fluid obstruction. There is a drug being tested for treatment of this problem in India. The drug Hyaloronidase is used for arachnoiditis associated with Tuberculosis lesion.  It is now being tested with 3 people suffering from ACM/Syringo related arachnoiditis.  It is too early to know whether it is a useful treatment or not. It is important to know that there can be further deterioration after surgery, in spite of our best efforts.

Does added trauma (whiplash etc) bring trouble for the ACM/syringo patient?
I never like to hear about my patients being involved in car accidents or falls or other mishaps because it can cause additonal problems for them. Trauma, even the slightest mishap can produce inflamamtion or even a slight bleed in the head.  Blood also causes further inflammation and this
reaction can block CSF pathways.  Pressure problems, and worsening of symptoms can result.  This is in addition to the physical affects of the mishap itself.  So please, avoid trauma!

If this condition happens in utero, why does it take so long for the symptoms to present themselves?
We don't know for sure!  Many of us who are studying this disease think that the initial congenital problem or problems may be sitting there silently until triggered by either a virus, or physical trauma.  It is the number one thing we hear in clinic about the presentation of this disease. People suffer a whiplash, or a fall  or even the birth of a child and they simply don't get better as expected  or symptoms are provoked.  Eventually an MRI is done and the ACM/syringomyelia is revealed.  Sometimes it may take many years to discover the cause of the patients symptoms.  This causes a big problem legally, when you have say an auto accident or work injury that triggers the condition to become symptomatic.  If surgery or disability results there can be quite a legal battle over whether the condition was preexisting or if the accident brought about the disability. Many of these cases end up being judged a 50/50 kind of thing.

How effective are spinal cord stimulators for pain and spaticity?
Quite some time ago these devices were used for spasticity, but they are not used for this anymore.  They were found to be largely ineffective for spasticity, and we have developed better medications for this problem.  We also utilise things like the baclofen pump for difficult spasticity with better result. It has better success when used for intractable pain, although we don't see it used as much anymore.

Is there some forum where neurosurgeons from around the world go to update information and discuss research into ACM/Syringomyelia?
No, not that I am aware of.  Every neurological conference will feature a session on ACM/Syringo for a few hours, but nothing that is soley for the purpose of research discussion for this condition.

Copyright © 1997 Darlene Long-Thompson, RN, MHSc. of the World ACM Association

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