The answers have been provided by Dr David Hilton-Jones, Dr Mary Reilly, Mrs Sue Edwards, and Professor Neva Haites. We thank them all for their time in responding to these queries.
A. Distal SMA is like CMT and is often called distal hereditary motor neuronopathy. The major difference is that there is no involvement of the sensory nervous system in dSMA. Three of the recent gene discoveries reported to cause distal SMA also cause 3 different forms of CMT2. Distal SMA is much less common than CMT. There is no specific treatment and it is usually inherited in an autosomal dominant pattern.
A. The first thing to stress is that this is very rare.
Two problems may be seen:
a) Involvement of the nerves to the diaphragm (the phrenic nerves) can cause weakness of the diaphragm. This can present as breathlessness, particularly when lying flat, but may also present with excessive daytime sleepiness – the reason for this is accumulation of carbon dioxide due to inefficient breathing.
b) Paralysis of the vocal cords – this impairs air entry and breathing can be very noisy (what is called stridor). Vocal cord involvement is said to be commonest in CMT type 2C, but probably can occur in other types.
I must stress again that breathing difficulties are very rare.
A. It would be appropriate to have breathing studies (simple and painless) and should be referred to a chest physician.
A. The same genetic defect is present in every peripheral nerve in the body. Why the longer nerves are affected first remains unknown.
As mentioned before, involvement of the phrenic nerve causing breathing difficulties is very rare, and tends to be seen only in some of the rarer genetic forms, not in the common type 1A.
Deafness is not a feature of type 1A (or if it is, only extremely rarely – also remember that deafness is a common problem in the general population and in most people with CMT and deafness, it is by chance rather than there being a specific association). Again, there are some rare genetic forms of CMT reported in which deafness is clearly a feature. .
A. This is a potential concern, but in general if the muscles are already so weak that AFO’s are required, then any further weakness caused by lack of use may not be that important. Some patients may find it helpful to use AFO’s only in certain situations – eg. walking to and from work but not in the house or when at work.
A. Knee pain can certainly be due to the mechanisms involved in CMT (wear and tear etc). In advanced CMT the thigh muscle is affected, particularly in its lowest part, and that might cause kneecap problems.
A. In brief, there is very little advantage in knowing the precise nature of the genetic mutation and indeed, for practical purposes, tests for several forms are not yet routinely available.
What is very important is to know the mode of inheritance (autosomal dominant, autosomal recessive or X-linked), as this will dictate the risk of siblings and children developing the condition.
It is true that if a specific mutation can be identified then this also tells you the type of inheritance, but often this information can easily be gleaned from the family history.
A. In broad terms, the earlier the onset, the more problems the condition is likely to cause in later life.
But, and it is a big but, it must be remembered that determining the age of onset is difficult. A rather typical situation is the person with no family history of CMT who is diagnosed in early adult life. They might think that the onset of their disease was, for example, at around 14 years. They then have a child, and notice odd shaped feet or slight clumsiness at age 3 years, and then worry that the onset is much earlier than in themselves – in fact, had the parent been assessed at the same age, similar abnormalities would have been noted.
During the growth spurt of adolescence, CMT often appears to worsen. This is largely due to increasing bone length, and mechanical factors relating to levers etc, rather than to any change in the underlying neuropathy.
In pregnancy, as we all observe every day, mobility changes in later pregnancy due to abdominal load. If gait is already compromised by CMT, then one can easily see how there will be much greater problems in the third trimester. After the birth, there is the extra burden of someone with a physical disability having to, literally, carry an extra load – this may also seem to indicate that the CMT has worsened.
But, in reality, over this period of time, the CMT will have changed no more than it would have done over any other similar time period without pregnancy.
A. A problem with diabetes can be marked loss of sensation in the feet. Therefore, diabetics with this problem can sustain injuries of which they are not aware because of lack of sensation, and these injuries can fester and become infected. The degree of loss of sensation in CMT is usually much less than this, and therefore, I wouldn’t expect any problems from using this sort of device. But it would be best to advise those few people with marked loss of sensation to avoid such devices.
A. No evidence at all. The decision should be based entirely on obstetric grounds.
A. Cold extremities, especially the feet, is a very common symptom.
It is due to two factors:
a) lack of movement, and therefore the normal heat generated by muscle activity is missing
b) the involvement of the autonomic nerves which control the blood vessels and therefore blood flow.
The skin is patchy also due to the autonomic nerves controlling blood flow.
A. The autonomic nervous system is a system of nerves over which we have no direct control, and sometimes people call it the automatic nervous system. It is responsible for controlling blood pressure, and it does that, in part, by dilating and contracting the blood vessels, thereby directing blood to where it is needed.
In CMT and other disorders that affect the autonomic nervous system, this tends to cause reduced blood flow in the skin of the feet and shins. It is this that causes the coldness and blue discolouration. It can be uncomfortable, but doesn’t cause any serious problems.
The autonomic nervous system also controls the bladder and bowels and penis (relating to erection) but these functions are not directly affected in CMT.
A. That is not an easy question to answer, and there hasn’t been much research. It may simply relate to weakness of the muscles that keep the back erect, but it can be very difficult to detect such weakness. What is also odd is that there isn’t an obvious correlation between the presence and degree of scoliosis and weakness elsewhere.
It is usually mild and doesn’t require specific treatment. In more severe cases corsets can be helpful. In other diseases in which scoliosis can be severe, it is possible to operate on the spine to straighten it, but I have never had to do that in CMT. It does not usually progress to any significant degree.
A. It’s very hard to be precise about any particular form of exercise. Most people with CMT have difficulties with balance, and any activity that SAFELY challenges the balance mechanism should be OK.
It is advisable to get advice from a neuro-physiotherapist with regard to specific exercises. Some find exercises in water helpful, whereas others find the temperature in a hydro-therapy pool too hot. However, exercises in a pool would not be particularly beneficial for the balance mechanism as the water holds you up!
A. There is no reason why people with CMT cannot be blood donors, as the condition is not blood borne. The main criterion of being a blood donor is that donating blood should not cause problems to the donor.
If you have a heart condition or high blood pressure, or you are so severely affected by CMT that you cannot get onto the donation beds unaided, then it would be unwise to donate.
If you need any further information about medical criteria, please contact your local blood donation centre or phone 0845 7711711, who will be pleased to assist you
A. The variability between people in the same family can be very marked. It is due to other genetic factors, none of which are known, and possible also to environmental factors.
It is not possible to identify any factors that may indicate severity in other family members.
A. Epidurals are as safe as in people without CMT.
A. There are no specific risks from vaccinations or anti-malaria tablets for people with CMT. Adequate cover is essential.
A. As I’m sure you are aware, conventional medicine increasingly relies on/believes in “evidence based” medicine. The name is self-explanatory and quite simply, it means that doctors will only recommend treatments that have been proven by rigorous scientific analysis rather than by gut feeling or hearsay.
There is NO scientific evidence of vaccines causing problems with CMT specific problems. Remember that CMT is a common disorder, and that the vast majority of them, for over 50 years, will have received full vaccination regimes – there is no published data to suggest problems in what, worldwide, must be millions of people.
A. There is no evidence that people with CMT react in a different way to painkillers.
Q. We have recently received this information about statins for lowering blood cholesterol:
“Medications used to lower blood cholesterol levels are associated with somewhat increased risk of damage to nerves and muscles.
The so-called statin drugs, with names like atorvastin (Lipitor), fluvastin (Lescol), lovastatin (Mevacor), pravastin (Pravachol) and simvastatin (Zocor), are taken by millions of middle-aged and elderly people and are considered highly beneficial in protecting against cardio-vascular disease when dietary, and other life-style measures fail.
However, several studies, including a large Danish study reported in 2002, suggest a need to increase awareness of potential side effects of these popular drugs. The Danish study found a slightly increased risk of nerve damage, while other studies have concentrated on muscle damage.
All studies so far have been done in patients without any underlying neuromuscular disease. It isn’t clear that people with neuromuscular diseases are unusually susceptible to the nerve or muscle damaging effects of statins.
However, a worsening neuromuscular disease in someone taking a statin medication could be a warning. Unusual muscle pain or cola-coloured urine in someone on statin may indicate acute muscle destruction and should prompt immediate call to a doctor."
Bearing in mind the potential life-saving benefit of taking these drugs for someone with high levels of blood cholesterol, should the above be taken very seriously? Clarification of this issue for people with CMT would be useful as statins are being prescribed more and more.
A. Statins cause muscle problems in about 0.1% of “normal” people. There have been one or two reports of people with muscle disease developing problems on these drugs, but it is really not certain that they are at any greater risk.
The evidence about neuropathy is, if anything, weaker. We feel that the risk is small and is, in itself, not a contraindication to using these drugs, which are of major benefit.
However, if people feel that there is any change in their symptoms, they should report it, or simply stop the drug if they are very worried. We are sure that overall far more people will benefit than suffer.
A. Pain is very rarely neuropathic in origin. But it is often secondary to the abnormal stresses and strains on joints, ligaments and soft tissues caused by the muscle weakness and associated abnormal posture.
We do not yet have any scientific evidence (ie. based on a properly conducted clinical trial) that cannabis or its derivatives, is any better than “conventional” painkillers /anti-inflammatory drugs.
People are often willing to take herbal treatments of unproven benefit, rather than conventional drugs whose worth has been proven in properly conducted trails in the naïve believe that because something is natural it must be safe. This is patently nonsense.
So, the simple answer is that, as yet, we cannot recommend cannabis because we do not have proof of benefit, or that if it does help, that the benefit/risk ratio is reasonable.
A. Many drugs are, of course, now used for conditions other than those for which they were first developed. Aspirin is a good example – now used for treating strokes and heart attacks as well as pain!
Gabapentin is widely used for treating pain due to nerve damage, and one of the commonest situations is in patients with diabetic neuropathy. It is arguable as to how much of the pain that some, but no means all, patients with CMT get is actually due to the nerve pathology.
Probably much more often the pain is secondary to abnormal stresses and strains due to the weakness rather than to the nerve problem itself. Having said that, some people may benefit from it.
Some anti-Parkinson’s drugs are of use in people with so-called “restless leg syndrome” and some people with CMT also complain of this. Again, worth a try.
A. Amitriptyline is very widely used to treat pain in a number of quite different settings. For example, it is widely used to treat migraine. I use it myself for treating pain in CMT. It is an antidepressant and has been around for donkey’s years.
For treating depression it has largely been replaced by more effective drugs such as Prozac. It is one of those drugs that has more than one use. It was found many years ago that low doses of amitriptyline, probably lower than would be effective for treating depression, can relieve pain.
It can sometimes cause tiredness, but as noted when treating pain, we use lower doses than when treating depression. Even so, we usually start at a very lose dose and build it up over a few weeks when further reduces the likelihood of it causing tiredness. If it does cause unacceptable side effects, as of course any drug can, then simply stop it and the symptoms will resolve within a few days
A. True neuropathic pain is rather uncommon in CMT. Having said that, the cause of pain in CMT is not always clear, although it is often mechanical in origin relating to the obvious weakness and joint instability.
Neuropathic pain is more commonly seen in patients with acquired neuropathies and certainly pregabalin and gabapentin can be useful.
A. There is no evidence that people with neuromuscular disorders differ in their reaction to local anaesthetics to those without such an underlying condition. I think there is a great variation in the general population relating in part to true variation in response, and in (possibly large) part to variation in clinical practice.
If you would like to submit a question to any of our medical advisers, please email: secretary@cmt.org.ukThis email address is being protected from spam bots, you need Javascript enabled to view it In order for these to be relevant to as many people as possible, we would ask you to keep your questions fairly impersonal.
