Electromyography in Pediatrics

It Is too Painful

Most pediatric electromyographers have experienced the referring practitioner telling parents their child was about to have “the most painful test they will have ever experienced.” This is an extraordinary thing for any colleague to communicate to a parent, but paradoxically the fact that they consider sending the child for such an appalling investigation suggests that they, perhaps subconsciously, realize that the test has an important role in the investigation of the child. It is not hard to imagine the kind of anxiety this produces in the parents and child and the effort needed to persuade them of the benign nature of the investigation.

In considering where this misconception arose, one has to acknowledge that the first pioneers of pediatric EMG, in the early 1970s, were working in much less favorable conditions. The initial needles used were far larger in diameter than those used currently and were reused multiple times. Those needles became blunt after repeated use and, despite admonishments to sharpen them, it was often difficult to do so. To add further difficulty, inserting the needles repeatedly often meant that they would bend and become permanently bent with the possible risk of breakage. This was particularly a problem if they were used in children. Today, disposable needles are universally used in the Western world. However, larger-bore needles are still in widespread use in adult EMG laboratories, perpetuating misconceptions about how the testing is performed on children in the hands of a skilled and thoughtful examiner.

The way we regard children has changed a great deal over the years. In England and the United States, the traditional view was that children were to be “seen but not heard,” but enlightenment regarding the rights of children has changed that attitude considerably in recent decades. Children are very much allowed to be heard, and if an investigation is uncomfortable for them we should recognize that and make strenuous efforts to diminish the discomfort. There is also now a realization, rather reluctant, that some of the discomfort produced in children resulted from inadequate knowledge among the people performing the pediatric EMG. There was a lack of appreciation of how children react and of the diseases they suffer. As an example, the correct investigational strategy to be used when discovering anterior horn cell disease in children depends on a differential diagnosis between whether the condition is segmental or generalized, which is quite different from encountering these findings in adults where the diagnostic question often involves motor neuron disease versus cervical and lumbar radiculopathy. In children, this question can be answered straightforwardly by sampling as few as two muscles.

So what is the reality with regard to the pain of pediatric EMG? Some studies have tried to answer this question. At Great Ormond Street Hospital in London, an informal analysis asked participants to rate the pain on a sliding scale after the examination had been completed, comparing it with blood tests. We also included venous cannulation as a further comparison, but the numbers for that comparison were less. To our satisfaction, the results of this unpublished analysis showed that the discomfort rests somewhere just above a blood test and a long way short of the cannulation. As a further observation, it was interesting to talk to parents about the stress of other maneuvers, some of which would not immediately be associated with discomfort. Among that list is the insertion of a nasogastric tube, which causes huge discomfort to both parents and children alike and is one of the major factors that upset children when lying down for investigations such as bulbar EMG and single fiber EMG. Since the first of these tests is often requested when a child is having feeding difficulty, it is important to realize the association and to be able to reassure parents.

What can one do about the pain of EMG? A variety of strategies is available to the practitioner. The first perhaps is the use of local anesthetic. This is now commonplace for nearly all children having blood tests and some very effective local anesthetics exist, some based on amethocaine and others using xylocaine as the active agent. The problem with their application in EMG is that in many ways the needle EMG, however it might be regarded by the parents or child, is not really the most painful experience. Motor nerve stimulation can be more painful. Perhaps because needle EMG takes longer than the motor stimulation and the child often becomes more upset, it is hard not to feel that local anesthetic would help. Of course, it only helps the passage of the needle through the skin, which if done skillfully only takes a matter of milliseconds.

Next there is a tendency to use sedation, sometimes termed conscious sedation. The problem of sedation, which is well recognized, is that a child who is asleep will be awakened by any painful experience and this situation is no different for a child who is sedated and having EMG. To achieve a degree of analgesia with sedation is only possible when you approach an anesthetic application. Clearly this will have important implications with regard to respiratory depression and inhalation and other serious complications. It is quite possible for children to be nearly anesthetized and then left to recover from their sedation with no awareness of how severely depressed they are. So, if sedation is used it is mandatory that care is taken to ensure there is adequate training for staff and adequate monitoring. Resuscitation equipment also needs to be readily available.

The next stage in the escalation of methods of reducing the discomfort is the use of inhalation anesthetics such as nitrous oxide. This in many ways is a logical step, as it is an anesthetic with significant analgesic effects, which are perhaps more than its sedative effects. It is perhaps salutary to remember that there are requirements for trained personnel to deliver this and significant dangers if the equipment is not maintained. During the administration of nitrous oxide to mothers in labor, they are required to clasp the mask across their face; when the anesthetic reaches a certain level the sedative effects cause the mother to then be unable to hold the mask against her face. This is a built-in safety measure, which prevents overdose. Unfortunately, children will not cooperate in this technique as well as adults and therefore the mask has to be held on the face by an anesthetic assistant. There are dangers if attendants do not realize how deep the children are.

At Boston Children’s Hospital, propofol general anesthesia has been used for EMG for over a decade. This medication is generally safe in the proper circumstances, which typically include monitoring by trained anesthesiologists and/or nurse anesthetists with cardiorespiratory telemetry in a properly equipped day surgery procedure room. The only significant effect on the quality of nerve conduction studies is that F responses are typically obliterated by propofol.

The downside of sedation and general anesthesia, if the previous discussions are not sufficient to curb enthusiasm, is that while they help the quality of nerve conduction studies, they have a deleterious effect on the needle EMG examination, as children will not respond to commands and will not contract as much as desired under these circumstances.

None of the above methods is entirely safe, even the use of local anesthetic, as a child may develop an allergy to the anesthetic and, at worst, an anaphylactic reaction, although fortunately this is very rare. This is more common with amethocaine as opposed to xylocaine.

At this juncture, it is perhaps opportune to make a case for not using sedation at all. In order for this to work, one must engage very actively with the children themselves, if they are old enough, and, if not, with their parents. In truth, regardless of the child’s age, it is imperative that the parents be brought on board with the procedure. Clearly it is essential that they not be excluded from the examination room and, indeed, any person accompanying the child should be encouraged to join in. The first step towards engagement is the requirement of complete honesty. There is no point in telling children or their parents that the procedure to follow will produce no feelings of discomfort. Certainly it does produce discomfort and it is important to be candid about this. Reassurance that it is perhaps no worse than a blood test is a good starting point. It is also very important to put all parties at their ease, and the social interactions which would normally be employed when talking to children or their parents outside a medical setting are perfectly acceptable methods. Some might regard this as unprofessional, but it can be very effective. Children will respond after a certain age to questions about what they love to do or their favorite subjects at school, and an anxious child can quite suddenly change and sometimes smile while discussing enjoyable experiences. It is preferable to talk to a child about their dreams of becoming a disco dancer rather than try to calm them by repeated reassurances that what they are experiencing is not uncomfortable, when they clearly disagree. Getting children to talk about favorite subjects can be immensely effective. Many instances of needle-phobic children passing through the EMG without any anxiety have occurred using this approach.

Another invaluable distraction technique is the use of portable electronic devices. Almost every parent will have games or music or even videos on their mobile phone, and many children will come with electronic tablets or similar devices. Whatever amuses them must be employed. Our experience has been that battery-powered devices (i.e. those powered by direct current) generate little to no electrical artifact, whereas nearly any device that is plugged into an electrical outlet (i.e. those powered by alternating current) tends to generate 60/50 Hz interference during the study. Although toys seem to be rather old-fashioned nowadays, a good supply of these is also important.

Another point that is important to emphasize, particularly in the younger patients, is that not all reactions are pain related. A lot of children become angry when they are investigated and asked to do things they do not want to do, even such things as simple as lying down on the couch. Parents recognize this kind of upset and can easily distinguish it from that caused by pain. If they appreciate that the practitioner working with them also understands this, it will firmly establish yet another measure of trust. Many of us have examples of instances when this has occurred. One of the authors (MCP) will always remember a child about two years old, who could only be described as “creating” during the EMG. The noise and anger generated were truly remarkable. Her grandmother, who was of Italian descent, was circling around the doctor, who feared the worst, anticipating a tirade of fury against him for being so unkind to her granddaughter. Instead, all she said was, “The Latin temperament!”