TO EMG or NOT: That is the question
The use of electromyography (EMG) in the treatment of cervical dystonia (CD) has long been debated amongst those physicians who treat patients with CD with botulinum toxin. The purpose of the article is to describe the process of EMG and the potential benefits and pitfalls of using this EMG to assist with botulinum toxin injections.
EMG is an electrical study of muscle. While ancient physicians first used electrical current of the black torpedo fish, it was not until the 17th and 18 th century when Galvani laid the foundation of clinical electrophysiology by studying muscle contraction in frogs. EMG involves introducing a needle into the muscle; watching and listening for specific patterns of electrical activity. The equipment includes a speaker, electrodes, amplifier and storage system (usually a computer). The needle is attached to a cable that transmits the electrical activity of the muscle to a computer that converts the impulse into pictures and sounds. A trained physician in EMG can identify normal muscle patterns by sounds alone, without seeing the screen. A screen converts the sounds into a visual display, called a wave form. It is this visual pattern on the screen and the sound associated with that pattern that allows the physician to determine the muscle activity.
When physicians are treating patients with cervical dystonia they only perform the EMG part of the test. EMG may be incorporated with botulinum toxin injections in 2 ways. First, before treating a patient with botulinum toxin, a physician may examine the muscle with an EMG needle as a way to determine what muscles are active or a physician may use the EMG as a guide while treating the patient with the botulinum toxin. In this case the EMG activity assists the physician in determining how much medication to give and in what muscles. When EMG is used the strength of the toxin injected is unchanged.
Some physicians who treat patients with botulinum toxin always use EMG, some use it only on the difficult patients and a few never use EMG while injecting botulinum toxin into the neck muscle. Often the technique chosen by the physician is an outgrowth of their experience and how they were trained to inject botulinum toxin. As part of their training some physicians may be trained to use EMG while treating CD and others not.
Botulinum toxin generally helps about 90-95% of those patients with CD. There are three reasons that botulinum toxin injections aren’t successful. First, too little drug was given or secondly the toxin was put in the wrong muscle. EMG only identifies that the needle is in a muscle, but it doesn’t identify what muscle. EMG can be used to avoid injecting in fat or to avoid injecting a muscle that is not active. EMG is not a substitute for knowledge of neck anatomy and how those muscles move the neck. If there is a concern about determining which muscles are involved in a head movement, EMG may help direct the muscle and dose selection for that patient. Lastly, very rarely a patient who may have once had benefit from botulinum toxin may at a later time develop immunity to the drug. This is called by physicians a “secondary non-responder”. The use of EMG in a patient with CD who has developed the immunity will not help make the injections effective
Success using EMG while treating CD has been documented in the literature ADDIN EN.CITE Comella19922410http://www.ncbi.nlm.nih.gov/htbin-post/Entrez/query?db=m&form=6&dopt=r&uid=1565246Comella, C. L.Buchman, A. S.Tanner, C. M.Brown-Toms, N. C.Goetz, C. G.AdultAgedBotulinum Toxins/*administration & dosage/therapeutic useElectromyographyFemaleHumanInjections/methodsMaleMiddle AgeMuscle Spasticity/*drug therapy/physiopathologyProspective StudiesTorticollis/*drug therapy/physiopathologyDepartment of Neurological Sciences, Rush-Presbyterian-St. Luke’s Medical Center, Chicago, IL 60612.1565246Neurology1992424 878-82. O’Brien19971340http://www.ncbi.nlm.nih.gov/htbin-post/Entrez/query?db=m&form=6&dopt=r&uid=9826989O’Brien, C. F.Anti-Dyskinesia Agents/*administration & dosageBotulinum Toxins/*administration & dosageElectric StimulationElectromyography/*methodsHumanInjections, Intramuscular/methodsNeuromuscular Diseases/diagnosis/drug therapyDepartment of Neurology, University of Colorado Health Sciences Center, Englewood 80110, USA.98269891997Muscle Nerve Suppl680 S176-80 Dubinsky19913880http://www.ncbi.nlm.nih.gov/htbin-post/Entrez/query?db=m&form=6&dopt=r&uid=2070367Dubinsky, R. M.Gray, C. S.Vetere-Overfield, B.Koller, W. C.AdultAgedBotulinum Toxins/*therapeutic useCervical VertebraeDystonia/*drug therapy/physiopathologyElectromyographyHumanMiddle AgeTorticollis/drug therapy/physiopathologyDepartment of Neurology, University of Kansas Medical Center, Kansas City 66103.2070367Clin Neuropharmacol1991143 262-7. [2-4], but nothing replaces the skill and confidence of an individual physician. If a patient is achieving good results with their injections, regardless of the use of EMG, then no changes should be made. Some physicians, such as myself, always use EMG. I feel that EMG allows me to deliver botulinum toxin directly to the over active muscle. EMG allows me to avoid injection of toxin into a non-involved muscle or into fat. If a patient feels that they may not be getting good results from their injections and EMG is not used, then a patient may ask their physician if EMG is available.
The use of EMG in the treatment of cervical dystonia has gained more and more popularity among physicians. However, the treatment of the individual patients needs to be tailored by their physician. It is important for all patients to have on-going conversations with their physicians about benefits of their injections at each visit. As part of these conversations, the use of EMG can be discussed if it is not already being used. It is important to remember that dystonia is thought to be a disease of the brain and as we all know the brain controls the body. I often tell my patients that the dystonia is smarter than the physician. The dystonia often changes the extent and location of involvement in particular muscle. When the physician is faced with such a challenging disease, EMG can be a helpful tool in the right setting.
Allison Brashear, M.D., Neurologist
Indiana University Medical Center
ADDIN EN.REFLIST 1. Kimura, J., Electrodiagnosis in Disease of Nerve and Muscle: Principles and Practice . 2 ed. 1989, Philadelphia: F.A.Davis Company. 709.
2. Comella, C.L., et al., Botulinum toxin injection for spasmodic torticollis: increased magnitude of benefit with electromyographic assistance. Neurology, 1992. 42 (4): p. 878-82.
3. O’Brien, C.F., Injection techniques for botulinum toxin using electromyography and electrical stimulation. Muscle Nerve Suppl, 1997. 6 (80): p. S176-80.
4. Dubinsky, R.M., et al., Electromyographic guidance of botulinum toxin treatment in cervical dystonia. Clin Neuropharmacol, 1991. 14 (3): p. 262-7.
My mom and I wanted to thank you for hosting such a great symposium this year. This was our third year and we are looking forward to next years. E. Mathews