EMG Guidance helps find the target
There are many reasons to use EMG guidance. The first is that EMG ensures that the needle is located in a muscle and in a muscle that is actively contracting in association with the disorder. Speelman and Brans (Cervical dystonia and botulinum treatment: is electromyographic guidance necessary? (Letter). Mov Disor 1995;10(6):802) showed that even the most experienced “blind” injectors were frequently inaccurate in identifying needle placement in muscles of the neck. The error rate ranged from 15% in an easily palpated superficial cervical muscle, such as sternocleidomastoid, to greater than 50% in deeper muscles, such as levator scapulae and semispinalis capitis (] Dressler D. Botulinum toxin therapy. New York: Theime Stuttgart; 2000).
Comella and colleagues (Botulinum toxin injection for spasmodic torticollis: increased magnitude of benefit with electromyographic assistance. Neurology 1992;42:878–82), in the only published study comparing experienced investigators using EMG versus palpation, showed that EMG was superior in terms of reducing side effects and obtaining clinical benefit.
Recent studies showed that both expert and novice needle placements improve with guidance when compared without, even in large easily accessible muscles.
(Manual Needle Placement: Accuracy of Botulinum toxin A Injections; October 2012; Muscle and Nerve 46 531-534; Alexis Schnitzler, MD, Nicholas Roche, MD, Philippe DeNormandie, MD, Christine Lautridou, MD, Bernard Parratte, MD, PhD, and Franc Ois Genet, MD)
A recent review article by Grigoriu et al., showed strong evidence that instrumented guided injections including Ultrasound, EMG and STIM, were more effective than manual needle placement for the treatment of spasmodic torticollis, and both upper and lower limb spasticity. (Grigoriu AI, Dinomais M, Rémy-Néris O, Brochard S. Impact of Injection-Guiding Techniques on the Effectiveness of Botulinum Toxin for the Treatment of Focal Spasticity and Dystonia: A Systematic Review. Arch Phys Med Rehabil. 2015 Nov;96(11):2067-78.e1. doi: 10.1016/ j.apmr.2015.05.002. Epub 2015 May 14.PMID: 25982240 )
These studies clearly illustrate that we all do better finding the optimal spots to locate the needles when using EMG guidance, regardless of whether the muscle is located easily on the surface, or deeper, or whether the needle insertions are being carried out by novice or experts.