The Benefits of Combined BoNT Injection Guidance Techniques

The Myoguide System

We have presented many resources about the Myoguide™ EMG/ESTIM BoNT injection guidance system, related to the value of EMG and Stimulation guidance (ESTIM) techniques, including:

  • The availability of EMG signal display
  • EMG audio and options such as audio mute
  • The application of 1.0mA and 0.1mA stimulation steps for ESTIM location procedures

We’d like to elaborate on these concepts when we consider the benefits of integrating these guidance options when ultrasound (US) guidance is being used

As we know, ultrasound may be used in conjunction with EMG and ESTIM guidance techniques to improve outcomes.   Combined guidance techniques are frequently used when approaching patients with complex conditions, such as cervical dystonia, limb dystonia and other conditions where numerous muscles may be involved establishing postures as part of the overall condition [1].

The Myoguide™ EMG/ESTIM BoNT injection guidance system offers a useful array of features to help support US evaluations in these cases

US provides accurate real time anatomical information in both cross-sectional and longitudinal views.  Visualization of the needle electrode is usually available. The hypodermic needle electrode will be able to pick up EMG at the tip of the needle. Outside of tissue distortion which may be visible on the ultrasound image, US device features to aid in needle visualization may include:

  • Needle brightening
  • Injection pathway indicator
  • Needle tip sparkle

The needle electrode will provide information about the activity of the muscle, and whether there is tonic activity.  This can uncover the muscle’s contribution to the observed abnormal posture.

EMG and ESTIM may also be used to for localization of motor points which performing neurolytic chemodenervation procedures [2,3]

The combination of ESTIM and US are typically used for:

  • Diagnostic nerve blocks
  • Neurolytic nerve blocks
  • Anaesthesia nerve blocks
  • Motor point nerve blocks
Motor endplate Microscope

The hypodermic needle electrode, which can be used for either EMG or ESTIM, would be inserted using US guidance.   ESTIM function is usually used for near nerve and motor end plate location procedures. [2,4-6].

Myoguide’s stimulator can be used to generate the stimulation pulse widths that can range from 50-500µs.  The amplitude of the stimulation pulse can be increased in 0.1ms, or 1.0ms increments, all the way up to 20mA.  Nerve stimulation, and motor endplate location procedures are generally better approached in 0.1ms increments due to the sensitivity of these areas to electrical stimulation.

The benefit of being able to stimulate and record with the same hypodermic needle electrode is that needle position can be adjusted while fine-tuning the stimulation levels (decreasing as you get closer to the neural target), until the optimal site is localized.  The agent can be injected, through the hypodermic needle electrode, once the target point is identified.

The level of imaging capable on US machines cannot visualize motor points but can help navigate the hypodermic needle electrode through the identified muscle.  ESTIM and/or EMG helps to better identify the motor point, closer to the motor endplate. 

Isolation of the nerve or motor point is not possible by US guidance alone [2,5]

Literature reviews illustrate that injection technique impacts the outcomes of BoNT procedures for limb spasticity.  Chan et al [8] reviewed many studies between 1990-2016.  The injection techniques were categorized into four types:

  • Localization technique
  • Site selection
  • Injectate volume

Based on their review the authors concluded that evidence supported that the following techniques are associated with improved outcomes when performing BoNT injections for limb spasticity:

  • Instrumented guidance (US, EMG, ESTIM) were found to be superior to manual needle placement
  • Injections targeting motor endplates were superior, or equivalent to multisite quadrant injections
  • High volume injections are similar to low volume injections
  • High volume injections distant to the motor endplates are more effective than low volumes near the motor endplates

While this review did not specifically compare the various instrumented techniques to one-another, Picelli et al showed US and ESTIM were equivalent, and both were superior, compared to manual guidance, for localization of the wrist and finger flexors [9].

Grigaui et al. reported the results of a systematic review of the impact of guidance technique on the outcomes of BoNT injections for spasmodic torticollis and spasticity in adults and children [10].

The authors concluded that there is strong evidence to support the superiority of the benefit of adopting EMG, ESTIM and/or US injection guidance for BoNT injections, compared to manual needle placement for patients with:

  • Spasmodic torticollis
  • Upper limb spasticity
  • Post stroke spastic equinus and spastic equinus in children with cerebral palsy.

Chin and colleagues evaluated the accuracy of manual needle insertion, subsequently confirmed by ESTIM or US, for upper and lower limb muscle injections in children with cerebral palsy [16].

They reported that the accuracy of manual placement was acceptable (>75% accuracy) only in the gastroc-soleus. Accuracy of needle placement was reported to be unacceptable for a range of other lower and upper limb muscles including:

  • Hip adductors (67%)
  • Medial hamstrings (46%)
  • Tibialis Posterior (11%)
  • Biceps Brachii (62%)
  • Forearm and hand muscles (13% to 35%).

Based on the results of this study, the authors recommended the use of ESTIM or other guidance techniques for needle placement in all muscles excepting gastroc-soleus [17].

Hong et al. compared the incidence of dysphagia in patients treated for cervical dystonia using EMG versus US. The incidence of dysphagia was 34.7% in patients where injections were guided by EMG alone. When the patients with dysphagia were converted to receiving BoNT injections using EMG and US guidance, the incidence of dysphagia fell to 0% [7].

Reducing adverse events, or side effects, associated with BoNT injections is a very important consideration for all conditions, and all guidance methods.

Myoguide™ can play an essential role in these procedures, as an essential adjunct to US, by supporting EMG and STIM guidance procedures with EMG audio and visual feedback, as well as a full featured stimulator.

The Value of EMG/ STIM Guidance in Combined Guidance Techniques

These studies clearly illustrate that we all do better finding the optimal spots to locate the hypodermic needles when using EMG guidance, regardless of whether the muscle is located easily on the surface or deeper.

It is the confirmation that you are indeed in the muscle you have identified requiring treatment, that is the point of the matter.  This will lead to improved results and a lower incidence of iatrogenic effects.

There are many compelling reasons to use EMG guidance. The first is that EMG ensures that the needle is located in a muscle. The second is confirmation that the needle is in a muscle that is actively contracting in association with the disorder.   

Speelman and Brans showed that even the most experienced “blind” injectors were frequently inaccurate in identifying needle placement in muscles of the neck [18].

Comella and colleagues illustrated that BoNT injection for spasmodic torticollis increased magnitude of benefit with electromyographic assistance. The article involved comparing experienced investigators using EMG versus palpation and showed that EMG was superior in terms of reducing side effects and obtaining clinical benefit [17].

Recent studies showed that both expert and novice needle placements improve with guidance when compared without, even in large easily accessible muscles [19].

A recent review article by Grigoriu et al, showed strong evidence that instrumented guided injections (Ultrasound, EMG, STIM) were more effective than manual needle placement for the treatment of Spasmodic Torticollis, and both upper and lower limb spasticity [10].

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.  

Myoguide is equipped with what is essentially a single channel EMG machine with a full featured, built in stimulator.

Studies clearly illustrate that we all do better finding the optimal spots to locate hypodermic 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. We have also learned that isolation of the nerve or motor point is not possible by ultrasound guidance alone [2,5, 17-19]

Myoguide™ EMG/ESTIM BoNT injection guidance system is designed to amplify EMG signals from muscle and provide audio and visual feedback to assist clinicians in locating areas of muscle activity.

The other useful feature is Myoguide’s ability to mute the audio.  This is a design feature for times when it is better to operate in silence, and rely upon the visual signal display.  This is pertinent in cases where patients are easily startled or are likely to have issues with hearing EMG audio, e.g. children, anxiety, etc..

Myoguide on a table

Myoguide also has an integrated and well featured stimulator, capable of stimulation in either 1.0 mA or 0.1 mA steps, for muscle, nerve, and motor endplate location procedures.

Myoguide supports injection of neuromodulators and both chemodenervation and neurolytic procedures, as well as, peripheral nerve stimulation. Learn more about how to use Myoguide

Myoguide™ EMG/ESTIM BoNT injection guidance system , hypodermic needle electrodes, surface electrodes required for these procedures, as well as Myoguide accessories, are available directly from the Myoguide Store!

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  1. Alter KE, Karp BI. Ultrasound Guidance for Botulinum Neurotoxin Chemodenervation Procedures. Toxins (Basel). 2017 Dec 28;10(1):18. doi: 10.3390/toxins10010018. PMID: 29283397; PMCID: PMC5793105.
  2. Alter K.K., Murphy K.P. Guidance techniques for botulinum toxins and other injections. In: Alexander M.M., Matthews D.J., editors. Pediatric Rehabilitation, Principles and Practice. 5th ed. Demos Medical Publishing; New York, NY, USA: 2015. pp. 153–169. 
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  9. Picelli A., Lobba D., Midiri A., Picelli A., Lobba D., Midiri A., Prandi P., Melotti C., Baldessarelli S., Smania N. Botulinum toxin injection into the forearm muscles for wrist and fingers spastic overactivity in adults with chronic stroke: A randomized controlled trial comparing three injection techniques. Clin. Rehabil. 2014;28:232–242. doi: 10.1177/0269215513497735. 
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  13. Antonakakis J.G., Ting P.H., Sites B. Ultrasound-guided regional anesthesia for peripheral nerve blocks: An evidence-based outcome review. Anesthesiol. Clin. 2011;29:179–191. doi: 10.1016/j.anclin.2011.04.008.
  14.  Wu T., Dong Y., Song H., Fu Y., Li J.H. Seminars in Arthritis and Rheumatism. Volume 45. WB Saunders; Philadelphia, PA, USA: 2016. Ultrasound-guided versus landmark in knee Arthrocentesis: A systematic review; pp. 627–632.
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