Myoguide Injection Guidance System = Peripheral Nerve Stimulator!

By Dr. Evan Friedman | April 13, 2022

While the Myoguide System is better known for being a world class, EMG/STIM BotNT injection guidance system, the USFDA classification includes “Electrical Peripheral Nerve Stimulator”.   We can underline the fact that Myoguide has a very well featured, integrated stimulator designed for both nerve and muscle stimulation. 

In fact, it is Myoguide’s capability of being continuously upgradeable, that has allowed us to update the stimulator to 0.1 mA capability as of December 2016.  Suffice it to say that all Myoguide units produced before that date can be updated to that capability, and all units shipped out after that date are fully capable.  Why not ensure that your essential equipment is protected from obsolescence!

This update has truly created an improvement to an already powerful tool for both nerve location and injection guidance procedures.  We will be addressing how Myoguide can be used as a peripheral nerve stimulator.

Nerve stimulation with a low-intensity electrical current has become a vital part of the performance of peripheral nerve blockade.

How does the Myoguide Injection Guidance system stand up to the accuracy and characteristics of peripheral nerve stimulators used in clinical practice in the United States and Canada?

All peripheral nerve stimulators perform uniformly well when set to deliver currents of 1.0 mA or more. Lower currents of all peripheral nerve stimulators tend to have a higher median error. 

The same is true for pulse width accuracy ranges. As far as the ability to ensure proper delivery of higher currents, this is up to the available compliance voltage.  This is the voltage that is available to generate the proper constant current level for a given load.  Myoguide has one of the highest levels of compliance, which is up to 300 Volts.  While this is more essential for ESTIM guidance, Myoguide will never run out available overhead for lower constant current stimulation levels.

Myoguide will deliver:

  • OUTPUT CURRENT: 0– 20mA; adjustable in 1.0 mA or 0.1 mA steps
  • Current less than 2mA: Average error > 30%
  • Current more than 2mA: equal or less than displayed current within 10%
  • STIMULATOR FREQUENCY:1,3,5,7, or 10 Hz +/- 5%
  • PULSE WIDTH: 50, 100, 200, or 500 μs pulse width +/- 1%
  • OUTPUT WAVEFORM: Monopolar square waveform
  • ELECTRODE IMPEDANCE: 200 – 10 kΩ
  • MAXIMUM EXCITATION: 300V

Use of Myoguide as a Peripheral Nerve Stimulator

The setup for Myoguide use as a peripheral nerve stimulator is fairly simple. 

  1. The black Input/Output connector, in this case “output” connector, connects to the needle electrode to be used for delivery of the pulse
  2.  The Reference (red) connector (surface electrode) is needed in order to generate the stimulation pulse. 

These electrodes should be located close together, or strategically placed if multiple stimulation points are needed, so the reference won’t have to be moved.

  • The ground (green) connector must be used to ensure a secure ground.

Myoguide will always default to EMG mode, when you turn it on. You need to get into STIM mode by holding the MODE button until you’ll hear the relay click and the “Stimulating” screen is shown.

  • The unit will default to 0.0mA and be in the 1.0mA step mode. Once you start increasing the stimulation from 0.0, you will see the yellow stimulation light illuminate to indicate the stimulation is live and actively working.
  • If you want to advance in 1.0mA steps and then fine tune with 0.1mA steps, you just need to move the left/right arrow buttons to highlight the 0.1mA side and use the up/down arrow buttons to modify the stimulation in 0.1mA steps.
  • You can select the stimulation frequency and pulse width, by moving the left/right arrow buttons to highlight these parameters and then the up/down arrows to increase or decrease your selection of pulse width and stimulation frequency.
  • Use the left/right arrow buttons to move the cursor to the current selection area. You will probably want to use the left/right arrow buttons to move the cursor to the .0 side of the mA symbol, to be in 0.1mA step mode. You will then be able to stimulate.
  • The stimulation pause function:   You can pause the stimulation at any time, by simultaneously pressing the left/right arrow buttons.  You can see the pause symbol above these. This will stop the stimulation and you will see the stimulation light turn off.  You can restart stimulation at the last stimulation setting, by simply pressing any button, and it will restart stimulating at the last setting.

Please explore all this functionality with your Myoguide, using surface electrodes on your hand, to help become more familiar with the process, before delivering treatment to your patients. The exercise will build confidence and help streamline your approach for patient encounters (see Test Drive Your Myoguide).

You can visit the Myoguide page for more product details, features, benefits, and specifications if you wish to learn more. Training resources are available on the Myoguide training page.

You may purchase your Myoguide EMG/ESTIM BoNT injection guidance system, accessories, and electrodes, directly from the Myoguide Store!  Credit card payments and quotations can be accommodated directly from our website, for your convenience.

References

Greenblatt GM, Denson JS: Needle nerve stimulator locator. Nerve blocks with a new instrument for locating nerves. Anesth Analg 1962;41:599–602.

Montgomery SJ, Raj PP, Nettles D, Jenkins MT: The use of the nerve stimulator with standard unsheathed needles in nerve blockade. Anesth Analg 1973;52:827–831.

Ford DJ, Pither CE, Raj PP: Electrical characteristics of peripheral nerve stimulators: Implications for nerve localization. Reg Anesth 1984;9:73–77.

Pither CE, Ford DJ, Raij PP: The use of peripheral nerve stimulators for regional anesthesia, a review of experimental characteristics, technique, and clinical applications. Reg Anesth 1985;10:49–58.

Andres, J.A., Vila, M., Bolinches, R.T., & Serrano, M.T. (1988). Use of a peripheral nerve stimulator in regional anaesthesia : clinical evaluation.

Admir Hadzic, Jerry Vloka, Nihad Hadzic, Daniel M. Thys, Alan C. Santos; Nerve Stimulators Used for Peripheral Nerve Blocks Vary in Their Electrical Characteristics. Anesthesiology 2003; 98:969–974

Hadzic A, Vloka JD, Claudio RE, Thys DM, Santos AC: Electrical nerve localization: Effects of cutaneous electrode placement and duration of the stimulus on motor response. Anesthesiology 2004;100:1526–1530.

Kaiser H, Neuburger M: How close is close enough—How close is safe enough? Reg Anesth Pain Med 2002;27:227–228.

Bollini, C.A., & Cacheiro, F. (2006). Peripheral nerve stimulation. Techniques in Regional Anesthesia and Pain Management, 10, 79-88.

Neuburger M, Rotzinger M, Kaiser H: Electric nerve stimulation in relation to impulse strength. A quantitative study of the distance of the electrode point to the nerve. Acta Anaesthesiol Scand 2007;51:942–948.

Bosenberg AT, Raw R, Boezaart AP: Surface mapping of peripheral nerves in children with a nerve stimulator. Paediatr Anaesth 2002;12:398–403.

Urmey WF, Grossi P: Percutaneous electrode guidance. A non-invasive technique for prelocation of peripheral nerves to facilitate peripheral plexus or nerve block. Reg Anesth Pain Med 2002;27:261–267.

Urmey WF, Grossi P: Percutaneous electrode guidance and subcutaneous stimulating electrode guidance. Modifications of the original technique. Reg Anesth Pain Med 2003;28:253–255.

Capdevilla X, Lopez S, Bernard N, et al: Percutaneous electrode guidance using the insulated needle for prelocation of peripheral nerves during axillary plexus blocks. Reg Anesth Pain Med 2004;29:206–211.

Tsui BC, Gupta S, Finucane B: Confirmation of epidural catheter placement using nerve stimulation. Can J Anesth 1998;45:640–644.

Tsui BC, Guenther C, Emery D, Finucane B: Determining epidural catheter location using nerve stimulation with radiological confirmation. Reg Anesth Pain Med 2000;25:306–309.

Tsui BC, Kropelin B: The electrophysiological effect of dextrose 5% in water on single-shot peripheral nerve stimulation. Anesth Analg 2005;100:1837–1839.

Tsui BC: Electrical impedance to distinguish intraneural from extra-neural needle placement in porcine nerves during direct exposure and ultrasound guidance. Anesthesiology 2008;109:479–483.

Urmey WF, Grossi P: Use of Sequential Electrical Nerve Stimuli (SENS) for location of the sciatic nerve and lumbar plexus. Reg Anesth Pain Med 2006;31:463–469.

Jochum D, Iohom G, Diarra DP, Loughnane F, Dupré LJ, Bouaziz H: An objective assessment of nerve stimulators used for peripheral nerve blockade. Anesthesia 2006;61:557–564.

Slavin, K.V. (2011). Peripheral nerve stimulation for neuropathic pain. Neurotherapeutics, 5, 100-106.

Klein, S., Melton, M.S., Grill, W.M., & Nielsen, K.C. (2012). Peripheral Nerve Stimulation in Regional Anesthesia. Regional Anesthesia & Pain Medicine, 37, 383 – 392.

Banks, G.P., & Winfree, C.J. (2019). Evolving Techniques and Indications in Peripheral Nerve Stimulation for Pain. Neurosurgery clinics of North America, 30 2, 265-273 .