The intramuscular injection of botulinum toxin in targeted muscles has emerged as a treatment of choice for the management of spasticity, as well as for numerous other conditions.
An essential factor influencing the treatment outcome is the need for better accuracy in delivering the toxin to the target muscle. The needle must be positioned within the targeted muscle, in or near: motor end plate zones, or motor points.
Electrophysiological and ultrasound guidance can both facilitate botulinum toxin (BoNT) injection accuracy.
Techniques employed for BoNT injection guidance include:
- Muscle injection by anatomical knowledge only (AKO)
- Motor end plate localization by electrical stimulation (eSTIM) guidance
- EMG guided injection
- Visualization of target muscles by ultrasound guidance (US).
EMG guidance increases the accuracy of placement compared to AKO placement by using muscle activation. eSTIM relies upon recognition of muscle twitch as the indicator of success.
Please check out our Blog “Myoguide™ EMG/ESTIM BoNT Injection Guidance System Improves Needle Placement”
Electrical stimulation and EMG guidance procedures are fairly straight forward; however, they do require experience and practice in electrophysiological techniques, as well as familiarity with the relevant anatomical landmarks.
Recent studies have shown that electrophysiological guidance techniques perform better than AKO, even very obvious large muscles, such as Gastrocnemius.
The potential advantage of using eSTIM as an adjunct to ultrasound, is that not only does it ensure that the injecting needle is in the target muscle, but that the needle is in close proximity to motor endplates and/or motor points.
Ultrasound does help to identify muscles by showing boundaries of individual muscles, each with characteristic landmarks, and by concurrent oscillations of the intramuscular echo produced by passive movement or tendon stretch. Ultrasound visualizes bones, blood vessels, and nerves and differentiates between the target muscle and neighboring structures.
Ultrasound guidance is non-invasive, precise, and real-time. It demands very little time, is painless, and does not expose subjects to radiation. It allows visually guided injection into the center of every targeted muscle belly; however, ultrasound does require extensive training, and the cost of the equipment is often prohibitive.
Patient factors can also present challenges with sonography. The injection of deep-seated muscles in larger extremities, especially those in obese patients, cannot be performed with the same visual acuity as in superficially seated muscles. Misaligned extremities demand the use of alternative strategies and expert spatial and anatomical knowledge.
Chronic spasticity is associated with substantial atrophy of muscle bulk and significant increases of muscle echogenicity, thus rendering the detection of contour lines far more difficult. An important consideration is that ultrasound cannot reliably localize endplate zones.
This is where the addition of eSTIM comes in, as an essential tool for injection site validation. Myoguide can help validate your sonography-based injection guidance procedures.
Myoguide Can Be Used to Improve Patient Outcomes by Supporting Improved Injection Accuracy.
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