Multi-segmented sites, such as the hand and foot, can require the use of stimulation (Estim) to identify the correct injection sites. EMG itself cannot separate the different fingers, or toes, as they all emit EMG signals. Stimulation will invoke a twitch response and identify the digit.
The process would involve using an integrated stimulator to challenge the injection site and invoke a twitch response. Stimulation location is essential in these areas. The site is located by palpation during digit movement. The hypodermic needle electrode is inserted, and the patient is asked to move the digit in question (if possible).
The site is reinforced as EMG is evoked when the movement is initiated. Stimulation through the same hypodermic needle electrode will confirm the injection site is related to that digit by evoking a muscle contraction.
Stimulation parameters must be able to be easily changed, and best off with a wide choice of pulse widths, frequency of pulse presentation, and constant current level. Stimulation evokes movement of the digit, as a twitch response, and is best achieved at a very comfortable stimulation current. Stimulation can be presented continuously in order to simplify the clinician’s work. There should always be a stimulator panel light illuminated when actively stimulating.
Clinicians will benefit if there is a stimulation PAUSE feature built into the device, to halt stimulation, as this might not be particularly comfortable for the patient.
If pause is present, it can be a very convenient way to halt stimulation yet retain all the stimulation parameters. This is useful while repositioning the needle to an improved location. Any button press will switch the stimulator back to the previously parameters and will continue stimulation.
Stimulation location (Estim) can also be used to help locate nerves and motor endplates. This is best approached only with stimulation that can be adjusted in 0.1mA steps, as these anatomical structures can be quite sensitive to even 1 mA of stimulation current.
Integrated stimulators that can present narrower pulse widths to further reduce the stimulation presented to the sites. These features provide a wide variety of choices as to how stimulation pulses are presented according to clinical demands.