1. You could do base of the neck at the shoulders. Higher up could interfere with brain function and nerve function as that is the communication center for the whole body. Also the area is more sensitive and more apt to get burns if the correct settings are not applied.
2. With areas above the neck, it is also stated not to use the TENS pads directly as the head is a very bad place to send electricity through. There is also the matter of resonating the area around the carotid arteries. While rare, it is possible to lock the muscles if you do something incorrectly and constrict the blood flow to your brain.
Not a great situation to be in. Therefore, when targeting areas of the head, use the areas of the shoulders for pad placement. As this gets the electricity closest to the area to be targeted safely.
3. To target my head I have used the back of the left shoulder and the front of the right shoulder. Works well for me.
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