When compared to 3-electrode units that require a ground on the back of the neck, the BioTENS is rated "much more comfortable" by patients. Clinicians appreciate BioTENS for its "precise control of left right balance." An optional electrode placement, on the posterior triangle of the neck, bilaterally, provides stimulation of the eleventh (XIth-accessory) cranial nerve, which contains the motor fibers to the trapezius and sternocleidomastoid muscles. Of course, many other electrode sites can also be used. Unlike drugs, QuadraTENS stimulation has no side effects (nausea, tiredness, etc.). In the past sixteen years, many clinicians and patients have found Quadra TENS to be remarkably helpful in managing facial, head and neck pains.