A shiatsu massage machine in which clients place their head between two heavy rotating balls has caused arterial problems in two cases, according to Reuters Health. Both incidents seem to have occurred once the machine’s twisting action placed pressure upon the neck, dissecting the carotid artery (and/or damaging surrounding tissue) and, thus, reducing the flow of blood to the head. Along with a headache, the nerve damage caused by the machine left both clients with a droopy eyelid — now permanent. Worse, the machine could have triggered a stroke. While this has only been reported in two cases, Dr. Lynne Taylor of the Virginia Mason Medical Center in Seattle, Wash., who treated both clients, stated such behavior is completely atypical of traditional, hands-on shiatsu from a professionally trained practitioner.