Spoke briefly with my doc and he said the vascular ultrasound on my arms showed Thoracic Outlet Syndrome (TOS). I have an appointment with him on Monday to get more info. So I checked out wiki - I don't seem to have any of these symptoms: From wiki: https://en.wikipedia.org/wiki/Thoracic_outlet_syndrome "TOS affects mainly the upper limbs, with signs and symptoms manifesting in the shoulders, neck, arms and hands. Pain can be present on an intermittent or permanent basis. It can be sharp/stabbing, burning, or aching. TOS can involve only part of the hand (as in the pinky and adjacent half of the ring finger), all of the hand, or the inner aspect of the forearm and upper arm. Pain can also be in the side of the neck, the pectoral area below the clavicle, the armpit/axillary area, and the upper back (i.e., the trapezius and rhomboid area). Discoloration of the hands, one hand colder than the other hand, weakness of the hand and arm muscles, and tingling are commonly present." My experience is that lifting things or raising my arms above my head causes me to be light headed, nauseous with a great need to be horizontal until my body stabilizes. I don't have pain. I also don't have delayed PEM. Mine is immediate or within minutes of exertion. In spite of my protestations, testing doesn't show memory impairment, but perhaps my brain fog is not in the memory part of my brain. But I thought this part was interesting: "...If left untreated, TOS can lead to neurological deficits as a result of the hypoperfusion and hypometabolism of certain areas of the brain and cerebellum." Perhaps I've had undiagnosed TOS and its causing my ME symptoms via hypometabolism of certain areas of my brain and/or cerebellum? And surgery may set me free from ME? Really trying not to get ahead of myself so am tempering my hope.