Sanchin Kyusho Tegumi
Part 7 in a Continuing Series
At first it will appear to be a Neurological problem where the recipient feels the pain shoot down the arm as if the arm was cramping. This is quickly followed with dizziness or a syncope (fainting) or they may also have a difficulty in speech, blurred vision or diplopia (Double Vision). These symptoms can become episodic, as the affects come and go with exertion, like trying to get back onto ones feet.
These symptoms occur because the Subclavian artery normally delivers the blood from Aorta to the upper limbs. If there is any blockage before the origin of subclavian artery there will no direct blood (and oxygen) flow to the arm. So the body acts to compensate for the lack of blood by taking it instead from the Vertebral artery which is an artery that supplies a portion of the brain (Brain Stem) with blood and oxygen. In resting or static state nothing significant will occur, but if the demand is increased with greater blood flow needed for the muscle actions, the needed supply is then redirected from vertebral artery to feed your arm and forearm. This is what will then cause all the associated neurological symptoms. Symptoms include; Vertigo, Diplopia, Dysarthria (speech dysfunction), Anarthria (total loss of speech), Visual Obscurations (loss of light sensitivity - field of vision dims to black) Nausea and Vomiting.
To simplify this a bit, your arm has a secret backdoor to the brains blood supply, which can be stolen when required.