Suddenly worsening discomfort, weakness, heaviness, pain, low skin temperature and low blood pressure in the left upper extremity, systolic blood pressure difference greater than 20 mm Hg when comparing both upper extremities, weakened or absent radial artery pulsation on the affected side, and symptoms such as dizziness or vertigo, visual impairment, ataxia, diplopia, syncope and other symptoms of inadequate blood supply to the brainstem, occipital lobe and cerebellum are significantly worsened by activity. Many symptoms are associated with cerebral ischemia in the posterior circulation. More than half of patients experience dizziness or vertigo, and syncope and dysarthria occur in 18% and 12.5% of patients, respectively. Patients with secondary vestibular dysfunction may present with visual symptoms and/or nystagmus, including a sense of object movement, inability to focus, and loss of vision in one or both eyes, with diplopia occurring in 19% of patients. Fortunately, these transient ischemic attacks rarely progress to cerebral infarction. Patients with subclavian artery steal syndrome have a common invariant sign, with an asymmetrical pulse between the arms and an arterial systolic pressure difference greater than 20 to 45 mm Hg (mean 30 mm Hg).