What causes lack of blood flow to the brain?

As a medical professional with expertise in neurology, I can explain the causes of insufficient blood flow to the brain. Brain ischemia can result from a variety of factors that impede the normal circulation of blood to the brain. Here are some of the primary causes: 1. Atherosclerosis: The hardening of arteries due to plaque buildup can narrow the arteries supplying the brain, reducing blood flow. 2. Thrombosis: A blood clot that forms within a blood vessel can obstruct blood flow. 3. Embolism: A clot or other particle that travels through the bloodstream and lodges in a blood vessel, blocking it. 4. Arterial dissection: A tear in the lining of an artery, which can cause blood flow to be disrupted. 5. Reduced cardiac output: Conditions that weaken the heart's ability to pump blood effectively can lead to decreased blood flow to the brain. 6. Hypertension: High blood pressure can damage the blood vessels and affect blood flow to the brain. 7. Vasospasm: A sudden narrowing of the blood vessels that can occur after a subarachnoid hemorrhage (bleeding in the space surrounding the brain). 8. Hypotension: Low blood pressure can also result in insufficient blood flow to the brain. 9. Anemia: A condition where there aren't enough red blood cells to carry oxygen to the body's tissues, including the brain. Each of these conditions can lead to cerebral hypoxia, where the brain does not receive enough oxygen, which can cause brain tissue death or an ischemic stroke.

Brain ischemia (a.k.a. cerebral ischemia, cerebrovascular ischemia) is a condition in which there is insufficient blood flow to the brain to meet metabolic demand. This leads to poor oxygen supply or cerebral hypoxia and thus to the death of brain tissue or cerebral infarction / ischemic stroke.