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The blood-brain barrier prevents most chemicals from reaching the brain, but in diseases like meningitis, HIV encephalitis, and brain tumors, it can be breached. Multiple sclerosis and Alzheimer’s disease also affect the barrier. De Vivo’s disease prevents necessary compounds from passing through the brain.
The blood-brain barrier prevents many of the chemicals in the bloodstream from reaching the brain. This usually means that viruses and bacteria in the bloodstream cannot reach the brain, however, in diseases such as bacterial meningitis or HIV encephalitis, this barrier is breached. The blood-brain barrier is also affected by multiple sclerosis, Alzheimer’s disease and some brain tumors.
In bacterial meningitis, the bacteria and the body’s inflammatory response can cause a partial breakdown of the blood brain barrier. This allows the bacteria to enter the brain, where it can cause some of the neurological symptoms of meningitis such as headaches and seizures. This degradation of the barrier also allows antibiotics to reach the brain more easily, which can make treatment more effective.
Like bacterial meningitis, HIV can sometimes breach the blood-brain barrier, causing HIV encephalitis, an inflammation of the brain. In patients with compromised immune systems, other viruses can also travel through the brain and cause disorders such as progressive multifocal leukoencephalopathy (PML). PML, caused by inflammation of the white matter of the brain, is a very serious and sometimes fatal disease.
Brain tumors can also affect this barrier. Often, the blood vessels in a tumor have an underdeveloped barrier, which allows some blood chemicals to enter the brain. A more aggressive tumor will do more damage to this barrier than a benign tumor.
Multiple sclerosis is another disease that affects the blood brain barrier. In multiple sclerosis, the immune system attacks myelin, which coats and protects nerve and brain cells. In some places, the immune system is able to cross the blood-brain barrier and attack cells in the brain.
Some evidence shows a weakening of the blood-brain barrier in patients with Alzheimer’s disease. This degradation allows chemicals from the bloodstream to enter the brain, which can cause some types of brain cells to die. This can cause or exacerbate the symptoms of Alzheimer’s disease.
De Vivo’s disease is another disease of the blood-brain barrier. Unlike many other diseases, which make it too easy for chemicals to enter the brain, De Vivo’s disease prevents necessary compounds from passing through the brain. De Vivo disease is a genetic defect in a type of cell that transports glucose across the blood-brain barrier. This means that the brain is not getting enough energy to function normally and can lead to neurological problems such as mental retardation.
