Is brain death reversible? (2023)

Brain death can be tricky: A person who is brain dead, meaning their brain is completely inactive, may appear to be simply in a coma and breathing on a ventilator. But is brain death reversible?

Unfortunately not: brain death is permanent. And based on aAmerican book lawsince 1981 it has been considered true death, as final as death when the heart stops.

Until the 1950s, there was no distinction between brain death, because when the heart stopped, the brain, deprived of oxygen, died in a matter of minutes. Conversely, any direct bodily injuryhuman brainSevere enough to damage the areas that control breathing, they inevitably led to cardiac and respiratory arrest. However, the advent of cardiopulmonary resuscitation (CPR), artificial ventilation, and extracorporeal membrane oxygenation (ECMO), which uses a heart-lung machine to oxygenate blood outside the body, has broken this inevitable connection. Now, even if the brain is not working, it is possible to keep the body alive and other organs working, at least for a while.

The rules for recognizing brain death can vary from place to place, and controversy sometimes arises when a patient's family disagrees with the doctor's assessment that their relative's condition is irreversible, or whenA medical error results in a misdiagnosis.. There are also debates about whether brain death should include more tests or criteria. Finally, some religious traditions also oppose brain death on religious grounds. In essence, however, doctors define brain death as the irreversible loss of all brain function, including the brain stem.

How does the brain die?

Brain death, also known as neurological death, is a relatively rare death, according to Dr. Panayiotis Varelas, chief of neurology at Albany Medical College. But it can occur with severe brain damage, either due to brain injury or prolonged lack of oxygen.

Varelas told Live Science that with injury or lack of oxygen, brain cells begin to die. This mass extinction is causinginflammationand edema, locking the brain in a vicious feedback loop: damage leads to edema, which leads to further damage as delicate nerve cells are pressed against the hard shell of the skull. The brain stem is compressed through the foramen magnum, the opening at the base of the skull where the spinal cord connects to the brain. This causes damage to the areas that control breathing and heartbeat. Varelas, meanwhile, said the increasing pressure inside the skull makes it harder for blood to reach the brain. More and more brain cells are dying. When these cells are lost, their complex interconnections are also lost, which can lead to irreversible damage.

Once the patient is down enough of this spiral, brain death is inevitable. In most cases, the rest of the body dies, even if the patient's other organs continue to receive oxygen from the ventilator. Varelas said that the other organs no longer respond to treatment.

"The whole body shuts down, which is a sign of how powerful the brain's control is over the rest of the body," he said. "When the central integrator, the brain, dies, the whole body disintegrates."

Read more:What is brain death? New guidelines provide answers

How is brain death diagnosed?

Brain death, however, means that a person can be pronounced dead before their heart stops beating. This may allow removal of artificial life support devices and useless treatments and, in some cases, allow organ donation. An experienced neurologist or neurosurgeon should perform an examination. To reach this point, several key criteria must be met: there must be a known cause for the patient's condition, consistent with catastrophic damage to the whole brain, and the patient's unresponsive state must not be due to secondary effects. of medication, according to a 2022 journal article: sedation or other potentially reversible causeintensive care diary.

If these conditions are met, the doctor may perform a clinical examination to detect reflexes that depend on a functioning brain stem. Many reflexes are tested, such as the reaction of the pupils to light and the closing of the eyelid when something touches the surface of the patient's eye. Another test involves rinsing the inner ear with cool water. In a patient with a functional brain stem, the eye will move toward this ear as part of a reflex that activates the body's sense of balance. There are also tests involving the gag reflex and other automatic muscle movements.

If a patient shows no signs of brainstem reflexes, doctors perform a final test called an apnea test: they remove the patient from mechanical ventilation to see if he begins to breathe spontaneously. A brain dead patient cannot breathe on his own.

"This is a very, very difficult time for families and for us doctors," Varelas said. Brain death often occurs as a result of medical emergencies or accidents, so the loss of a loved one is often unexpected and extremely difficult to swallow, she added.

Doctors can try to reduce inflammation in the damaged brain and prevent brain death, Varelas said, and treat patients as aggressively as possible until brain death is declared. But once complete brain function is lost, there is no hope of recovery.

"That's why they call it coma dépassé, or 'beyond the coma,'" Varelas said, referring to the name two French neurologists gave the condition in 1959. "Here we're talking about loss of function of the whole brain."

Originally posted on Live Science