Brain transplant is not a reality for humans or for any living organism. But there are human research experiments in which transplanted brain cells are used to help treat several diseases that affect the brain. So far, there are very few results and measured outcomes of brain cell transplant, but the concept of transplanting brain tissue has shown some promise in preliminary studies.
If you are interested in having a brain cell transplant procedure, you can talk to your healthcare provider and look for a university or research center where brain cell transplant procedures are being done. These procedures tend to be part of research studies, so you will likely need to enroll in a research study if you want to have this type of treatment.
Reasons for a Brain Transplant
The brain is composed of many different regions and cells. Neurons in the brain have dedicated functions, and they do not typically heal when they are damaged. Parkinson’s disease, stroke, multiple sclerosis (MS), epilepsy, Alzheimer’s disease, and head trauma are among the conditions for which brain cell transplant has been used for humans in an experimental setting.
Parkinson’s disease is a degenerative condition in which neurons in the nigrostriatal region of the brain do not produce dopamine as they normally would. Dopamine is a neurotransmitter that controls muscle function. These cells have been shown to degenerate throughout the course of the disease, causing tremors and slow physical movements. While medication to replace the action of dopamine has been effective in reducing symptoms of Parkinson’s disease, there have been studies in which cells are transplanted into the brain to replace degenerated cells themselves—and, in some instances, the transplanted brain cells can make dopamine.
Alzheimer’s disease is a degenerative condition characterized by memory loss and behavioral changes. This condition typically develops after the age of 65 and it is characterized by degeneration of the cells of the hippocampus, a region of the brain that is associated with memory. There are no medications that can cure Alzheimer’s disease, and some attempts at hippocampal cell transplant have been initiated in animals.
Another type of brain cell transplant, stem cell transplant, has been used in research studies as a treatment for conditions in which the brain cells are damaged, such as stroke, MS, head trauma, and Parkinson’s disease.
While they are not considered true brain cell transplants, retinal and corneal transplants are procedures in which certain parts of the eye are transplanted to treat eye disease. Your eyes are directly connected to your brain with nerves and blood vessels. These types of transplants are better established than brain cell transplants, and they affect the visual areas of your brain.
Types of Brain Transplant
There are several types of brain cell transplantation. Two of the types that are studied in research experiments are autologous stem cell transplant and fetal dopaminergic transplantation.
Autologous Stem Cell Transplant
Autologous stem cell transplantation is injection of your own stem cells into your blood or into your cerebrospinal fluid (CSF). Your CSF is the fluid that surrounds your brain and spinal cord.
Autologous transplant is often considered advantageous because your own cells are more readily available than donor cells, and because your immune system is unlikely to reject your own cells.
Fetal Cell Transplantation
Dopaminegic or hippocampal cell transplantation uses donor fetal cells. In experimental studies, the cells are placed directly into the nigrostriatal area or the hippocampal area with a surgical procedure or into the CSF with intrathecal injection.
Cells that have the potential to develop into the deficient cell (such as dopaminergic cells in Parkinson’s disease or hippocampal cells in Alzheimer’s disease) can be selected and used. Donor cells are considered advantageous because they can be selected, standardized and used for more than one recipient.
It is not completely clear if and why stem cell transplant would help in the treatment of brain disease. Experts have suggested that these cells may develop into the degenerated cells (such as hippocampal cells or dopaminergic cells) and imitate their function. Additionally, it has also been theorized that the injected cells can reduce inflammation in the brain, which may be one of the causative factors of the disease-inducing brain damage.
Whole Brain Transplant
When you think of a brain transplant, you may think of transplant of the whole brain. This is not possible with the current state of technology. The reason that a whole brain transplant is not possible is that the brain is attached to the rest of the body with blood vessels and through the spinal cord.
Arteries in the neck supply the brain with blood. This blood is rich in nutrients and oxygen, and the brain needs these materials to survive. If the blood supply were interrupted during a brain transplant procedure, then the brain would be unable to survive—even for a few minutes.
The brain also sends important hormones to the body through these blood vessels. Organs, such as the kidneys and heart, cannot survive without a constant supply of these hormones.
The brain is attached to the spinal cord. If this physical attachment is cut during a transplant procedure, then the nerves that stimulate muscles to move cannot survive, resulting in permanent paralysis.
Donor Recipient Selection Process
Brain cell transplant can be autologous (using your own cells) or may use donor fetal cells. The use of fetal cells is somewhat controversial because these cells are typically obtained using aborted fetal material—and many people are opposed to using these types of cells.
Certain infections may be more likely with brain cell transplant than with other types of brain surgery. Prion diseases, which are rare conditions caused by harmful proteins, include Creutzfeldt-Jakob disease (CJD). This condition can occur as a complication of corneal transplant and other transplants that involve nerves or nerve tissue. Pre-screening all donor tissue for the presence of this protein is necessary prior to corneal transplant.
Types of Donors
If you are going to have a brain cell transplant, there is a big chance that you will have this procedure as part of a research experiment. The protocol regarding types of donors will be specified as part of the study design.
Autologous stem cells may be obtained from your blood or your bone marrow, depending on the study protocol. Fetal cells may need to be matched to your blood type to improve the chances that the transplant will be successful.
Before surgery, you will need to have a number of diagnostic tests. These may include brain magnetic resonance imaging (MRI) or functional brain imaging tests. You may also need tests that evaluate your brain function, such as electroencephalogram (EEG).
If you are having this treatment as part of a research study, there may also be certain tests you need to take to see if you meet the criteria of the study. For example, some studies specify that participants have had a recent stroke, or a small stroke, or a stroke affecting muscle strength.
Additionally, you may need to have tests to establish your baseline level of functioning before the procedure. For example, you may have a rating that evaluates the severity of your Parkinson’s disease before and after the procedure.
When you have a brain cell transplant, the procedure may be a surgical operation (brain surgery) or it may be an intrathecal (into the spinal canal) injection of cells. Prior to consenting, you will hear about the details of your procedure from your healthcare provider and your medical team.
Injection into the CSF requires an intrathecal injection, which is similar to a lumbar puncture. An intrathecal injection is a procedure in which your healthcare provider cleans a small area on your lower back and places a needle containing the transplant cells into your CSF. This procedure can be uncomfortable, and it doesn’t typically result in complications, although it can cause a headache.
Brain surgery generally includes removal of a portion of the skull so that your healthcare provider can gain access to the brain. Brain surgery is a major procedure that typically entails a long recovery period.
Intrathecal injection can cause a spinal fluid leak, which may cause a severe headache. In some instances, infectious or inflammatory meningitis can occur, causing headaches, a stiff neck, and a fever. The meninges are thin layers of tissue that cover the brain underneath the skull.
There are complications that can occur after a brain cell transplant. Brain surgery may cause bleeding, infections, or blood clots. And after brain surgery or intrathecal injection, the transplanted cells may be rejected, which could result in an ineffective transplant or an inflammatory reaction.
An intrathecal injection generally requires that you lie down for several hours.
After brain surgery, it can take days to feel fully alert again. Recovery may be slow and you will be closely monitored as you recover.
Because brain cell transplant procedures are not well established, it is hard to predict your prognosis. When you are having any type of brain cell transplant procedure, it is important that you learn everything you can about the illness for which you are being treated. Additionally, you can ask your medical team about outcomes of procedures similar to the one you are having and about the anticipated prognosis of the specific procedure you are having.
Support and Coping
Because brain cell transplantation is often an experimental procedure, you can ask about what type of follow up and support you should expect as part of the research. Often, with experimental treatment, there are more frequent follow-up evaluations than there would be with standard medical care.