Can Humans Function with Only Half a Brain?

Epileptic seizures can be devastating to a child. This is especially true when the epilepsy is severe, causing dozens of seizures each day. Sometimes these seizures cannot be controlled with medication, and the severity and sheer number of them begin to cause injury to the healthy parts of the brain. When this happens, a neurosurgeon may consider the drastic measure of completely removing the half of the brain where the seizures begin. This operation is called a hemispherectomy. It is performed only when a child is very young, because at so young an age our brains are much more adept at recovery and even reinvention.

During a hemispherectomy, the surgeon will cut away a portion of the skull and underlying protective tissue, sever all of the connections between the two sides of the brain, remove the unhealthy half of the brain, and replace the tissue and skull. The resulting cavity is left empty, filling with cerebrospinal fluid in a day or so. The first hemispherectomy was performed at Johns Hopkins University in 1923. Hopkins is still the major hospital for these procedures. The patient must be young for the procedure to be successful. The youngest patient was 3 months old, and the surgery is rarely performed on children older than 10 years old.

Personally, if I was told that my child needed to have half of his or her brain removed, I would be terrified. It seems like such an extreme measure, but is sometimes necessary to save the child in the long run. The good news is that our brains are such amazing organs, there are surprisingly good outcomes from this procedure. Recovery takes about 6 to 8 weeks, and the personality and memory of the patient is left remarkably intact. These individuals are high functioning and have age-appropriate language skills. Another positive outcome is that, once the debilitating seizures have stopped, the patient goes on to live a life that is much improved.

One study was conducted that compared individuals having only one brain hemisphere with individuals with intact brains. The team thought they might find weaker connections in the participants with one hemisphere, since our brain connections usually involve both the right and left sides of our brains. Instead, they found surprisingly normal connectivity. In fact, the surgery patients often had stronger connections than those in the group who had intact brains. One young man who had a hemispherectomy went on to become a state chess champion.

Not surprisingly, there are a few down sides to this surgery. You probably know that the left side of your brain controls the right side of your body and vice versa. After the removal of one side of the brain, the patient loses vision in the eye on the opposite side of the hemispherectomy. They also lose much of the function in the arm on that side. However, choosing between these handicaps and suffering dozens of brain-injuring seizures each day is, if you’ll pardon the pun, a no-brainer.