Hemispherectomy is a neurosurgical procedure in which a cerebral hemisphere (half of the upper brain, or cerebrum) is removed or disconnected. It is used to treat a variety of refractory or drug-resistant seizure disorders (epilepsy).
Results
Overall, hemispherectomy is a successful procedure. A 1996 study of 52 individuals who underwent the surgery found that 96% of patients experienced reduced or completely ceased occurrence of seizures post-surgery. Studies have found no significant long-term effects on memory, personality, or humor, and minimal changes in cognitive function overall. For example, one case followed a patient who had completed college, attended graduate school and scored above average on intelligence tests after undergoing this procedure at age 5. This patient eventually developed "superior language and intellectual abilities" despite the removal of the left hemisphere, which contains the classical language zones.
When resecting the left hemisphere, evidence indicates that some advanced language functions (e.g., higher order grammar) cannot be entirely assumed by the right side. The extent of advanced language loss is often dependent on the patient's age at the time of surgery. One study following the cognitive development of two adolescent boys who had undergone hemispherectomy found that "brain plasticity and development arise, in part, from the brain's adaption of behavioral needs to fit available strengths and biases...The boy adapts the task to fit his brain more than he adapts his brain to fit the task." Neuroplasticity after hemispherectomy does not imply complete regain of previous functioning, but rather the ability to adapt to the current abilities of the brain in such a way that the individual may still function, however different the new way of functioning may be.
Christina Santhouse (now Paravecchia) underwent a hemispherectomy on February 13, 1996, performed by Ben Carson when she was eight years old. Previously, she had had Rasmussen's encephalitis, which caused her to experience around 150 seizures a day. After the surgery, her family was told that she would never be able to do many normal activities, such as driving a car or holding a normal job. However, she far surpassed everyone's expectations by going on to earn a master's degree in speech pathology and by getting married and having children of her own.
Traumatic hemispherectomy
There are cases where a person that received major trauma to one side of the brain, such as a gunshot wound, and has required a hemispherectomy and survived. The most notable case is that of Ahad Israfil, who lost the right side of his cerebrum in 1987 in a gun-related work accident. He eventually regained most of his faculties, though he still required a wheelchair. It was noted that reconstructive surgery was difficult due to the gunshot shattering his skull, and he lived with a large indentation on that side of his head.