hemispherectomy. To confirm this candidacy, a set of tests is required that usually includes electroencephalograph (EEG ), brain imaging in the form of brain magnetic resonance imaging (MRI ) and in certain cases further testing such as positron emission tomography (PET) and functional MRI (fMRI) are also required. The EEG shows the electrical signature of seizures. Brain MRI helps determine the presence of lesions and their exact location. PET scans help determine the level of metabolism of the brain where areas of the brain that produce seizures typically show a low level of metabolism. Functional MRI helps determine the presence of any functions based on alteration in the blood flow and response to certain tasks. It should be noted, however, that not all tests are required in order to make the determination whether hemispherectomy is applicable or not, rather there is a degree of variation between different patients. The determination of which kind of hemispherectomy procedure is most suitable for a patient depends on multiple factors including the kind of pathology that caused epilepsy, the anatomy of the brain, and the experience of the neurosurgeon. However, anatomical hemispherectomy is almost never utilized anymore given the high rate of complications, rather variations of functional hemispherectomy are the mainstay of treatment. Outcomes Hemispherectomy is arguably the most successful surgical procedure among all procedures used to treat epilepsy. Regardless of the kind of hemispherectomy, whether anatomical or functional, seizure freedom is achieved in 80-90% of patients. A recent study compared the different subtypes of functional hemispherectomy and found that they were all equally successful in treating seizures. Furthermore, with advancements in surgical techniques, anesthesia and perioperative care, the risks of severe complications such as cerebral hemosiderosis and death have greatly diminished. The improvement after hemispherectomy is not limited to seizure control, as there is a comprehensive body of literature showing that early seizure control results in developmental and cognitive gains in most patients undergoing hemispherectomy. This is thought to be a result of removing the negative impact of seizures on the good hemisphere allowing it to "reorganize" its functions due to the plasticity of the brain. The plasticity is most evident in young children, in whom hemispherectomy is mostly utilized. In fact, it has been shown that the brain in the first few years of life is able to significantly recover major functions such as memory and language after hemispherectomy further supporting the