The Wada test (internal carotid artery isopentobarbital test, IAP) was first reported and used clinically by John Wada in 1949, and is now widely used for preoperative assessment of language, memory, and motor function and to assist in the determination of epileptogenic foci, and has become an important preoperative assessment method for patients requiring hemispherectomy, anterior temporal lobectomy, or resection of epileptic foci. When the time interval between the two hemispheres is less than 30 seconds, the presence of bilateral language dominance should be considered. (1) The most common type: if there is language loss or impaired language function (dysarthria, dysphasia) on one side after drug injection, but language function is not affected on the opposite side after drug injection, then the drug-injected side is the dominant hemisphere. (2) Rare types: ① All language functions are disrupted after drug injection in one hemisphere, while a slight but meaningful language disruption occurs after drug injection in the contralateral side. (ii) Separation of types of language deprivation (e.g., naming disorder on one side and comprehension disorder on the other). ③ Equally pronounced language disruption in both hemispheres. ④ No significant language disruption was found in either hemisphere. 2. Memory function (1) Prediction of complete amnesia after temporal lobectomy It is difficult to rely on IAP to accurately predict postoperative amnesia, and the following is a guideline: ① Those who still have good memory function (able to pass IAP) after drug injection in the ipsilateral hemisphere of the epileptogenic focus will mostly not have significant amnesia after surgery. (2) For those with poor memory function (unable to pass the IAP) after ipsilateral hemisphere injection, the risk of memory loss after surgery is high, and the surgery is often abandoned or the hippocampus and parahippocampal gyrus are resected in a controlled manner. Even so, the residual memory capacity after surgery may be reduced to varying degrees. (2) Prediction of selective memory deficits The prediction of selective memory deficits after temporal lobectomy by IAP is a challenging task. Drug injection contralateral to the epileptogenic focus is important in predicting alterations in material-specific memory after surgery, and patients with left temporal lobe epilepsy with high memory scores in the contralateral IAP test are at greater risk for postoperative verbal memory deficits. 3. Motor function The deficit of motor function after surgery can be simulated by the changes in limb motor function after drug injection. Especially in patients with extensive hemispheric brain damage, the IAP can provide insight into residual motor function, which is especially important in patients proposed for hemispherectomy. 4. Lateralization of the epileptogenic area IAP is most significant for patients with amnesia and a decrease in memory scores of 33% or more compared to the contralateral side in IAP.