Intermittent explosive disorder (IED) is characterized by a difficulty to resist the urge to carry out a recognized harmful behavior. The central symptom is aggressiveness, expressed in isolated episodes. Executive function impairments are habitually found in impulse control disorders. Neuropsychology of impulsivity is related to dysfunctions in the orbito-frontal cortex, dorsolateral cortex and anterior-cingulated regions, being consequently involved in cognitive mechanisms of inhibition. Lesions in those areas are common in IED. In the most severe cases of IED, surgical procedures are required for treatment. In this study, we examined JML; a patient suffering from a severe case of IED. He experienced frequent episodes of auto and heteroaggression and multiple psychiatric admissions, and thus stereotactic surgery was the recommended treatment. The procedure consisted of an electrode situated lateral to the lateral ventricle, targeting the projections between frontal and subcortical affected regions. We aimed to study the neuropsychological functioning of JML, before and after electrode implantation. Our results suggested that surgery in IED improves cognitive performance at some levels. JML significantly improved his cognitive flexibility, measured with WCST, and alternate attention assessed with CPT and TMT-B tests, after electrode implantation. Cognitive flexibility deficits may be also related to increased aggressiveness. Therefore, improvements at this level may involve a reduction of impulsivity and aggressive behavior.