The most direct effect of severing the corpus callosum would be that

Corpus callosum connects the hemispheres of the brain. It is consisted of around 200 million axons, and it is primarily used to integrate sensory, cognitive and motor performances of the two sides of the cerebral cortex. It is essential in sharing information, but for people with epilepsy, it serves as a bridge that transmits seizure impulses. Cutting or severing the corpus callosum is the best surgical treatment for patients with severe epilepsy. For normal individuals, this can result in poor coordination between the right and left side of the brain.