After my brother constantly complained about headaches, strange sensations in his left leg and arm a regular doctor checkup turned out to be just the start of a horrible nightmare. CT scan showed the symptoms are caused by right temporal lobe tumor. Since then his speech has also become kinda slurry and we’re waiting for surgery for the tumor to be removed, but it is simply devastating to watch him getting worse and not know what benefits will the surgery and the radiation he will also undergo afterward bring. In the worst case scenario, which brain functions can get lost if his right temporal lobe gets too damaged either by the tumor or by the surgery?

Thanks for any help,