Hi, Welcome to HealthcareMagic Forum.
I am sorry to tell you this but there is no cure for this, but through effective treatment strategies the symptoms can be controlled. He will have to take the Medicines as directed by his ENT Specialist
. If the medications are not helping, there are surgical treatments like Labyrinthectomy, Vestibular nerve
section or Endolymphatic sac procedures. You should be discussing these Procedures with your Doctor to ascertain which one suits him better .
Wish him Good Health, Take Care.