How to treat a person with moderate to severe receptive and expressive language disorder?

At what age? What : are the person's non-verbal abilities? What is the genetic or other medical cause of the person's Neurodevelopmental Disorder? Remediation is more successful in children, especially if begun in infancy or < age 2; circumvention, in older children & adults. Give verbal information at the person's language level, promote his verbal expression & find alternate methods of communication for him.