Up to around age 10 or so, GL would lose all ability to speak or respond to speech during a meltdown. We found that he could, however, respond to sign. If I gave verbal instructions, he couldn't process them, but by signing, I could get him to a calming environment (usually the bathtub.) We set about learning ASL as a family. An ASL interpreter in our church gave us lessons. We later moved away and haven't found another teacher and, while it is still difficult, he can now process speech to some extent during a meltdown. (He can also speak, usually yelling inappropriate things.) But I mention this because it was helpful to us at the time. Now when he gets annoyed, but before he gets to angry shouting, he will sign "No!" or "Sit Down!" repeatedly at the person he's frustrated with.