what is causing my dogs nightly head shaking episodes?

if anyone has experienced this I'd be eternally grateful for a response - vet can't come till Tuesday. Dog is 13, has had vestibular disease, arthritis and hypothyroidism, all of which are controlled through medication. She is fine daily, eating, drinking and going out outside. But every night this week, approximately 30 minutes after eating she starts shaking her head and rubbing her head on the floor for 20-30 minutes. She is obviously in discomfort during this time but only for 20-30 minutes every night after dinner. I've changed food from Blue to Evo and tonight reduced her thyrotab from 1/2 to 1/4. With dinner she gets the thyrotab and 500 mg of Glucosomine or Cosequin. With breakfast she gets 1/2 Previcox, 1/2 8mg Thyrotab, 500 mg of Glucosimine. She is normal all day but every night after dinner these episodes begin for 20-30 minutes. This doesn't seem to be idiopathic head tremor because she's voluntary shaking her head as if she's trying to get something out of it.

Asked by Member 1151927 on Jan 26th 2013 Tagged headshaking in Health & Wellness