I'm sorry that your question wasn't answered in a timely manner. Tyler's altered mentation (mental status) in conjunction with autonomic signs (nausea/seeming to vomit) indicate a complex partial seizure rather than one of the vestibular syndromes we see in dogs. We can see nystagmus with these seizures although nystagmus is usually associated with vestibular disorders. Complex partial seizure (previously called petit mal and now also called psychomotor seizure) is described as abnormal focal or asymmetric sensory or motor activity affecting any part of the body and which may be associated with autonomic signs, (salivation, vomiting, e.g.) and is associated with a change in mentation (mental status) and/or behavioral abnormalities. Sleep is the most common post-ictal (post-seizure) symptom. Mark your calendar for this event and for just what you witnessed. Tyler's vet will need all the information you can gather when deciding if Tyler should be prescribed an anticonvulsive drug. Most of us will accept one mild (lasting less than 5 minutes, no thrashing about, no loss of consciousness) event monthly before prescribing such a drug. Should Tyler suffer another event within 24 hours of a previous one clustering is diagnosed and that may presage status epilepticus - the state in which seizure activity doesn't abate unless I heavily sedate or anesthetize my patient. He would then need the attention of a vet at your earliest convenience.
Seizures first arising between the ages of 1-5 years are usually considered idiopathic (unknown cause) epilepsy. Seizures arising after 6 years of age are often caused by brain tumor or, less commonly, adult onset epilepsy. Please respond with further questions or concerns if you wish.