Here is a video of a dog that presented with acute vestibular disease.  Note the nystagmus, which is the movement of the eyes back and forth:

What are the symptoms?

Classically, a head tilt is present.  There is often a nystagmus.  Patients are nauseous and sometimes have a history of vomiting or not eating.  In severe cases they are often non-ambulatory and have a history of falling or rolling to the side (the equilibrium is abnormal).

With peripheral disease, there are no other cranial nerve deficits (except in Horner's syndrome when CN VII is affected) and no postural reaction deficits.  If there is lack of conscious proprioception or other cranial nerve deficits are present, then it is most likely due to a central (brain) lesion. (i.e. decreased gag reflex, decreased tongue movement, decreased facial sensation) Central cases also often have mentation changes.

Peripheral vestibular disease is caused by pathology in the inner ear region.  Because of the way the nerves exit from the brainstem, the facial nerve can be affected, and Horner’s syndrome can occur.

What is the cause of this syndrome?

There are several possible causes:

1. Idiopathic- often called “old dog vestibular”, the cause is unknown. Patients often recover from the disease with supportive/nursing care within a week.
2. Neoplasia
3. Hypertension- a vascular accident or blood clot to the nervous system (often referred to as a "stroke")
4. Trauma/inflammatory
5. Inner ear disease/infection
6. Drug toxicity (metronidazole)

How is it treated?

1. Patients are placed on an anti-emetic to help with nausea. Meclizine (Dramamine) or maropitant (Cerenia) are most commonly used.
2. Supportive care/nursing care are important to prevent injury.
3. Treat the underlying cause if identified and applicable. (Hypertension, ear disease, metronidazole toxicity, etc.)

Brain imaging using MRI can be helpful to look for an underlying cause so appropriate therapy can be instituted.