Vestibular DCI

After diving on 40 meters, about one hour, a diver felt very intensiv vertigo and start vomiting. They went to Sibenik to hospital, and diagnosis of decompressin sicknes was established (vestibulocohlear form). He was transported to hyperbaric chamber in Split, where they have started with hyperbaric treatment. For now, he is in hospital, neurologic department, with hyperbaric oxygen sesson every day. I am going to visit him tomorrow.
Interest thing is that incident happens after the perfectly normal profile of diving. Most of all, the decompression was made with oxygen (without cutting). My question is, could it be a neuronitis vestibularis instead of decompression sickness, and how differential diagnosis is achived. Please, let me hear your opinion.

The possibility of a labyrintitis cannot be excluded, the coincidence with a relatively deep dive is suspect - even in the presence of oxygen use during decompression.
No test - electrophsysiological or CAT / MR imaging - would help to resolve the problem, I am afraid. Have all the clinical tests been performed to exclude a damage of the round window and a possible perilinph fistula? This would match with the delay in onset. Have there been any - even slight - problem with ear-drum equalization during the dive? The oto-neurologists will immediately spot the difference between a central and a peripheral oto-neurological damage, and this will help our differential diagnosis. Is there any hearing loss? As an additional investigation, the possibility of a PFO should also be considered for future reference and prevention.
The fact that there is a response to HBO will also be not so enlightening, as it is known that inner ear acute vascular or barotraumatic injuries can be positively affected by HBOT.