Recurring hearing loss (low frequencies) & vestibular loss

I have a recurring problem where I partially lose the hearing in one of my ears.

The sequence of events is:

1) First I start noticing a severe low frequency pulsatile tinnitus in one ear.

2) Then I no longer hear low frequency sounds in that ear (it sounds like people have inhaled helium and are talking in a high squeaky voice)

3) After that I notice a general loss of hearing, still with a pronounced loss of low frequencies, and the odd feeling that ear is "full".

4) The ear the regains hearing gradually in a period of several days.

This has happened six or more times in my left ear, and twice in my right ear.

Also, eight months ago I suffered a severe loss of vestibular function, which was diagnosed as bilateral vestibular loss, possible due to viral labyrithitis and destruction of the labyrinth(s) via an overly aggressive immune reaction. The vestibular problems persist despite six months of vestibular physiotherapy.

I have discussed this hearing loss with several ENT's and they are perplexed. Also any advice re the vestibular problem would be appreciated.

Thanks!