I know someone who suddenly had severe vertigo recently and was diagnosed with labyrinthitis, inflammation of inner ear. Other ear conditions can cause vertigo.
If you know how to use Kent's Repertory, you can search 10 pages of vertigo rubrics.
For example, sudden, is a rubric within vertigo that would help narrow down remedy choices.
http://www.homeoint.org/hidb/kent/repertory.htm
Of interest, NYU Langone Medical Center found a homeopathic combo remedy Vertigoheel worked as well as usual allopathic drug treatment, here antihistimines.
Since we discourage use of combos here as being non-classical and possibly vital force damaging, you can look at the remedies within the combo, Ambra grisea, Conium, Petroleumm, and Cocculus, then use the Reversed Kent Repertory to see which remedy best fits your situation.
http://www.homeoint.org/hidb/kent/index.htm
As mentioned in the study, there are 2 opposing remedies in the combo where one could make vertigo worse, the other better, depending on the type of vertigo you have. Thus the issue with combos.
http://www.med.nyu.edu/content?ChunkIID=38345
Susan