Hearing outcomes
All groups of patients with UMD exhibited a mean tonal threshold
corresponding to moderate hearing loss, with a greater degree of
low-frequency hearing loss at the beginning of the disease. These
thresholds evolved to a more severe degree of hearing loss by the end of
follow-up.
Significant differences were observed when the extent of hearing loss
was considered in association with the different clinical models (Table
2).
4.DISCUSSION
Evolution of vertigo episodes and clinical models
Understanding the general evolution of vertigo episodes and taking into
account our clinical experience and the individual revision of each
case, we observed that the evolution of vertigo episodes differed
considerably between cases during the first 10 years of the disease. We
decided to define a series of criteria according to which the whole
cohort of patients could be assigned to different subgroups.
We defined a series of subgroups based on the evolution and behaviour of
vertigo episodes, although there are many ways of grouping the clinical
variations typical of MD (6–8).
In our view, the most relevant work in this regard is that in which five
subgroups of patients were defined (7): classic MD, delayed MD, familial
MD, MD associated with migraine and MD associated with autoimmune
disorders. In our models, familial association and a history of
autoimmune diseases are not taken into account, although some
hypothetical associations and comparisons could be made with these
groups. Our model number 2 was that in which patients most frequently
also suffered from migraine and that in which there was an earlier
disease onset, as previously reported for the subgroup of patients with
MD associated with migraine. Model number 3 had the highest proportion
of patients that suffered a Tumarkin crisis and no patient with
migraines, and it was the model in which the patients experienced the
largest number of vertigo episodes, as reported previously(7), as the
subgroup of patients with MD associated with autoimmune diseases.
Accordingly, in different studies in this field groups of patients have
been classified based on specific criteria(6,7). However, as they share
common features, it would appear that there are different forms of MD
that can be distinguished on the basis of the criteria used in these
studies.