Evolution of vertigo episodes and clinical models
In the UMD group of patients, the mean incidence of annual episodes reached a maximum value of 7.56 in the first year (SD ±13.68), 4.36 (±7.44) in the second year, and 2.94 (± 5.47) in the third and fourth years of follow-up. Subsequently, the number of episodes stabilized to a value of less than 2 episodes per year until the tenth year, and they reduced until there was a cessation in the episodes in subsequent years (figures 1 and 2).
In the subgroup of patients followed from the onset of the disease, after analysing each case individually, specific criteria were defined by which all these patients can be grouped into 3 behavioural or evolutionary models based on the number of vertigo episodes/year experienced during the first 10 years of the disease (Figure 3).
Model 1: Sudden onset with no further episodes from the fourth year after disease onset. These patients experience episodes of vertigo in consecutive years during the first four years of the disease (N=39, 44.8%).
Model 2: Sudden onset followed by a period of relapse. Episodes of vertigo are experienced in the first four years of the disease followed by a period with no episodes that lasted for at least one-year, with a subsequent relapse or occurrence of episodes of vertigo in one or more consecutive years (N=30, 34.5%).
Model 3: Multiple relapses throughout the course of the disease or with a worst evolution. During the first 10 years of disease, episodes of vertigo are recorded in at least 7 years, whether consecutively or followed by intercritical periods of one or two years with no episodes (N=18, 20.7%).