First, the patterns of the dysphonia are different. SD is not usually intermittent, that is, it rarely goes away all together once it begins. Patients with SD often note that they have a good voice for a brief period of time when they first arise in the morning. This is because, like other dystonias, SD disappears during sleep. When voice breaks do occur with MTD, they are different, and can be distinguished by spectral analysis.
Spectral analysis appears to be invaluable in the differentiation of MTDs from laryngeal dystonias.
See the summary table below. For clinicians who want a copy of the manuscript, write to The Voice Center and request one. Even though the site of the lesion of SD remains uncertain, several treatments have been utilized, with varying rates of success. It now appears that the initial success rates and the long-term success rates of recurrent nerve section are quite different. Although it has been suggested that late failures are the result of neural regeneration, the paralysed vocal cord does not regain mobility in these cases.