A benign neurological voice disorder caused by laryngeal dystonia. Atypical cases of spasmodic dysphonia (SD) may be challenging to diagnose, even by clinicians with some experience with the disorder. Examples of reasons that this may be so: In the atypical case, contrary to what is usually seen, singing may be more affected than talking; falsetto/head voice may be more affected than chest voice, and so forth. There may also be no phonatory arrests in the less common tonic variant spasmodic dysphonia.