Is segmental/multifocal onset a distinct presentation of idiopathic adult-onset dystonia?

Background: Idiopathic adult-onset dystonia (IAOD) is classically considered to begin focally, although segmental or multifocal onset has been reported in retrospective series. Whether this reflects a true early presentation or recall bias remains uncertain. Objectives: To determine whether segmental/multifocal onset represents a distinct presentation of IAOD and to assess whether these patients differ from those with focal onset. Methods: We analyzed dystonia body distribution at first neurological evaluation in 863 patients from the Italian Dystonia Registry, all examined by expert neurologists within one year of symptom onset to minimize recall bias. Results: Segmental or multifocal onset occurred in 10 % of cases. This proportion remained stable across increasing intervals between symptom onset and first evaluation, arguing against recall bias. Patients with segmental/multifocal onset did not differ from those with focal onset in sex, age at onset, family history of dystonia, frequency of thyroid disease, or subsequent spread to additional body regions. Conclusions: IAOD can present with segmental or multifocal onset, and this is unlikely to reflect recall bias. Moreover, patients with segmental/multifocal onset do not differ in factors potentially linked to disease initiation or subsequent spread compared with those with focal onset. These findings may have implications for prognostic counseling in IAOD.