Comparative study between idiopathic and non-idiopathic dystonia: a prospective observational study

Background: There are very few studies based on the updated dystonia classification. However, a comparison of the idiopathic and non-idiopathic dystonias based on the newer classification has not been done previously.

Objectives: To study and compare the clinicoetiological profile of patients with idiopathic and non-idiopathic dystonia attending a movement disorder clinic of a tertiary care teaching institution.

Methods: All the consecutive dystonia patients from October 2017 to September 2019 fulfilling the inclusion criteria were subjected to a detailed clinical evaluation. Investigations were performed as per requirement. Patients were classified according to the consensus update on phenomenology and classification of dystonia.

Results: A total of 183 patients with dystonia were included, with 61.7% (113) males and 38.3% (70) females. The idiopathic group revealed a significantly earlier age of onset with cases slightly outnumbering (n = 96/183, 52.5%) the non-idiopathic group (n = 87/183, 47.5%). Focal dystonias were the commonest type in both the idiopathic (n = 58/96, 60.4%) and non-idiopathic groups (n = 30/87, 34.5%), while generalized dystonia accounted for 26.4% (n = 23/87) of the non-idiopathic cases and only 3.1% (n = 3/96) of the idiopathic cases. The majority of idiopathic cases were isolated dystonia (n = 93/96, 96.9%), while all hemidystonias were non-idiopathic.

Conclusion: Focal dystonias were the commonest in both idiopathic and non-idiopathic groups, while generalized dystonia was significantly commoner in the non-idiopathic group. Acquired causes like drugs, perinatal insult were the commonest etiology in the non-idiopathic group. Hemidystonia was found exclusively in the non-idiopathic acquired group.