Pediatric paroxysmal movement disorders - A clinical epidemiological study in an Irish cohort

Background: Paroxysmal movement disorders (PxMD) are characterized by episodic involuntary movements and include paroxysmal dyskinesias (PD) and episodic ataxias (EA). Although reported in the medical literature since 1892, the exact prevalence in children is unknown. Objectives: To determine the prevalence and clinical characteristics of PxMD in the pediatric population in the Republic of Ireland. Methods: Cross-sectional cohort study across pediatric neurology services in the Republic of Ireland incorporating retrospective chart, telephone and clinical reviews. Results: Seventy-nine cases met the inclusion criteria (PD = 37, EA = 38, Alternating Hemiplegia of Childhood = 4). Point prevalence for all PxMD was 6.5 cases per 100,000 persons aged less than 18 years (PD 3/100,000, EA 3.1/100,000, Alternating Hemiplegia of Childhood 0.3/100,000). Sixty-four cases were clinically reviewed by the research team (PD = 33, EA = 31). A cause was identified in 38 % (24/64). The highest investigation yield was from single-gene testing (38 %, 9/24) followed by gene panels (25 %, 11/44). Variable evolution patterns were seen. In PD, 55 % (18/33) resolved and 30 % (10/33) improved. This was due to medication in 61 % (20/33), trigger avoidance in 6 % (2/33) and spontaneous remission in 18 % (6/33). In EA, 45 % (14/31) resolved and 42 % (13/31) improved, with spontaneous remission or improvement in 48 % (17/33). Discussion: This study adds to the PxMD knowledge base by determining PxMD prevalence in a pediatric population for the first time. This prevalence is higher than previous adult population estimates. An aetiology was identified in one-third. A large proportion can expect symptom improvement either with medications, trigger avoidance or spontaneous remission over time.