Abstracts

Rationale: A number of movement disorders have been reported to be associated with the administration of antiseizure medications (ASMs). In this systematic review, we aimed to identify and catalogue the abnormal movements associated with ASMs and record relevant clinical and demographic characteristics of patients manifesting these movement disorders.

Methods: We conducted a systematic literature review following PRISMA guidelines of all current ASMs (33 different drugs) and movement disorder phenomenology by searching CINAHL, Cochrane Library, EMBASE, MEDLINE, PsycINFO, and Scopus from inception to April 2021. We excluded studies that were not in English, not peer-reviewed, limited to animal studies, or contained no original data. The included reports must have been focused on a movement disorder that developed de novo in association with an ASM. We categorized the onset of the movement disorder as acute if it developed within 3 days of the initiation of ASM or its increased dose, subacute if it developed between 3 days and 3 weeks later, and chronic if developed with latency >3 weeks. Due to the large volume of studies identified by the search, in this preliminary analysis, we limited the review to case reports and case series with ≤ 5 patients.

Results: The search yielded 7469 manuscripts, of which 269 fulfilled eligibility criteria. In the analysis of all studies published since 2006 (n = 132), new onset movement disorders were reported in 159 patients taking 15 different ASMs. The median age of patients was 40 (interquartile range, IQR 18-63) years, and 54% were female. The ASMs were indicated for seizures in 102 (64%) of the patients. The most frequent culprits associated with movement disorders were lamotrigine, phenytoin, valproic acid, gabapentin, and pregabalin. The most commonly reported movement disorders were ataxia (35, 22%) and myoclonus (35, 22%) followed by various orofacial dyskinesias (28, 17.6%) and different types of nystagmus (28, 17.6%). Of the reports that had latencies to onset of abnormal movements recorded, the onset was acute in 48 (31%) patients, subacute in 30 (19%) patients, and chronic in 79 (50%) patients. In most patients, abnormal movements resolved following discontinuation of the ASM (75%). Of 135 patients with a reported complete resolution or substantial improvement of symptoms, 63 (47%) improved within 3 days following cessation or dose reduction of the ASM.

Conclusions: Several commonly used ASMs have been found to be associated with new-onset movement disorders, which were largely reversible following dose adjustment or medication discontinuation. Further work will be focused on identifying the clinical and demographic factors that may contribute to the higher risk of developing these disorders in patients using ASMs.

Funding: Please list any funding that was received in support of this abstract.: O.T. received AES Junior Investigator Research Award and AES-NORSE Seed grant.