Movement Disorders in Patients With Genetic Developmental and Epileptic Encephalopathies.

Abstract

Movement disorders are underrecognized in the developmental and epileptic encephalopathies (DEEs). There are now over 800 genes implicated in causing the DEEs; relatively few of these rare genetic diseases are known to be associated with movement disorders. We identified patients with genetic DEEs who had movement disorders, classified the nature of their movement disorders and asked whether specific patterns correlated with the underlying mechanism. We classified the type of movement disorders associated with specific genetic DEEs in a large international cohort of patients and analysed whether specific patterns of movement disorders reflected the underlying biological dysfunction. Our cohort comprised 77 patients with a genetic DEE with a median age of 9 (range 1-38) years. Stereotypies (37/77, 48%) and dystonia (34/77, 44%) were the most frequent movement disorders, followed by chorea (18/77, 23%), myoclonus (14/77, 18%), ataxia (9/77, 12%), tremor (7/77, 9%) and hypokinesia (6/77, 8%). In 47% of patients, a combination of movement disorders was seen. The movement disorders were first observed at a median age of 18 months (range day 2 - 35 years). Dystonia was more likely to be observed in non-ambulatory patients, while ataxia was less likely. In 46% of patients, therapy was initiated with medication (34/77, 44%), DBS (1/77, 1%), or intrathecal baclofen (1/77, 1%). We found that patients with channelopathies or synaptic vesicle trafficking defects were more likely to have dystonia; whereas, stereotypies were most frequent in individuals with transcriptional defects. Movement disorders are often underrecognized in patients with genetic DEEs but recognition is critical for the management of these complex neurological diseases. Distinguishing movement disorders from epileptic seizures is important in tailoring patient treatment. Understanding which movement disorders occur with different biological mechsnisms will inform early diagnosis and management.