Abstract

Professor Marina A. J. de Koning-Tijssen (http://www.rug.nl/staff/m.a.j.tijssen/) is a clinical expert in the area of hyperkinetic movement disorders. Following her residency in neurology, during which she worked at Johns Hopkins University, Baltimore, MD, USA, and at the Institute of Neurology and Neurosurgery, University College London, UK, she established what has become an internationally renowned group working on movement disorders. The group was initially in based Amsterdam, but since 2012 it has been hosted by the University Medical Centre Groningen, Netherlands. She supervises PhD students performing genetic and translational research into dystonia syndromes and jerky movements, and her research covers the whole field from basic to clinical research. She has strong collaborative links in the Netherlands, which have led to the Dutch network ‘DystonieNet'. Internationally, she leads the clinical line of the European COST dystonia platform and is a member of several of the Movement Disorder Society's committees.

Patients with hyperkinetic jerky movements can suffer from mycolonus, functional jerks, or a tic disorder. Differential diagnosis can be difficult in this borderland between neurology and psychiatry and even experienced movement disorder specialists only moderately agree on the clinical diagnosis of these jerky movements.¹

Clinical diagnosis is mainly based on positive clinical symptoms. Electrophysiological tests, like electromyography (EMG), polymyographic-EMG and Readiness Potentials can be supportive for one of the diagnoses, but sensitivity and specificity of these tests is lacking.

Symptom characteristics, disease course, psychopathology and supportive neurophysiologic tests in organic and functional jerks can discriminate between the types of jerks. Supportive features of a functional jerk are: sudden onset, precipitation by a physical event, variable, complex and inconsistent phenomenology, suggestibility, distractibility, and entrainment. With electrophysiological testing the presence of a readiness potential is supportive.² It should be noted that functional jerks and tics present with many overlapping features. Specific symptoms supporting the diagnosis of a tic are: symptom onset in childhood, waxing and waning, presence of a premonitory urge, rostro-caudal development of the tics, and the ability to suppress the tic to a certain degree.³ Organic forms of myoclonus have a broad phenotypic spectrum. The clinical and electrophysiological features are mainly based on the anatomical origin of the myoclonus: cortical, subcortical, spinal and peripheral. Supportive for the diagnosis myoclonus are the insidious onset, simple and consistent phenomenology, and response to medication like Clonazepam.⁴ Specific features with electrophysiological tests include short burst duration, consistent pattern with polymyographic-EMG and a cortical correlate.