Objective: To evaluate the diagnostic and treatment strategies in Myoclonus Dystonia Syndrome (MDS) used by experts from the European Reference Network for rare neurological diseases (ERN-RND).

Background: MDS is a rare genetic movement disorder characterized by myoclonus, dystonia, and psychiatric comorbidity [1-3]. Mutations in SGCE are the most frequent cause [4]. No targeted therapies are available and oral medications have limited efficacy. Bilateral deep brain stimulation (DBS) is effective in severe cases [5].

Method: A questionnaire was distributed among neurologists from ERN-RND, addressing: experts and demographic information, clinical and genetic tools, and management.

Results: 29 adult and child neurologists (86% movement disorders experts) from 14 countries replied. 69% of patients were diagnosed in childhood. In half of the cases, it took >3 years from the disease onset until the expert’s evaluation. 89% applied diagnostic criteria [6]. The majority (68%) did not use specific tools to assess myoclonus, while 76% used dystonia scales (BFM and UDRS). Despite all experts asked for psychiatric symptoms, only 25% referred for formal psychiatric evaluation. 97% of experts recognized potential difficulties on school performance. Genetic diagnosis was offered in 75% of cases, and >50% had mutations in SGCE. The most effective drugs were benzodiazepines, levetiracetam, and trihexyphenidyl; however, drug-resistance (> 3 drug trials) was reported in the majority. Botulinum toxin (cervical, upper limbs, cranial) was used by 65%, with 25-75% efficacy. DBS was offered to most severe cases obtaining >50% efficacy in 86%. Treatments for psychiatric symptoms were mainly serotonin re-uptake inhibitors (n=19) and benzodiazepines (n=12), with limited efficacy.

Conclusion: MDS is well known among movement disorders experts; however, there´re delays in referring patients to the specialist. A systematic assessment is usually followed and early genetic confirmation is offered in most cases. There are variable opinions about pharmacological treatments, and most of them are found to have limited efficacy for motor and non-motor symptoms. Botulinum toxin and DBS are identified as options in selected patients. A survey for patients and families is being distributed to assess their opinion about the diagnostic and treatment strategies being offered.

References: 1. Asmus F, Gasser T. Inherited myoclonus-dystonia. Adv Neurol. 2004;94:113-9. 2. Peall KJ, Dijk JM, Saunders-Pullman R, Dreissen YE, van Loon I, Cath D, et al. Psychiatric disorders, myoclonus dystonia and SGCE: an international study. Ann Clin Transl Neurol. 2016;3(1):4-11. 3. Timmers ER, Smit M, Kuiper A, Bartels AL, van der Veen S, van der Stouwe AMM, et al. Myoclonus-dystonia: Distinctive motor and non-motor phenotype from other dystonia syndromes. Parkinsonism Relat Disord. 2019;69:85-90. 4. Nardocci N, Zorzi G, Barzaghi C, Zibordi F, Ciano C, Ghezzi D, et al. Myoclonus-dystonia syndrome: clinical presentation, disease course, and genetic features in 11 families. Mov Disord. 2008;23(1):28-34. 5. Kosutzka Z, Tisch S, Bonnet C, Ruiz M, Hainque E, Welter ML, et al. Long-term GPi-DBS improves motor features in myoclonus-dystonia and enhances social adjustment. Mov Disord. 2019;34(1):87 6. Roze E, Lang AE, Vidailhet M. Myoclonus-dystonia: classification, phenomenology, pathogenesis, and treatment. Curr Opin Neurol. 2018;31(4):484-90.

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MDS Abstracts - https://www.mdsabstracts.org/abstract/diagnosis-and-management-of-myoclonus-dystonia-syndrome-a-survey-of-the-european-reference-network-for-rare-neurological-diseases/