Quiz Form

Question Date: 17/10/2023

Question: An 8-year-old girl presents with jerky movements of the hands and arms (noted since 3 years of age). She was initially diagnosed with essential tremor based on a family history of perceived tremor in her mother. Now that the patient is in second grade, the jerks have impaired her ability to write. On examination, she is noted to have resting and action-induced axial-predominant myoclonic jerks. While holding a pencil to write, she displays an abnormal hand posture and exacerbation of the myoclonus in the neck<br><br>Which of the following is the most likely diagnosis?

Options:

• Orthostatic myoclonus
• Juvenile myoclonic epilepsy
• Myoclonus-dystonia
• Opsoclonus-myoclonus

Correct Answer: Myoclonus-dystonia

Explaination: This child is manifesting axial-predominant segmental myoclonus as well as dystonia in the hand induced by writing (with exacerbation of the myoclonus in the cervical region). This is consistent with a diagnosis of myoclonus-dystonia, an autosomal dominant disorder. The condition is caused by a mutation in the epsilon-sarcoglycan gene on chromosome 7. Opsoclonus-myoclonus would manifest with abnormal saccadic eye movements as well as myoclonus. Orthostatic myoclonus occurs in adults and is associated with myoclonus in the upright posture. Juvenile myoclonic epilepsy is not associated with dystonia.

Reference: Espay AJ, Chen R. Myoclonus. Continuum (Minneap Minn). 2013 Oct19(5 Movement Disorders)1264-86. doi 10.121201.CON.0000436156.54532.1a. PMID 24092290.