Objective: To report three patients with atypical causes of myoclonus which were completely reversible.

Background: Myoclonus is characterised by sudden brief jerky movements caused by abrupt muscle contraction or sudden cessation of ongoing muscular activity. Given the large number of possible causes of myoclonus, it is essential to take a good history, clinically characterize myoclonus and to look for additional findings on examination in order to limit the list of possible investigations.

Method: This is a series of three cases which demonstrate three unsual causes of reversible myoclonus.

Results: Case 1: A 55-year-old lady presented with tremulousness of both upper limbs for three months associated with excessive daytime hypersomnolence. She was under therapy with amisulpride 400 mg/day for three years for a psychiatric diagnosis of depression with somatisation. On examination, there were bilateral arythmic jerky movements involving fingers of both upper limbs with dystonic posturing of left hand [Video 1], on posture holding, not present at rest without any worsening on action. The diagnosis of amisulpiride-induced tardive myoclonus was made; the offending drug was stopped and at one month of follow-up, her MMSE score was 30 with complete resolution of myoclonus.

Case 2: A 42-year-old lady on treatment for MS with teriflunomide 14 mg per day, presented with upper limb tremulousness for one month. On neurological examination, she had bilateral asterixis of the upper limbs, with higher amplitude on the right side (Video 2) with no ataxia, rest or intention tremor, loss of proprioception or stimulus sensitivity. She was treated with intravenous methylprednisolone with complete response.

Case 3: A 39-year-old woman presented with a month history of episodic painful spasms of her lower limbs, abnormal posturing of her upper limbs and involuntary jerky movements of both upper and lower limbs. (Video 3). There was Grade 3 bilateral symmetrical appendicular rigidity in all four limbs with distal predominant myoclonus and myoclonic jerks of the abdominal muscles at rest, increased by action with no aggravation by any external stimulus. Anti Thyroid Peroxidase antibodies were elevated (1200 IU/L). She recovered completely with steroids.

Conclusion: Accurate identification of the etiology of a myoclonic syndrome is essential, which can expedite recovery and appropriate patient outcomes

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MDS Abstracts - https://www.mdsabstracts.org/abstract/unusual-causes-of-reversible-myoclonus-a-video-based-case-series/