Objective: To illustrate the electrophysiological and clinical findings in a patient with secondary orthostatic tremor (OT) associated with hyperthyroidism

Background: Orthostatic tremor is a rare movement disorder that may be primary or secondary. Secondary OT associated with hyperthyroidism has been reported in some

Method: A case report

Results: A 60-year-old male patient presented to our department with a six-month history of leg tremor. He described that tremor in his lower limbs appeared immediately when standing, lessened with quickly walking, and disappeared when sitting or lying. He had a feeling of unsteadiness during stance. His medical history was unremarkable. Neurological examination revealed symmetrical postural tremor with a very low amplitude in the upper limbs, palpable tremor of the lower limbs during standing, and no other abnormalities. These clinical findings are compatible with orthostatic tremor. The patient also had tachycardia at a heart rate of 108 beats/min. Multiple-channel surface electromyography (EMG) recordings from lower limb muscles revealed 7-8 Hz tremor when standing (Figure 1). The leg tremor activities would disappear when sitting or lying. An analysis of thyroid hormone levels revealed hyperthyroidism (TSH: 0.005 mU/L; free T4: 5.8 ng/dL; negative antithyroid antibodies). The patient was treated with propranolol and thiamazol. Four weeks later, he showed a significant clinical improvement. A follow-up laboratory test revealed normalized thyroid hormone levels (TSH: 0.005 mU/L; free T4: 1.29 ng/dL). Follow-up EMG recordings did not show rhythmic burst activity in the lower limbs when standing.

Conclusion: Our clinical case showed that slow-frequency orthostatic tremor can be an atypical manifestation in patients with hyperthyroidism. Using a combination of an anti-thyroid drug and propranolol can help to improve tremor in these cases.

Figure 1: EMG from lower limb muscles

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MDS Abstracts - https://www.mdsabstracts.org/abstract/secondary-orthostatic-tremor-associated-with-hyperthyroidism-a-case-report/