Clinical and electromyographic examination of tremor in patients with thyrotoxicosis

Tremor is a well-known symptom of thyrotoxicosis, yet no detailed clinical and electromyographic (EMG) examination of it has been published. The aim o f this investigation was to establish the clinical and EMG pattern of tremo r in patients with thyrotoxicosis and to compare it with the well-known pat tern of enhanced physiological tremor caused by anxiety. Twenty-six patient s with thyrotoxicosis and tremor and 30 patients with tremor and generalise d anxiety disorder were investigated. Tremor was scored clinically in all p ossible limb positions. EMG examination of tremor activity from antagonist hand muscles was performed. A postural and kinetic tremor with characterist ics of an enhanced physiological tremor was found in patients with thyrotox icosis and generalised anxiety disorder. Tremor involved only the upper lim bs in all patients. In conclusion, tremor in thyrotoxicosis and generalised anxiety disorder is an enhanced physiological tremor which cannot be separ ated clinically or by EMG measurement. Both types of tremor have similar me chanisms and can be distinguished only by the circumstances responsible for their occurrence. Despite only a moderate correlation between tremor inten sity and thyroid hormone levels, successful treatment of thyrotoxicosis res ults in a dramatic improvement of tremor.