Polymyoclonus aggravated by neck flexion as the isolated presenting symptom of Hirayama disease: case report.

HD usually presents with unilateral distal hand weakness, muscle atrophy and tremor. Although it is a benign and self-limiting disease, early diagnosis may lead to less clinical deterioration. Moreover, electromyography should be completed in the differentiation of young male patients who present with polymyoclonus without hand weakness or atrophy.