Early neurologists recognized resting tremor as the most distinctive feature of typical Parkinson's disease, and placed patients who had unusual, intermittent tremor patterns or no tremor into the clinical category termed "Parkinson's disease without tremor" (3,4). Some of these cases actually had tremor, but the movements were mild in severity or intermittent and primarily induced with emotion or action (3). It is possible that myoclonus, a feature frequently seen in corticobasal degeneration, and mild action tremor that can be seen in multiple system atrophy would have been categorized as one of these intermittent tremors. Myoclonus was appreciated in the 19th century, especially by Germanic and Austrian researchers (6,7), but not specifically designated as an aspect of atypical Parkinson's disease. Charcot studied tremor extensively and drew attention to its typical features in Parkinson's disease. He conducted his tremor examination with patients at rest and during activity. In addition to clinical observation, he used tremor oscillometers (Fig. 1) and small portable lamps that he attached to the shaking extremities in order to record the trajectory movements on light-sensitive paper (8). To accentuate an appreciation of very mild tremor, he attached feathers or other lightweight objects to the shaking body part to magnify the oscillations. He held strongly that titubation was not part of typical Parkinson's disease, but lip and tongue tremors could occur. Because parkinsonian cases without tremor were still considered as variants of the primary disease, Charcot advocated the use of the term Parkinson's disease, rather than "paralysis agitans," as coined by Parkinson himself (3,4).
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