Cogwheel rigidity

In 1817, Sir James Parkinson, in his handbook Essay on the Shaking Palsy, described a new disease characterized by "involuntary tremulous motion, which lessened muscular power, in part not in action and even when supported; with a propensity to bend the trunk forward, and to pass from a walking to a running place; the senses and intellect being uninjured."(p3) The clinical picture of this newly described disease was further clarified during the 19th century, in particular by Jean-Martin Charcot and Alfred Vulpian. Besides providing the first description of micrographia and bradykinesia and characterizing resting tremor, they proposed naming the disorder after James Parkinson, stating that the terms shaking palsy or paralysis agitans were not appropriate for a disease not always characterized by tremor and without a typical paralysis. Other clinical features of Parkinson disease were described in the following years. This article focuses on the first descriptions of cogwheel rigidity. During the first 2 decades of the 20th century 3 neurologists, apparently unaware of each others' work, described the same sign, leaving the paternity of this sign uncertain.