For a number of years I have observed a symptom in paralysis agitans that is not recorded in the literature. For the want of a better term, I have ventured to call it the "cog-wheel" resistance of the extremities. This is suggested by the use of such terms as "lead-pipe" and "waxy" flexibility. These terms describe a resistance which is felt where there is impaired motility in passive movements of the extremities. The term "cogwheel" is proposed as in a certain sense descriptive of a jerky or intermittent resistance of the extremities, when the sign is looked for. It is elicited by the examiner grasping the wrist with one hand and steadying the arm with the other, above the elbow. Rapid flexion and extension of the arm is made. Instead of an even movement, without resistance, when there is no involvement of motility, one, two or, perhaps, three slight hindrances
MOYER HN. A NEW DIAGNOSTIC SIGN IN PARALYSIS AGITANS: THE COG-WHEEL RESISTANCE OF THE EXTREMITIES. JAMA. 1911;LVII(27):2125. doi:10.1001/jama.1911.04260120315009
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