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Brought to you by the Resident and Fellow Section of Neurology®.
June 8, 2011
The ‘hung-up’ knee jerk, first described by Bing, is a specific but rarely appreciated clinical sign of Huntington disease (HD) and Sydenham chorea. During an elicited knee jerk, the extended lower leg may not relax immediately but may remain elevated for several seconds due to sustained contraction of the quadriceps femoris. It is felt to be secondary to hypertonic quadriceps activation as part of a long loop reflex originating in the basal ganglia. This reflex may appear to mimic spontaneous choreic movements in HD, and has been described as ‘induced’ or ‘reflex’ chorea.
Partha S Ghosh, MD
Disclosure: Dr. Ghosh reports no disclosures.
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