Jaw Clonus: A Rhythmic Oscillatory Movement, but Not Tremor
Abstract
Background: Jaw clonus is rhythmic, oscillatory contraction of jaw muscles induced by stretch and is caused by lesions of the descending motor neurons in the corticopontine tracts.
Phenomenology shown: We illustrate jaw clonus elicited with jaw activation and upon testing of the jaw jerk in a patient with amyotrophic lateral sclerosis.
Educational value: This video clearly demonstrates the uncommon sign of jaw clonus, a finding which needs to be distinguished from tremor and should direct the examiner to consider lesions of the corticopontine fibres, including amyotrophic lateral sclerosis.
© 2020 Laura Williams, Marie Ryan, Ronan Kilbride, Yudy Llamas Osorio, published by Ubiquity Press
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