Bing Reflex

BING REFLEX, SYMPTOM (V^). Bing reflex, plantar flexion of the foot, is caused by percussion of the anterior line of the ankle joint or the distal parts of the malleoli. The foot should be in a position midway between flexion and extension, as when eliciting the Achilles reflex. Bing considers his reflex pathognomonic for lesions of the pyramidal system. In reality, it is often encountered even in cases without organic lesions of the central nervous system. The Bing symptom is based on the fact that in cases of normal middle ear condition, bone conduction of sound from a tuning fork placed on the mastoid process is more prolonged when the external auditory meatus is closed than when it is open. Method of examination: the patient is asked to indicate the moment when he stops hearing the vibration of the tuning fork; accordingly, the external auditory canal is immediately closed; with normal middle ear condition, the sound continues to be perceived.