OBSERVATIONS ON BLINK REFLEXES

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Abstract
Observations were made on 70 patients of blink reflexes elicited by various means of stimulation. The reflex produced by glabella tap had two components, the first proprioceptive with a latency between 11 and 18 msec, and the second, nociceptive with a latency between 23 and 46 msec. That produced by electrical stimulation of the supra-orbital nerve had two similar components but the latencies were 4 msec. shorter. Corneal stimulation produced variable reflex discharges with latencies ranging from 25 to 40 msec. and a loud click produced discharges with latencies between 18 and 38 msec. Both of these responses were found to be present in the decerebrate child. A bright flash of light elicited a response with as many as four components with latencies of about 50, 64, 68 and 74 msec. No reflex of this type was found in the decerebrate child or in a patient with cortical blindness. The motor component of the facial nerve is the final common pathway of all blink reflexes. Lesions of the facial nerve reduced activity of motor units and delayed latencies. Unilateral primary optic atrophy in several patients showed no blink response upon stimulation of the abnormal eye with a bright flash of light while others blinked with a latency not significantly different from the normal side. Hemianopsia produced no changes in latency. Profound changes in reflex amplitude and latency on the abnormal side were found in trigeminal lesions and asynchronous reflexes and delayed latency for the abnormal side were found following lesions of the eighth nerve. Mild hemiplegia exaggerated the first component of the glabella tap while the second component was small. absent or easily habituated. In paralysis agitans both components were large and of long duration. Present findings show (1) that the afferents of the proprioceptive component of the blink reflex to glabella tab may depend on individual differences in anatomy. but in most subjects run in the trigeminal nerve with a small number in the facial nerve; and (2) that the second component is nociceptive.

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