Quantitative analysis of the glabellar reflex in patients with hemiplegic disorders

The glabellar reflex (GR) was investigated in 15 patients with hemiplegia and in 10 control subjects. The reflex was elicited mechanically by a light tap on the glabella. The EMG-responses were recorded bilaterally from the orbicularis oculi muscles by pairs of surface electrodes. The EMG activities were averaged and integrated off-line. In addition, the latencies of the early and late components were determined. Two major types of the GR alterations could be distinguished. These two patterns probably indicate a lowered excitability of the brainstem trigeminal systems or brainstem facial systems respectively. A loss of facilitatory influences associated with the hemispheral lesion seems probable. The alterations of the early component showed essential linkage to those of the late component. The latencies of GR responses on both sides were frequently prolonged. This fact and the decrease of the GR responses on the unaffected side as well as on the affected side indicates that the glabellar reflex can be altered bilaterally in hemiplegic patients.