[Influence of hemisphere lesions on the contralateral blink reflex]

Electrically elicited blink reflexes were investigated in 28 patients with unilateral hemispheral lesion. The reflex evoked by electrical stimulation of the supraorbital nerve contralateral to the side of the hemispheral lesion was absent or depressed in 14 out of 28 cases. The abnormal patterns of the blink reflexes were devided into four different types (Type AB, Type AD, Type EB, and Type AB-EB). The Type AB, recorded in 4 cases, consisted of bilateral absence of late component (R2) when the supraorbital nerve on the non-lesion side was stimulated. In contrast, the reflex responses were almost normal bilatarally when the stimulus was applied to the nerve on the lesion side. The Type AD was observed in 2 cases. When the stimulus applied on the non-lesion side, both ipsilateral and consensual R2 were markedly delayed in latency. The Type EB was seen in one case. In this type the absence of the late component (R2) was confined to the clinically affected side independent of the side of stimulation. The Type AB-EB was observed in 4 cases. This type consisted of bilateral absence of R2 component after stimulation on the non-lesion side as seen in Type AB. However, when the stimulus applied on the lesion side, R2 component was only elicited on the ipsilateral side of stimulation. Based on our results, the authors emphasize that abnormality of the contralateral blink reflex in the patients with unilateral hemispheral lesion showed not only Type AB or Type AD but also Type AB-EB which may indicate lowered excitability of bulbar lateral reticular formation of the lower brain stem as well as spinal trigeminal system. This type was presumably due to loss of facilitatory influences associated with the contralateral hemispheral lesion, closely correlated with the lower postcentral region advocated by Ongerboer de Visser.