Late blink reflex changes in patients with pure sensory stroke due to geniculo-thalamic infarct: A contribution to the long loop theory

Seven patients with a pure sensory stroke due to a geniculo-thalamic infarct underwent blink reflex (BR) and median nerve somatosensory evoked potential studies to explore the mechanism subserving the R2 response. Both ipsilateral and contralateral R2 responses to stimulation of the affected side were significantly delayed in comparison with those obtained with stimulation of the nonaffected side (P < 0.001). Furthermore, in the five patients tested, cortical N20 following median nerve stimulation of the affected side was absent, delayed, or significantly reduced. These findings are consistent with the hypothesis of the transcortical generation of the late component of the BR. BR study appears to be a useful tool to assess long tract function, because changes have also been observed in patients with no demonstrable deficits on sensory examination.