The pathogenesis of cluster accompaniments remains unknown. Generally these manifestations are considered to be the result of sympathetic paralysis and parasympathetic overactivity. However, no definitive studies have so far been done to support this idea.

These accompaniments were studied clinically in 44 patients. Detailed autonomic function testing was undertaken in 7 of them utilizing the techniques described in the accompanying paper. We conclude from this study that the accompaniments can be explained on the basis of (1) sympathetic paralysis alone, and (2) that the site of lesion in the sympathetic pathway is located in the third neuron, most likely in the pericarotid region.