In contrast, Silberstein et al. (2016b) proposed that stimulation of the vagus nerve affects hypocretin and orexin pathways in people with cluster headache, while Kinfe et al. (2015b) hypothesized that tVNS may help counteract the decline in thalamocortical activity in people with migraine and sleep disturbances. Here, HCRT is linked to sleep disorder.