Electrical neurostimulation of the SPG has been shown in numerous animal testing as well as in initial human studies to induce vasodilatation. Animal studies have shown improvement in neuro-motor and cognitive functions.

Vasodilatation
It has been shown in numerous animal models, as well as on human subjects, that electrical stimulation of the SPG induces vasodilatation of the cerebral blood vessels. The following image shows this effect on the circle of Willis at the base of the brain of a dog, where the left SPG was stimulated, which resulted in vasodilatation on the left side of the brain. (Ref: D. Yarnitsky et al. Brain Research 1018 [2004] 236-240)

Stroke treatment in rats
Functional impairment has been attained by a transient (tMCAo) or a permanent (pMCAo) occlusion resulting in neurological deficits and long-term or permanent motor dysfunction.  The consequences of either mode of occlusion has been assessed in terms of infarct size, and neurological and cognitive improvement using verified scoring systems.

Evaluation of efficacy parameters on either tMCAo or pMCAo rats which received SPG stimulation showed an increase in Cerebral Blood Flow, a decrease in infarct volume and improvement in neurological function as measured by a series of behavioral tests detailed in the literature.

Improvement of the above parameters can be shown after extended delays (up to 24 hours) following occlusion. Beneficial effects can be observed up to 4 weeks after the MCA occlusion, and may be attributed to either the long-term influence of SPG stimulation, or to a long-term rehabilitation process.

Conclusions
Based on the data in which SPG stimulation was applied 24 hours after the onset of stroke, it is hypothesized that SPG stimulation may expand the therapeutic window from the current 3 hours (for treatment with tPA) to 24 hours for patients with ischemic stroke.