Effect of unilateral pre- and postganglionic lesioning of the trigeminal nerve on the development of cerebral vasospasm in the squirrel monkey: angiographic findings.

Bilateral carotid angiography was performed in the squirrel monkey before and after unilateral pre- and postganglionic trigeminal lesioning. A unilateral postganglionic lesion caused a significant constriction of about 27% of the ipsilateral cerebral arteries, while a preganglionic lesion did not change the baseline arterial diameter. Following a subarachnoid haemorrhage (SAH) the degree of vasoconstriction in the animals with a preganglionic lesion did not differ significantly from that seen in controls. In the postganglionically lesioned animals, the vasoconstriction was more pronounced (12% at both 10 min and 6 days post SAH) on the lesioned as compared with the non-lesioned side. At day 6 post SAH the degree of vasoconstriction was 19% more pronounced on the lesioned side in post- as compared with the preganglionically lesioned animals. There was no difference in the degree of spasm on the non-lesioned side between the two groups. The findings indicate that the trigeminal system has both a peripheral and a central function. The peripheral, or axon reflex mechanism, exerts a tonic effect on the cerebral vessels. Following a SAH the axon reflex seems to attenuate cerebral vasospasm.