CSF serotonin concentrations and cerebral arterial spasm in patients with ruptured intracranial aneurysm

In 26 patients with recent rupture of an intracranial saccular aneurysm the CSF concentrations of serotonin (5-HT) were measured repeatedly by a radioimmunoassay. The 5-HT level in ventricular CSF collected between the 2nd and 15th day after SAH ranged between less than 2 and 5 nmol/l. These did not differ from the levels found in the ventricular CSF (less than 2-3 nmol/l) and lumbar CSF (less than 2-3 nmol/l) of control patients. 5-HT concentrations did not correlate with the severity of angiographical vasospasm, nor with CSF pressure or clinical grade. In two patients with severe postoperative vasospasm, however, cisternal CSF collected during operation and contaminated by fresh blood showed 5-HT concentrations exceeding 25 nmol/l. Thus, although these results do not support the conception that 5-HT plays a major role in sustaining delayed vasospasm, they suggest that 5-HT liberated from platelets may be operative in the initiation of cerebral arterial spasm.