In humans there is anecdotal evidence that TNF alpha plays a role in cerebral artery vasospasm as demonstrated by peak elevations of CSF TNF alpha levels on the days corresponding to peak vasospasm time in patients who have had a subarachnoid hemorrhage and in those showing elevated flow velocities on transcranial doppler after a subarachnoid bleed [14]. This evidence concerns the gene TNF and subarachnoid hemorrhage.