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aneurysmal subarachnoid hemorrhage.
It may be possible that traumatic subarachnoid hemorrhage has the same effect that aneurysmal subarachnoid hemorrhage has. If you look at the Fisher grade for head trauma patients, where grade I is no blood and grade II is a modest or small amount of diffuse blood, grade III is thick subarachnoid layers, and grade IV is intracerebral hemorrhage plus subarachnoid hemorrhage. According to Dr. Neil Martin it is those patients with a subarachnoid hemorrhage and trauma who develop the highest incidence of spasm. Since subarachnoid blood is not the only blood compartment that is filled with blood in traumatic head injury patients, Dr. Martin looked at other areas of bleeding, such as subdural hemorrhage, intraventricular hemorrhage, and intraparenchymal contusions, and correlated this with whether or not they are associated with cerebral vasospasms as measured by transcranial Doppler. It is the subarachnoid hemorrhage, subdural hemorrhage and intraventricular hemorrhage, which is associated with the highest degree of post-traumatic cerebral vasospasms. Intraparenchymal hemorrhages and contusions, although were also associated with cerebral vasospasms, were not at the same level as the other three. The reason for this is that subarachnoid, subdural and intraventricular hemorrhages are all associated with leakage of blood into the subarachnoid spaces. The more lesions associated with subarachnoid blood the more of the risk of vasospasms. The severity of spasm correlates with the fissure grade on CT in traumatic head injury patients. The lowest cerebral blood flow and the duration of spasm also correlates with the Fisher grade. The cerebral vasospasms can be demonstrated in any blood vessel. In the basilar artery if the transcranial Doppler shows flow greater than 90, this is usually attributed to significant vasospasm. Extradural blood is not associated with cerebral vasospasm.
Flow velocity by Doppler can go up when blood flow is up and when spasm occurs. You can't sort the two out effectively unless you are also measuring cerebral blood flow. The combination of low blood flow and high velocities are the most dangerous and can cause ischemia and infarction. In those patients with high blood flow and high velocity, they tend to be okay. These are usually patients with arterial narrowing, but they have collateral flow or they have a bit of hyperemia that drives the flow velocity up. They do not get the ischemic deficit. In the first three days when the blood flows are rising, the high velocities are usually associated with higher blood flows. These are patients with increased flow volume, but later when the patients have high velocities and low blood flow they have spasm.
Overall about 30 to 40% of all patients had cerebral blood spasm in traumatic head injury. Those patients who had no spasm primarily had good outcome. The patients who had spasm in both anterior and posterior circulation almost always had a bad outcome. It suggests one of two things. Either the patients come in in such bad (Continued on page 99)
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