What tests are used to diagnose cerebral vasospasm?

CT, digital subtraction angiography (DSA) and transcranial Doppler flow analysis (TCD) are three examination methods that we often use to check whether patients suffer from cerebral vasospasm. If you suspect that you have this disease, you can go to a regular hospital for examination.

1. The accuracy of CT diagnosis for SAH is over 99%, but the detection rate for aneurysms and cerebral vascular malformations is only 34%, so it cannot be used as the only means of diagnosing the cause.

2. Clinically, the severity of cerebral vasospasm can be estimated based on the amount of bleeding shown on CT, namely the Fischer grade. According to this standard, grade 0 means no bleeding and the incidence of cerebral vasospasm is about 3%; grade 1 means bleeding only in the basal cistern and the incidence of vasospasm is 14%; grade 2 means bleeding in the peripheral cerebral cistern or sylvian fissure cistern and the incidence of vasospasm is 38%; grade 3 means extensive SAH with intraparenchymal hematoma; grade 4 means thick blood accumulation in the basal cistern, peripheral cerebral cistern and sylvian fissure cistern, and the corresponding incidence of vasospasm exceeds 50%.

3. Whole-brain angiography has a high positive detection rate for aneurysms and cerebral vascular malformations. It can clearly display the branches of cerebral blood vessels at all levels, the location and size of aneurysms, or the morphological distribution of malformed blood vessels, providing a reliable and objective basis for treatment. Therefore, it has always been used as the gold standard for judging cerebral vasospasm. However, it also has certain disadvantages. For example, it is an invasive examination, relatively expensive, and complicated to operate, which is sometimes not accepted by patients.

4. TCD is also a good method to monitor cerebral vasospasm after SAH, especially because it can be monitored multiple times within a day and dynamically observe the changes in cerebral hemodynamics after SAH, which is of great value for the diagnosis and prognosis of cerebral vasospasm. The basic principle is to estimate the degree of lumen stenosis by changes in blood flow velocity. The most important detection site is usually the bilateral MCA, and the blood flow status of the extracranial internal carotid artery can also be monitored.

5. The normal MCA blood flow velocity is 30~80 cm/s. The general diagnostic criteria for cerebral vasospasm is a blood flow velocity exceeding 120 cm/s. The advantages of TCD are easy operation, low price, and no trauma to patients. However, it indirectly diagnoses cerebral vasospasm through blood flow velocity, which has high specificity but relatively low sensitivity. Therefore, some people have proposed lowering the TCD standard for diagnosing vasospasm from 120 cm/s to 80 cm/s. If vasospasm is suspected, TCD examinations should be performed continuously during the entire treatment period.