Value of brain perfusion single-photon emission computed tomography in the diagnosis of post subarachnoid hemorrhage (SAH) vasospasm

Objectives Cerebral vasospasm is a major cause of morbidity and mortality among patients after subarachnoid hemorrhage (SAH) from ruptured intracranial aneurysms. Two major types of imaging modalities are available clinically as screening tests attributable to their high sensitivities: transcranial Doppler (TCD) ultrasound and single photon emission computed tomography (SPECT). Significant discrepancy exists in the literature regarding each test’s value in detection of post SAH vasospasm.

Methods To reconcile this discrepancy, we reviewed the brain SPECT perfusion scans performed during 1992-2011 in our center and compared the findings to that of angiographies performed within 48 hours of SPECT as the gold standard to assess the accuracy of brain SPECT in predicting post SAH vasospasm.

Results Among the 600 reviewed patients, 72 (12% of total) individuals with angio-proven vasospasm are included based on the criteria of inclusion: 30 female and 42 male with age 39-85. Based on brain CT, we classified the patients into two different groups: with pre-existing visible cerebral defect (W, such as surgical resection and infarction) and without pre-existing defect (WO). When all the cases (W and WO) are included the SPECT demonstrates a suboptimal sensitivity of 43% (n=72). However, the sensitivity improves significantly to 90% when only the WO cases (n=39) are included.

Conclusions Cerebral perfusion SPECT is a valuable screening test given its high sensitivity, wide availability and low radiation dose if the prerequisite of no major cerebral pre-existing defect such as infarct or surgical resection is present. The current discrepancy in the literature, regarding the value of SPECT on post SAH vasospasm, can be attributed to suboptimal detection of change if vasospasm occurs in the vascular territory of the pre-existing major cerebral defect, such as from surgical resection or infarction. A pretest screening for major cerebral defect by a physician is necessary for the purpose of appropriate utilization.