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Published on: January 18, 2018
Appropriate use of CT perfusion following aneurysmal subarachnoid hemorrhage: a Bayesian analysis approach
R P Killeen1, A Gupta, H Delaney
1From the Departments of Radiology (R.P.K., A.G., H.D., C.E.J., A.J.T., J.C., P.C.S.).
Insights
CT Perfusion (CTP) effectively detects delayed cerebral ischemia and vasospasm in subarachnoid hemorrhage (SAH) patients. Positive CTP guides treatment, while negative CTP supports a no-treatment approach.
Area of Science:
- Neurology
- Radiology
- Neurocritical Care
Background:
- Cerebral CT Perfusion (CTP) is increasingly used for evaluating delayed cerebral ischemia and vasospasm post-subarachnoid hemorrhage (SAH).
- Accurate detection of these complications is crucial for timely intervention and improved patient outcomes.
Purpose of the Study:
- To determine the diagnostic accuracy of CTP in identifying delayed cerebral ischemia and vasospasm in SAH patients.
- To utilize Bayesian analysis to identify patient subgroups who would most benefit from CTP.
Main Methods:
- Retrospective analysis of SAH patients who underwent CTP between days 6-8 post-rupture.
- Delayed cerebral ischemia defined by infarction or permanent neurologic deficits; vasospasm by Digital Subtraction Angiography (DSA).
- Calculation of CTP test characteristics and Bayesian analysis for conditional probabilities; neurologist survey for treatment thresholds.
Main Results:
- CTP showed high sensitivity and specificity for delayed cerebral ischemia (0.84, 0.73) and vasospasm (0.97, 0.76).
- Positive CTP findings were observed in 84% of patients with delayed cerebral ischemia and 97% with vasospasm.
- Negative CTP findings had high negative predictive values for both conditions (0.88 for ischemia, 0.94 for vasospasm).
Conclusions:
- CTP is a valuable tool for diagnosing delayed cerebral ischemia and vasospasm in SAH.
- Positive CTP findings warrant consideration for aggressive therapies like induced hypertension or intra-arterial treatment.
- Negative CTP findings can confidently guide decisions against initiating such treatments.
Background And Purpose:
In recent years CTP has been used as a complementary diagnostic tool in the evaluation of delayed cerebral ischemia and vasospasm. Our aim was to determine the test characteristics of CTP for detecting delayed cerebral ischemia and vasospasm in SAH, and then to apply Bayesian analysis to identify subgroups for its appropriate use.
Materials And Methods:
Our retrospective cohort comprised consecutive patients with SAH and CTP performed between days 6 and 8 following aneurysm rupture. Delayed cerebral ischemia was determined according to primary outcome measures of infarction and/or permanent neurologic deficits. Vasospasm was determined by using DSA. The test characteristics of CTP and its 95% CIs were calculated. Graphs of conditional probabilities were constructed by using Bayesian techniques. Local treatment thresholds (posttest probability of delayed cerebral ischemia needed to initiate induced hypertension, hypervolemia, and hemodilution or intra-arterial therapy) were determined via a survey of 6 independent neurologists.
Results:
Ninety-seven patients with SAH were included in the study; 39% (38/97) developed delayed cerebral ischemia. Qualitative CTP deficits were seen in 49% (48/97), occurring in 84% (32/38) with delayed cerebral ischemia and 27% (16/59) without. The sensitivity, specificity, and positive and negative predictive values (95% CI) for CTP were 0.84 (0.73-0.96), 0.73 (0.62-0.84), 0.67 (0.51-0.79), and 0.88 (0.74-0.94), respectively. A subgroup of 57 patients underwent DSA; 63% (36/57) developed vasospasm. Qualitative CTP deficits were seen in 70% (40/57), occurring in 97% (35/36) with vasospasm and 23% (5/21) without. The sensitivity, specificity, and positive and negative predictive values (95% CI) for CTP were 0.97 (0.92-1.0), 0.76 (0.58-0.94), 0.88 (0.72-0.95), and 0.94 (0.69-0.99), respectively. Treatment thresholds were determined as 30% for induced hypertension, hypervolemia, and hemodilution and 70% for intra-arterial therapy.
Conclusions:
Positive CTP findings identify patients who should be carefully considered for induced hypertension, hypervolemia, and hemodilution and/or intra-arterial therapy while negative CTP findings are useful in guiding a no-treatment decision.
