Abstract
Background:
Impaired perfusion may be an important determinant of outcomes in intracranial atherosclerotic disease (ICAD). CT and MRI perfusion imaging patterns of stenosis due to MCA ICAD have not been studied in detail. We characterized CT and MRI perfusion imaging measures of subacute ischemia subjects with MCA stenosis to create a novel atlas and define specific blood flow parameters.
Methods:
A retrospective, 5-year, analysis of consecutive ICAD patients evaluated with CT or MRI perfusion imaging for recent TIA or stroke (0-7 days) due to sub-occlusive (50-99%) MCA stenosis was conducted. CT/MRI volumes of core and hypoperfusion (>5 ml) were extracted with RAPID (iSchemaView, Inc.) and analyzed with respect to clinical variables. Descriptive statistics were used to quantify and map patterns of impaired perfusion.
Results:
194 (median age 71, range 30-102 years; 53% women) patients with subacute ischemia were evaluated with MRI (n=161) or CT (n=33) perfusion imaging. Median initial NIHSS was 5 and median inpatient length of stay (LOS) was 4 (1-42) days. Hypoperfusion with Tmax>4s delay volumes (median 66.5 ml, mean 107.5 ml) were noted in 162 (84%) patients, Tmax>6s delay volumes (median 11.0 ml, mean 41.5 ml) in 118 (61%), Tmax>8s delay volumes (median 0 ml, mean 23.4 ml) in 81 (42%) and Tmax>10s delay volumes (median 0 ml, mean 16.9 ml) in 61 (31%). Hypoperfusion intensity ratios (Tmax>10s/Tmax>6s) were median 0.08 and mean 0.24. Ischemic core volumes on MRI (ADC<620) were mean 10.3±33.2 ml and mean 5.6±16.1 ml on CT (rCBF<30%). Mismatch volumes were mean 32.0±79.8 ml and mismatch ratios mean 4.8±9.9 ml. The extent of Tmax>6s hypoperfusion was unrelated to initial NIHSS (r=0.17, p=NS) or LOS (r=0.11, p=NS).
Conclusions:
Hypoperfusion is common in recently symptomatic ICAD patients with MCA stenosis. Tmax delay volumes and hypoperfusion intensity ratios are distinct from acute MCA occlusion. Mapping and understanding these specific patterns of perfusion will be instrumental in planning future ICAD trials.