This blog reports on an interesting study performed in Germany that looked into early CT perfusion studies (post-bleed days 3-5) in the prediction of delayed cerebral infarction (DCI) and delayed ischemic neurologic deficits (DIND).
All aneurysmal SAH were clipped or coiled within 48 hours. From Days 0 to 14, patients remained in ICU, were maintained on normovolemia, and were given IV nimodipine.
Routine studies included, daily TCDs, CT on POD#1 and PBD#10, CTA with first post-op CT.
TCD vasospasm was diagnosed when blood flow velicity (BFV) exceeds 120 cm/sec. DIND was diagnosed when new neurologic deterioration was noted after exclusion of hydrocephalus, rebleed, seizures and metabolic disturbances. DCI was diagnosed when a new hypodensity was seen on CT.
Hemodynamic augmentation was started with noradrenaline to an SBP goal 160-180mm Hg upon diagnosis of TCD vasospasm. IA nimodipine, balloon dilatation or both was performed when conservative antivasospastic treatment has been maximized and patient still had symptomatic vasospasm plus CTP-proven perfusion deficits in the corresponding arterial territory.
In this study, routine CTP was performed on:
- if BFV increases by > 50 cm/sec within 24 hours on TCDs
- PBD#7 if comatose and/or sedated
On CTP, 3D perfusion parameter maps showed the distribution of hypoperfusion. The parameter maps included:
- CBF: cerebral blood flow
- CBV: cerebral blood volume
- MTT: mean transit time
- TTS: time to start
- TTP: time to peak
- TTD: time to drain
The CTP map was assessed for the presence of a focal hypoperfused area. If present, a vascular territory was assigned and vasospasm or occlusion was identified in one of the following blood vessels:
- A1 = proximal ACA
- M1/M2 = MCA
- P1 = PCA
Of course, perfusion abnormalities from other causes (e.g. initial hemorrhage, old ischemia, surgical intervention) are excluded prior to diagnosis of vasospasm.
CTP parameter maps were then used to make treatment decisions. Patients with symptoms of vasospasm, increased BFV in TCDs, abnormal CTP (i.e. >1/3 of a vascular territory) and vasospasm on CTA were considered for DSA +/- endovascular treatment.
The study found that DIND occurred in 30% within 2 weeks (54% of which was reversible and 46% was permanent). Vasospasm-associated DCI was noted in 26%
More importantly, the study found that early CTP can predict the risk of DIND with a Sn = 77%, Sp 87% PPV 71% and NPV 90% and it can predict risk of DCI with Sn = 82% Sp 84% PPV 64% NPV 93%.
Malinova, Vesna et al. “Early Whole-Brain CT Perfusion For Detection Of Patients At Risk For Delayed Cerebral Ischemia After Subarachnoid Hemorrhage”. Journal of Neurosurgery (2015): 1-9. Web. 14 Jan. 2016.