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Is local hypoperfusion the reason for transient neurological deficits after STA-MCA bypass for moyamoya disease?
Nitin Mukerji1, Douglas J Cook, Gary K Steinberg
1Department of Neurosurgery and Stanford Stroke Center, Stanford University School of Medicine, Stanford, California.
Object:
Hyperperfusion is believed to be the cause of transient neurological events (TNEs) in patients with moyamoya disease (MMD) who have undergone an extracranial-to-intracranial (EC-IC) bypass between the superficial temporal artery (STA) and the middle cerebral artery (MCA). The objective of this study was to evaluate this possibility by analyzing cerebral blood flow (CBF) data obtained with thermal diffusion probes used at the authors' center.
Methods:
The authors examined postoperative cerebral perfusion in 31 patients with MMD who underwent a direct EC-IC STA-MCA bypass. A Hemedex Q500 flow probe was placed in the frontal lobe adjacent to the bypass and connected to a Bowman cerebral perfusion monitor, and CBF data were statistically analyzed using JMP 8.0.2 software. Seven patients experienced a TNE after surgery in the left hemisphere (that is, after left-sided surgery), manifesting as dysphasia approximately 24 hours postoperatively and which had improved by 48 hours. No TNEs were observed after right-sided surgeries. Operative and postoperative CBFs in the left side with the TNE were compared with those in the left side with no TNE and on the right side.
Results:
A detailed analysis of 64,980 minute-by-minute flow observations showed that the initial postbypass CBF was higher on the left side where the TNEs occurred. This CBF increase was followed by a widely fluctuating pattern and a statistically significant and sharp drop in perfusion (p < 0.001, mean difference of CBF between groups, paired t-test) associated with a TNE not observed in the other 2 groups.
Conclusions:
On the basis of the authors' initial observations, an early-onset altered pattern of CBF was identified. These findings suggest local hypoperfusion as the cause of the TNEs. This hypoperfusion may originate from competing blood flows resulting from impaired cerebral autoregulation and a fluctuating flow in cerebral microcirculation.
Insights
Transient neurological events (TNEs) after moyamoya disease (MMD) surgery may be caused by hypoperfusion, not hyperperfusion. This study found a significant drop in cerebral blood flow (CBF) associated with TNEs following superficial temporal artery-middle cerebral artery bypass.
Area of Science:
- Neurosurgery
- Cerebrovascular Diseases
- Medical Devices
Background:
- Moyamoya disease (MMD) is a rare cerebrovascular disorder.
- Extracranial-to-intracranial (EC-IC) bypass surgery, specifically superficial temporal artery-middle cerebral artery (STA-MCA) bypass, is a treatment for MMD.
- Transient neurological events (TNEs) are a potential complication following EC-IC bypass surgery.
Purpose of the Study:
- To investigate the cerebral blood flow (CBF) patterns associated with TNEs after STA-MCA bypass in MMD patients.
- To evaluate the hypothesis that hyperperfusion causes TNEs in MMD patients post-EC-IC bypass.
Main Methods:
- Analysis of postoperative CBF data from 31 MMD patients undergoing direct STA-MCA bypass using thermal diffusion probes.
- Monitoring of CBF with a Hemedex Q500 flow probe and Bowman cerebral perfusion monitor.
- Statistical comparison of CBF in hemispheres with and without TNEs.
Main Results:
- A statistically significant drop in cerebral blood flow (CBF) was observed in patients experiencing TNEs.
- Initial post-bypass CBF was higher on the side where TNEs occurred, followed by fluctuating patterns and a sharp decrease.
- TNEs, characterized by dysphasia, were observed only after left-sided surgeries.
Conclusions:
- The study suggests that local hypoperfusion, not hyperperfusion, is the cause of early-onset TNEs after STA-MCA bypass in MMD patients.
- Impaired cerebral autoregulation and fluctuating microcirculation may contribute to this hypoperfusion.
- Altered CBF patterns identified post-surgery indicate a need for closer monitoring of cerebral perfusion.
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