Applications

Cerebral Ischemia

Clinical and clinical research assessments with the laser Doppler technique are a progression from the experimental applications for the stroke model (MCA occlusion) and experimental observations of spreading cortical depression.

Cortical spreading depolarization (CSD) describes a wave of neuronal depolarization associated with influx of cat-ions and water which blocks normal cerebral activity. CSD induces changes to microvascular tone with the vasoconstriction phase (Cortical Spreading Ischemia, CSI) there is associated risk of progressive damage. CSI has been observed experimentally, replicating conditions following aneurysmal subarachnoid haemorrhage.

Clinical assessments of CSI have been made using LDF monitoring (moorVMS-LDF) in combination with ECG electrodes. Intra operative assessments, using the moorFLPI speckle imager, have been applied by Hecht et al, 2009:

Potential Indications:

Potential neurovascular indications for which a direct or indirect assessment of tissue perfusion
can become critical include:

1. Identification of clip-related vessel stenosis or occlusion,
2. Assessment of bypass patency,
3. Confirmation of adequate flow replacement following revascularization for parent vessel sacrifice (Hunterian ligation)

Methods used (Hecht et al, 2009)

The device was centred over the surgical field about 30 cm above the cortical surface. Direct illumination of the surgical field by light sources other than the moorFLPI was avoided. The live laser speckle image with its corresponding grey scale image was visualized on the laptop screen. The image was focused and recordings made for a period of 5 minutes.

Live imaging was performed over the surgically exposed area during a standard STA-MCA bypass procedure, before and after anastomosis. To assess the flow contribution of the radial artery bypass after proximal occlusion of the ICA, live and single-point moorFLPI imaging was performed over the distal end of the Sylvian fissure on completion of the anastomosis during temporary bypass occlusion and subsequent release in the radial artery graft.

The moorFLPI is shown above with a microstand, other stands are available so contact us for more detail.

Observations

Good visualization of relative CBF in addition to flow imaging in both the bypass graft and the cortical vasculature. After a test occlusion of the radial artery graft and subsequent flow initiation through the bypass, moorFLPI allowed immediate visualization and measurement of relative CBF in excellent spatiotemporal resolution. It was concluded that moorFLPI offered a non-invasive and rapid intra-operative assessment of relative CBF, which can be used for optimizing neurovascular procedures.

References

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