Nuclear Medicine and Brain Vascularity: A Case Study

Age: 57

Gender: Male

History: Large recurrent sphenoid wing meningioma with both intracranial and extracranial components. Right internal carotid artery involved with tumour. For possible high flow bypass.

High flow bypass: Bypass grafts may include low-flow (superficial temporal to middle cerebral) and high-flow bypass grafts using either the radial artery or saphenous vein.

MRI Imaging and Results: The known large ethmoid air cell mass is well demonstrated, measuring approximately 69 x 44 x 76mm, with invasion into the cranial vault through the floor of the anterior cranial fossa, displacing the surrounding parenchyma leading to oedema within it. There is also bulging and extension through the lamina papyracea on the right as well as towards the orbital apex and into the region of the anterior aspect of the sellar turcica, optic chiasm, pituitary stalk and Circle of Willis.

CEREBRAL ANGIOGRAM & TEST OCCLUSION RIGHT INTERNAL CAROTID ARTERY Result: The balloon guide catheter was positioned in the distal cervical internal carotid artery and inflated for a period of 30 minutes. The right cerebral hemisphere is reliant on principally the posterior communicating artery, with some additional assistance from the anterior communicating artery and the ophthalmic artery. Mild narrowing of the supraclinoid right internal carotid artery noted consistent with tumour encasement. During the period of occlusion, the patient remained neurologically entirely stable, and the mean pressures in the right internal carotid artery stump remained at >80% of mean arterial pressure in the systemic circulation. Results would suggest that RT.ICA sacrifice would have no adverse effects.

Nuclear Medicine Procedure to Determine viability of vessel sacrifice. Camera: GE Hawkeye SPECT/CT Imaging: Baseline study imaged at 60min post injection of Tc99m-HMPAO. Patient in darkened quite room for 60min prior to injection. Balloon occlusion in Angiography suite: This procedure was performed 48 hours after the baseline study. Internal carotid artery occluded for 15min, Tc-99m HMPAO injected IV, occlusion remains for another 15 minutes, balloon removed and patient prepped for transfer to MMI for imaging. Patient imaged 50minutes post Tc99m-HMPAO injection. Images: Baseline and post balloon occlusion SPECT/CT images acquired with exact same parameters and exact patient positioning. Comparison below.

Baseline SPECT/CT Post Angio-balloon Occlusion SPECT/CT

Comparison Images: Baseline and Post Angio-balloon occlusion. Arrows indicate mismatched defects. 

Baseline images: Images demonstrate a focal severe perfusion defect in the left inferior frontal region in a parasagittal location. There is also a mild reduction in perfusion to the left caudate nucleus and in the region of the putamen and a smaller wedge-shaped defect in the left frontoparietal region. Baseline perfusion defects in the left inferior frontal lobe possibly secondary to mass effect. Balloon Occlusion: The post-occlusion images demonstrate stable severe perfusion defect in the left inferior frontal region most likely secondary to mass effect. There are new right cerebral perfusion defects including mildly reduced perfusion in the right frontal lobe superiorly, moderately reduced perfusion posteriorly in the frontal lobe and adjacent right parietal lobe, the right caudate and putamen. Additionally there is significantly reduced perfusion on the post-occlusion study in the right posterior parietal lobe and in the right temporal lobe inferiorly including the inferior temporal gyrus with normal preservation of occipital lobe perfusion.

Conclusion: Nuclear Medicine scan findings are in keeping with reduced perfusion in the right internal carotid artery territory following balloon occlusion which suggests the patient at risk of neurological deficits with complete surgical occlusion of the right internal carotid artery. Results in this detailed molecular imaging procedure prove to be far more sensitive than angiography alone.

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