|Year : 2011 | Volume
| Issue : 2 | Page : 82-85
Tc99m-ECD brain SPECT in patients with Moyamoya disease: A reflection of cerebral perfusion status at tissue level in the disease process
Raghava Kashyap1, Bhagwant Rai Mittal1, Hejjaji Venkataramarao Sunil1, Anish Bhattacharya1, Baljinder Singh1, Kanchan Kumar Mukherjee2, Sunil Kumar Gupta2
1 Department of Nuclear Medicine, Postgraduate Institute of Medical Education and Research, Chandigarh, India
2 Department of Neurosurgery, Postgraduate Institute of Medical Education and Research, Chandigarh, India
|Date of Web Publication||25-Nov-2011|
Bhagwant Rai Mittal
Department of Nuclear Medicine, Postgraduate Institute of Medical Education and Research, Chandigarh-160 012
Source of Support: None, Conflict of Interest: None
| Abstract|| |
Background: Moyamoya disease is a rare, progressive cerebrovascular disorder caused by intracranial stenosis of the circle of Willis, resulting in successive ischemic events. Computed tomography (CT) and magnetic resonance imaging (MRI) play a major role in diagnosis. Objective: The aim of the study was to describe the spectrum of findings on brain SPECT in patients with Moyamoya disease and to compare the findings with other investigations. Materials and Methods: Tc99m-ECD SPECT scans of seventeen patients (7 children and 10 adults) were analysed to study the brain perfusion. Results: Features of Moyamoya disease were detected on DSA in 11 patients, CTA in one, MR angiography in one patient. Brain perfusion SPECT analysis showed unilateral perfusion defects in 11 patients, normal perfusion in 2 and bilateral defects in 4 patients. No perfusion defects despite bilateral vascular changes were noted in one patient. Cerebral infarcts were detected on MRI unilaterally in three subjects while multiple infarcts were identified in one. Tc99m-ECD Brain SPECT showed perfusion defects that were more extensive compared to those detected on MRI. Post acetazolamide studies for assessment of cerebrovascular reserve were done in three patients. Two of them showed good cerebrovascular reserve (>1). Follow-up studies post-surgical procedures (Myo-dura synangiosis) done in two patients showed partial resolution of perfusion defects in the involved areas. Conclusion: Brain perfusion scintigraphy is an important adjunct in evaluation of patients with Moyamoya disease yielding information about the direct end results of the pathology in the vessels and also prognostic information.
Keywords: Brain SPECT, Moyamoya disease, Tc99m-ECD
|How to cite this article:|
Kashyap R, Mittal BR, Sunil HV, Bhattacharya A, Singh B, Mukherjee KK, Gupta SK. Tc99m-ECD brain SPECT in patients with Moyamoya disease: A reflection of cerebral perfusion status at tissue level in the disease process. Indian J Nucl Med 2011;26:82-5
|How to cite this URL:|
Kashyap R, Mittal BR, Sunil HV, Bhattacharya A, Singh B, Mukherjee KK, Gupta SK. Tc99m-ECD brain SPECT in patients with Moyamoya disease: A reflection of cerebral perfusion status at tissue level in the disease process. Indian J Nucl Med [serial online] 2011 [cited 2020 Jan 21];26:82-5. Available from: http://www.ijnm.in/text.asp?2011/26/2/82/90257
| Introduction|| |
Moyamoya disease is a rare occlusive disorder of cerebral vasculature of unknown aetiology.  The disease is characterized by progressive intracranial vascular stenosis of the circle of Willis, resulting in successive ischemic events. Hemorrhagic events can also occur. Diagnosis is established by the typical appearance on cerebral angiography i.e.; "puff of smoke" and refers to the appearance of multiple compensatorily dilated striate vessels seen on angiography.  CT and MRI play a major role in documenting the regions of infarction/hemorrhage. We performed this study to analyze the role of brain perfusion SPECT in diagnosis and management of Moyamoya disease.
| Materials and Methods|| |
A retrospective analysis of the records of 17 patients (10 male, 7 female) referred for brain perfusion scintigraphy between May 2005 and Dec 2009 was conducted [Table 1]. The aim of the study was to describe the spectrum of findings on brain SPECT in patients with Moyamoya disease and to compare the findings with other investigations when available. Of these 17 patients, 7 were children of age group 3 to 16 years and 10 adults between 23 to 50 years. All patients underwent a baseline technetium-99m ethyl cysteinate dimer (Tc99m-ECD) brain perfusion scintigraphy as per the established procedure guidelines.  Four patients had a follow up brain perfusion scintigraphy. One patient had a follow up scan at six months after surgical procedure (Myo-dural Synangiosis). Three patients underwent both a baseline and post diamox brain perfusion scintigraphy for evaluation of cerebrovascular reserve.
|Table 1: Showing the characteristics of perfusion defects in the brain on Tc99m-ECD brain perfusion study |
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For children, an intravenous line was secured and the child was placed in a quiet, dimly lit room along with one of the parents. Child was instructed not to speak. Once the child had calmed down, Tc99m-ECD in a dose of about 10 MBq per kg body weight was injected via the intravenous cannula. Five min after the tracer injection intravenous sedatives were administered under close monitoring, as per the institutional sedation protocol. For adults, no sedation was used. They were allowed to stay in a dimly lit room and instructed not to speak. Tc99m- ECD was injected through an intravenous cannula that was secured priorly. Images were acquired 45 minutes after the injection. Child was secured on a paediatric palette and head immobilized by strapping. For preparation of ECD, Tc99m was obtained from a generator that had been eluted previously within 24 hrs. We used oral diamox for assessment of the cerebrovascular reserve. Tablets of diamox up to 1,200 mg crushed to form powder were given orally at least 30 minutes before the tracer injection. Applying manually drawn regions of interest the ratio of the counts in the region with perfusion defect to corresponding contralateral normal cerebral cortex was determined both in the baseline and post-diamox study. Cerebrovascular reserve was calculated as the proportion of this ratio in the post diamox study to that in the baseline study. A ratio greater than one was considered as adequate reserve.
Tomographic images of the brain were acquired in 128 x 128 matrix, circular orbit and continuous 360 0 acquisition. The acquired data were processed using Butterworth filter, order 0.45, cut off 10 and Chang attenuation correction method was applied. Images were displayed on 256 continuous colour scale transverse, sagittal and coronal sections. Visual interpretation of the perfusion state was made using a rating scale of 0 to -3, in which; 0 was baseline perfusion, -1 mild and -2 moderate reductions in perfusion. A score of -3 was given to a region of deficit which was defined as a clear disconnection in brain ECD uptake in more than 3 continuous slices.
| Results|| |
The presenting clinical features were noted and patients' records were scrutinized for reports of NCCT, MRI, DSA, and CT angiography (CTA). Four of the patients presented with hemiparesis as the presenting symptoms. Headache was the presenting symptom in 7, seizures in one, loss of vision in one. Four patients had multiple presenting symptoms. All the patients in pediatric age group presented with neurological defect as the presenting feature. While majority of the adult subjects had headache and vomiting as the presenting symptom but one patient had sub-arachnoid hemorrhage. Following the initial presentation, preliminary investigations were done. Features of Moyamoya disease were detected on DSA in 11 patients, CTA in 1, MR angiography in 1. Four patients had evidence of parenchymal infarcts on MRI and evidence of haemorrhage in two.
In our study, unilateral perfusion defects were seen in 10 patients, normal perfusion in 2 and bilateral defects in 5 patients. However, unilateral features of Moyamoya disease were found in angiography only in three of them (Pts 4, 5 and 11). In one of these patients (Pt 11) there was retrograde filling of the middle cerebral artery from the posterior circulation and hence no demonstrable perfusion defects. The presence of bilateral perfusion defects in patient number 4 was not explained. No perfusion defects despite bilateral vascular changes were noted in one patient (Pt 14).
Cerebral infarcts were detected on MRI unilaterally in three subjects while multiple infarcts were identified in one. Tc99m-ECD Brain SPECT showed bilateral perfusion defects in one patient with unilateral MRI infarcts while in the rest of the patients the defects were more extensive compared to MRI.
Post acetazolamide studies for assessment of cerebrovascular reserve were done in 3 patients. Two of them showed good cerebrovascular reserve (>1). Follow up studies following surgical procedures (Myo-dura synangiosis) was done in two patients and showed partial resolution of perfusion defects in the involved areas. Perfusion defects of the individual patients in the respective cerebral areas are depicted in the table.
| Discussion|| |
Moyamoya disease is characterised by steno-occlusive changes in the terminal internal carotid artery and involving the proximal portions of the anterior or the middle cerebral arteries with abnormal vascular networks seen in the vicinity of the steno-occlusive disease. Probable diagnosis is established if the findings are seen unilaterally. Progression to bilateral disease is frequently seen. No accompanying systemic signs are seen. Extensive fibocellular intimal thickening and deposits of thrombi and lipids with proliferation of smooth muscle cells is the pathogenic feature of the disease. Inflammatory cells are usually absent unlike in vasculitis and atherosclerosis. 
Cerebral angiography is considered the gold standard investigation in Moyamoya disease as the demonstration of the internal carotid stenosis with formation of collaterals is very effective. Magnetic resonance angiography is a non-invasive method of demonstrating the same. Both these investigations show very effectively the extent of disease. MRI and CT scans also demonstrate the squeal of the pathology in the form of infarcts and intra-cerebral, subarachnoid and intra-ventricular haemorrhages.
Tissue level changes of the altered flow dynamics have not been well elucidated in Moyamoya disease. In our study we have found that though vascular changes are seen bilaterally (5/14 i.e. 35.7%), in majority of the cases unilateral perfusion defects alone are noted. In their study, Ogata et al,  found that the rate of vascular events was lower in patients with unilateral SPECT perfusion defects
Middle cerebral artery territory, i.e. frontal lobe and parts of the parietal lobe and basal ganglia are most frequently involved [Figure 1]. However occipital lobe involvement was also noted in three subjects [Figure 2]. The presence of artero-venous malformation along with features of Moyamoya disease in one patient can possibly explain such a phenomenon (Pt 13). Posterior circulation can be involved in up to 43% cases of Moyamoya disease.  Infarctions and cerebral atrophy are more frequently associated with posterior cerebral lesions. Progression of posterior circulation defects after revascularisation has been described in a study by Huang et al. It has been associated with decreased cerebrovascular reserve and cerebral blood flow. 
Good cerebrovascular reserve was found post acetazolamide in two patients [Figure 3]. Though the drawback in our study was the usage of oral acetazolamide preparation, obvious visual improvement was noted in the images suggesting adequate effect of the drug. Presence of good cerebro-vascular reserve is a known good prognostic factor indicating lesser chances of future events or interventions. 
|Figure 1: Tc99m-ECD brain perfusion SPECT Images in transaxial, sagittal and coronal views showing extensive perfusion defects in the left frontal and parietal lobes|
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|Figure 2: Tc99m-ECD brain perfusion SPECT Images in transaxial, sagittal and coronal views showing moderate perfusion defects in the right occipital cortex (posterior circulation) along with the parietal, temporal and the thalamus|
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|Figure 3: Tc99m-ECD brain perfusion SPECT Images in transaxial views showing perfusion defect in the right Broca's area (a) which shows improvement (b) in the post acetazolamide study|
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Our study demonstrates that though the pathological process occurs in the arteries, TC99m-ECD Brain SPECT reflects the result of these pathogenic changes on the cerebral tissue. The perfusion defects might involve both anterior and posterior circulations unilaterally or bilaterally and are better delineated in perfusion imaging compared to anatomical imaging modalities. Normal perfusion can also be found in certain cases. Demonstration of infarcts in posterior cerebral artery territory adds prognostic value, predicting occurrence of future infarcts. Better cerebrovascular reserve is also a good prognostic factor. Oral acetazolamide is also effective in demonstration of cerebrovascular reserve though not the ideal mode of administration. Our study is lacking adequate follow-up of the patients to show the prognostic implications of the findings of perfusion scintigraphy.
| Conclusion|| |
We conclude that brain perfusion scintigraphy is an indispensible adjunct in evaluation of patients with Moyamoya disease yielding information about the direct end results of the pathology in the vessels and also prognostic information.
| References|| |
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[Figure 1], [Figure 2], [Figure 3]