A Diagnostic Investigation Of Moyamoya Disease With Magnetic Resonance Imaging And Magnetic Resonance Angiography

Background and Objectives: Moyamoya comes from a Japanese word meaning "puff of smoke", moyamoya disease (MMD) is a rare idiopathic cerebrovascular occlusive disorder characterized by single or usually double sided obstruction and progressive stenosis of the internal carotids and of the afferent and efferent channels of Willis Circle, which causes a collateral circulation, responsible for the typical angiographic image of a 'puff of smoke'. Moyamoya Disease was first described in Japan in 1957 by Takeuchi and Shimizu and more than 6000 cases have been reported all over the world with female to male ratio of 1.8:1 and noted bimodal peak of age, either in the first decade or in the third and fourth decades of life. The exact etiology of this disease is unknown. MMD presents with common presentations like headache, dizziness, sensory impairment, hemiparesis, monoparesis etc. and adults experience hemorrhage more commonly whereas cerebral ischaemic events are more common in children. The earlier the diagnosis, the better outcome the disease has, surgical management being better than medical treatment and diagnosis of disease depends completely on radiological evaluation. Magnetic resonance imaging (MRI) and magnetic resonance angjography (MRA) have been widely used in assessing MMD because of its capacity to illustrate anatomic details and vascular architecture. Also MRA demonstrates blood flow in vessels without the need for catheters or contrast agent. The aim of this study is to analyze the MRI and MRA films of MMD patients and explore the diagnostic value of MRI and MRA for MMD.Materials and Methods: We retrospectively analyzed the gross clinical materials, MRI and MRA findings of 50 cases of MMD proved by DSA or operation. We studied the cases lying in the period between January 2005 to April 2007. All patients had the history of headache, dizziness and sensory impairment, typical history of seizure attacks in 12 children and history of hemiparesis, monoparesis in 18 adults. Previous CT scan studies in 11 patients revealed cerebral infarction mostly in frontal and parietal regions in 7 pediatric patients and cerebral hemorrhage mostly in basal ganglia and parietal regions in 4 adults. All patients were imaged with MRI and MRA with a superconductive machine of 1.0 Tesla (Impact) from Siemens Medical System by using a head coil fitted with a mirror. T₁WI was acquired with TR = 450 ms, TE = 15 ms and T₂WI with TR = 1800 ms of spin echo (SE) sequence, TE = 80 ms, matrix = 256x256, field of view (FOV) = 23cm and slice thickness of 7mm with 1mm interval between them. MR angiography sequences were acquired using flow-void effects and time of flight (TOF) techniques with TR = 36.0 ms, TE = 10.0 ms and FOV = 20cm. We then studied about the age and sex distribution in MMD, the incidence of hemorrhage and ischaemia/infarction in adults and in children respectively, the MRA appearances of internal carotid artery (ICA), middle cerebral artery (MCA), anterior cerebral artery (ACA) or posterior cerebral artery (PCA) stenosis and presence or absence of collateral moyamoya pattern of vessels in the base of the brain. Then, statistical analysis was made by using Statistical Package for Scientific Studies (SPSS) 11.0 software packages and the P value less than 0.05 ( P < 0.05) was considered to be significantly different.Results: There were 29 (58%) female and 21 (42%) male patients with mean age of 19.36 years and female to male ratio of 1.4:1. The age of the patients ranged from 4 to 47 years, 23 being paediatric patients (upto 14 years) and 27 adults (4 in 15-19 years, 15 in 20-29 years, 6 in 30-39 years, and 2 in 40-47 years).MRI revealed infarctions represented as low signal intensities on T₁WI and high signal intensities on T₂WI and hemorrhages represented as mixed high or low signal intensities on both T₁WI and T₂WI. Out of 23 paediatric patients, 19 experienced cerebral infarctions, 1 had hemorrhage in the left temporal lobe and 3 had no infarction and hemorrhage on MRI scan. In children, infarctions were noted as follows: 5 had frontal lobe infarction (1 bilateral, 2 left and 2 right), 3 had parietal lobe infarction (2 bilateral and 1 right), 3 had left temporal lobe infarction, 3 had left fronto-parietal region infarction, 2 had right parieto-temporal region infarction, 1 had left fronto-temporal region infarction, 1 had right occipital lobe infarction and 1 had multiple infarctions in bilateral cerebral cortex. Cerebral hemorrhage was noted in 22 adult patients, 2 showed cerebral ischaemia (1 in the right basal ganglia and 1 in bilateral frontal lobes) and 3 had no infarction and hemorrhage on MRI scan. In adults, hemorrhages were distributed as 6 patients had hemorrhage in the basal ganglia region (1 bilateral, 3 left and 2 right), 7 had in the parietal region (4 left and 3 right), 3 had in the temporal region (2 right and 1 left), 2 had in the left frontal lobe, 1 had in the right frontal and left temporal regions, 2 had overlying the left lateral ventricle and 1 had in the parieto-temporal region. The comparative study between patients' age and characteristic MRI findings in the study groups was analyzed by using SPSS 11.0 software packages and the P value less than 0.05 i.e. (P < 0.05) was considered to be significantly different. In adults, the incidence of hemorrhage was 81.5% (22/27) and that of infarction was 7.4% (2/27) whereas in children, the incidence of infarction was 82.6% (19/23) and that of hemorrhage was 4% (1/23) respectively with x²= 32.826 and P = 0.000. i.e. P < 0.05. Low signal intensity moyamoya vessels which were located in thalamus-basal ganglia were shown on T₁WI and T2WI of SE sequence in 48 cases. Diagnostic positive rate of MRI was 96% (48/50). Moyamoya vessels of suprasellar cistern were seen clearly on T2WI in 27 of 50 cases.MRA revealed that ICA stenosis was noted in 23 patients (bilateral ICA in 16, right sided ICA in 3 and left sided ICA in 4 patients), ICA occlusion was noted in 10 patients (bilateral ICA in 8, right sided in 1 and left sided in 1 patient) and 17 patients had normal ICA. MCA stenosis was noted in 35 patients (bilateral MCA in 25, right sided in 5 and left sided in 5 patients), MCA occlusion was noted in 9 patients (right sided MCA in 3 and bilateral in 6 patients) and 6 patients had normal MCA. ACA stenosis was noted in 18 patients (bilateral ACA in 8 and left sided in 10 patients), ACA occlusion was noted in 10 patients (right sided ACA in 2 and bilateral in 8 patients) and 22 patients had normal ACA. Lastly, PCA stenosis was noted in 2 patients, both had right sided PCA stenosis, PCA occlusion was noted in 7 patients (bilateral in 6 and right sided in 1 patient) and 41 patients had normal PCA. Characteristic smoky vessels or "moyamoya vessels" representing collaterals were evident in 46 cases. Out of 46, 43 patients had basal cerebral moyamoya vessels, 22 patients had collaterals from other collateral vessels: 16 from PCA and 6 from external carotid artery (ECA). These pathological vessels found on MRA were also correlated with the SE sequence MRI to a great extent. 2 cases had no moyamoya vessels on MRA but evidence on MRI scans. Diagnostic positive rate of MRA was 92% (46/50). The diagnostic results of MRI and MRA had P value calculated by x² test to be 0.854 i.e. (P>0.05), notifying the diagnostic accuracy of MRI and MRA to be not significantly different. MRI and MRA combined revealed the findings of MMD features in 48 cases.Conclusion: 1.MRI or MRA is an effective method to diagnose Moyamoya disease. 2. MRI is a good method to find complications of Moyamoya disease (e.g. infarction or hemorrhage). 3. Combining MRI and MRA could diagnose Moyamoya disease more effectively, may become gold standard for determining Moyamoya disease. 4. Cerebral infarction in Moyamoya disease occurs more often in children and cerebral hemorrhage more often in adults.