Leptomeningeal Contrast Enhancement in the MR Diagnosis of Moyamoya Disease Cerebral catheter angiography is essential for the diagnosis of moyamoya disease. However, catheter angiography has its potential risk of complication. We have prospectively studied its risk in our hospital, which indicated 0.8% of permanent neurological complication and 2.0% of temporary/transient neurological complication. These results are not high in comparison to the other reports, but in the pediatric patients with moyamoya disease, the risk of catheter angiography might be higher because its requires general anesthesia and expected risks of hyperventilation. We believe that catheter angiography should be minimally applied to the pediatric moyamoya patients and magnetic resonance imaging and/or angiography should be the first line diagnostic methods. The purposes of cerebral angiography in moyamoya disease are to establish the diagnosis of moyamoya disease, to check the efficacy of bypass surgery, and evaluate the progression of the disease. In the diagnosis of moyamoya disease using magnetic resonance imaging, conventional tomographic study and angiography are always performed. Enhanced study using gadolinium contrast material has not been commonly used in the past. It is reported that in moyamoya disease contrast enhancement is observed on the brain surface, which resembles the ivy creeping on the stone. Thus, this is called "ivy sign." This leptomeningeal enhancement (ivy sign) is more prominent when brain ischaemia is more profound. After effective bypass surgery, this leptomeningeal enhancement reduces, indicating the good collateral blood flow through the bypass. Using this phenomenon, catheter angiography could be omitted in the selected situation. It is assumed that leptomeningeal contrast enhancement is inversely proportional to the cerebral blood flow. This sign can be used to study the cerebral blood flow indirectly. References 1. Komiyama M, Yamanaka K, Nishikawa M, Izumi T: Prospective analysis of complications of catheter cerebral angiography in the digital subtraction angiography and magnetic resonance era. Neurol Med Chir (Tokyo) 38: 534-540, 1998 [abstract] 2. Komiyama M, Nakajima H, Nishikawa M, Yasui T, Kitano S, Sakamoto H: Leptomeningeal contrast enhancement in moyamoya: its potential role in the postoperative assessment of circulation through the bypass. Neuroradiology 43: 17-23, 2001 [abstract]