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We report on a 13 year old boy who presented with a focal left sided motoric seizure and a history of progressive headaches since 6 years of age. On neurological examination, motor function of the limbs, deep tendon reflexes, and sensory examination were normal, but there was slight left sided bradydisdiadochokinesis. Routine blood tests and anti-immune antibody screening as well as cerebrospinal fluid (CSF) analysis were normal.
Magnetic resonance imaging (MRI) showed multiple curvilinear areas of high signal intensity in leptomeninges (fig 1A) and diffuse enhancement along leptomeningeal surfaces (fig 1B). Digital subtraction angiography demonstrated severe stenoses of both distal internal carotid artery (ICA) segments (fig 1C) as well as extensive leptomeningeal collaterals (fig 1D).
Leptomenigeal enhancement on postcontrast T1 weighted MR images has been reported in association with meningitis, meningeal carcinomatosis, and angiitis. Common among these diseases is pathologic inflammation or carcinomatous infiltration of the leptomeninges, with or without involvement of the small leptomeningeal vessels.
In 1995 Ohta et al1 reported diffuse leptomeningeal enhancement on postcontrast T1 weighted MRI in children with moyamoya disease and named these finding the “ivy-sign”, because it resembles ivy creeping on stones. The ivy-sign can be found on fluid attenuation inversion recovery (FLAIR) images, as well as on contrast enhanced MRI.2,3
The characteristic enhancement is caused by an engorged pial network via leptomeningeal anastomosis. The source of leptomeningeal high signal intensity on FLAIR images is not clear but it seems largely due to slow flowing vessels of the engorged pial network.2 Thus, the mechanism of the leptomeningeal ivy-sign can be explained by an engorged pial network and possibly the congested meninges.