Ivy signs on FLAIR images before and after STA-MCA anastomosis in patients with Moyamoya disease

BACKGROUND

Leptomeningeal high signal intensity (ivy sign) on fluid-attenuated inversion-recovery (FLAIR) MR imaging is one of the features of Moyamoya disease. However, the correlation between ivy sign and cerebral perfusion status has not been fully evaluated.

PURPOSE

To characterize ivy sign on FLAIR images in Moyamoya disease and compare this finding with hemodynamic alterations on perfusion single-photon emission CT (SPECT) obtained before and after bypass surgery.

MATERIAL AND METHODS

Sixteen patients with angiographically confirmed Moyamoya disease who underwent superficial temporal artery-middle cerebral artery (STA-MCA) anastomosis were included in the study. The presence of ivy sign on FLAIR images was classified as 'negative', 'minimal' and 'positive'. We evaluated the relationship between ivy sign and findings of SPECT, including cerebral vascular reserve (CVR) before and after surgery.

RESULTS

Minimal or positive ivy sign was seen in 13 (81%) of 16 patients, and 21 (66%) of 32 hemispheres. CVR in the areas with positive or minimal ivy sign was lower than that in the areas with negative ivy sign. After STA-MCA anastomosis, ivy sign disappeared or decreased in all 21 hemispheres demonstrating ivy sign. SPECT demonstrated apparent hemodynamic improvement in areas demonstrating disappearance or decrease of ivy sign.

CONCLUSION

Ivy sign on FLAIR image is seen in areas with decreased cerebral perfusion. The sign is useful for non-invasive assessment of cerebral hemodynamic status before and after surgery.

Constructive interference in steady state imaging of moyamoya disease

The diagnostic accuracy of three-dimensional constructive interference in steady state (CISS) magnetic resonance (MR) imaging was evaluated for the assessment of idiopathic moyamoya disease. Six consecutive patients underwent MR angiography, CISS imaging, and digital subtraction angiography. MR angiography and CISS imaging visualization of the steno-occlusive changes in the distal internal carotid arteries and the development of moyamoya vessels in the basal cistern were compared to the results obtained by digital subtraction angiography. MR angiography revealed the steno-occlusive changes correctly in nine and overestimated the changes in three of 12 hemispheres examined. CISS imaging showed the steno-occlusive changes defined as decreased caliber of the internal carotid artery correctly in two, underestimated the changes in nine, and overestimated the changes in one of the 12 hemispheres. MR angiography detected moyamoya vessels correctly in five and underestimated the vessels in seven of the 12 hemispheres. CISS imaging revealed the moyamoya vessels correctly in 10, underestimated the vessels in one, and overestimated the vessels in one of the 12 hemispheres. CISS imaging can supplement MR angiography in the non-invasive diagnosis of moyamoya disease, especially for the evaluation of moyamoya vessels.

MRI and MR angiography in moyamoya disease

The role of radiological imaging in moyamoya disease includes screening of the disease based on clinical findings, evaluation of the changes in vasculature and brain parenchyma, and clinical follow-up. The imaging findings in moyamoya disease are classified as primary and secondary. The primary findings essentially consist of occlusion of the circle of Willis and collateral formation, including moyamoya vessel formation. The secondary findings include cerebral infarction, white matter lesions, atrophy, and hemorrhage. For the visualization of the primary and secondary findings as well as postoperative results, MRI and MR angiography are the most reliable methods and play important roles because of their excellent diagnostic yield and noninvasiveness.

Moyamoya disease

Moyamoya disease is a rare cerebrovascular condition of uncertain aetiology commonly affecting young persons. The disease is mainly seen in Japanese patients. We report two cases of moyamoya disease in Caucasian women and review the postulated aetiological factors and associated conditions as well as the spectrum of invasive and non-invasive imaging modalities useful in the diagnosis and follow-up of the disease, with particular reference to the developing role of magnetic resonance imaging and angiography.

Diffuse leptomeningeal enhancement, "ivy sign," in magnetic resonance images of moyamoya disease in childhood: case report

We report three cases of children with moyamoya disease who revealed prominent leptomeningeal enhancement on postcontrast magnetic resonance (MR) images. Two of the children underwent bilateral extracranial-intracranial bypass operations because of ischemic symptoms. During the operations, a profuse pial arterial network was observed, which was considered to be the origin of the enhancement. The ischemic episodes disappeared after the operations, and the follow-up MR images showed marked reduction of the leptomeningeal enhancement. One of the three patients had an extracranial-intracranial bypass operation on one side, but postoperative MR images have not yet been obtained. We named this finding on postcontrast MR images "ivy sign," because it resembles ivy creeping on stones. Ivy sign seems to be a unique, characteristic feature of the pial network observed in moyamoya disease.

Diagnosis of moyamoya disease with magnetic resonance angiography

BACKGROUND AND PURPOSE

Present criteria for the diagnosis of moyamoya disease emphasize the use of conventional cerebral angiography as an indispensable requirement. However, magnetic resonance angiography (MRA) is fast becoming a reliable diagnostic modality for occlusive cerebrovascular diseases. The purpose of this study is to assess the accuracy of MRA compared with conventional angiography.

METHODS

Thirty-nine patients (23 children and 16 adults) with moyamoya disease confirmed by conventional angiography (78 side views) were examined with MRA (three-dimensional time-of-flight technique with a 256 x 256 or 256 x 512 matrix). T1- and T2-weighted MR images were also taken.

RESULTS

The stenotic or occlusive change at the carotid fork was clearly revealed by MRA, which correlated well with conventional angiography (83% good correlation, 17% overestimation). Apparent moyamoya vessels were clearly shown as a signal void on the MR image and fine unusual vessels on MRA, particularly in children with moyamoya disease (82%). However, small moyamoya vessels were poorly shown on both MR images and MRA, particularly in adults (63%).

CONCLUSIONS

MRA can be an alternative to conventional angiography in typical moyamoya disease cases (the bilateral type of moyamoya disease in children). However, in the early or the end stages of moyamoya disease, diagnosis by means of MRA should be carefully evaluated.