Diagnosis

The diagnosis of Moyamoya disease is made by:

• MRI scanning; this is one of the first tests to perform in the diagnostic algorithm because it is sensitive and non-invasive. Slowing of flow can be demonstrated by the linear hyperintensities following the sulcal pattern, known as 'ivy sign' (1)
• Magnetic Resonance Angiography (MRA). This is a gold standard test and provides preliminary information on cerebral arteries and the degree of narrowing. MRA also shows the development of collaterals around the steno-occlusive lesions in the form of 'puff of smoke'. (1)
• intracerebral angiography - reveals characteristic basal cerebral changes and carries the highest specificity about the area and degree of narrowing
• CT - may show multiple, often bilateral, areas of infarction with a predilection for watershed zones
• Transcranial Doppler (TCD) is an adjunctive method for monitoring cerebral haemodynamics in Moyamoya disease(2)
• Electroencephalography (EEG). This is necessary for patients presenting with seizures - there is a distinctive EEG finding in half of Moyamoya patients, known as the 'rebuild-up' phenomenon. This refers to a reappearance of slow waves of higher amplitude (normally seen during hyperventilation), within 20-60 seconds following termination of hyperventilation which is not seen in any other pathology. (3)

Reference

1. Hishikawa T, Sugiu K, Date I. Moyamoya Disease: A Review of Clinical Research. Acta Med Okayama. 2016 Aug;70(4):229-36.
2. Yeh SJ et al. Color Doppler ultrasonography as an alternative tool for postoperative evaluation of collaterals after indirect revascularization surgery in Moyamoya disease. PLoS One. 2017;12(12)
3. Frechette ES et al. Electroencephalographic features of moyamoya in adults. Clin Neurophysiol. 2015 Mar;126(3):481-5.