Moyamoya disease mimicking a spontaneous internal carotid artery dissection on Doppler ultrasound.

Moyamoya disease and spontaneous internal carotid artery dissections are rare conditions, but both tend to affect young adults with potentially devastating consequences. A 43-year-old non-Japanese patient presented with neurological symptoms, which, following carotid Doppler ultrasound and angiography, was labelled as being due to a spontaneous internal carotid artery dissection. Repeat imaging at 3 months showed normalisation of the carotid Doppler findings which coincided with the formation of "moyamoya" vessels on the angiogram. This case report illustrates the changes on carotid ultrasound in early moyamoya disease which may mimic the appearances of an internal carotid artery dissection and demonstrates the change of the spectral Doppler waveform that occurs with the formation of new vessels at the base of the brain.