Background and aims Moyamoya disease (MMD) is an uncommon chronic progressive cerebrovascular occlusive disease of the bilateral internal carotid arteries that leads to a compensatory abnormal vascular network at the base of the brain. Reported incidence in the USA is approximately 0,086 per 100,000 patients. It can be primary or associated with other conditions.

Methods Retrospective analysis of clinical files of patients diagnosed with MMD currently followed in the Paediatric Neurology ambulatory unit of Vila Nova de Gaia Hospital, Portugal.

Results There are three cases of MMD, all male, two associated with neurofibromatosis type 1 (NF-1) and one case of primary MMD. All diagnosis were based on brain magnetic resonance angiography (MRA) findings: stenotic lesions in the distal carotid arteries, increased signal in the leptomeninges and perivascular spaces. Idiopathic MMD presented in an 11 year old with acute hemiparesis and disartria. Brain CT revealed an ischaemic stroke and MRA was consistent with MMD. In both cases of NF-1, MMD was diagnosed during follow up of the disease. Patients were 1 and 4 years old and were assymptomatic at time of diagnosis. In one case, neurologic symptoms developed during follow-up and revascularisation surgery was necessary.

Conclusions The natural history of MMD tends to be progressive. Association between MMD and NF-1 is rare, but poses a potencial risk. In previously healthy patients who present with acute neurologic symptoms, a high index of suspicion is necessary. In both cases, prompt diagnosis and appropriate management are crucial to improve long-term prognosis.