BACKGROUND Children with PHACES syndrome (PS) and visual impairment or stridor show a dramatic and immediate response to propranolol. However, this beta-blocking drug could be responsible for an eventually increased risk of ischemic stroke due to the underlying cerebral vascular disease. To more accurately understand the effects of propranolol on brain vascularization, we examined PS patients treated with this drug for airway or visual complications using brain perfusion SPECT (Single Photon Emission Computed Tomography). In the past, this examination has been shown to be useful in the management of patients with different neurovascular disorders. METHODS Clinical records and imaging studies were reviewed in 7 patients with a diagnosis of PS. All patients underwent magnetic resonance angiography (MRA), echocardiography, chest X-ray and ophthalmologic, neurological, and cardiologic assessments. They received 2-3 mg/kg/day propranolol in an attempt to treat stridor or avoid ophthalmologic occlusion. We performed SPECT after 3-6 months of treatment. RESULTS SPECT showed a normal uptake in the frontal and temporal regions despite vascular abnormalities found with MRA imaging. Significant improvements of symptoms and in the volume of the hemangioma were noted in all cases without signs of a reduction of brain blood perfusion. CONCLUSIONS Propranolol treatment was safe in our patients who did not show signs of perfusion changes. The high sensitivity for detecting functional impairment makes brain perfusion SPECT useful in the diagnosis and follow-up of patients with PS considered at risk of neurovascular impairment. Accurate knowledge of its pathophysiological basis, together with the appropriate technique and careful interpretation of reporting, will enhance the clinical use of brain SPECT in those patients.