Peduncular hallucinosis in a patient with subclavian steal syndrome: usefulness of Doppler ultrasonography.

The subclavian steal syndrome is characterized by retrograde flow within a vertebral artery ipsilateral to proximal subclavian artery high-grade stenosis or occlusion. It can cause vertebrobasilar insufficiency and hence diverse brainstem symptoms. Peduncular hallucinosis consists of visual images of brief duration that are related to thalamic or rostral brainstem lesions. We describe a patient with peduncular hallucinosis in the setting of subclavian steal syndrome. Inducing a hemodynamic challenge to the vertebrobasilar circulation elicited the patient́s visual symptoms. Thus, careful ultrasonographic evaluation with dynamic testing contributed to explain the physiopathology of the clinical symptoms.