KEYWORDSArteries, abnormalities; Hypoplasia internal carotid artery; Extracranial duplex sonography; Transcranial duplex sonography.Abstract Introduction: Hypoplasia of the internal carotid artery (HICA) is a rare congenital anomaly caused by an incomplete development of the organ, and only a few cases are reported in the literature. The prevalence of HICA (including agenesia and aplasia) is estimated to about 0.01%. Case report: We describe a case of a 66-year-old man with hearing loss on the left side and no other symptoms or signs related to vascular impairment. HICA was discovered incidentally by color duplex sonography of the extracranial cerebral vessel and confirmed by magnetic resonance imaging angiography (angio MRI) and computed tomography (CT) of the head. Discussion: Compensatory flow allows HICA patients to remain asymptomatic, but complications may occur. The pathways of the collateral circulation in association with aplasia or HICA are described. A differential diagnosis was made on the basis of ultrasonographic (US) detection of diffuse luminal narrowing of the internal carotid artery (ICA). Recognition of this disease has important clinical implications.Sommario Introduzione: L'ipoplasia della carotide interna è una rara anomalia congenita che si verifica per un incompleto sviluppo dell'organo. Soltanto pochi casi sono stati riportati in letteratura. La prevalenza dell'ipoplasia se calcolata insieme alla agenesia e alla aplasia è stimata essere dello 0.01%. Caso clinico: Descriviamo il caso di un uomo di 66 anni affetto da ipoacusia all'orecchio sinistro e nessun segno di problemi vascolari. L'ipoplasia della carotide interna fu scoperta accidentalmente durante un ecocolordoppler dei tronchi sovraortici e venne confermata da angio risonanza magnetica e tomografia assiale computerizzata del cranio. Discussione: I flussi di compenso permettono a questi pazienti di rimanere asintomatici per molti anni ma possono essere causa nel tempo di complicazioni. Vengono descritti i pattern di circolazione collaterale associati alla ipoplasia della carotide interna. Vengono messi in evidenza i segni ultrasonografici che permettono la diagnosi differenziale in caso di diffuso * Corresponding author. Geriatric Department, Ospedale Madonna delle Grazie, 75100 Matera, Italy.E-mail addresses: nicolettix@libero.it, giusnicoletti@gmail.com (G. Nicoletti). restringimento del lume vascolare della arteria carotide interna. Inoltre, sottolineiamo che il riconoscimento di tale condizione ha importanti implicazioni nella pratica clinica. ª

IntroductionWe describe the case of a 79-year-old Caucasian Italian woman with a transient basilar occlusion monitored by transcranial Doppler, with subsequent recanalization and clinical shrinking deficit. This is the first case of transient basilar occlusive disease diagnosed and monitored by transcranial Doppler. This case is important and needs to be reported because transient basilar occlusion may be easily diagnosed if transcranial Doppler is performed.Case presentationA 79-year-old woman affected by chronic atrial fibrillation and not treated with oral anticoagulants, cardioverted to sinus rhythm during a gastric endoscopy. She then showed a sudden-onset loss of consciousness, horizontal and vertical gaze palsy, tetraparesis and bilateral miosis and coma. Two hours later, the symptoms resolved quickly, leaving no residual neurologic deficits. Transcranial Doppler examination showed a dampened flow in the basilar artery in the emergency examination and a restored flow when the symptoms resolved.ConclusionThis is the first case of transient basilar occlusive disease diagnosed and monitored by transcranial Doppler. We believe that transcranial Doppler should be performed in all cases of unexplained acute loss of consciousness, in particular, if associated with signs of brainstem dysfunctions.