Transcranial insonation.

Insonation of the intracranial cerebral arteries, veins, and sinus is performed with transcranial Doppler or color duplex sonography. The orbital window is mainly used to identify the ophthalmic artery and carotid siphon, which can be detected in most patients. The temporal window allows the investigation of the anterior, middle, and posterior cerebral and the terminal (C1) segment of the internal carotid arteries, and the deep middle cerebral and basal veins in 80-84% of cases. Intracranial vessels located in the periphery of the temporal insonation field [postcommunicating (A2) anterior cerebral artery, the carotid siphon and more proximal parts of the internal carotid artery, the insular (M2) and opercular (M3) parts of the middle cerebral artery, the quadrigeminal (P3) part of the posterior cerebral artery, the great cerebral vein, the straight and transverse sinus] will be missed more often, particularly in patients who are older, of female gender, or Black or Asiatic ethnicity. The foraminal window is used to assess the intracranial (V4) vertebral and basilar arteries, which are detected in 79-94% and 89-96%, respectively. Echo contrast agents increase the detection rate and diagnostic confidence of transtemporal and -foraminal insonation. The frontal and occipital bony windows are rarely used to insonate the basal cerebral arteries and the internal cerebral vein, and the straight sinus, respectively.