Probe placed laterally under the jaw, anteromedially to SCM with indicator pointing slightly upwards and medial ( Figure 2B) Side bend and rotate head to one direction and place probe just below and medial to mastoid process, directing transducer slightly medially towards bridge of the nose or contralateral eye ( Figure 2C)ĭetermination of flow signals from ipsilateral vertebral artery Ultrasound probe (with indicator pointed towards the patient’s face) placed over temporal area, slightly above zygomatic arch and immediately in front of tragus of the ear ( Figure 2A)Įvaluation of MCA measurements useful in observing cerebral vasospasm and ischemic stroke Table 3: Transducer windows and clinical application 3 There are four primary probe locations in TCD: transtemporal, suboccipital, orbital, and submandibular, as detailed in Table 3. Now that we have reviewed the relevant anatomy, let’s review the transducer placement, which is key to obtaining a good acoustic window. OA: ophthalmic artery, ICA: internal carotid artery, MCA: middle cerebral artery, BA: basilar artery, VA: vertebral artery, PCA: posterior cerebral artery, PCOM: posterior communicating artery, ACA: anterior cerebral artery.3 B) View of Circle of Willis and right MCA from transtemporal positioning of 2Mhz probe. Also shown is flow direction of various arteries and depths of insonation (in mm) for an average human skull. A ) A review of the major intracranial arteries in the Circle of Willis. The Circle of Willis is of central importance in TCD (see Figure 1). In this section, we will review the anatomy, probe locations, as well as basic concepts and definitions. Understanding the current and future applications of TCD in the emergency department first requires a review of basic concepts. Monitor cerebral perfusion pressure during resuscitation 17,18 Indications for Transcranial DopplerĬerebral vasospasm (including post subarachnoid hemorrhage) 6,7 While we will focus on these four aspects, there are many more indications for TCD as detailed in Table 2. Here, we will review the relevant anatomy in TCD, followed by a review of the literature on four promising applications of emergency TCD: rule-in vasospasm, MCA occlusion, midline shift, and pediatrics. 5 In the scope of emergency medicine practice, four promising applications for TCD have been increasingly recognized in the literature for their potential to aid providers in the care of neurologic emergencies. In addition to the aforementioned clinical uses, cranial ultrasound has been shown to have emerging roles in the evaluation of pediatric skull fracture and other cranial pathologies. Reduced acoustic view in 5-20% of patients 4 Not as accurate as current gold standard brain imagingīedside technique that is easily repeatable Provides real-time information on status of cerebral arteries Advantages and Disadvantages of TCD in the ED A comparison of the advantages and disadvantages can be seen in Table 1. While it can be difficult to obtain a good acoustic window in 5-20% of patients, 4 TCD allows us an opportunity to diagnose and treat intracranial pathologies when other modes of brain imaging are not available. TCD has the ability to provide dynamic, real-time information on intracranial processes in a way that a single snapshot in time, as obtained by CT, cannot. Neurologic emergencies rely heavily on speed of provider recognition and appropriate escalation of care. 2,3 While TCD is at a disadvantage to CT in definitive diagnostic ability, it boasts distinct advantages that CT cannot replicate. 1 Since then, it has gained momentum as a tool to evaluate intracranial emergencies including post-aneurysmal hemorrhage, middle cerebral artery (MCA) vasospasm, cerebral ischemia/arterial occlusion, and midline shift. Transcranial Doppler (TCD) ultrasound was first utilized in 1982 as a noninvasive way to evaluate cranial blood flow, particularly of the middle, anterior, and posterior cerebral arteries (MCA, ACA, and PCA, respectively). Transcranial Doppler offers exciting potential - but in what settings? This literature review evaluates its use in trauma, ICU, pediatric, rural, and international settings.
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