When can Transcranial Doppler (TCD) be used in adults?

When Transcranial Doppler Can Be Used in Adults

Transcranial Doppler (TCD) should be used in adults primarily for detecting and monitoring cerebral vasospasm after subarachnoid hemorrhage, screening for intracranial stenosis or occlusion in acute stroke, monitoring sickle cell disease patients for stroke risk, detecting microembolic signals in high-risk cardiac conditions, and assessing intracranial pressure when invasive monitoring is not feasible. 1, 2

Primary Clinical Indications

Vasospasm Detection After Subarachnoid Hemorrhage

• TCD is the standard screening tool for vasospasm after SAH, with 90% sensitivity and 92% negative predictive value for predicting delayed cerebral ischemia 1, 2
• Daily bedside TCD screening is frequently used in at-risk populations during the first 10 days post-SAH 1
• Flow velocities >200 cm/s predict high likelihood of vasospasm 2
• The Lindegaard ratio distinguishes true vasospasm from hyperemia 2
• Screening beyond day 10 post-SAH does not increase detection of delayed cerebral ischemia and should be discontinued 1

Acute Ischemic Stroke Evaluation

• For anterior circulation intracranial stenoses, TCD demonstrates 70-90% sensitivity and 90-95% specificity 1, 3
• TCD detects middle cerebral artery (MCA) occlusion with equal effectiveness to other modalities 1
• For posterior circulation vessels, sensitivity drops to 55-80% with specificity up to 95% 1
• TCD provides real-time monitoring of recanalization after thrombolytic therapy, offering immediate feedback on treatment success 3
• Within the 3-hour IV tPA window, TCD can be performed without delaying treatment 3

Sickle Cell Disease Screening

• TCD identifies children and adults at high stroke risk, with mean maximum velocities ≥200 cm/s in ICA or MCA indicating increased ischemic stroke risk and need for transfusion therapy 1, 2, 3

Microembolic Signal Detection

• TCD detects high-intensity transient signals from embolic material in real-time 1
• Useful for risk stratification in prosthetic heart valves, atrial fibrillation, patent foramen ovale, aortic arch plaque, and during cardiopulmonary bypass 1, 3
• Provides indication of relative stroke risk from underlying cardiac conditions 1

Intracranial Pressure Assessment

• The European Society of Intensive Care Medicine recommends B-mode TCCD insonation of the MCA with qualitative waveform analysis and pulsatility index measurement to rule out intracranial hypertension impairing cerebral perfusion 1, 2
• Increased ICP and decreased cerebral perfusion pressure produce characteristic Doppler waveform changes: decreased diastolic velocity and increased pulsatility index 1
• Elevated pulsatility index (calculated as [Peak systolic velocity - End diastolic velocity] / Mean velocity) suggests increased ICP or reduced cerebral perfusion 2
• TCD has potential to assess mass effect and track ICP changes dynamically 1

Extracranial Carotid Disease Assessment

• In hemodynamically significant extracranial internal carotid artery stenosis, TCD shows significant flow dynamic abnormalities in the anterior circulation 4
• TCD assesses intracranial collateral flow patterns in patients with extracranial arterial occlusive disease 5
• TCD may determine hemodynamic significance of known carotid stenosis but is not recommended for surveillance of asymptomatic carotid stenosis 1

Critical Limitations and When NOT to Use TCD

Absolute Contraindications to Sole Reliance on TCD

• When carotid endarterectomy or carotid angioplasty/stenting is contemplated, ultrasound alone should NOT be used—DSA remains the gold standard 3
• For determining degree of stenosis requiring surgical intervention, either DSA or two noninvasive techniques combined (ultrasound plus CTA or MRA) must be used 3
• For distal branch occlusions, subacute to chronic stenoses, vasculitis, or dissection, DSA surpasses TCD and should be used instead 3

Technical Limitations

• 10-20% of patients lack adequate temporal bone acoustic windows, making TCD impossible in these individuals 2, 3
• Significantly reduced accuracy for distal vessels and posterior circulation 2
• Operator dependency is significant—examiners must be sufficiently trained with quality standards defined before clinical use 3
• On-site interpretation by experienced investigators is essential; offline analysis is less reliable 3

Not Indicated For

• Initial imaging of intracerebral hemorrhage, aneurysms, or arteriovenous malformations 3
• Suspected cerebral venous sinus thrombosis 1
• Suspected CNS vasculitis 1
• Surveillance of asymptomatic carotid stenosis 1
• Cervical vascular dissection or injury 1

Optimal Clinical Integration

When TCD Provides Maximum Value

• TCD's primary value stems from its non-invasive nature, bedside availability, real-time monitoring capability, and absence of interference from temperature or sedatives 2
• Most useful when an endovascular team is available and intra-arterial therapy is being considered 3
• Ideal for serial monitoring in ICU settings where repeated assessments are needed 1, 6

Integration with Advanced Imaging

• The European Society of Intensive Care Medicine recommends TCD as an initial screening tool, followed by confirmatory imaging with CTA, MRA, or conventional angiography for definitive diagnosis 2
• For patients presenting >3 hours after stroke symptom onset, formal vascular study (CTA/MRA/DSA) is strongly recommended, especially if endovascular intervention is contemplated 3
• CTA and DSA are more accurate than TCD for determining precise stenosis severity and should be used for definitive diagnosis 3

Common Pitfalls to Avoid

• Do not rely on TCD alone when surgical decisions are being made—this misclassifies up to 28% of patients 3
• Do not attempt TCD without adequate extracranial vascular assessment, as extracranial obstruction affects intracranial hemodynamics interpretation 3
• Avoid using TCD as first-line imaging for intracerebral hemorrhage or vascular malformations 3
• Despite high sensitivity for vasospasm detection, there is no current high-quality literature relating detection of vasospasm on TCD to improved patient outcomes 1
• Very high-grade stenosis (string sign) may be underestimated by TCD due to artifactual velocity reduction 1