The Plan

Members with conditions affecting blood flow to the brain may meet the medical necessity for a Transcranial Doppler (TCD). TCD is a non-invasive technique that can be used to evaluate blood flow in the brain. An ultrasound probe is placed against the head, and sound waves detect blood flow. TCD can be used during surgery that involves the blood vessels that supply the brain to make sure that blood flow is not interrupted during surgery.TCD is also used outside of surgery to detect some rare forms of abnormal blood flow in the brain. When blood vessels are narrowed, have clots, or have other structural irregularities, TCD can sometimes be used to detect these problems. Only specific blood flow problems in certain parts of the brain can be seen with TCD. Only a licensed physician may order and interpret TCD.If a single test is being ordered for intracranial pathology in adults, computed tomography (CT), magnetic resonance imaging (MRI), Computed Tomographic Angiography (CTA), or Magnetic Resonance Angiogram (MRA) are more generally acceptable first-line tests; in the absence of specific contraindications.

In patients aged 2-16 years with sickle cell disease, current expert recommendation calls for annual screenings with TCD.¹

Definitions

"Transcranial Doppler (TCD)" is a non-invasive technique that uses ultrasound waves to detect blood flow in the brain's blood vessels.

"Carotid Endarterectomy" is a surgical procedure that corrects narrowing of the carotid artery by removing plaque from the inside of the artery to improve blood flow to the brain and reduce the risk of strokes.

"Arteriovenous Malformation (AVM)" is an abnormality of blood vessels that occurs when there is an abnormal connection between an artery and vein, resulting in the bypassing of the capillary system that normally serves as the bridge between the two systems. AVMs are most often asymptomatic, but can cause pain, neurologic symptoms, and even fatal bleeding in some cases.

"Stenosis" is an abnormal narrowing of any structure such as an artery.

"Carotid Bruit" is a physical exam finding in which abnormal blood flow sounds are heard while listening to the carotid artery with a stethoscope.

"Parkinson's disease" (PD) is a neurodegenerative movement disorder characterized by tremor and muscle rigidity. The later stages may be associated with dementia symptoms, but dementia rarely occurs in isolation. It occurs due to loss of cells in a part of the brain that plays a role in motor function called the substantia nigra. Signs and symptoms suggestive of possible PD include the following:

• Resting tremor
• Shuffling gait
• Slow movements
• Muscle rigidity
• Impaired posture
• Speech changes
• Writing changes

Clinical Indications

The Plan considers Transcranial Doppler medically necessary when ONE of the following criteria are met:

1. Assessing blood flow and/or microemboli of intracranial arteries during carotid endarterectomy; or
2. Evaluating blood flow in infants meeting any ONE of the following criteria:
   1. Screening for intraventricular hemorrhage in infants born at 30 weeks' gestation or less; or
   2. When cerebrovascular evaluation is needed for evaluating blood flow through the circle of Willis or to evaluate for cerebral sinovenous thrombosis in high-risk infants; or
3. Detecting and re-screening stroke risk of patients aged 2-16 with sickle cell disease; or
4. Diagnosing dissection of vertebral artery; or
5. Diagnosing non-cardiac right-to-left shunt when the member has ONE of the following:
   1. Suspected patent foramen ovale; or
   2. Clinical signs of paradoxical embolism; or
6. Evaluating and monitoring for vasospasm after non-traumatic subarachnoid hemorrhage; or
7. Evaluating collateral circulation in patients known to have severe occlusion or severe stenosis of intracranial vessels, such as in Moyamoya syndrome; or

Experimental or Investigational / Not Medically Necessary

Transcranial Doppler for any other indication is not considered medically necessary by the Plan, as it is considered experimental, investigational, or unproven. Non-covered indications include, but are not limited to, the following:

• Brain tumors
• Diagnosing infectious or inflammatory conditions
• Diagnosing or evaluating response to antithrombotic therapy
• Diagnosis or evaluation of cerebral arteriovenous malformations
• Dural arteriovenous fistula
• Epilepsy
• Evaluating cerebral aneurysm
• Evaluating risk of stroke in adults with sickle cell disease
• Evaluating veins, including but not limited to sinus thrombosis and other conditions that involve venous pathology
• Following placement or evaluating an intra-cerebral arterial stent
• Idiopathic intracranial hypertension
• Managing trauma
• Migraine headaches
• Neurofibromatosis
• Non-parkinsonian dementia (e.g., Alzheimer's dementia) or other neurodegenerative conditions
• Parkinson's disease, screening asymptomatic patients at risk for Parkinson's disease, or to differentiate between secondary parkinsonism.
• Predicting outcomes in patients with ischemic infarction (hemorrhagic conversion) or vertebrobasilar stroke
• Psychiatric disorders
• Screening for arterial stenosis in patients with fibromuscular dysplasia
• Screening for carotid stenosis in asymptomatic patients
• Stroke, either ischemic or hemorrhagic, except as described in clinical indications for medical necessity
• Diagnosing or evaluating traumatic brain injury

Evidence for Non-Coverage of Above Indications

Brain tumors

Ickenstein and colleagues conducted a feasibility study in 2008 evaluating the use of TCD combined with a contrast injection to identify the area of involvement in patients with known glioblastoma. Although the technique appeared to have some merit in identifying these tumors and their blood flow, the utility of such information remains unknown. There have been no clinical trials to establish TCD’s role in usual clinical care of brain tumors.

Diagnosing infectious or inflammatory conditions

There are very few case reports of clinicians using TCD in the care of patients with intracranial infectious or inflammatory conditions. Most studies involving TCD involve experimental use of TCD to evaluate systemic processes such as sepsis and their effects on intracranial blood flow rather than for direct patient care. Marquez-Romero and colleagues described an extremely rare case of an aneurysm caused by neurocysticercosis. Cantu and colleagues explored the use of TCD in a more common complication of neurocysticercosis, intracranial arteritis. This 1998 study included 9 patients and did find that TCD provides useful information in this very specific group, but even so its use has been overshadowed by widespread availability of magnetic resonance imaging (MRI) and computed tomography.

Diagnosis or evaluation of cerebral arteriovenous malformations

AAN guidelines state that there is "insufficient evidence" to guide the use of TCD in the detection and monitoring of cerebral AVMs. Furthermore, UpToDate guidelines currently recommend MRI, MRA, CT and make no mention of TDU/TCD for the evaluation or workup of these malformations. Further evidence is needed to determine the clinical role of TCD in AVM management.

Epilepsy

TCD does not play a role in the usual management of epilepsy. There are few clinical trials that include both epilepsy and TCD, reflecting its uncommon use even in the research setting. One interesting study did compare TCD to the Wada test.

The Wada test

The Wada test (anesthetizing one side of the brain during angiography) is the gold standard for establishing language dominance which becomes an important consideration in patients with refractory epilepsy disease in presurgical planning. Knake and colleagues compared TCD with the Wada test and found TCD to produce similar outcomes with respect to lateralization of the dominant hemisphere. Importantly, 2 of the 13 patients were unable to be evaluated using TCD due to suboptimal imaging.⁴

Evaluating response to antithrombotic therapy

TCD is sometimes used in the research setting to evaluate the effectiveness of antithrombotic therapy following acute ischemic stroke. Its role in clinical practice is yet to be determined. Saqqur and colleagues used TCD as part of a multifaceted program to predict which patients would do poorly after antithrombotic therapy to help stratify patients who may be candidates for interventional therapy. While this approach does appear promising, improved outcomes with this method have yet to be demonstrated. The American Academy of Neurology agreed in its clinical guidelines that TCD probably does provide information in evaluating patients after antithrombotic therapy, but it also stated that the clinical utility of this information remained unclear.

The most exciting use of TCD in recent years has centered on treatment of stroke in combination with antithrombotic therapy. Early studies indicated that use of ultrasound waves may help to expose more of the thrombus to the antithrombotic medication. While some waves were found to be too strong and lead to hemorrhage, milder ultrasound waves appear safe. However, the large multicenter trial evaluating this technique, the CLOTBUST-ER trial, was terminated early after enrolling 675 of the planned 800 patients due to futility of treatment.

Evaluating veins

While evaluation of the arterial system with TCD is common and established, evaluation of venous pathology is much less common. A 2008 review by Stoltz found that the false negative rate was unacceptably high when using TCD to evaluate cerebral venous thrombosis. Other imaging modalities are more commonly accepted for this application.

Managing trauma

There have been numerous studies citing the potential of TCD to improve clinical outcomes in traumatic brain injury (TBI). This potential has largely been explored in response to TBI becoming the defining injury in recent wars in Iraq and Afghanistan for United States service members. Amyot and colleagues wrote a 2016 review describing the effectiveness of different neuroimaging techniques and found TCD to be useful, especially in the military setting in which access to other less portable modalities is limited.

Use of TCD in the civilian setting in the management of TBI has been described, but clinical outcome studies are lacking. The American Academy of Neurology guidelines note that TCD probably does provide some useful information in evaluating traumatic vasospasm but that its clinical utility remains to be determined. The review by Amyot and colleagues noted that because TCD has the potential to identify vasospasm prior to the development of neurologic deficits, it may offer clinicians a window of time to intervene and prevent neurologic deterioration. While this potential seems clearly worth exploring, to date there are no studies that have demonstrated prevention of stroke or improvement in other outcomes with the use of TCD following TBI. TCD may also be useful in evaluating intracranial pressure following TBI, but it is unlikely to supplant direct pressure monitoring as the gold standard.⁵

Migraine headaches

Because migraines are a vasomotor disorder, TCD provides real-time visualization of one of the underlying processes leading to this type of headaches. TCD has been used in the research setting to evaluate patient response to therapy such as triptan medications, beta blockers and acupuncture.

Outside of the experimental setting, though, evidence for its use is lacking. A 2017 systematic review by Shayestagul and colleagues found that there were no changes in blood flow velocity in the middle cerebral artery during migraine attacks. The data hinted that perhaps there was a decrease in blood flow velocity early on in the attacks, and the authors suggested that future studies should focus on this early phase of migraine attacks when researching TCD and migraine headaches.

Neurofibromatosis

Neurofibromatosis is a hereditary syndrome that is sometimes associated with vasculopathy. A 2013 retrospective analysis by Ghosh and colleagues looking at 312 patients, 15 (4.8%) had evidence of vasculopathy. In this series of patients, magnetic resonance angiography (MRA), the gold standard, was used to evaluate intracranial disturbances in blood flow.

TCD’s role in this condition is much less defined. Paschoal and colleagues used TCD to screen patients with Neurofibromatosis for cerebral vascular disease prior to performing MRA. Three of the four patients with abnormal TCDs were confirmed to have disease on confirmatory testing with MRA, resulting in a positive predictive value of only 75%. And because MRA was not done on the patients with a normal TCD, negative predictive value and sensitivity, the numbers typically used to help select a screening test, cannot be calculated.

Parkinson's Disease (PD)

As per UpToDate’s last update in 2021, although transcranial doppler is being studied for its potential role for PD, further research is necessary to establish utility and diagnostic accuracy. Furthermore, in the 2015 Movement Disorder Society Clinical Diagnostic Criteria for Parkinson's disease (PD) does not include transcranial doppler.

Psychiatric disorders

The use of TCD in the evaluation or management of psychiatric disorders is experimental and is not a routine use of the technique. Mijajlovic and colleagues in a 2014 review describe a potential research avenue using TCD to evaluate the brainstem for the diagnosis and monitoring of patients with unipolar depression. Schupbach and colleagues performed a 2007 trial evaluating cerebral blood flow changes in patients with schizophrenia. Clinical application of TCD for psychiatric disorders remains rare even in experimental settings, and it currently does not play a clinical role in the diagnosis or management of psychiatric disorders.⁶