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Blue Cross and Blue Shield of Montana (BCBSMT) may consider Transcranial Doppler (TCD) Ultrasound medically necessary when used for any of the following:
- Monitoring for vasospasm in patients with subarachnoid hemorrhage;
- Assessment of patients suspected of having steno-occlusive disease of the intracranial arteries;
- Assessing initial collateral blood flow and embolization during carotid endarterectomy (CEA) in order to reduce the risk of stroke by detecting severe ischemia and the possible need for a shunt to be placed;
- As a tool to determine risk for transient ischemic attacks (TIA) or cerebrovascular accidents (CVA) in patients with sickle cell disease;
- As a confirmatory test in support of a clinical diagnosis of brain death;
- Assessment and detection of patent foramen ovale (PFO) and/or to determine cause of cryptogenic stroke when transesophageal echocardiography (TEE) is contraindicated. NOTE: Examples of contraindications for TEE include, but are not limited to:
- Unrepaired tracheoesophageal fistula;
- Esophageal obstruction or stricture;
- Perforated hollow viscus;
- Poor airway control;
- Severe respiratory depression;
- Uncooperative, unsedated patient;
- History prior esophageal surgery;
- Esophageal varices or diverticulum;
- Gastric or esophageal bleeding;
- Vascular ring, aortic arch anomaly with or without airway compromise;
- Oropharyngeal pathology;
- Severe coagulopathy;
- Cervical spine injury or anomaly.
- Evaluating hemodynamic significance of extracranial vascular atherosclerosis;
- Evaluating cerebral blood flow following trauma;
- Assessing migraine and tension headaches;
- Assessing cerebral blood flow and embolic events during cardiopulmonary bypass surgery;
- Evaluating blood flow patterns in central nervous system infections;
- Evaluating dementia;
- Evaluating glaucoma;
- Detection and assessment of the circulatory patterns of arteriovenous malformations (AVM);
- Assessing hydrocephalus;
- Testing vasomotor reactivity (VMR) to detect abnormalities of cerebral hemodynamics;
- Detecting cerebral microemboli signals for diagnostic uses, or for monitoring response to antithrombotic therapy;
- Monitoring vasodilator therapy as a treatment of behavior or developmental disorders including, but not limited to, attention deficit hyperactivity disorder (ADHD), autism, or Tourette’s syndrome.
Routine Transcranial Doppler (TCD) examination of the intracranial arteries was demonstrated to be possible in 1982. TCD is primarily a technique for measuring relative changes in flow. One fact that has to be constantly kept in mind when utilizing TCD is that the value obtained for a particular artery is the velocity of blood flowing through the vessel, and unless the diameter of the vessel is established by other means it is not possible to determine the actual blood flow.
In 1998 Adams, R.J., et al., reported on a trial of chronic blood transfusions in 130 children with sickle cell anemia and abnormal results on TCD. A total of 63 patients were randomized to receive transfusions to achieve a target hemoglobin S concentration; children received transfusions every three to four weeks. The remaining 67 patients received standard care. There was a significant decrease in the incidence of stroke in the transfusion group, leading to premature termination of the trial. In their 2004 technology assessment, the American Academy of Neurology (AAN) concluded that the clinical utility of TCD is established for assessing stroke risk in children with sickle cell disease.
Brain death is a clinical diagnosis that can be supported by TCD evidence of absent cerebral blood flow; diagnostic criteria for cerebral circulatory arrest or brain death using TCD have been published, with sensitivity and specificity of 91 to 100% and 97 to 100%, respectively. The specificity is imperfect as absence of middle cerebral artery (MCA) flow may be transient or basilar artery (BA) flow may still be present; when systolic spikes are present in multiple intracranial compartments, recovery is unlikely. TCD is especially helpful in patients with suspected brain death who have loss of brainstem function due to isolated brainstem lesions or who received sedative or paralytic agents that render clinical examination or interpretation of electroencephalogram (EEG) difficult. Based on the evidence, the AAN assessment concluded that TCD can confirm the clinical diagnosis of brain death, and is a useful adjunct test for the evaluation of cerebral circulatory arrest associated with brain death.
Intracranial atherosclerosis is responsible for up to 10% of transient ischemic attacks (TIA) and strokes. TCD ultrasound offers a noninvasive method of detecting discrete stenoses or occlusions of the intracranial vessels. The Blue Cross Blue Shield Association (BCBSA) policy, which is based partially on the BCBSA Technology Evaluation Center 1994 (TEC) Assessment, concluded that aggregate evidence suggests TCD ultrasound is moderately to highly (73-95%) sensitive and highly (90-100%) specific relative to cerebral angiography for detection of intracranial stenosis or occlusion in patients who have TIA or cerebrovascular accident (CVA) of unknown etiology, after cardiac and extracranial carotid artery evaluation; TCD results can occasionally influence the use of therapeutic options. In addition, the AAN assessment states that TCD is probably useful for the evaluation of patients with suspected intracranial steno-occlusive disease, but that data are insufficient to give a recommendation regarding replacing conventional angiography with TCD.
The principal cause of stroke following carotid endarterectomy (CEA) is embolism from the operative site. Available evidence suggests that intraoperative TCD measurements of collateral flow after carotid clamping for CEA are fairly accurate. The BCBSA TEC assessment noted at least two large studies that suggest intraoperative shunting reduces the CVA rate for patients who have poor collateral flow and increases the CVA rate for patients who have good collateral flow, as measured by TCD. These findings provide direct evidence of a reduced perioperative stroke rate for patients undergoing CEA when TCD ultrasound is used to guide selective intraoperative shunt use and severe ischemia is used as the criterion for intraoperative shunting. The AAN assessment also states that CEA monitoring with TCD can provide feedback that may help the surgeon take appropriate measures at all stages of the operation to reduce risk of perioperative stroke.
Contrast transcranial Doppler ultrasonography (cTCD) has been studied as a diagnostic technique for assessing cardiac right-to-left shunt (RLS), such as PFO. Spencer et al. reported 98% sensitivity and 94% accuracy when detecting PFO with power motion-mode transcranial imaging, compared with 91% sensitivity and 99% accuracy with transesophageal echocardiography (TEE). However, the presence of microbubbles in the cerebral circulation is not exclusive to an interatrial communication. Any cause of RLS, including ventricular septal defect and pulmonary arteriovenous malformation, can lead to a positive transcranial Doppler reading for a cardiac RLS, thus lowering the specificity of this test. The AAN technology assessment states “Data show a high correlation between contrast-enhanced TCD and contrast-enhanced TEE, with essentially 100% concordance for the “clinically significant” high number of particles shunted. Nevertheless, the sensitivity and specificity of contrast TCD for detecting right-to-left cardiac or extracardiac (pulmonary arteriovenous) shunts may vary by center, protocol, and diagnostic criteria. The routine performance of the Valsalva maneuver during testing can improve sensitivity and specificity. The sensitivity of contrast TCD can also be improved by using a higher volume of agitated saline (10 mL instead of 5 mL), use of Echovist (especially Echovist-300) instead of agitated saline, or repeating the Valsalva maneuver if the initial result is negative. Contrast TCD is comparable with contrast TEE for detecting RLS due to PFO. However, TEE is better than contrast TCD because it provides direct anatomic information regarding the site and nature of the shunt or presence of an atrial septal aneurysm. Whereas the number of microbubbles reaching the brain can be quantified by TCD, the therapeutic impact of this additional information is unknown. The AAN concluded that, although TCD is able to provide information, other tests are typically preferable for diagnosing right-to-left cardiac shunts; TEE is superior because it can provide direct information regarding the anatomic site and nature of the shunt.
The AAN technology assessment reported that there is probable evidence that vasomotor reactivity (VMR) testing techniques with TCD can detect abnormalities of cerebral hemodynamics in patients with risk factors for or symptoms of cerebrovascular disease, and is probably useful for detection of impaired cerebral hemodynamics in patients with asymptomatic severe (>70%) stenosis of the extracranial internal carotid artery, extracranial internal carotid artery occlusion, and cerebral small artery disease. However, how the results from these techniques can be used to influence therapy and affect patient outcomes remains to be determined.
The AAN also reported that new hardware and software technical capabilities may help detection of microembolic signal, and discrimination from artifact. However, accurate and reliable characterization of embolus size and composition is not possible with current technology, and data have not shown that detection of microemboli signals leads to improved patient outcomes. In addition, although TCD is probably useful to detect cerebral microemboli signals in a wide variety of cardiovascular/cerebrovascular disorders and/or procedures, current data do not support the use of microemboli detection with TCD for diagnosis, or for monitoring response to antithrombotic therapy in ischemic cerebrovascular disease.
TCD has been proposed as a technique to monitor vasodilator therapy in patients with developmental or behavioral disorders. It has been hypothesized that these disorders are related to cerebral vasospasm that can be relieved by vasodilator therapy. However, a search of the MEDLINE database failed to identify any peer-reviewed articles focused on this therapy.
Neither the BCBSA nor the AAN technology assessments found sufficient data to support the routine use of TCD for other indications including, but not limited to: migraine; cerebral venous thrombosis; evaluating hemodynamic importance of extracranial atherosclerosis; monitoring during cerebral angiography; evaluation of arteriovenous malformations (AVM); evaluation of cerebral autoregulation in other settings; evaluating hydrocephalus, dementia, or glaucoma; evaluating blood flow patterns in central nervous system infection; assessing cerebral blood flow during cardiopulmonary bypass surgery or after head trauma.
A search of peer reviewed literature through June 2012 identified no new clinical trial publications or any additional information that would change the coverage position of this medical policy.
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