title: Relative energy index of microembolic signal can predict malignant microemboli.
abstract: OBJECTIVE
  Microembolic signals (MES) found on transcranial Doppler range from harmless air bubbles to large, solid, particulate emboli from the heart and large vessels. The presence of MES is not always associated with poor clinical outcome. The purpose of our study was to determine whether the relative energy index of MES measured by power M-mode Doppler can distinguish malignant from benign MES and to identify patients with worse prognosis.
  
  
  METHODS
  We prospectively collected transcranial Doppler emboli monitoring data from patients with symptomatic carotid stenosis presenting with TIA or ischemic stroke. For each patient, we calculated the relative energy index of MES and categorized those >1.0 as malignant MES. We compared the clinical characteristics, number, and volume of diffusion-weighted imaging lesions, and degree of stenosis and plaque characteristics on CT angiogram of patients with malignant and benign MES.
  
  
  RESULTS
  We enrolled 92 patients, 29 with TIA and 63 with stroke, within 48 hours of symptom onset. Twenty-six patients had a total of 319 MES; of these, 82.4% were benign and were 17.6% malignant. Malignant MES traveled further within intracranial vessels than benign MES. The 9 patients with >1 malignant MES had significantly larger baseline diffusion-weighted imaging lesion volume, had a higher prevalence of intraluminal thrombus on CT angiogram of the neck and plaque ulceration, and were more likely to have a poor clinical outcome (modified Rankin Score > or = 2) than those with benign MES (OR, 6.5; 95% CI, 1.47-28.68). The presence of malignant MES led to the institution of more aggressive secondary prevention measures.
  
  
  CONCLUSIONS
  Power M-mode transcranial Doppler identifies a subgroup of patients with malignant MES. These signals are more frequent in longer arterial trajectory. Patients with malignant MES have larger baseline infarcts, a higher prevalence of intraluminal thrombus or ulcerated plaque in the carotid artery, and worse clinical outcome.
authors.affiliation: Department of Neurology and Psychiatry, St. Louis University, St. Louis, MO 63110, USA. ybinchoi@gmail.com
authors.forename: Youngbin
authors.initials: Y
authors.lastname: Choi
authors.forename: Maher
authors.initials: M
authors.lastname: Saqqur
authors.forename: Eileen
authors.initials: E
authors.lastname: Stewart
authors.forename: Caroline
authors.initials: C
authors.lastname: Stephenson
authors.forename: Jayanta
authors.initials: J
authors.lastname: Roy
authors.forename: Jean-Martin
authors.initials: JM
authors.lastname: Boulanger
authors.forename: Shelagh
authors.initials: S
authors.lastname: Coutts
authors.forename: Andrew M
authors.initials: AM
authors.lastname: Demchuk
mesh_terms: D000368:Aged; D016893:Carotid Stenosis / Q000150:complications / Q000000981:diagnostic imaging / Q000473:pathology; D004617:Embolism / Q000000981:diagnostic imaging* / Q000209:etiology / Q000473:pathology*; D006801:Humans; D002546:Ischemic Attack, Transient / Q000000981:diagnostic imaging / Q000209:etiology; D008297:Male; D008875:Middle Aged; D011446:Prospective Studies; D020521:Stroke / Q000000981:diagnostic imaging / Q000209:etiology; D017585:Ultrasonography, Doppler, Transcranial