**12. Prognosis**

Prognosis depends on how fast the blockage occurs and how effective the collateral circulation is established. Fifty to sixty-six percent of patients will have the progression of the disease, and they have a poor outcome. Pediatric patients who were surgically treated were found to have disease progression in an estimated 2.6% of patients only. Among untreated asymptomatic patients, the annual stroke rate was found to be 3.2% and disease progression in 80% [52, 53].
