This document addresses the use of mechanical thrombectomy for acute ischemic stroke. Mechanical thrombectomy is an endovascular technique for removal of a thrombus or embolus from an intracranial blood vessel to reestablish blood flow.

Clinical Indications

Medically Necessary:

Intra-arterial mechanical embolectomy or thrombectomy is considered medically necessary in the treatment of ischemic stroke when any of the following criteria sets (I, II, III, IV or V) have been met:

1. Anterior cerebral artery (A1 or A2), middle cerebral artery (M1 or M2) or intracranial carotid artery occlusion when all criteria are met:
   1. Mechanical embolectomy is performed within 6 hours of onset of symptoms; and
   2. NIH Stroke Scale (NIHSS) score of 2 or greater; and
   3. Neuroimaging has ruled out intracranial hemorrhage or arterial dissection.
2.   Intracranial internal carotid artery or middle cerebral artery (M1) occlusion when all criteria are met:
   1. Mismatch between the severity of the clinical deficit and the infarct volume, as defined in any of the following situations:
      1. 80 years of age or older: NIHSS score of 10 or higher and an infarct volume of less than 21 ml; or
      2. Less than 80 years of age: NIHSS score of 10 or higher and an infarct volume of less than 31 ml; or
      3. Less than 80 years of age: NIHSS score of 20 or higher and an infarct volume from 31 to 50 ml;
         and
   2. Last known to be well 6 to 24 hours earlier; and
   3. Neuroimaging has ruled out intracranial hemorrhage or arterial dissection.
3. Intracranial internal carotid artery or proximal middle cerebral artery (M1) occlusion when all criteria are met:
   1. Mismatch between ischemic tissue and infarct volume, as defined by both of the following:
      1. Initial infarct volume of less than 70 ml; and
      2. A ratio of the volume of ischemic tissue to infarct volume of 1.8;
         and
   2. Last known to be well 6 to 16 hours earlier; and
   3. Baseline NIHSS score greater than or equal to 6; and
   4. Modified Rankin Scale (mRS) score less than or equal to 2 prior to qualifying stroke; and
   5. Neuroimaging has ruled out intracranial hemorrhage or arterial dissection.
4. Large ischemic core infarct due to intracranial internal carotid artery or proximal middle cerebral artery (M1) occlusion (or both) when all criteria are met:
   1. Infarct as defined by any of the following:
      1. Alberta Stroke Program Early Computed Tomography Score (ASPECTS) value of 3 to 5 on non-contrast CT; or
      2. An estimated ischemic-core volume of 50 ml or greater;
         and
   2. Last known to be well up to 24 hours earlier; and
   3. Baseline NIHSS score of greater than 6; and
   4. mRS score less than or equal to 2 prior to qualifying stroke; and
   5. Neuroimaging has ruled out intracranial hemorrhage or dissection.
5. Basilar artery occlusion when all of the following criteria are met:
   1. Last known to be well up to 24 hours earlier; and
   2. Baseline NIHSS falls into any of the following categories:
      1. NIHSS score of greater than or equal to 10 if presenting within 12 hours of when last known to be well; or
      2. NIHSS score of greater than or equal to 6 if presenting between 12 - 24 hours of when last known to be well;
         and
   3. mRS score less than or equal to 2 prior to qualifying stroke; and
   4. Neuroimaging has ruled out intracranial hemorrhage or arterial dissection.

Not Medically Necessary:

Intra-arterial mechanical embolectomy or thrombectomy is considered not medically necessary in the treatment of stroke in all other circumstances when the criteria above have not been met.