Appeal type: unknown
Decision: unknown

 
The rules say that plans must pay for a medical service or item if regular Medicare would pay for it in this case. 
You can find this rule at 42 Code of Federal Regulations (CFR) Section 422.101. 
 
The rules say that CT scans are covered if there is literature to support its use for the patients condition and the 
scan is reasonable and necessary for the patient. You can find this rule in the Centers for Medicare and 
Medicaid Services, Internet Only Manual, Publication 100-03, Medicare National Coverage Determinations 
Manual, Section 220.1(A). 
The rules also say that CTP (using automated post-processing software algorithmic analysis) is medically 
reasonable and necessary in patients with small acute ischemic stroke (AIS) caused by unilateral large vessel 
occlusion (LVO) in the proximal anterior circulation evaluated at stroke centers; CTP can be used to aid in 
selection for endovascular mechanical thrombectomy (EVT) if 1 of the following other conditions is fulfilled: 
1. Treatment (femoral puncture) can be started within 6-24 hours of the time last known to be at 
neurologic baseline and who meet the pre-CTP inclusion/exclusion criteria as defined by the DAWN 
trial,
1
 or 
2. Treatment (femoral puncture) can be started within 6-16 hours of the time last known to be at 
neurologic baseline and who meet the pre-CTP inclusion/exclusion criteria as defined by the DEFUSE 
3 trial.
2
 
*excluding criteria purely related to study mechanics (e.g., able to return for protocol required follow-up visits, 
etc.) 
  Table 1: Key Inclusion Criteria for DAWN and DEFUSE 3 
mRS= modified Rankin scale, NIHSS= National Institutes of Health Stroke Scale, ICA= internal carotid artery, 
MCA= middle cerebral artery 
Parameter DAWN DEFUSE 3 
Prestroke baseline mRS (0-6) mRS 1 (no significant disability) 
mRS 2 
(slight 
disability) 
Last known well to treatment time 6-24 h 6-16 h 
Minimum NIHSS score (0-42) 10 (moderate stroke) 
6 (moderate 
stroke) 
LVO by MR or CT angiography 
ICA (intracranial) and/or M1 
segment of MCA 
ICA 
(cervical or 
intracranial) 
and/or M1 
segment of 
MCA 
Background 
Stroke is the leading cause of adult disability in the United States (U.S.) with limited treatment options.
3
 The 
U.S. Food and Drug Administration (FDA) approved treatment for stroke is intravenous tissue plasminogen 
activator (tPA)within 3 hours after onset of symptoms. Often treatment is not initiated since most patients do 
not present within this narrow time window, resulting in only 4% of patients receiving tPA treatment. Even 
with treatment, only 12-25% benefit as irreversible injury may have already occurred, or the treatment fails to 
recanalize the occluded artery with reported recanalization rate of 10-50%.
2,4
 Endovascular stroke therapy 
involves mechanical removal of blood clots or intra-arterial administration of thrombolytics. This offers an 
alternative to patients who fail tPA or are not eligible. Recanalization rates are as high as 82% for 
thrombectomy.
5
 Initial studies on EVT failed to demonstrate clinical benefits.
2
 Further investigation suggested 
the lack of benefit was related to patient selection. Subsequent studies identified imaging criteria to determine 
patients with potentially salvageable tissues and improved outcomes from EVT.
6-8 
In stroke victims, there is the 
ischemic penumbra, potentially salvageable tissue, and ischemic core, which is irreversibly injured. Patients 
with >50% reperfusion have been shown to have an improved outcome compared to those with <50% 
reperfusion. Treatment of patients with a higher likelihood of improved outcomes demonstrates the benefit of 
EVT in select patients. Expansion of the treatment window up to 16-24 hours has promising results in 
appropriately selected patients expanding the possibility for acute stroke treatment.
2,9
 CTP plays a role, as it 
can be used to calculate the ischemic penumbra and help to identify which patients may benefit from EVT. 
Reperfusion treatment was found to be more common in patients who had imaging with CT 
angiography (CTA) (13%) or CTP (17.6%).
10 
Noncontrast CT (NCCT) is the mainstay for initial AIS imaging 
due to widespread availability, rapid scan times, and detection of intracranial hemorrhage (which leads to very 
different management from infarction). Multimodal CT includes NCCT, CTA (to assess the site of vascular 
occlusion), and CT Perfusion Imaging (CTP). CTP is typically performed after NCCT and consists of a 
temporal sequence of head CT scans obtained during the wash-in and wash-out of an IV bolus of iodinated 
contrast agent. Post-acquisition data analysis by dedicated software allows the creation of 
multiple hemodynamic parametric maps (based on contrast time-density curves) for clinical interpretation. 
Hemodynamic parameters include time to maximum contrast intensity (Tmax), mean transit time (MTT), 
cerebral blood flow (CBF), and cerebral blood volume (CBV), mathematically related by the equation CBF = 
CBV/MTT.
11
 The CBV is calculated as the millimeters of blood per 100g of brain tissue. These maps can 
estimate brain regions with a high probability of irreversible infarction (ischemic core) versus areas of 
potentially reversible ischemia (penumbra). Both core and penumbra are estimates of probabilistic tissue fate. 
Penumbra imaging has been proposed as a useful predictor of hemorrhagic transformation (HT) in AIS.
12 
HT occurs in up to 40% of stroke patients and is related to rapid deterioration and poor outcomes. CTP has been 
studied in AIS for decades,
13
 only recently was it found likely to influence treatment decision.
14
 Subsequently, 
2 level I randomized controlled trials (RCTs) (DAWN and DEFUSE 3) found CTP helped determine eligibility 
for EVT in the late time period (6-24 hr) of an acute (<24 hr) ischemic stroke (AIS),
2,9
 a paradigm shift away 
from confinement to the early window (< 6 hr) CTP has the advantage of being able to be performed by most 
multi-slice scanners and add minimal time, usually less than 10 minutes, to the evaluation. There are limitations 
to CTP technology, emphasizing that CTP must be performed in properly selected patients. There are potential 
technical issues, such as patient movement and poor contrast bolus that can impact results. While experienced 
providers can typically recognize abnormalities caused by artifacts, calculations provided by the software may 
include artifacts, risking overestimating the penumbral volume. This requires manual correction to avoid 
miscalculations. Another challenge is there are multiple CTP vendor software and postprocessing techniques, 
which may lead to variations in calculated core and mismatch.
11,15
 Ideally, the software programs would be 
standardized, but given the variability, providers must be familiar with the software package being used and 
potential variations in calculated values. Automation has the potential to reduce human variability; however, 
even with fully automated software, a significant clinician interpretation learning curve remains.
16 
Limitations 
of arterial flow, which can be caused by low cardiac output, arrhythmias, chronic carotid stenosis, may result in 
overestimations. Chronic infarction, vascular stenosis, chronic white matter changes, seizures, and vasospasm 
can demonstrate abnormal CTP patterns and potentially mimic acute ischemia, so the provider must consider 
the full medical picture when interpreting results.
11,17 
CTP requires contrast, so those with renal failure or 
known serious allergy to iodine and previously refractory to pretreatment medications may not be candidates. 
Protocols should include care to avoid excess radiation exposure and avoid treatment delays. 
 
You can find this information under Local Coverage Determination (LCD) Computed Tomography Cerebral 
Perfusion Analysis (L38769). 
If you want to read these Medicare rules, you can go to this website www.medicareappeal.com. 
 
The Plan contract says that the Plan covers items and services in accordance with Medicare rules.