What is the initial assessment and treatment for a stroke patient with distal cerebral vascular occlusions?

Assessment of Stroke Patients with Distal Cerebral Vascular Occlusions

For distal cerebral vascular occlusions (M2/M3 MCA segments, ACA, or PCA), perform immediate non-contrast CT to exclude hemorrhage, followed by CT angiography to precisely localize the occlusion, then administer IV alteplase if within 4.5 hours and no contraindications exist, while simultaneously consulting neurointerventional radiology for potential mechanical thrombectomy in selected cases. 1

Initial Imaging Protocol

Non-Contrast CT (NCCT) - First Priority

• Obtain NCCT immediately to exclude intracranial hemorrhage, which is the absolute contraindication to thrombolytic therapy 1
• Look specifically for hyperdense hemorrhagic foci that would exclude acute treatment 1
• Assess for early ischemic changes and estimate infarct core size using ASPECTS score (≥6 suggests small-to-moderate core) 1
• NCCT has acceptable radiation dose of 3 mSv and is more time-efficient than MRI 1

CT Angiography (CTA) - Second Priority

• Perform arch-to-vertex CTA to confirm vessel occlusion and precisely localize the distal occlusion site 1
• CTA has high accuracy for detecting distal occlusions with high interrater reliability 1
• Accurate clot localization is vital to determine if the distal occlusion is amenable to endovascular therapy 1
• Consider multiphase CTA (adds peak-venous and late-venous phases) to assess collateral circulation, which predicts better response to treatment 1
• Total radiation dose for NCCT plus multiphase CTA is approximately 8.5 mSv 1

Alternative: MRI-Based Assessment

• If MRI is immediately available without delaying treatment, DWI can detect ischemia more sensitively than CT 1
• Time-of-flight MRA can visualize intracranial vessels without contrast, useful in contrast allergy 1
• However, MRI should only be used if it does not delay IV alteplase administration 1

Clinical Assessment Priorities

Three Critical Questions to Answer

1. Is there evidence of intracranial hemorrhage? (determines alteplase eligibility) 1
2. Is there a vessel occlusion, and where is it located? (guides treatment strategy) 1
3. What is the risk/benefit ratio for treatment? (considers infarct size, time, and patient factors) 1

Distal Occlusion-Specific Considerations

• Distal occlusions (M2/M3, ACA, PCA) have higher spontaneous recanalization rates with IV alteplase compared to proximal occlusions 1
• Patients without visible occlusion or with only distal occlusions have lower baseline NIHSS scores (median 10-15 vs 18 for M1 occlusions) 2
• Despite higher recanalization potential, mechanical thrombectomy is increasingly performed for distal occlusions 1, 3

Treatment Algorithm

Within 4.5 Hours of Symptom Onset

Step 1: Immediate IV Alteplase

• Administer IV alteplase (0.9 mg/kg) if no contraindications, regardless of plans for endovascular therapy 1
• Do not delay alteplase to wait for endovascular team mobilization 4
• Alteplase remains cornerstone therapy even for large vessel occlusions 1

Step 2: Simultaneous Neurointerventional Consultation

• Contact neurointerventional radiology immediately upon confirming distal occlusion on CTA, even if alteplase is being administered 4
• Do not wait to assess clinical response to IV alteplase before considering thrombectomy, as every 30-minute delay decreases good outcomes by 8-14% 4

Step 3: Determine Thrombectomy Candidacy

• For M2 proximal segments: Consider thrombectomy, especially if NIHSS ≥6 4
• For M3 and more distal segments: Thrombectomy may be reasonable in carefully selected patients, though evidence is limited 4
• Distal occlusions can be treated safely with endovascular therapy, achieving TICI 2b-3 reperfusion in 83% of cases with 4% symptomatic hemorrhage rate 3
• Specialized small-caliber devices (3.5mm stent retrievers) are available for distal vessel thrombectomy 5

Beyond 6 Hours from Symptom Onset

Perform advanced imaging to assess salvageable tissue:

• CT perfusion (CTP) or MRI with DWI/perfusion to identify core-penumbra mismatch 1
• Patients with favorable perfusion mismatch may benefit from thrombectomy up to 24 hours 1
• Use software providing reproducible measurements of ischemic core and penumbra 1

Risk Stratification

Favorable Prognostic Indicators

• Absence of proximal occlusion on CTA predicts 5-fold higher odds of early improvement and 6.8-fold higher odds of independence at day 7 2
• Patients with patent vasculature or occult distal occlusions have 0% symptomatic hemorrhage rate vs 23.3% with visible occlusions 2
• Good collateral circulation on multiphase CTA predicts better outcomes 1

High-Risk Features

• Large ischemic core (ASPECTS <6) increases reperfusion hemorrhage risk 1
• Multiple vessel occlusions (carotid-T, basilar plus MCA) have lower recanalization rates and worse outcomes 2, 6
• Anticoagulation status: EVT may still be considered in anticoagulated patients if otherwise eligible, though hemorrhagic transformation risk is higher 1

Common Pitfalls to Avoid

• Never withhold neurointerventional consultation based solely on "distal" location - M2 and even M3 occlusions can cause devastating deficits and may benefit from thrombectomy 4, 3
• Do not delay mechanical thrombectomy to assess response to IV alteplase - time-dependent outcomes mandate parallel processing 4
• Do not skip vascular imaging even within 3 hours - knowing occlusion location guides treatment intensity and predicts outcomes 1, 2
• Avoid routine urinary catheter insertion before thrombolysis unless patient has acute urinary retention 1
• Do not routinely reverse anticoagulation in DOAC patients to give alteplase - EVT remains an option 1

Specific Vessel Considerations

M2/M3 MCA Occlusions

• Median NIHSS typically 8.5-15 (lower than M1 occlusions) 3, 2
• Thrombectomy achieved TICI 2b-3 in 73.9% using small-caliber devices 5
• Consider thrombectomy as primary strategy or rescue after proximal recanalization 3

ACA Occlusions

• Can be treated alone or in combination with MCA occlusions 3
• Successful endovascular treatment feasible with standard techniques 3

PCA Occlusions

• Less commonly treated but endovascular therapy is feasible 3
• Consider basilar artery involvement and extended time windows up to 24 hours given devastating natural history 4