When should a non‑contrast head CT, MR angiography, and carotid Doppler be performed, and what are the standard treatment protocols for complicated cases with comorbidities, specifically for transient ischemic attack, acute ischemic stroke, and intracerebral hemorrhage?

Imaging and Treatment Protocols for Acute Cerebrovascular Events

Start with non-contrast head CT immediately for all suspected acute stroke or TIA patients—this is the mandatory first step to distinguish hemorrhagic from ischemic stroke, which fundamentally determines all subsequent treatment decisions. 1

Imaging Algorithm by Clinical Scenario

For Acute Stroke Candidates (Within Treatment Window)

Step 1: Non-Contrast CT Head (NCCT)

• Always perform first to exclude hemorrhage and assess for large infarct 1
• This is non-negotiable before any thrombolytic therapy
• Can be performed within minutes and should never delay initial assessment

Step 2: Add CTA Head and Neck immediately after NCCT if:

• Patient is candidate for IV tPA (0-4.5 hour window) 1
• Endovascular therapy is being considered 1
• Do not perform CTA alone without preceding NCCT—you will miss hemorrhage and cannot safely anticoagulate 2

Step 3: Consider CT Perfusion (CTP)

• Add if patient is within extended window (6-24 hours) to assess salvageable tissue 1
• Must not delay tPA decision if within 4.5-hour window 3
• Useful for patient selection in late-window thrombectomy candidates

For TIA or Minor Stroke (Non-Acute Presentation)

Primary focus shifts to secondary prevention and vascular imaging:

• NCCT head to exclude hemorrhage and alternative diagnoses 4
• Vascular imaging is mandatory: CTA, MRA, or carotid Doppler ultrasound to assess carotid stenosis 1
  • CTA neck preferred for speed and accuracy in detecting carotid stenosis 4
  • MRA head and neck (without and with contrast) if MRI available—preferred modality per guidelines 1
  • Carotid Doppler ultrasound acceptable but less sensitive for vertebral arteries and plaque characterization 5
• MRI with DWI/FLAIR/GRE if available—more sensitive than CT for acute infarction and helps risk stratification 1, 6, 1

For Suspected Intracerebral Hemorrhage (ICH)

NCCT head is diagnostic 7

Then add CTA head and neck acutely if:

• Age <70 years with lobar ICH 7
• Age <45 years with deep/posterior fossa ICH 7
• Age 45-70 years with deep ICH but no hypertension history 7
• Primary intraventricular hemorrhage with no parenchymal source 7

Purpose: Exclude macrovascular causes (aneurysm, AVM, dural fistula, venous thrombosis)

Follow with MRI/MRA if CTA negative to evaluate for cavernous malformation, CAA, or tumor 7

Consider catheter angiography (DSA) if:

• CTA/MRA suggests vascular malformation 7
• Primary IVH with no identified source 7
• Young patient with negative noninvasive imaging 7

When to Use Each Modality

Non-Contrast CT Head

• First-line for all acute presentations 1
• Rapid (minutes), widely available
• Excellent for hemorrhage detection
• Limited sensitivity for acute ischemia <6 hours

CTA Head and Neck

• Add immediately after NCCT in acute stroke candidates 1
• Evaluates large vessel occlusion for thrombectomy
• Assesses carotid stenosis for secondary prevention
• Never perform without preceding NCCT if anticoagulation/thrombolysis considered 2

MRI/MRA

• Preferred for TIA when available 24/7 1
• More sensitive than CT for acute infarction 6
• Better for small vessel disease, demyelination, infection 2
• Limitation: Longer acquisition time may delay treatment 2
• Use when CT negative but high clinical suspicion persists

Carotid Doppler Ultrasound

• Acceptable alternative for carotid assessment in TIA 1
• Non-invasive, no contrast needed
• Limitations: Operator-dependent, poor for vertebral arteries, cannot assess intracranial vessels 5
• Rated "usually not appropriate" as sole modality in acute stroke 6

Treatment Protocols by Stroke Type

TIA Protocol

Immediate Management:

1. Dual antiplatelet therapy (aspirin + clopidogrel) within 24 hours for high-risk TIA (ABCD² ≥4) or minor stroke 8

   • Continue for 21 days, then single antiplatelet 8
   • Reduces stroke risk from 7.8% to 5.2% 8
   • Exception: Do not use if atrial fibrillation or severe carotid stenosis identified

2. Anticoagulation if cardioembolic source (atrial fibrillation) 8

3. Carotid revascularization within 48 hours if symptomatic stenosis ≥50% 4, 8

Comorbidity Considerations:

• Renal failure: Use MRA instead of CTA (avoid iodinated contrast) 6
• Contrast allergy: MRA without contrast acceptable 6
• Atrial fibrillation: Anticoagulation supersedes antiplatelet therapy 8

Acute Ischemic Stroke Protocol

Within 0-4.5 Hours:

• IV alteplase (tPA) if no contraindications 8
  • Requires BP <185/110 mmHg pre-treatment 3
  • Maintain BP <180/105 mmHg for 24 hours post-treatment 3
  • Improves functional independence: 39% vs 26% (0-3 hours), 35.3% vs 30.1% (3-4.5 hours) 8

Within 0-6 Hours (or 6-24 Hours with Favorable Imaging):

• Mechanical thrombectomy for large vessel occlusion 8
  • Requires CTA confirmation of occlusion 1
  • 46% vs 26.5% functional independence at 6 hours 8
  • Extended window (6-24 hours) if perfusion imaging shows salvageable tissue 8

Blood Pressure Management:

• Do NOT routinely lower BP unless SBP ≥220 mmHg or DBP ≥120 mmHg 3
• If lowering needed, reduce by only 15% over 24 hours 3
• Exception: Must achieve BP <185/110 mmHg before thrombolysis 3

Comorbidity Modifications:

• Hypertension: Avoid aggressive lowering acutely; target <130/80 mmHg chronically 9
• Diabetes: Check glucose—hypoglycemia mimics stroke 10
• Anticoagulation use: Increases hemorrhage risk—NCCT mandatory before reversal decisions
• Renal failure: Avoid contrast if possible; use MRI/MRA 6

Intracerebral Hemorrhage Protocol

Acute Management:

• Rapid BP lowering to SBP <140 mmHg within 1 hour 7, 11
  • Use IV calcium channel blockers (nicardipine preferred) 3
  • Avoid excessive drops or variability
  • Do NOT lower if SBP <220 mmHg initially per some protocols 9

Avoid:

• Prophylactic anticonvulsants (no benefit, possible harm) 3
• Antiplatelet or anticoagulation therapy acutely
• Aggressive early mobilization within 24 hours 11

Comorbidity Considerations:

• Anticoagulation: Immediate reversal required
• Hypertension: Target SBP <140 mmHg acutely, <130/80 mmHg long-term 9
• Suspected vascular malformation: Proceed to CTA/DSA per age-based algorithm above 7

Critical Pitfalls to Avoid

1. Never start antiplatelet/anticoagulation without brain imaging—ICH can mimic TIA with transient symptoms 12

2. Never perform CTA alone without NCCT first in acute setting—you cannot assess for hemorrhage on CTA 2

3. Do not delay tPA for advanced imaging (MRI, perfusion) if within 4.5-hour window and NCCT shows no contraindication 1, 3

4. Do not aggressively lower BP in acute ischemic stroke unless meeting thrombolysis criteria or SBP ≥220 mmHg 3, 9

5. Do not rely on carotid Doppler alone for acute stroke workup—inadequate for intracranial assessment 6, 5

6. Do not skip vascular imaging in TIA—20% will have stroke within 90 days, 80% preventable with proper workup 4, 13

7. Do not assume young patients have benign etiology—macrovascular causes present in 1 in 4-7 patients <70 years with ICH 7