What is the management approach for a suspected posterior circulation stroke?

Management of Suspected Posterior Circulation Stroke

Patients with suspected posterior circulation stroke require immediate IV thrombolysis within 4.5 hours if eligible, followed by consideration for endovascular thrombectomy, with the critical caveat that these strokes are frequently missed due to non-specific symptoms and low NIHSS scores that belie their devastating potential. 1

Immediate Recognition and Assessment

Maintain High Clinical Suspicion

• Posterior circulation strokes present with non-specific symptoms that delay diagnosis and treatment compared to anterior circulation strokes. 1
• Common presentations include: loss of consciousness, headache, nausea, vomiting, dizziness, double vision, hearing loss, vertigo, imbalance, and unilateral extremity weakness 1
• Physical examination findings: ataxia (especially truncal ataxia), nystagmus, visual field defects, cranial nerve palsies 1
• Critical pitfall: Patients can have NIHSS score of 0 with only headache, vertigo, and nausea, yet still have devastating basilar artery occlusion. 1

Syndrome-Specific Presentations

• Top of basilar syndrome: somnolence, peduncular hallucinosis, convergence nystagmus, skew deviation, vertical gaze paralysis 1
• Mid-basilar occlusions: various pontine syndromes 1
• Proximal basilar occlusions: "locked-in" syndrome 1

Immediate Triage and Stabilization

• Activate stroke team immediately upon suspicion, with same priority as acute myocardial infarction or serious trauma. 2
• Perform ABCs (airway, breathing, circulation) stabilization 2
• Monitor cardiac rhythm continuously as cardiac abnormalities frequently accompany stroke 2
• Check vital signs at minimum every 30 minutes in emergency department 2

Diagnostic Imaging Protocol

Non-Contrast CT (First-Line)

• Complete non-contrast CT within 25 minutes of hospital arrival for potential thrombolysis candidates. 2
• Exclude hemorrhage and evaluate for life-threatening edema and mass effect in posterior fossa 1
• Look for hyperdense basilar artery sign: sensitivity 71%, specificity 98% for basilar occlusion; optimal density cut-off is 40-42 Hounsfield units 1
• Hyperdense basilar artery predicts poor outcome at 6 months (mRS >2, OR 5.6). 1
• Beam hardening artifact limits posterior fossa assessment but vessel hyperdensity is often visible 1

CT Angiography (Essential)

• Perform CTA immediately at time of brain CT to assess both extracranial and intracranial circulation ("aortic arch-to-vertex"). 1
• CTA is the primary method to identify large vessel occlusion 1
• CTA collateral score and patency of distal third of basilar artery correlate with good outcomes (mRS ≤3 at 3 months) 1
• CT interpretation should occur within 45 minutes of arrival 2

Advanced Imaging for Extended Window

• For patients beyond 6 hours from symptom onset, CT or MR perfusion scanning can demonstrate perfusion mismatch and determine ischemic core extent 2

Acute Reperfusion Therapy

Intravenous Thrombolysis (IV tPA)

• Administer IV tPA (0.9 mg/kg: 10% bolus over 1 minute, remainder over 59 minutes) within 4.5 hours of symptom onset if eligible. 1, 3
• Do not delay IV tPA for vascular imaging in patients within the treatment window—begin tPA before transport for additional imaging or endovascular therapy. 1, 3
• Thrombolysis in posterior circulation has similar benefits and potentially lower hemorrhage risks compared to anterior circulation. 4, 5
• Critical pitfall: Door-to-needle time is often significantly longer for posterior circulation strokes due to difficulty in timely recognition. 1

Endovascular Thrombectomy

• Recent ATTENTION and BAOCHE trials demonstrate that thrombectomy benefits basilar artery occlusion strokes. 4
• Consider thrombectomy for large vessel occlusions, particularly basilar artery occlusion 1, 4
• Evidence for thrombectomy at other posterior circulation occlusion sites remains uncertain 4
• Intra-arterial fibrinolysis may be considered for patients ineligible for IV tPA, particularly within 6 hours for basilar artery occlusion 1

Blood Pressure Management

Pre-Thrombolysis

• If systolic >185 mmHg or diastolic >110 mmHg: Labetalol 10-20 mg IV over 1-2 minutes (may repeat ×1) OR nitropaste 1-2 inches OR nicardipine drip 5 mg/h, titrate up by 2.5 mg/h at 5-15 minute intervals (maximum 15 mg/h) 1
• If blood pressure not reduced and maintained at desired levels (systolic ≤185 mmHg and diastolic ≤110 mmHg), do not administer tPA. 1

Post-Thrombolysis

• Monitor blood pressure every 15 minutes for 2 hours, then every 30 minutes for 6 hours, then every hour for 16 hours 1
• If systolic 180-230 mmHg or diastolic 105-120 mmHg: Labetalol 10 mg IV over 1-2 minutes, may repeat or double every 10-20 minutes to maximum 300 mg 1
• If diastolic >140 mmHg: Sodium nitroprusside 0.5 μg/kg/min IV infusion as initial dose, titrate to desired blood pressure 1

Antiplatelet Therapy (Post-Acute Phase)

• For high-risk TIA or minor stroke within 48 hours: Initiate dual antiplatelet therapy (aspirin 80 mg + clopidogrel 75 mg daily) after 24-hour post-thrombolysis scan excludes hemorrhage 1
• In dysphagic patients: ASA 80 mg daily and clopidogrel 75 mg daily by enteral tube OR ASA 325 mg daily by rectal suppository 1
• For patients with high-grade carotid stenosis requiring urgent intervention, coordinate with surgeon regarding antiplatelet selection to reduce perioperative bleeding risk. 1

Prognostic Considerations

Poor Outcome Predictors

• Mortality in basilar artery occlusion ranges from 45% to 86% without recanalization. 1
• Predictors of poor outcome: older age, higher NIHSS score, lack of recanalization, atrial fibrillation, intracranial hemorrhage, pc-ASPECTS ≤8 1
• Embolic strokes fare worse than in situ atherosclerosis. 1

NIHSS Limitations

• NIHSS significantly underestimates posterior circulation stroke severity due to focus on limb/speech impairments rather than cranial nerve lesions. 1
• Baseline NIHSS cut-off for favorable 3-month outcome is significantly lower in posterior versus anterior circulation stroke 1

Neurosurgical Considerations

• Space-occupying cerebellar strokes (ischemic or hemorrhagic) can benefit from decompressive craniectomy. 4
• Monitor for life-threatening edema and mass effect in posterior fossa on initial imaging 1

Etiologic Differential and Secondary Prevention

• Differential diagnosis includes: thromboembolism, cardiogenic embolism, artery-to-artery embolism, in situ thrombosis from atherosclerotic disease, or dissection 1
• Small vessel disease occurs more frequently in posterior circulation strokes (33.3% vs 6.1% in anterior circulation). 6
• Basilar artery stenosis is better treated with aggressive medical therapy than stenting due to high peri-procedural risk 4