Top of Basilar Syndrome: Acute and Secondary Management
Clinical Recognition
Top of basilar syndrome is a devastating posterior circulation stroke requiring immediate recognition and aggressive endovascular intervention in appropriately selected patients, with treatment decisions driven primarily by stroke severity (NIHSS score) and time from symptom onset.
Top of basilar syndrome presents with a characteristic constellation of findings including somnolence, peduncular hallucinosis, convergence nystagmus, skew deviation, oscillatory eye movements, vertical gaze paralysis, and retraction/elevation of the eyelids 1, 2. Motor deficits occur in 67-92% of patients, ataxia (particularly truncal) is a hallmark finding, and altered consciousness occurs in approximately 50% of cases 2. The mortality rate ranges from 45-86%, with good clinical outcomes occurring in only 20% despite advanced care 1, 2.
Acute Management Algorithm
Immediate Imaging and Assessment (Within Minutes)
- Obtain CT angiography immediately to confirm basilar artery occlusion 1, 3
- Calculate posterior circulation ASPECTS (pc-ASPECTS) on non-contrast CT or MRI to quantify ischemic burden 1, 3
- Document NIHSS score for treatment stratification 1, 3
- Establish time from last known well as this determines treatment windows 1, 3
Treatment Decision Based on Stroke Severity
For Patients with NIHSS ≥10 (Severe Symptoms)
Endovascular thrombectomy (EVT) plus best medical treatment (BMT) is strongly recommended over BMT alone 1, 3.
Time-based treatment windows:
- Within 0-12 hours from last known well: Thrombectomy is indicated (Class I, Level B-R) 1, 3
- Within 12-24 hours from last known well: Thrombectomy is reasonable (Class IIa, Level B-R) 1, 3
- Beyond 24 hours: Thrombectomy may be considered case-by-case (Class IIb, Level C-EO) 1
The ATTENTION trial demonstrated 46% good outcomes (mRS 0-3) with EVT+BMT versus 23% with BMT alone, with mortality of 37% versus 55% respectively 1, 3. The treatment effect is stronger for proximal and middle basilar occlusions compared to distal locations 1, 3.
For Patients with NIHSS <10 (Mild-Moderate Symptoms)
Best medical treatment alone is recommended over EVT+BMT 1, 3. BMT appeared safer than EVT without clear evidence of superior efficacy in this population 1, 3. This represents a critical treatment-modifying effect where more intervention is not better 1.
Imaging Selection Criteria
For pc-ASPECTS 7-10 (non-extensive ischemic changes):
For pc-ASPECTS 0-6 (extensive ischemic changes):
- Consider other prognostic variables including pre-stroke disability, age, and frailty before offering reperfusion therapy 1, 3
- This represents territory beyond what was studied in randomized trials 1
Intravenous Thrombolysis Decision
For eligible patients without contraindications, administer IV thrombolysis (IVT) immediately—do not delay IVT while arranging EVT 3. The combination of IVT + EVT is recommended over direct EVT when IVT is not contraindicated 3. IV thrombolysis can be administered up to 24 hours from last known well in basilar artery occlusion 3.
Endovascular Technique
Direct aspiration is suggested as the first-line endovascular strategy over stent retriever 1, 3. However, all commonly used techniques (aspiration, stent retriever, combined) were effective in recent trials 1.
Critical technical considerations:
- Intracranial angioplasty and stenting were performed in 40% of ATTENTION patients and 55% of BAOCHE patients, reflecting high rates of underlying intracranial atherosclerotic disease (ICAD) 1
- For suspected ICAD with severe underlying stenosis after failed initial thrombectomy, expert consensus (10/10 members) suggests angioplasty and/or stenting 3
- Intravenous tirofiban (GP2b3a inhibitor) was administered in 40-54% of patients in recent trials 1
- General anesthesia was used in 56-65% of cases 1
Rescue Antithrombotic Strategy
For patients treated with EVT without concomitant IVT where the procedure is complicated or fails, additional antithrombotic treatment is suggested during or within 24 hours after EVT 3. This should be used as a rescue strategy after evaluating bleeding risk 3.
Secondary Prevention and Recovery
Post-Procedure Management
- Avoid high FiO2 (>0.8) during recovery as it may worsen atelectasis formation 3
- Monitor closely for symptomatic intracranial hemorrhage (occurred in 5% of EVT patients in ATTENTION) 1
- Procedural complications occurred in 14% of cases in ATTENTION, including arterial perforation 1
Prognostic Factors
Poor outcome predictors include:
- Older age 1, 2
- Higher NIHSS score (though NIHSS underestimates posterior circulation severity) 1, 2
- Lack of recanalization 1, 2
- Atrial fibrillation 1, 2
- Intracranial hemorrhage 1, 2
- pc-ASPECTS ≤8 1, 2
Critical Pitfalls to Avoid
Do not assume all basilar artery occlusions require EVT: Patients with NIHSS <10 have better outcomes with medical therapy alone, and EVT may cause harm in this population 1, 3.
Do not delay diagnosis due to atypical presentations: Top of basilar syndrome can mimic other conditions with non-specific symptoms like headache, vertigo, and nausea, potentially leading to dangerous delays 1, 2. Patients can present with NIHSS score of 0 where truncal ataxia is the only finding 1.
Do not withhold IVT while arranging EVT: Start thrombolysis immediately in eligible patients—the availability of EVT should not preclude IVT administration 3.
Do not overlook the extended time window: Unlike anterior circulation strokes, basilar artery occlusion can be treated up to 24 hours and potentially beyond, reflecting the extended prodrome and delayed diagnosis common in these patients 1, 3.