Ruling Out Posterior Circulation Stroke in the Elderly
A high index of clinical suspicion combined with rapid vascular imaging via CT angiography (CTA) is essential for ruling out posterior circulation stroke in elderly patients, who often present with non-specific symptoms that can be easily misattributed to other conditions. 1, 2
Clinical Presentation Challenges
Posterior circulation strokes present unique diagnostic challenges, particularly in the elderly:
Non-specific symptoms that can mimic other conditions:
Key pitfall: Posterior circulation strokes often have lower NIHSS scores than anterior circulation strokes with similar severity, making them easy to miss 1
Most common neurological sign in patients with posterior circulation stroke but NIHSS score of 0: truncal ataxia 1
Diagnostic Algorithm
Step 1: Identify High-Risk Patients
- Elderly patients (sixth/seventh decades) are at higher risk for intrinsic atherosclerosis of posterior circulation 1
- Risk factors: Older age, higher NIHSS score, atrial fibrillation, and pc-ASPECTS ≤8 predict poor outcomes 1
Step 2: Immediate Vascular Imaging
- CT angiography (CTA) is the gold standard for rapid identification of posterior circulation large vessel occlusion 2
- Look for hyperdense basilar artery on non-contrast CT (sensitivity 71%, specificity 98% for basilar occlusion) 1
- Optimal cut-off: 40-42 Hounsfield units
- Hyperdense basilar artery is an independent predictor of poor outcome (OR 5.6)
Step 3: Advanced Imaging When Available
- MRI with diffusion-weighted imaging (DWI) is superior for detecting posterior fossa lesions 3
- CT perfusion (CTP) adds diagnostic value with higher sensitivity (74%) and negative predictive value (80%) compared to non-contrast CT 1
Location-Specific Findings
Basilar Artery Occlusion
- Top of basilar syndrome: Somnolence, peduncular hallucinosis, convergence nystagmus, skew deviation, oscillatory eye movements, retraction/elevation of eyelids, vertical gaze paralysis 1
- Mid-basilar occlusions: Various pontine syndromes 1
- Proximal basilar occlusions: "Locked-in" syndrome 1, 2
Vertebral Artery Disease
- Typically affects first portion of vertebral arteries or extends from plaques at origin 1
- Midportion lesions may cause symptoms with head turning due to osteophyte compression 1
Common Diagnostic Pitfalls
- Delayed recognition due to non-specific symptoms leads to longer door-to-needle times compared to anterior circulation strokes 4
- Relying solely on NIHSS which emphasizes limb and speech impairments but underemphasizes cranial nerve lesions 1
- Misattribution of symptoms to peripheral vestibular disorders, cardiac arrhythmias, or orthostatic hypotension 1
- Beam hardening artifact on CT limiting assessment of posterior fossa structures 1
Differential Diagnosis
- Thromboembolism (more common in younger patients)
- In-situ thrombosis of vertebrobasilar stenosis due to atherosclerotic disease
- Cardiogenic or artery-to-artery embolism
- Dissection (more common in trauma) 1
- Vestibular disorders
- Cardiac arrhythmias
- Orthostatic hypotension 1
Urgency of Diagnosis
Posterior circulation strokes, particularly basilar artery occlusions, have mortality rates of 45-86% without treatment, making rapid diagnosis critical 1, 2. The high eloquence of brainstem structures means even small infarctions can be clinically devastating 1.
Key Recommendations for Elderly Patients
- Maintain high clinical suspicion for posterior circulation stroke in elderly patients with vague neurological symptoms
- Proceed directly to vascular imaging (CTA) when posterior circulation stroke is suspected
- Look for hyperdense basilar artery on non-contrast CT as an early sign
- Use MRI with DWI when available for definitive diagnosis of posterior fossa lesions
- Remember that normal NIHSS does not exclude posterior circulation stroke
By following this approach, clinicians can improve detection of posterior circulation strokes in elderly patients, reducing the risk of devastating outcomes from missed or delayed diagnosis.